⟦eef6f249b⟧

TextFile

%!
% This file is a NONconforming PostScript file.
(TeXPS: dvi->PostScript Driver dvi2ps, Version 3.11 of September 5, 1990\n)print flush
(TeXPS: release number dvi2ps of 3.11\n)print flush
% Copyright 1989 Stephan v. Bechtolsheim (unless otherwise stated)
% applies to various prologue files. Read documentation for details.
save
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/texpre.pro"
/@bop0
{
PsPrintEnabled { (Pass0: Page ) print == flush } {pop} ifelse
}	def
/@eop0 {
pop
}	def
/@bop1
{
PsPrintEnabled { (Pass1: Page ) print == flush } {pop} ifelse
save
DviTranslateVector-X DviTranslateVector-Y translate
DviOrientationMatrix concat
Page-H-Offset Page-V-Offset translate
3 1 roll
translate
0 0 moveto
Draft-Flag { @Draft } if
/DriverDelta 0 def
} def
/@eop1 {
pop
showpage
restore
} def
/@end {
(Done!\n) print flush
} def
/@ReportVmStatus {
(\n@ReportVmStatus: ) print
print (: ) print
vmstatus
(max: ) print 20 string cvs print
(, used: ) print 20 string cvs print
(, level: ) print 20 string cvs print
(\n) print flush
} def
/@ReportVmStatusNew {
(VM: ) print
exch print
(, printer: ) print
/Vmfree vmstatus pop exch pop def Vmfree (       ) cvs print
(, driver: ) print dup (      ) cvs print
(, delta: ) print
Vmfree sub (      ) cvs print
(\n) print flush
} def
/@Draft {
gsave
Page-H-Offset neg Page-V-Offset neg translate
-45 rotate
-150 0 moveto
/Helvetica-Bold findfont
[120.0 0 0 -120.0 0 0 ] makefont setfont
(DRAFT)  true charpath stroke
grestore
gsave
Page-H-Offset neg Page-V-Offset neg translate
300 -100 moveto
/Helvetica-Bold findfont
[60.0 0 0   -60.0 0 0 ] makefont setfont
Date-and-Time		show
(   ::   )	      	show
Dvi-File-Name		show
grestore
} def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/texpre.pro"
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/pos.pro"
/a { rmoveto } def
/DriverDelta 0 def
/b { exch p dup /DriverDelta exch def 0 rmoveto } def
/c { p DriverDelta 4 sub dup /DriverDelta exch def 0 rmoveto } def
/d { p DriverDelta 3 sub dup /DriverDelta exch def 0 rmoveto } def
/e { p DriverDelta 2 sub dup /DriverDelta exch def 0 rmoveto } def
/f { p DriverDelta 1 sub dup /DriverDelta exch def 0 rmoveto } def
/g { p DriverDelta 0 rmoveto } def
/h { p DriverDelta 1 add dup /DriverDelta exch def 0 rmoveto } def
/i { p DriverDelta 2 add dup /DriverDelta exch def 0 rmoveto } def
/j { p DriverDelta 3 add dup /DriverDelta exch def 0 rmoveto } def
/k { p DriverDelta 4 add dup /DriverDelta exch def 0 rmoveto } def
/l { p -4 0 rmoveto } def
/m { p -3 0 rmoveto } def
/n { p -2 0 rmoveto } def
/o { p -1 0 rmoveto } def
/q { p 1 0 rmoveto } def
/r { p 2 0 rmoveto } def
/s { p 3 0 rmoveto } def
/t { p 4 0 rmoveto } def
/p { show } def
/w { 0 exch rmoveto } def
/x { 0 rmoveto } def
/y { 3 -1 roll p rmoveto } def
/u-string ( ) def
/u { u-string exch 0 exch put
u-string show
} def
/v { u-string exch 0 exch put
currentpoint
u-string show
moveto
} def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/pos.pro"
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/rules.pro"
/z
{   /dy exch def
/dx exch def
currentpoint
currentpoint
transform round exch round exch itransform
newpath
moveto
dx 0 rlineto
0 dy rlineto
dx neg 0 rlineto
closepath
fill
moveto
}
def
/z
{   /dy exch def
/dx exch def
currentpoint
0.2 0.2 rmoveto
currentpoint
newpath
moveto
dx 0 rlineto
0 dy rlineto
dx neg 0 rlineto
closepath
fill
moveto
}
def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/rules.pro"
letter
/Dvi-File-Name (simson.dvi) def
(Dvi file name: ") print Dvi-File-Name print (".\n) print
/Draft-Flag false def
/#copies 1 def
/NumCharsInPixelFonts 256 def
/HostName (bambi.jvnc.net) def
(This PostScript file was produced on host \") print HostName print (\".\n) print
/PsPrintEnabled true def
/Page-H-Offset   0.000000 def
/Page-V-Offset   0.000000 def
/ExecPsConv {0.30 mul} def
/Date-and-Time (Mon Jun 24 16:51 1991) def
/DviTranslateVector-X   72.000 def
/DviTranslateVector-Y  720.000 def
/DviOrientationMatrix [    0.240    0.000    0.000
	   -0.240 0.0 0.0 ] def
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/pixel-fonts.pro"
/@newfont
{
/newname exch def
newname 7 dict def
newname load begin
/FontType 3 def
/FontMatrix [1 0 0 -1 0 0] def
/FontBBox [0 0 1 1] def
/BitMaps NumCharsInPixelFonts array def
/BuildChar {CharBuilder} def
/Encoding NumCharsInPixelFonts array def
0 1 NumCharsInPixelFonts 1 sub {Encoding exch /.undef put} for
end
newname newname load definefont pop
} def
/ch-image {ch-data 0 get} def
/ch-width {ch-data 1 get} def
/ch-height {ch-data 2 get} def
/ch-xoff  {ch-data 3 get} def
/ch-yoff  {ch-data 4 get} def
/ch-tfmw  {ch-data 5 get} def
/CharBuilder
{
/ch-code exch def
/font-dict exch def
/ch-data font-dict /BitMaps get ch-code get def
ch-data null eq not
{
ch-tfmw   0
ch-xoff neg
ch-height ch-yoff sub neg
ch-width  ch-xoff neg add
ch-yoff
setcachedevice
0 0 transform round exch round exch itransform translate
ch-width ch-height true
[1 0  0 1 ch-xoff ch-height ch-yoff sub] {ch-image} imagemask
}
if
} def
/@dc
{
/ch-code exch def
/ch-data exch def
currentfont /BitMaps get
ch-code ch-data put
currentfont /Encoding get
ch-code (   ) cvs   % convert the character code to a string
cvn
ch-code exch put
} def
/@sf /setfont load def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/pixel-fonts.pro"

1 @bop0
/@F1 @newfont
@F1 @sf
[<
800FF000807FFC00C1F01E00C7000700EC000380F80001C0F00000E0E00000E0E00000F0C0
000070C00000788000007880000078800000788000007880000078000000F8000000F80000
00F0000001F0000003F0000007E000001FE00000FFC0000FFF8000FFFF0003FFFC0007FFF8
000FFF80001FF800003FC000003F0000007E0000007C000000F8000000F8000020F0000020
F0000020F0000020F0000060F000006070000060700000E0780000E0380001E03C0003E01E
0006E00F001C6007C0786001FFE020007F8020>
	 29 51 -4 49 37] 83 @dc
[<
001FC00000F0300001C00C00078002000F0002000E0001001E0000803C0000803C0000007C
00000078000000F8000000F8000000F8000000F8000000F8000000F8000000FFFFFF80F800
0780F80007807800078078000F807C000F003C000F001C000F001E001E000E001E0007003C
000380380000E0E000003F8000>
	 25 31 -2 30 29] 101 @dc
[<
003F8000E0600380180700040F00021E00021E00013C00017C00007C0000780000F80000F8
0000F80000F80000F80000F80000F80000F80000F800007800007C00087C003E3C003E1C00
3E1E001E0F000407000403801800E060003F80>
	 24 31 -3 30 29] 99 @dc
[<
001FC0FF80007030FF8001C008F80003C004F000038002F000078001F000078001F0000780
01F000078000F000078000F000078000F000078000F000078000F000078000F000078000F0
00078000F000078000F000078000F000078000F000078000F000078000F000078000F00007
8000F000078000F000078000F000078000F000078000F0000F8001F000FF801FF000FF801F
F000078000F000>
	 33 31 -2 30 37] 117 @dc
[<
FFFE00FFFE000FC00007800007800007800007800007800007800007800007800007800007
800007800007800007800007800007800007800007800007800007800007C00007C00007C0
0007C03807A07C0F907CFF907CFF8C180783E0>
	 22 31 -2 30 25] 114 @dc
[<
FFF8FFF80FC007800780078007800780078007800780078007800780078007800780078007
80078007800780078007800780078007800F80FF80FF800780000000000000000000000000
0000000000000000000007000F801F801F800F800700>
	 13 48 -2 47 18] 105 @dc
[<
001F000078C000E04001E02001C02003C01003C01003C01003C01003C01003C01003C01003
C01003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C0
0003C00003C00003C00003C000FFFFE01FFFE00FC00007C00003C00001C00001C00000C000
00C00000C000004000004000004000004000004000>
	 20 44 -1 43 25] 116 @dc
[<
1F8000000030400000007030000000F810000000F808000000F80C00000070040000000004
00000000020000000002000000000100000000010000000001000000000080000000008000
000001C000000001C000000001C000000003E000000003E000000007D00000000790000000
07900000000F080000000F080000001F040000001E040000001E040000003C020000003C02
0000007C0100000078010000007801000000F000800000F000800001F000400001E0004000
01E000400003C000200003C000200007C000300007800038000FC0007C00FFF801FF80FFF8
01FF80>
	 33 45 -1 30 35] 121 @dc
[<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>
	 46 50 -2 49 50] 65 @dc
[<
FFFCFFFC0FC007800780078007800780078007800780078007800780078007800780078007
80078007800780078007800780078007800780078007800780078007800780078007800780
0780078007800780078007800780078007800F80FF80FF800780>
	 14 50 -2 49 18] 108 @dc
[<
FFFFFFFFF0FFFFFFFFF007E0000FF003E00001F803E000007803E000003803E000001803E0
00001803E000000803E000000C03E000000C03E000000403E000000403E000000403E00000
0403E000000203E000800203E000800203E000800003E000800003E000800003E001800003
E001800003E007800003FFFF800003FFFF800003E007800003E001800003E001800003E000
800003E000800003E000800003E000800003E000800803E000000803E000000803E0000008
03E000001003E000001003E000001003E000001003E000003003E000003003E000007003E0
0000F003E00001E007E0000FE0FFFFFFFFE0FFFFFFFFE0>
	 39 49 -4 48 45] 69 @dc
[<
FFC007FFC0FFC007FFC01F8003F800078001F000018001E000008003C00000C007C0000040
0F800000200F000000101E000000183E000000087C000000047800000002F000000001F000
000003E000000003C000000007C00000000FA00000000F300000001E100000003C08000000
7C040000007802000000F003000001E001000003E001800003C001E0000FE001F800FFF803
FF00FFF803FF00>
	 34 31 -1 30 35] 120 @dc
[<
03FC03E00F0307F03E008F087C005E0478003E04F8003E04F8003E04F8001E04F8001E04F8
001E047C001E003C001E003E001E001F001E000F801E0003E01E0000FC1E00000FFE000000
1E0000001E0000001E0008001E003E001E003E001E003E001C003C003C0010003800100070
000C00E0000303C00000FE0000>
	 30 31 -3 30 33] 97 @dc
[<
80FE00C301C0CC0060F00030F00038E00018E0001CC0001CC0001C80001C80003C80003C00
00F80001F8003FF003FFE00FFFC01FFF003FF0007E0000F80000F00010E00010E00010E000
10E000306000303000701800F00E033001FC10>
	 22 31 -2 30 26] 115 @dc
/@F0 @newfont
@F0 @sf
[<
FFFFFFC0FFFFFFC0FFFFFFC0FFFFFFC0FFFFFFC0FC000000FC000000FC000000FC000000FC
000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC00
0000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC0000
00FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000
FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC000000FC
000000FC000000FC000000FC000000>
	 26 50 -6 49 36] 76 @dc
[<
001FE00000FFFC0001FFFF0007FFFF800FF01F801FC003801F0000803E0000003E0000007C
0000007C000000F8000000F8000000F8000000F8000000F8000000FFFFFF80FFFFFF80FFFF
FF80FFFFFF807C0007807C000F007C000F003E001F003F001E001F803E000FE0FC0007FFFC
0003FFF80000FFE000003F8000>
	 25 31 -2 30 30] 101 @dc
[<
003FE00001FFFC0007FFFF000FFFFF803FE03FE03F0007E07E0003F0FC0001F8F80000F8F8
0000F8F80000F8F80000F8FC0001F87C0003F03E000FF03FFFFFE01FFFFFC00FFFFF801FFF
FF001FFFF8001E0000003C0000003C0000003C0000001C7F00001DFFC0001FFFE0000FFFF0
000FC1F8001F80FC001F007C001F007C003E003E003E003E003E003E003E003E003E003E00
3E003E001F007C001F007C001F80FC000FC1FC0007FFFFFC03FFFFFC01FFC7FC007F00F8>
	 30 46 -2 30 34] 103 @dc
[<
0FE07C1FFC7C3FFF7C7FFFFC7F07FCFC01FCF800FCF8007CF8007CF8007CF8007C7C007C3F
007C3FC07C0FFFFC07FFFC00FFFC0007FC00007C00007C00007C00007C00007C20007C3000
F83800F83F03F03FFFE01FFFC007FF8000FE00>
	 22 31 -3 30 32] 97 @dc
[<
F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8F8
F8F8F8F8F8F8F8F8F8F8F8F8F8>
	 5 50 -5 49 16] 108 @dc
[<
7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C7C000000000000
0000000000FCFCFCFCFCFC>
	 6 48 -4 47 16] 105 @dc
[<
007E0000FFC001FFF001FFF003F0E003E02003E00003E00003E00003E00003E00003E00003
E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003E0
0003E00003E000FFFFE0FFFFE0FFFFE0FFFFE003E00003E00003E00003E00003E00003E000
03E00003E00003E000>
	 20 40 -1 39 24] 116 @dc
[<
01FE001FFFC07FFFE0FFFFF0FE03F8F800F860007C40007C00007C00007C00007C0000FC00
03F8003FF803FFF00FFFE01FFF803FFE007FE0007E0000FC0000F80000F80000F80000F800
007C00307E01F83FFFF81FFFF80FFFE001FF00>
	 22 31 -2 30 26] 115 @dc
/@F4 @newfont
@F4 @sf
[<
81FC00C60700C80180F000C0E000C0C00060C0006080007080007080007080007000007000
00F00000F00001E00007E0003FC003FF800FFF001FFE003FF0007F0000780000F00000F000
00E00020E00020E00020E00060E000606000607000E03001E01802600C0C6003F020>
	 20 36 -3 34 27] 83 @dc
[<
FFC00E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E001E
00FE000E00000000000000000000000000000000001C001E003E001E001C00>
	 10 34 -1 33 14] 105 @dc
[<
FFE3FF8FFE0E003800E00E003800E00E003800E00E003800E00E003800E00E003800E00E00
3800E00E003800E00E003800E00E003800E00E003800E00E003800E00E003800E00E003800
E00E003800E00F003C00E00F003C00E01E807201C0FE60E183800E1FC07F00>
	 39 21 -1 20 41] 109 @dc
[<
8FC0D030E018C008C00C800C800C801C003C01F80FF03FE07F80F000E008C008C008C01860
1830780F88>
	 14 21 -2 20 19] 115 @dc
[<
01FC000707000E03801C01C03800E07800F0700070F00078F00078F00078F00078F00078F0
0078F000787000707000703800E01800C00C018007070001FC00>
	 21 21 -1 20 24] 111 @dc
[<
FFE7FF0E00700E00700E00700E00700E00700E00700E00700E00700E00700E00700E00700E
00700E00700E00700E00700F00700F00701E80E0FE60C00E1F80>
	 24 21 -1 20 27] 110 @dc
[<
0007F000003C0C0800E0031801C000B8038000B8070000780F0000781E0000781E0000783C
0000783C0000787C00007878000078780000F8F8001FFFF8000000F8000000F8000000F800
0000F8000000F8000000F800000078000008780000087C0000083C0000183C0000181E0000
181E0000380F00003807000078038000F801C001B800E00218003C0C180007F008>
	 32 36 -3 34 38] 71 @dc
[<
0FC1E03C2390781708F00F08F00708F00708F007087007007807003C07001E070007C70000
FF000007000007000007001807003C0E003C0C001838000FE000>
	 21 21 -2 20 24] 97 @dc
[<
FFF00F000E000E000E000E000E000E000E000E000E000E000E000E000E000F000F060F0F1E
8FFE460E3C>
	 16 21 -1 20 19] 114 @dc
[<
7FE1FF80070038000700380007003800070038000700380007003800070038000700380007
00380007003800070038000700380007003800070038000700380007003800070038000700
380007007800FFFFF800070000000700000007000000070000000700000007000000070000
000700300007007800038078000180380000C0100000702000001FC000>
	 25 35 0 34 27] 12 @dc
[<
FFE3FE0E00F80E00F00E01E00E01C00E03C00E07800E07000E0E000E1E000F1C000EF8000E
38000E10000E08000E04000E02000E01800E01C00E01F00E03FC0E00000E00000E00000E00
000E00000E00000E00000E00000E00000E00000E00001E0000FE00000E0000>
	 23 35 -1 34 26] 107 @dc
[<
00FC000703000E00801C0040380020780020700000F00000F00000F00000F00000F00000FF
FFE0F000E07000E07801E03801C01C01C00C038007070001FC00>
	 19 21 -1 20 22] 101 @dc
[<
FFE00E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E
000E000E000E000E000E000E000E000E000E000E000E000E000E001E00FE000E00>
	 11 35 -1 34 14] 108 @dc
[<
FFFE07C0038003800380038003800380038003800380038003800380038003800380038003
800380038003800380038003800380038003800380F3800F8003800080>
	 15 33 -4 32 24] 49 @dc
[<
0FC000103000201800700C007806007807003003000003800003800001C00001C00001C003
E1E00619E00C05E01805E03803E07003E07001E0F001E0F001E0F001E0F001E0F001E0F001
C0F001C0F001C07003807003803803801807000C0600060C0001F000>
	 19 34 -2 32 24] 57 @dc
[<
03F0000E0E001803003000806000C0600040C00060C00060C00060C00060C000E06000E060
01C03007C0100F80083F80067F0003FC0003F8000FF8001FC4003F02003E01007801807000
C06000C06000C06000C02000C0200180100180080300060E0001F800>
	 19 34 -2 32 24] 56 @dc
[<
01800003C00003C00003C00003C00003C00003C00003C00003C00001C00001C00001C00001
C00000C00000C00000E0000060000060000060000020000030000010000008000008000004
00800200800200800100C001004000807FFFC07FFFC07FFFE0600000400000>
	 19 35 -3 33 24] 55 @dc
/@F2 @newfont
@F2 @sf
[<
00003FF800000003FFFF0000000FFFFFC000003FF007E00000FF8000F80001FE00003C0003
FC00001E0007F000000E000FF0000007001FE0000007001FE0000003803FC0000003803FC0
000003807FC0000003807F80000000007F8000000000FF8000000000FF8000000000FF8000
000000FF8000000000FF8000000000FF8000000000FF8000000000FF8000000000FF800000
00007F80000000007F80000003807FC0000003803FC0000003803FC0000007801FE0000007
801FE0000007800FF000000F8007F000001F8003FC00003F8001FE00007F8000FF8001FF80
003FF007DF80000FFFFF87800003FFFE038000003FF00180>
	 41 41 -4 40 50] 67 @dc
[<
003FE00001FFFC0007F07F000FC01F801F800FC03F800FE03F800FE07F0007F07F0007F0FF
0007F8FF0007F8FF0007F8FF0007F8FF0007F8FF0007F8FF0007F8FF0007F87F0007F07F00
07F07F0007F03F0007E03F800FE01F800FC00FC01F8003F07E0001FFFC00003FE000>
	 29 27 -2 26 34] 111 @dc
[<
FFFE3FFF80FFFE3FFF80FFFE3FFF800FE003F8000FE003F8000FE003F8000FE003F8000FE0
03F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8
000FE003F8000FE003F8000FE003F8000FE003F8000FF003F8000FF003F8000FD803F8000F
D803F0000FCE03F000FFC787E000FFC1FFC000FFC07F0000>
	 33 27 -3 26 38] 110 @dc
[<
001F8000FFC001F86003F87003F03807F03807F03807F03807F03807F03807F03807F00007
F00007F00007F00007F00007F00007F00007F00007F00007F00007F00007F00007F000FFFF
F0FFFFF01FFFF007F00003F00003F00001F00000F00000F00000F000007000007000007000
007000>
	 21 38 -1 37 27] 116 @dc
[<
001FF00000FFFE0003F81F0007E003800FC001C01F8000E03F8000E07F0000007F0000007F
000000FF000000FF000000FF000000FFFFFFE0FFFFFFE0FF0007E0FF0007E07F0007E07F00
07C07F000FC03F800FC01F800F800F801F8007C01F0003F07E0001FFF800003FE000>
	 27 27 -2 26 32] 101 @dc
[<
C1FF00F7FFC0FF01E0FC0070F80038F00038F0003CE0003C60007C0000FC0003FC00FFF807
FFF81FFFF03FFFE07FFF807FFE00FFE000FC0000F80070F00070F000707000703800F01E03
F00FFFF003FE30>
	 22 27 -2 26 27] 115 @dc
/@F6 @newfont
@F6 @sf
[<
FFFF80FFFF8003E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003
E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003E00003E000F3E0
00FFE0000FE00001E00000E000>
	 17 29 -4 28 26] 49 @dc
[<
FFFFFFFF07E007E007E007E007E007E007E007E007E007E007E007E007E007E007E007E007
E007E007E007E007E007E007E007E007E007E007E0FFFFFFFF>
	 16 31 -2 30 20] 73 @dc
[<
FFE3FFFFE3FF1F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F
00F81F00F81F00F81E80F81EC0F81E61F0FE3FE0FE0FC0>
	 24 20 -3 19 29] 110 @dc
[<
01F003F807CC0F860F860F860F860F860F800F800F800F800F800F800F800F800F800F80FF
FCFFFC3F800F800780038003800380018001800180>
	 15 29 -1 28 20] 116 @dc
[<
FFF000FFF0001F00001F00001F00001F00001F00001F00001F00001F00001F00001F00001F
00001F03001F8FC01E8FC01E8FC01ECFC0FE7F80FE3E00>
	 18 20 -2 19 22] 114 @dc
[<
01FF0007FFC01F83F03E00F83E00F87C007C7C007CFC007EFC007EFC007EFC007EFC007EFC
007E7C007C7C007C3E00F83E00F81F83F007FFC001FF00>
	 23 20 -1 19 26] 111 @dc
[<
03F8FF0FFEFF1F07F83E01F87E00F87C00F87C00F8FC00F8FC00F8FC00F8FC00F8FC00F8FC
00F87C00F87C00F87E00F83E01F81F83F80FFEF801F8F80000F80000F80000F80000F80000
F80000F80000F80000F80000F80000F80007F80007F8>
	 24 32 -2 31 29] 100 @dc
[<
03F8FF07FCFF0F06F81F01F81F01F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F
00F81F00F81F00F81F00F81F00F81F00F8FF07F8FF07F8>
	 24 20 -3 19 29] 117 @dc
[<
01FC0007FF001F81C03F00C03E00607E00007C0000FC0000FC0000FC0000FC0000FC0000FC
00007C03007C0FC03E0FC03E0FC01F0FC007FF8001FE00>
	 19 20 -2 19 23] 99 @dc
[<
FFE0FFE01F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F00FF
00FF000000000000000000000000001C003E007F007F007F003E001C00>
	 11 33 -2 32 15] 105 @dc
[<
03FC001FFF803C0FC07807E0FC03F0FE03F0FE03F8FE03F87C03F83803F80003F80003F000
03E00007C0000F8001FC0001FC00001F00000F80000FC01E0FC03F07E03F07E03F07E03F07
E01E0FC00E0F8007FF0001FC00>
	 21 29 -2 28 26] 51 @dc
[<
FFFFC0FFFFC07FFFC03FFFC01FFFC01C00E00E006007006003806001C00000E00000F00000
7800003E00001F00001F80000FC0000FC0000FE03807E07C07E0FE07E0FE0FE0FE0FC0FE0F
C07C1F80383F001FFE0007F000>
	 19 29 -3 28 26] 50 @dc
[<
00018000300000000380003800000003C0007800000007C0007C00000007C0007C00000007
E000FC0000000FE000FE0000000FF001FE0000000FF001FE0000001FB001FB0000001F9803
F30000003F9803F38000003F1803F18000003F0C07E18000007E0C07E0C000007E0E0FE0C0
00007E060FC0C00000FC060FC0600000FC031F80600001FC031F80700001F8031F80300001
F801BF00300003F001BF00180003F001FF00180003F000FE00180007E000FE000C0007E000
FE000C000FE000FC000E000FC000FC000E00FFFE0FFFC0FFE0FFFE0FFFC0FFE0>
	 51 31 -1 30 54] 87 @dc
[<
FFE3FFFFE3FF1F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F00F81F
00F81F00F81F00F81F80F81FC0F81F61F01F3FE01F0FC01F00001F00001F00001F00001F00
001F00001F00001F00001F00001F0000FF0000FF0000>
	 24 32 -3 31 29] 104 @dc
[<
0FE07E3FF8FE7E0DE0FC05E0F803E0F803E0F803E07C03E03C03E01F03E007FBE0007FE000
03E00C03E03F03E03F03E03F07C03F0F801FFF0007FC00>
	 23 20 -1 19 25] 97 @dc
[<
00FF8007FFE00F80701E00183E00187C00007C0000FC0000FC0000FC0000FFFFF8FFFFF8FC
00F87C00F87C00F03E00F01E01E00F83C007FF8001FE00>
	 21 20 -1 19 24] 101 @dc
[<
C7F0FFFCF81EF006E007C007C007001F03FE1FFE3FFC7FF8FFC0F800E006E006600E701E3F
FE0FE6>
	 16 20 -2 19 21] 115 @dc
[<
181F801C7FE01EC1F81F807C1F007C1F003E1F003E1F003F1F003F1F003F1F003F1F003F1F
003F1F003E1F003E1F007E1F807C1FE0F81F7FF01F1FC01F00001F00001F00001F00001F00
001F00001F00001F00001F00001F0000FF0000FF0000>
	 24 32 -2 31 29] 98 @dc
[<
001C0000001C0000003E0000003E0000007F0000007F000000FF800000F9800001F9C00001
F0C00001F0C00003E0600003E0600007C0300007C030000F8018000F8018001F001C00FFE0
7F80FFE07F80>
	 25 20 -1 19 28] 118 @dc
[<
01C00003E00007F00007F00007F00003E00001C00000000000000000000000000000C00000
C00000C00000C00000C00000C00000E00000E000007000007C00003E00001F00301F80780F
C0FC0FC0FC0FC0FC0FC0780F80381F801FFE0007F800>
	 18 32 -3 31 25] 63 @dc
[<
00FFFE00FFFE0007C00007C00007C00007C00007C00007C0FFFFFEFFFFFEE003C07003C038
03C01803C00C03C00E03C00703C00383C00183C000C3C00063C00073C0003BC0001FC0000F
C00007C00007C00003C00001C0>
	 23 29 -1 28 26] 52 @dc
[<
03FFFFC003FFFFC00007E0000007E0000007E0000007E0000007E0000007E0000007E00000
07E0000007E0000007E0000007E0000007E0000007E0000007E0000007E0000007E0000007
E000C007E006C007E006C007E006C007E006E007E00E6007E00C6007E00C7007E01C7C07E0
7C7FFFFFFC7FFFFFFC>
	 31 30 -2 29 36] 84 @dc
[<
FFE3FF8FFEFFE3FF8FFE1F007C01F01F007C01F01F007C01F01F007C01F01F007C01F01F00
7C01F01F007C01F01F007C01F01F007C01F01F007C01F01F007C01F01F007C01F01F807E01
F01E807E01F01E407D01F01E70F9C3E0FE1FF07FC0FE0FE03F80>
	 39 20 -3 19 44] 109 @dc
[<
387CFEFEFE7C38000000000000387CFEFEFE7C38>
	 7 20 -4 19 15] 58 @dc
[<
FFE000FFE0001F00001F00001F00001F00001F00001F00001F00001F1F801F7FE01FC1F81F
80FC1F007C1F007E1F003E1F003F1F003F1F003F1F003F1F003F1F003F1F003E1F007E1F00
7E1F80FC1FE1F8FF7FF0FF1FC0>
	 24 29 -2 19 29] 112 @dc
[<
01FF000FFFE03F01F878003C78003CF0001EF0001EF0001E70003E3C007C1FFFFC07FFF80F
FFF01FFF801C000018000018000009FC000FFF000F07801E03C03E03E03E03E03E03E03E03
E03E03E01E03DE0F079E07FFFE01FC3C>
	 23 30 -1 19 26] 103 @dc
[<
1E0000007F800000E1C00000C0E00000FC600000FC30000078300000001800000018000000
1C0000001C0000003E0000003E0000007F0000007F000000FF800000F9800001F9C00001F0
C00001F0C00003E0600003E0600007C0300007C030000F8018000F8018001F001C00FFE07F
80FFE07F80>
	 25 29 -1 19 28] 121 @dc
[<
2070180C0E060603033B7FFFFFFE7C38>
	 8 16 -4 6 15] 44 @dc
[<
0030018000007803C000007803C000007803C00000FC07E00000FC07E00001F60FB00001F6
0F300001F60F300003E31E180003E31E180007C1BE0C0007C1BC0C0007C1BC0C000F80F806
000F80F806001F00F803001F00F00300FFE7FE1FE0FFE7FE1FE0>
	 35 20 -1 19 38] 119 @dc
[<
07F0001FFC00381F00600F80780FC0FC07C0FC07E0FC07E0FC07E07807E00007E00007E000
07C01007C0380F803C1F0037FE0033F8003000003000003000003000003F80003FF0003FFC
003FFE003FFF003FFF80380380>
	 19 29 -3 28 26] 53 @dc
[<
FFFF0FFFF0FFFF0FFFF007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0
007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E
0007FFFFFE0007FFFFFE0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007
E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E0007E00FFFF0F
FFF0FFFF0FFFF0>
	 36 31 -2 30 41] 72 @dc
[<
01FE0007FF800F07C01E03E03E01F03C01F07C01F87C01F87C01F8FC01F8FC01F8FC01F8FC
01F8FE01F0FE01F0FD03E0FDFFC0FCFF00FC10007C00007C01E07C03F03E03F01E03F01F03
F00F81E007E0E001FFC0003F00>
	 21 29 -2 28 26] 54 @dc
[<
81FF00E7FFC0FE01E0F80070E00078E00038C0003CC0003CC0003C00003C00007C0000FC00
07F800FFF807FFF00FFFF01FFFE03FFF807FFE007FC000FC0000F80000F00018F00018F000
387000387000783800F81E03F80FFF3803FC08>
	 22 31 -3 30 29] 83 @dc
[<
FFFF0000FFFF000007E0000007E0000007E0000007E0000007E0000007E0000007E0000007
E0000007E0000007E0000007E0000007E0000007FFFE0007FFFF8007E00FE007E003F007E0
01F807E001F807E001FC07E001FC07E001FC07E001FC07E001FC07E001F807E001F807E003
F007E00FE0FFFFFF80FFFFFE00>
	 30 31 -2 30 36] 80 @dc
[<
FFE0FFE01F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F
001F001F001F001F001F001F001F001F001F001F001F00FF00FF00>
	 11 32 -2 31 15] 108 @dc
[<
00C00001E00003F00003F00003F00003F00003F00003F00001F00001F00001F00001F00000
F00000F000007000007800003800003800001800000C00C00600C00300C00300E001807FFF
C07FFFE07FFFF07FFFF87FFFF8600000>
	 21 30 -3 29 26] 55 @dc
[<
03FC000FFF803E03C07C00E0780070F00070F00078F00078F000F8F001F87803F8780FF03C
3FF01FFFE007FFC007FF800FFE001FFF001FE3803FC3C03F01E03E01E03C01E03C01E01C01
E01E03C00F078007FF0001FC00>
	 21 29 -2 28 26] 56 @dc
[<
FFFFFF00FFFFFFE007C007F007C003F807C001FC07C000FC07C000FE07C000FE07C000FE07
C000FE07C000FE07C000FC07C001FC07C001F807C003F007FFFFC007FFFF8007C00FE007C0
07F007C003F807C001F807C001FC07C001FC07C001FC07C001FC07C001FC07C001F807C003
F007C007E0FFFFFFC0FFFFFE00>
	 31 31 -2 30 37] 66 @dc
[<
FFC3FFFFC3FF1E00F81E01F01E01E01E03C01E07C01E0F801F0F001F9E001FFC001F7C001F
18001F0C001F07001F03801F00C01F00F01F01FE1F01FE1F00001F00001F00001F00001F00
001F00001F00001F00001F00001F0000FF0000FF0000>
	 24 32 -2 31 28] 107 @dc
[<
07F0001FFC00381F003C07807E07C07E03E07E03E07E01F03C01F00001F00041F807F9F81F
FDF83E05F87C03F87C03F8FC01F8FC01F8FC01F8FC01F8FC01F0FC01F0FC01F07C01E07C03
E03E03C01F07800FFF0001FC00>
	 21 29 -2 28 26] 57 @dc
[<
FFFFC0FFFFC07C03C03E01C03F00C01F80E00F806007C06003E06003F00001F80000F80060
7C00603E00603F00701F80380F803C07C03FFFE03FFFE0>
	 19 20 -1 19 23] 122 @dc
[<
01FC0007FF001F8FC01E03C03E03E07C01F07C01F07C01F0FC01F8FC01F8FC01F8FC01F8FC
01F8FC01F8FC01F8FC01F8FC01F8FC01F8FC01F8FC01F8FC01F87C01F07C01F07C01F03E03
E01E03C01F07C007FF0001FC00>
	 21 29 -2 28 26] 48 @dc
[<
FFE00FFFE0FFE00FFFE00E0000FE00060000FC00060001FC00030001F800030001F8000180
03F000018003F00001FFFFF00000FFFFE00000C007E00000600FC00000600FC00000701FC0
0000301F800000303F800000183F000000183F0000000C7E0000000C7E0000000EFE000000
06FC00000006FC00000003F800000003F800000001F000000001F000000001F000000000E0
00000000E00000>
	 35 31 -2 30 40] 65 @dc
/@F8 @newfont
@F8 @sf
[<
FFFE07C0038003800380038003800380038003800380038003800380038003800380038003
800380038003800380038003800380F3800F8003800180>
	 15 30 -4 29 23] 49 @dc

1 @eop0

0 0 1 @bop1 617 381 a @F1 @sf(Securit)n(y)22 b(Article)h(Extracts)-487 92 y 
@F0 @sf(Legalities)-312 171 y @F4 @sf(Simson)16 b(Gar\014nk)o(el)-231 147 y
(1987)-1022 238 y @F2 @sf(Con)n(ten)n(ts)-269 147 y @F6 @sf(1)42 b(In)o
(tro)q(duction)1568 b(3)-1950 147 y(2)42 b(Who)18 b(are)f(the)h(sub)o(v)o
(er)o(ters?)o 1289 x(4)-1950 146 y(3)42 b(Three)17 b(terms:)22 b(op)q
(erating)c(system,)e(accoun)o(ts)i(and)g(passw)o(ords)o 568 x(5)-1950 147 y
(4)42 b(Ho)o(w)17 b(m)o(uc)o(h)f(securit)o(y?)1390 b(6)-1950 147 y(5)42 b
(Securit)o(y)16 b(through)i(obscurit)o(y)1240 b(6)-1950 147 y(6)42 b(Ph)o
(ysical)16 b(Securit)o(y)1460 b(7)-1950 147 y(7)42 b(Hardw)o(are)1631 b(7)
-1950 147 y(8)42 b(Bac)o(kups)1665 b(7)-1950 147 y(9)42 b(Sanitizing)1630 b
(8)-1950 147 y(10)16 b(Authen)o(tication)1513 b(9)-1950 147 y(11)16 b(P)o
(assw)o(ords)o 1620 x(9)-986 183 y @F8 @sf(1)-987 b
1 @eop1

2 @bop0
@F6 @sf
[<
0007FC00003FFF8000FE01C003F0007007E000380FC000181F80000C3F00000C3F0000067F
0000067E0000067E000000FE000000FE000000FE000000FE000000FE000000FE000000FE00
00007E0000067E0000067F0000063F00000E3F00000E1F80001E0FC0001E07E0003E03F000
FE00FE03DE003FFF0E0007FC02>
	 31 31 -3 30 38] 67 @dc
[<
3FFC003FFC0007C00007C00007C00007C00007C00007C00007C00007C00007C00007C00007
C00007C00007C00007C00007C00007C000FFFC00FFFC0007C00007C00007C00007C00007C0
0007C3C007C7E003C7E003E7E001F3E000FFC0001F80>
	 19 32 -1 31 16] 102 @dc
[<
1FC03FF07878FC7CFC3C783E303E003E003E003E003E003E003E003E003E003E003E003E00
3E003E003E003E003E003E003E003E003E01FE01FE0000000000000000000000000038007C
00FE00FE00FE007C0038>
	 15 42 3 32 16] 106 @dc
[<
000070000000007000000000F800000000F800000001FC00000001FC00000003FE00000003
F600000003F600000007E300000007E30000000FE18000000FC18000001FC1C000001F80C0
00003F80E000003F006000003F006000007E003000007E00300000FC00180000FC00180001
FC000C0001F8000C0003F8000E0003F000060007F000070007E000030007E0000380FFFE00
3FF8FFFE003FF8>
	 37 31 -1 30 40] 86 @dc
@F8 @sf
[<
01F000061C000C0E001807003807003803807003807003C07003C0F003C0F003C0F003C0F0
03C0F003C0F80380F80380F80700F40600F21C00F1F0007000007000007800003800003803
001C07800C07800E0380070100018200007C00>
	 18 31 -2 29 23] 54 @dc
[<
70F8F8F870>
	 5 5 -4 4 13] 46 @dc
[<
FFE0C1FFF81F00C01F800E00C00F000401E00F000401E00F000401E00F000403900F000403
900F000407080F000407080F000407080F00040E040F00040E040F00040E040F00041C020F
00041C020F00041C020F000438010F000438010F000438010F000470008F000470008F0004
70008F0004E0004F0004E0004F0005C0002F0005C0002F0005C0002F000780001F000F8000
1F80FF80001FF8>
	 37 31 -2 30 42] 77 @dc
[<
01F800070E001C03803801C03801C07000E07000E0F000F0F000F0F000F0F000F0F000F0F0
00F07000E07000E03801C03801C01C0380070E0001F800>
	 20 20 -1 19 23] 111 @dc
[<
03E3F80E1B801C0780380780380380700380700380F00380F00380F00380F00380F00380F0
03807003807003803803803803801C0780061B8003E3800003800003800003800003800003
80000380000380000380000380000380003F80000380>
	 21 32 -2 31 25] 100 @dc
[<
01F8000706000C0100180080380080700000700000F00000F00000F00000FFFF80F00380F0
03807003807007003807003807001C0E000E1C0003F000>
	 17 20 -1 19 20] 101 @dc
[<
FFE7FE7FE00E00E00E000E00E00E000E00E00E000E00E00E000E00E00E000E00E00E000E00
E00E000E00E00E000E00E00E000E00E00E000E00E00E000E00E00E000E00E00E000E00E00E
000F00F00E000F00F00E000E81C81C00FE618618000E1F01F000>
	 35 20 -1 19 38] 109 @dc
[<
8F80D060E030C018C01880188018803800700FF03FE07F807800E000C010C010C010403030
701F90>
	 13 20 -2 19 18] 115 @dc
/@F7 @newfont
@F7 @sf
[<
70F8F8F870>
	 5 5 -4 4 13] 58 @dc
@F8 @sf
[<
FFFF807FFF803FFF801000801800400C004006004003000001800000C00000600000700000
3800001C00000E00000F000007800007800007C02007C0F803C0F803C0F803C0F007C08007
80400780200700100E000C1C0003F000>
	 18 30 -2 29 23] 50 @dc
[<
000FC0000070380001C0040003800200070001000E0000801E0000801C0000403C0000407C
0000407C00004078000000F8000000F8000000F8000000F8000000F8000000F8000000F800
0000F8000000F8000000780000407C0000407C0000403C0000C01C0000C01E0000C00E0001
C0070003C0038005C001C009C0007030C0000FC040>
	 26 33 -3 31 33] 67 @dc
[<
0F83C0386720781E10F01E10F00E10F00E10F00E10780E00380E001E0E00078E0000FE0000
0E00000E00000E00300E00781C007818003030001FE000>
	 20 20 -2 19 23] 97 @dc
[<
FFE00E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E
000E000E000E000E000E000E000E000E000E000E000E00FE000E00>
	 11 32 0 31 13] 108 @dc
[<
083E000CC3000D01C00F00E00E00E00E00700E00700E00780E00780E00780E00780E00780E
00780E00700E00700E00E00F00E00F01C00EC3800E3E000E00000E00000E00000E00000E00
000E00000E00000E00000E00000E0000FE00000E0000>
	 21 32 -1 31 25] 98 @dc
[<
03F00E0C1C023801380170007000F000F000F000F000F000F00070007000380C381E1C1E0E
0C03F8>
	 16 20 -2 19 20] 99 @dc
[<
FFCFF80E03E00E03C00E03800E07800E07000E0E000E1E000E1C000F38000EF8000E70000E
30000E10000E08000E04000E02000E03000E03C00E0FF00E00000E00000E00000E00000E00
000E00000E00000E00000E00000E0000FE00000E0000>
	 21 32 -1 31 24] 107 @dc
[<
FFE7FC0E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E
01C00E01C00E01C00F01C00F01C00E8180FE43000E3E00>
	 22 20 -1 19 25] 110 @dc
[<
FFE0000E00000E00000E00000E00000E00000E00000E00000E00000E3E000EC3000F01C00F
01E00E00E00E00F00E00700E00780E00780E00780E00780E00780E00780E00700E00F00E00
E00F00E00F01C0FEC3800E3E00>
	 21 29 -1 19 25] 112 @dc
[<
004008000060180000E01C0000E01C0000F03C0001D03A0001D0320003C873000388710003
8861000704E0800704C0800707C0800E03C0400E0380400E0380401C0380201C0300603C07
8070FF9FE1FC>
	 30 20 -1 19 33] 119 @dc
[<
FFE00E000E000E000E000E000E000E000E000E000E000E000E000E000E000F0C0F1E0F1EFE
8C0E78>
	 15 20 -1 19 18] 114 @dc
@F8 @sf
[<
03F0001C3C00200E00400F00400780F00780F807C0F807C0F807C02007C00007C000078000
0780000F00000E00003C0003F000003800001C00000E00000F00000F00000F80380F807807
80780780780F80200F00100E000C1C0003F000>
	 18 31 -2 29 23] 51 @dc
[<
01F1FC030DC00603C00E03C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E
01C00E01C00E01C00E01C00E01C00E01C0FE1FC00E01C0>
	 22 20 -1 19 25] 117 @dc
[<
01E0031006100E080E080E080E080E080E000E000E000E000E000E000E000E000E000E000E
00FFF83E000E000E0006000600020002000200>
	 13 28 -1 27 18] 116 @dc
[<
FFE001001F0003000E000300040007000400070004000F0004001F0004001F0004003D0004
003D00040079000400F1000400F1000401E1000401E1000403C1000407810004078100040F
0100040F0100041E0100043C0100043C0100047801000478010004F0010005E0010005E001
0007C0038007C007C0FF803FF8>
	 29 31 -2 30 34] 78 @dc
@F8 @sf
[<
00FFE0000E00000E00000E00000E00000E00000E00000E00FFFFF0C00E00400E00200E0020
0E00100E00080E00080E00040E00020E00020E00010E00008E00008E00004E00002E00002E
00001E00000E00000E00000600000600>
	 20 30 -1 29 23] 52 @dc
@F6 @sf
[<
FFFFFFF0FFFFFFF007E003F007E000F807E0007807E0003807E0001807E0001807E0001807
E0000C07E0600C07E0600C07E0600007E0E00007E1E00007FFE00007FFE00007E1E00007E0
E00007E0600007E0603007E0603007E0003007E0003007E0007007E0006007E000E007E001
E007E007E0FFFFFFE0FFFFFFE0>
	 30 31 -2 30 34] 69 @dc
@F8 @sf
[<
03000007800007800007800007800007800007800007800003800003800003800003800001
800001C00000C00000C0000040000040000020000020000010000008000008008004008002
008002004001007FFF807FFF807FFFC0400000>
	 18 31 -3 29 23] 55 @dc
[<
000400020000000C00030000000E00070000000E00070000001E00078000001F000F800000
1F000F8000001F000F8000003C801E4000003C801E4000003C801E40000078C03E20000078
403C20000078403C200000F0403C100000F02078100000F02078100001F02078080001E010
F0080001E010F0080003E010F00C0003C009E0040003C009E0040003C009E00400078007C0
0200078007C00200078007C002000F0007C001000F00078001000F00078003801F800FC007
C0FFF07FF81FF0>
	 44 32 -1 30 47] 87 @dc
[<
FFE7FC0E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E01C00E
01C00E01C00E01C00F01C00F01C00E81800E43000E3E000E00000E00000E00000E00000E00
000E00000E00000E00000E00000E0000FE00000E0000>
	 22 32 -1 31 25] 104 @dc
[<
FFC00E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E000E007E
000E000000000000000000000000001C001E003E001E001C00>
	 10 31 0 30 13] 105 @dc
[<
3C0000620000F10000F08000F0800000400000400000400000200000200000700000700000
700000E80000E80001EC0001C40001C4000382000382000382000701000701000E00800E00
800E00801C00C01E01E0FF83F8>
	 21 29 -1 19 24] 121 @dc
[<
07000F800F800F800700000000000000000000000200020002000200020002000300010001
80018000C000E000700038603CF03CF03CE03C4038403830700FC0>
	 14 32 -3 31 21] 63 @dc
@F8 @sf
[<
03E0000C3800100E00200600400700400380E00380F003C0F003C07003C00003C00003C000
03C0000380000380100780100700180E00161C0011F0001000001000001000001000001000
001000001FE0001FF8001FFC001FFE00180300>
	 18 31 -2 29 23] 53 @dc
@F8 @sf
[<
7FF00700070007000700070007000700070007000700070007000700070007000700070007
00FFF007000700070007000700070007000706038F018F00C6007C>
	 16 32 0 31 14] 102 @dc
[<
FFFFFF800F800F8007800180078000C0078000C00780004007800040078000400780002007
80002007800020078080000780800007808000078080000781800007FF8000078180000780
80000780800007808000078080800780008007800080078000800780018007800100078003
00078003000F800F00FFFFFF00>
	 27 31 -2 30 31] 69 @dc
@F8 @sf
[<
FFFC3FFC0FC007E0078007C0078007800780078007800F0007801E0007801E0007803C0007
803C00078078000780F00007C0F00007A1E0000791E0000793C000078F8000078780000783
00000781000007808000078040000780200007801000078008000780040007800200078001
00078001800FC003E0FFFC0FFC>
	 30 31 -2 30 35] 75 @dc
[<
03FC001C03803000C0600060C00030C00030C00030C000306000703001E00FFFC01FFF803F
FE0030000030000020000020000033E0001E38001C1C00380E00780F00780F00780F00780F
00780F00380E001C1C300E3C3003E3300000E0>
	 20 31 -1 20 23] 103 @dc
@F8 @sf
[<
03F0000C0C00100200200100600180C00080C000C0C000C0C000C0C001C04001C060038030
0F80103F000C7E0007FC0003F8000FF0001FC8003F06003E03007803007001806001806001
806001802001803003001006000C0C0003F000>
	 18 31 -2 29 23] 56 @dc
[<
FFFC00000FC000000780000007800000078000000780000007800000078000000780000007
800000078000000780000007800000078000000780000007FFE0000780780007801C000780
1E0007800F0007800F8007800F8007800F8007800F8007800F8007800F8007800F0007801E
0007801C000F807800FFFFE000>
	 25 31 -2 30 31] 80 @dc
[<
FFC0FFC0>
	 10 2 -1 10 15] 45 @dc
@F8 @sf
[<
7FC3FE0700E00700E00700E00700E00700E00700E00700E00700E00700E00700E00700E007
00E00700E00700E00700E00700E00700E00700E0FFFFE00700000700000700000700000700
000700000701E00701E00381E001C0C000E0C0003F00>
	 23 32 0 31 25] 12 @dc
@F6 @sf
[<
FFF00C03FFF8FFF01E03FFF806001E001F0006003F001F0006003F001F0006003F001F0006
007D801F0006007D801F000600F8C01F000600F8C01F000601F0601F000601F0601F000603
E0301F000603E0301F000607C0181F000607C0181F000607C0181F00060F800C1F00060F80
0C1F00061F00061F00061F00061F00063E00031F00063E00031F00067C00019F00067C0001
9F0006F80000DF0006F80000DF0006F80000DF0007F000007F00FFF000007FF8FFE000003F
F8>
	 45 31 -2 30 50] 77 @dc

2 @eop0

0 0 2 @bop1 195 w @F6 @sf(12)16 b(What)i(mak)o(es)f(a)g(secure)g(passw)o
(ord?)1089 b(10)-1950 147 y(13)16 b(Smart)h(Cards)1538 b(10)-1950 147 y
(14)16 b(Authen)o(tication)i(of)f(the)h(computer:)k(The)c(T)l(ro)s(jan)g
(Horse)e(problem)448 b(11)-1950 147 y(15)16 b(Computer)h(Viruses)o 1410 x
(11)-1950 147 y(16)f(T)l(elecomm)o(unications)1367 b(12)-1882 101 y @F8 @sf
(16.1)23 b(Mo)q(dems)i @F7 @sf(:)d(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h
(:)f(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f
(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(12)-1777 
102 y(16.1.1)o 28 x(Call)14 b(bac)o(k)h(and)h(passw)o(ord)e(mo)q(dems)33 b 
@F7 @sf(:)23 b(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)h(:)f
(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(13)-1882 101 y(16.2)23 b
(Computer)14 b(Net)o(w)o(orks)39 b @F7 @sf(:)23 b(:)f(:)g(:)h(:)f(:)g(:)h
(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f
(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(14)-1950 147 y 
@F6 @sf(17)16 b(Encryption)1575 b(15)-1882 101 y @F8 @sf(17.1)23 b(What)
14 b(is)h(encryption?)34 b @F7 @sf(:)23 b(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)h
(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)h(:)f
(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(15)-1882 102 y(17.2)23 b
(Wh)o(y)15 b(encryption?)27 b @F7 @sf(:)22 b(:)g(:)h(:)f(:)g(:)h(:)f(:)g
(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h
(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(16)-1882 101 y
(17.3)23 b(Costs)14 b(of)h(Encryption)41 b @F7 @sf(:)23 b(:)f(:)g(:)h(:)f
(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g
(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(17)-1882 
102 y(17.4)23 b(Key)15 b(Managemen)o(t)k @F7 @sf(:)j(:)g(:)h(:)f(:)g(:)h
(:)f(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f
(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(17)-1882 
101 y(17.5)23 b(Encryption)15 b(as)f(a)h(defense)h(against)e(crac)o(k)o
(ers)24 b @F7 @sf(:)f(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f
(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(17)-1882 102 y
(17.6)23 b(Encryption)15 b(in)g(practice)28 b @F7 @sf(:)22 b(:)g(:)h(:)f
(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g
(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(18)-1882 
101 y(17.7)23 b(Public-k)o(ey)15 b(encryption)40 b @F7 @sf(:)22 b(:)g(:)h
(:)f(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f
(:)g(:)h(:)f(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(18)-1882 
102 y(17.8)23 b(Con\014dence)16 b(in)f(the)g(encryption)g(program)36 b 
@F7 @sf(:)22 b(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)h
(:)f(:)g(:)h(:)f(:)g(:)h(:)f(:)g(:)h(:)41 b @F8 @sf(18)-1950 146 y @F6 @sf
(18)16 b(Micro)q(computer)h(Securit)o(y)f(Issues)1118 b(19)-1950 147 y(19)
16 b(Auditing)1627 b(20)-1950 147 y(20)16 b(Alarms)1663 b(20)-1950 147 y
(21)16 b(P)o(olicy)g(and)i(Proto)q(col)1376 b(21)-986 195 y @F8 @sf(2)-987 b
2 @eop1

3 @bop0
@F6 @sf
[<
0007FC0600003FFF8E0000FE01FE0003F000FE0007E0007E000FC0007E001F80007E003F00
007E003F00007E007F00007E007E00007E007E00007E00FE003FFFE0FE003FFFE0FE000000
00FE00000000FE00000000FE00000000FE000000007E000006007E000006007F000006003F
00000E003F00000E001F80001E000FC0001E0007E0003E0003F000FE0000FE03DE00003FFF
0E000007FC0200>
	 35 31 -3 30 41] 71 @dc
[<
FFFF007F80FFFF01FFC007E003F86007E007F03007E00FE03007E00FE00007E00FE00007E0
0FE00007E00FC00007E00FC00007E00FC00007E00F800007E00F800007E01F000007E03E00
0007FFFC000007FFFF000007E01FC00007E007E00007E003F00007E003F00007E003F80007
E003F80007E003F80007E003F80007E003F00007E003F00007E007E00007E01FC000FFFFFF
0000FFFFF80000>
	 36 31 -2 30 39] 82 @dc
/@F10 @newfont
@F10 @sf
[<
FFC07FFEFFC07FFE0C0007E00E000FE006000FC006000FC003001F8003001F8003FFFF8001
FFFF0001803F0000C07E0000C07E0000E0FE000060FC000061FC000031F8000031F800001B
F000001BF000001FF000000FE000000FE0000007C0000007C0000007C00000038000000380
00>
	 31 28 -2 27 36] 65 @dc
[<
1C3F001EC1E01F80701F00781F003C1F003C1F003E1F003E1F003E1F003E1F003E1F003E1F
003C1F003C1F00781F80701FE1E01F3F801F00001F00001F00001F00001F00001F00001F00
001F00001F0000FF0000FF0000>
	 23 29 -1 28 27] 98 @dc
[<
CFC0F830E018E01CC01CC01C007C07FC1FF87FF07FE0FF80F000E018E018601830781FD8>
	 14 18 -2 17 19] 115 @dc
[<
03F007980F081F0C1F0C1F0C1F0C1F001F001F001F001F001F001F001F001F00FFFC3FFC0F
000F00070007000300030003000300>
	 14 26 -1 25 19] 116 @dc
[<
FFF000FFF0001F00001F00001F00001F00001F00001F00001F00001F00001F00001F00001F
07001E8F801E8F801E8F80FE4700FE3E00>
	 17 18 -1 17 20] 114 @dc
[<
0FE1F83E13F8780BC0F807C0F807C0F807C07C07C03C07C01F07C007E7C0007FC00007C01C
07C03E07C03E07803E0F801C1E000FF800>
	 21 18 -1 17 23] 97 @dc
[<
03F8000E0E001C03003C0180780180780000F80000F80000F80000F80000F80000F8000078
0E00781F003C1F001C1F000E0E0003FC00>
	 17 18 -2 17 21] 99 @dc
/@F9 @newfont
@F9 @sf
[<
FF8000FFC000FF80001C00001C00001C00001C00001C00001C00001C1C001C1C001FFC001F
FC001FFC001C1C001C1C001C00001C00001C00E01C00E01C00E01C00E0FFFFE0FFFFE0FFFF
E0>
	 19 25 -1 24 22] 70 @dc
[<
FFFC00FFFC00FFFC0007000007000007000007000007000007000007000007000007800007
800007C00007F040FF7FE0FF3FE0FF0FC0>
	 19 18 -1 17 22] 114 @dc
[<
03E0000FF8001FFC003C1E00780F00700700F00780E00380E00380E00380E00380E0038070
0700780F003C1E001FFC000FF80003E000>
	 17 18 -2 17 22] 111 @dc
[<
FE3C78FE7CF8FE7CF83870E03870E03870E03870E03870E03870E03870E03870E03870E038
70E03C78E03C78E0FFFFE0FFEFC0F9C380>
	 21 18 0 17 22] 109 @dc
[<
C7F000FFFC00FFFE00F80F00E00700E00380600380000380000380000700000F0000FE0007
FC001FF0003F8000780000F00000E00000E00700E00700F00700781F003FFF001FFF0007E3
00>
	 17 25 -2 24 22] 83 @dc
[<
7FFFFFFF7FFF01C001C001C001C001C001C001C001C001C001C001C001C07FC07FC07FC000
00000000000000018003C003C00180>
	 16 26 -3 25 22] 105 @dc
[<
C7E0FFF8FFFCF81EF00EE00E600E003C07F81FF07F807000E01CE01CF03C7FFC3FFC0FEC>
	 15 18 -3 17 22] 115 @dc
[<
7FC7F0FFE7F87FC7F00E03800E03800E03800E03800E03800E03800E03800E03800E03800E
03800F03800F87807FFF00FEFE007E3C00>
	 21 18 0 17 22] 110 @dc
[<
FFFFE0FFFFE0FFFFE01C00E01C00E01C00E01C00E01C00401C00001C00001C00001C00001C
00001C00001C00001C00001C00001C00001C00001C00001C00001C0000FFC000FFC000FFC0
00>
	 19 25 -1 24 22] 76 @dc
[<
70F8F8F870>
	 5 5 -8 4 22] 46 @dc
[<
03E70007F7000FFF001E1F003C0F00380F00700700700700F00700E03F80E07FC0E03F80E0
0000E00000E00000E00000F000007007007007003807003C0F001E1F000FFF0007FF0003E3
00>
	 18 25 -2 24 22] 71 @dc
[<
0F83E03FE7E07FFFE0783E00E00E00E00E00E00E00700E003E0E001FFE0003FE00000E0000
0E00300E00783C007FF8003FF0001FE000>
	 19 18 -2 17 22] 97 @dc
[<
3FFE007FFF003FFE0001C00001C00001C00001C00001C00001C00001C00001C00001C00001
C00001C00001C000FFFF00FFFF007FFF0001C00001C00001C30001E78000FF80007F80001F
00>
	 17 25 -1 24 22] 102 @dc
[<
7F87F0FFCFF07F87F00E07800E07000E0E000F1E000FBC000FF8000FF0000EF0000E78000E
3C000E1E000E0F000E7FE00E7FE00E7FE00E00000E00000E00000E00007E0000FE00007E00
00>
	 20 25 0 24 22] 107 @dc
[<
03F00FFC1FFE3C0F78077007E000E000FFFFFFFFFFFFE0077007780E3C1E1FFC0FF803E0>
	 16 18 -3 17 22] 101 @dc
[<
FFFF80FFFF80FFFF8001C00001C00001C00001C00001C00001C00001C00001C00001C00001
C00001C00001C00001C00001C00001C00001C00001C00001C00001C000FFC000FFC000FFC0
00>
	 17 25 -2 24 22] 108 @dc
[<
000180000780001F80003E0000F80001F00007C0000F80003E0000FC0000F00000FC00003E
00000F800007C00001F00000F800003E00001F80000780000180>
	 17 21 -2 22 22] 60 @dc
[<
03F8000FFE003FFF807C07C07001C0E000E0E000E0E000E0E000E07803C03FFF801FFF001F
FC001800003800001BE0001FF0000FF8001C1C00380E00380E00380E00380E00380E001C1C
C00FFFE007F7E003E3C0>
	 19 28 -1 17 22] 103 @dc
[<
00FC0003FF0007FFC00F03C01C3C00387E0078FF0071C38071C380E381C0E381C0E381C0E3
81C0E381C0E381C0E381C071C3C071C3C078FF80387F801C3F800F070007FE0003FC0000F8
00>
	 18 25 -2 24 22] 64 @dc
[<
03F00FF81FFC3E0E78077007F000E000E000E000E000E0007000780C3C1E1FFE0FFC03F8>
	 16 18 -3 17 22] 99 @dc
[<
03E3F007FBF80FFFF00E0F800E03800E03800E03800E03800E03800E03800E03800E03800E
03800E03800E03807E1F80FE3F807E1F80>
	 21 18 0 17 22] 117 @dc
[<
7F1FC0FF3FE07F1FC00E0E00071C00073C0003B80001F00001E00000E00001F00003F00003
B800073C000F1C007F1FC07F3FC07F1FC0>
	 19 18 -1 17 22] 120 @dc
[<
063C000EFF000FFF800F83C00F01E00E00E00E00700E00700E00700E00700E00700E00700E
00E00F00E00F83C00FFF800EFF000E3E000E00000E00000E00000E00007E0000FE00007E00
00>
	 20 25 0 24 22] 98 @dc
[<
07C7E00FE7F01FFFE03C1F00700F00700F00E00700E00700E00700E00700E00700E0070070
0700780F003C1F001FFF000FF70003C700000700000700000700000700003F00007F00003F
00>
	 20 25 -1 24 22] 100 @dc
[<
C00000F00000FC00003E00000F800007C00001F00000F800003E00001F80000780001F8000
3E0000F80001F00007C0000F80003E0000FC0000F00000C00000>
	 17 21 -2 22 22] 62 @dc
[<
07FC000FFE0007FC0000E00000E00000E00000E00000E00000E00000E00000E00000E00000
E00000E00000E00000E00000E00000E000E0E0E0E0E0E0E0E0E0E0E0E0FFFFE0FFFFE07FFF
E0>
	 19 25 -1 24 22] 84 @dc
[<
70F8F8F870000000000000000070F8F8F870>
	 5 18 -8 17 22] 58 @dc
[<
00F80001FC0003FE0007870007038007038007038007010007000007000007000007000007
0000070000070000FFFF00FFFF007FFF00070000070000070000070000030000>
	 17 23 -1 22 22] 116 @dc
[<
3C00003F00007F80007BC00079C00001C00000E00000E00000E00000F00000F00000F00001
B80001B800039800039C00039C00071C00071C00070E000E0E000E0E000E07001C07007F1F
C0FF9FE07F1FC0>
	 19 27 -1 17 22] 121 @dc
[<
3F807FC0FFE0F0F06070003800380038003800380038003800380038003800380038003800
38003800380038003800381FF81FF81FF800000000000000000030007800780030>
	 13 35 -2 25 22] 106 @dc
[<
FFFEFFFEFFFE03800380038003800380038003800380038003800380038003800380038003
80038003800380FFFEFFFEFFFE>
	 15 25 -3 24 22] 73 @dc
[<
40E0F078381C1C1C1C3C7C7830>
	 6 13 -8 24 22] 39 @dc
[<
00E00001F00001F00003B80003B80003B800071C00071C00071C00071C000E0E000E0E000E
0E001E0F001C07007F1FC0FF1FE07F1FC0>
	 19 18 -1 17 22] 118 @dc
[<
07E0001FF8003FFC00781E00E00700F00380F003806003800003800003803007003C0F003F
FE003FFC003BF0003800003800003800003800003800003800003800003FFE003FFE003FFE
00>
	 17 25 -2 24 22] 53 @dc
[<
03E0000FF8001FFC001E3C003C1E00780F00700700700700F00780E00380E00380E00380E0
0380E00380E00380E00380E00380700700700700780F00380E001E3C001FFC000FF80003E0
00>
	 17 25 -2 24 22] 48 @dc
[<
003FE0007FF0003FE000070000070000070000070000070000070007C7001FE7003FF7003C
3F00700F00700F00E00700E00700E00700E00700E00700E00700700F00700F003C1F001FF7
000FE70007C700>
	 20 27 -2 17 22] 113 @dc
[<
7FC7F0FFE7F87FC7F00E03800E03800E03800E03800E03800E03800E03800E03800E03800E
03800F03800F87800FFF000EFE000E3C000E00000E00000E00000E00007E0000FE00007E00
00>
	 21 25 0 24 22] 104 @dc
[<
0F1E000F1E000F1E001DB7001DB7001DB7001DB70019B30019F30019F30038E38038038038
0380380380380380FF1FE0FFBFE0FF1FE0>
	 19 18 -1 17 22] 119 @dc
[<
60F0781C1E0E3E7E7E7C38>
	 7 11 -7 4 22] 44 @dc
[<
7FC000FFE0007FC0000E00000E00000E00000E00000E00000E00000E3C000EFF000FFF800F
83C00F01E00E00E00E00700E00700E00700E00700E00700E00700E00E00F00E00F83C07FFF
80FEFF007E3E00>
	 20 27 0 17 22] 112 @dc
[<
FFFF80FFFF80FFFF80>
	 17 3 -2 13 22] 45 @dc
[<
1803803807C03807C01C0EE01C0EE00E0EE00E0EE00E0EE00707C00707C003838003800001
C00001C00001C00000E00000E0000070000070000070003838007C38007C1C00EE1C00EE0E
00EE0E00EE0E00EE0700EE07007C03807C0380380180>
	 19 32 -1 28 22] 37 @dc
[<
00E001E0038007000E001C001C0038003800700070007000E000E000E000E000E000E000E0
00E000E000700070007000380038001C001C000E000700038001E000E0>
	 11 33 -6 28 22] 40 @dc
[<
01F00007FC000FFE001F0F003C0700380380700380700380F00000E00000E00000E00000E0
0000E00000E00000E00000F000007003807003803803803C07801F0F800FFF8007FB8001F1
80>
	 17 25 -2 24 22] 67 @dc
[<
C000E000700038001C000E000E000700070003800380038001C001C001C001C001C001C001
C001C001C0038003800380070007000E000E001C0038007000E000C000>
	 10 33 -5 28 22] 41 @dc
[<
7FF87FFC7FF8038003800380038003800380038003800380038003800380038003807380FF
807F800F800780038003800180>
	 14 25 -4 24 22] 49 @dc
[<
0F80001FE0003FF000707800781C00780E003007000007000007000FE3801FFB803FFF8078
0F80700780E00780E00380E00380E00780E00700700700700E003C1E001FFC000FF80003E0
00>
	 17 25 -2 24 22] 57 @dc
[<
07F0001FFC003FFE007C1F00700700F00780E00380E00380E00380F007807007003C1E001F
FC0007F0001FFC007C1F00700700E00380E00380E00380F007807C1F003FFE001FFC0007F0
00>
	 17 25 -2 24 22] 56 @dc
[<
07000007000007000007000007000007000007000003800003800003800003800001C00001
C00001C00000E00000E000007000007800003800001C00E01E00E00F00FFFF80FFFF80FFFF
80E00000>
	 17 26 -2 25 22] 55 @dc
[<
FE0FE0FE0FE0FE0FE038038038038038038038038038038038E38038E38039F38039B38039
B38039B38039B3803BBB803B1B803B1B803B1B803B1B803B1B803A0B80FE0FE0FE0FE0FC07
E0>
	 19 25 -1 24 22] 77 @dc
@F8 @sf
[<
FFFC0FC0078007800780078007800780078007800780078007800780078007800780078007
8007800780078007800780078007800780078007800FC0FFFC>
	 14 31 -1 30 16] 73 @dc
[<
81F800CE0C00F00600E00300C00380C001808001C08001C08001C08001C00001C00003C000
03C0000780001F8003FF000FFE001FFC003FF0007F0000780000F00000F00000E00080E000
80E00080E001806001806001803003801007800C198007E080>
	 18 33 -3 31 25] 83 @dc
[<
FFC03FFE1F0007E00E0003C0040003C002000780020007800200078001000F0001000F0001
000F0000FFFE0000801E0000801E0000403C0000403C0000403C0000207800002078000020
78000010F0000010F0000010F0000009E0000009E0000009E0000007C0000007C0000007C0
0000038000000380000003800000010000>
	 31 32 -1 31 34] 65 @dc
[<
FFFE00000FC000000780000007800000078000000780000007800000078000000780000007
800000078080000780800007808000078080000781800007FF800007818000078080000780
80000780800007808000078000800780008007800080078000800780018007800100078003
00078003000F800F00FFFFFF00>
	 25 31 -2 30 30] 70 @dc
[<
FFFFFC0F807C07801C07800C07800407800407800607800207800207800207800207800007
80000780000780000780000780000780000780000780000780000780000780000780000780
000780000780000780000780000FC000FFFE00>
	 23 31 -2 30 28] 76 @dc
[<
0020004000800100020006000C000C00180018003000300030007000600060006000E000E0
00E000E000E000E000E000E000E000E000E000E00060006000600070003000300030001800
18000C000C00060002000100008000400020>
	 11 46 -3 33 18] 40 @dc
[<
FF07FE1E01E00601E00201C0030380010700008700004E00007C00003C0000380000780000
EC0000E40001C2000381000701800701C00F01E07FC3FC>
	 23 20 0 19 24] 120 @dc
[<
00200000700000700000700000E80000E80001EC0001C40001C40003820003820003820007
01000701000E00800E00800E00801C00C01E01E0FF83F8>
	 21 20 -1 19 24] 118 @dc
[<
800040002000100008000C00060006000300030001800180018001C000C000C000C000E000
E000E000E000E000E000E000E000E000E000E000E000C000C000C001C00180018001800300
0300060006000C0008001000200040008000>
	 11 46 -3 33 18] 41 @dc
@F2 @sf
[<
7FFFFE7FFFFE7FFFFE00FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000
FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE
0000FE0000FE0000FE0000FE0000FE0000FE0000FE00F8FE00FFFE00FFFE0007FE00007E00
001E00000E00>
	 23 39 -5 38 34] 49 @dc
[<
FFFFFCFFFFFCFFFFFC01FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001
FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE
0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE0001FE00
01FE00FFFFFCFFFFFCFFFFFC>
	 22 41 -2 40 26] 73 @dc
[<
FFFF00FFFF00FFFF000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000F
E0000FE0000FE0000FE0000FE0000FE0000FE0000FF01C0FF03E0FF07F0FD87F0FD87FFFCE
3EFFC7FCFFC1F0>
	 24 27 -2 26 28] 114 @dc
[<
003FC3FF8000FFF3FF8003F03BFF8007C00FF8000F8007F8001F8003F8003F8003F8007F00
03F8007F0003F8007F0003F800FF0003F800FF0003F800FF0003F800FF0003F800FF0003F8
00FF0003F800FF0003F8007F0003F8007F0003F8007F0003F8003F8003F8001F8003F8000F
C007F80007E00FF80003F03FF80000FFFBF800001FE3F800000003F800000003F800000003
F800000003F800000003F800000003F800000003F800000003F800000003F800000003F800
000003F800000003F80000003FF80000003FF80000003FF800>
	 33 42 -2 41 38] 100 @dc
[<
003FC3FF8001FFF3FF8003F03BFF8007E00FF80007E007F8000FE007F8000FE003F8000FE0
03F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8
000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000F
E003F8000FE003F800FFE03FF800FFE03FF800FFE03FF800>
	 33 27 -3 26 38] 117 @dc
[<
001FE00000FFFC0003F01E0007E007000FC003801F8001C03F8001C07F8000007F0000007F
000000FF000000FF000000FF000000FF000000FF000000FF000000FF0000007F0000007F00
00007F800E003F801F001F803F800FC03F8007E03F8003F01F0000FFFE00001FF800>
	 26 27 -2 26 31] 99 @dc
[<
FFFEFFFEFFFE0FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00F
E00FE00FE00FE00FE00FE0FFE0FFE0FFE0000000000000000000000000000007000F801FC0
3FE03FE03FE01FC00F800700>
	 15 43 -3 42 19] 105 @dc
@F8 @sf
[<
FFFFE0000F803C0007800E000780070007800380078003C0078001E0078001E0078000F007
8000F0078000F0078000F8078000F8078000F8078000F8078000F8078000F8078000F80780
00F8078000F8078000F0078000F0078001F0078001E0078001E0078003C007800380078007
0007801E000F803C00FFFFE000>
	 29 31 -2 30 35] 68 @dc
[<
40201010080804040474FCFCF870>
	 6 14 -4 31 13] 39 @dc
[<
001F800000F0F00001C0380007801E000F000F000E0007001E0007803C0003C03C0003C07C
0003E07C0003E0780001E0F80001F0F80001F0F80001F0F80001F0F80001F0F80001F0F800
01F0F80001F0F80001F0780001E0780001E07C0003E03C0003C03C0003C01E0007800E0007
000F000F0007801E0001C0380000F0F000001F8000>
	 28 33 -3 31 35] 79 @dc
[<
40201010080804040474FCFCF870>
	 6 14 -4 4 13] 44 @dc

3 @eop0

0 0 3 @bop1 195 w @F6 @sf(22)16 b(Sub)o(v)o(ersi)o(on)1581 b(21)-1950 147 y
(23)16 b(Crac)o(king)1625 b(21)-1950 147 y(24)16 b(Conclusion)1579 b(24)
-1950 147 y(25)16 b(Glossary)1631 b(24)-1950 147 y(26)16 b(References)h
(and)h(Credits)1297 b(25)-1066 130 y @F10 @sf(Abstract)-892 100 y @F9 @sf
(From)21 b(Simson)f(L.)i(Garfinkel)o 21 x(<simsong@)o(cunix)o(c.co)o(lum)p
(bi)o(a.edu)o(>)-1240 50 y(To:)f(security@)o(red.r)o(utger)o(s.)p(edu)o 
-611 49 a(Subject:)o 21 x(security)f(article)-546 100 y(I've)h(gotten)f
(over)h(50)g(requests)g(for)g(this)g(article.)f(I'm)h(not)g(answering)f
(them)-1504 50 y(any)h(more.)g(Instead,)o 21 x(I'm)g(posting)f(the)h
(article)g(to)g(the)g(list...)-1243 99 y(-simson)-154 100 y(%)g(\(C\))g
(1987,)g(Simson)g(L.)g(Garfinkel.)o -698 50 a(%)g(May)g(not)h(be)f
(transmitte)o(d)f(or)i(copied)e(without)h(permissio)o(n)-536 137 y @F8 @sf
(In)o(tro)q(duction)15 b(to)g(Securit)o(y)-755 101 y(An)g(In)o(tro)q
(duction)g(to)g(Computer)f(Securit)o(y)h(F)l(or)g(La)o(wy)o(ers)-1490 137 y
(\(Most)f(of)h(the)g(examples)g(in)g(this)f(article)h(are)f(based)i(on)f
(actual)f(ev)o(en)o(ts.\))-1295 186 y @F2 @sf(1)69 b(In)n(tro)r(duction)
-481 146 y @F8 @sf(A)13 b(small)f(business)i(has)f(its)g(accoun)o(ting)g
(records)g(erased)g(b)o(y)h(a)f(malicious)f(high)h(sc)o(ho)q(ol)f(studen)o
(t)i(using)f(a)g(home)-1950 57 y(computer)h(and)g(a)g(mo)q(dem.)19 b(Did)
14 b(the)g(business)g(tak)o(e)f(reasonable)h(securit)o(y)f(precautions)g
(to)h(prev)o(en)o(t)f(this)h(sort)-1951 56 y(of)h(damage?)-225 102 y(A)f
(friend)g(giv)o(es)g(y)o(ou)g(a)g(public)g(domain)g(program)f(whic)o(h)h
(greatly)f(impro)o(v)o(es)g(y)o(our)g(computer's)h(p)q(erformance.)-1950 
56 y(One)19 b(da)o(y)l(,)g(y)o(ou)f(\014nd)h(that)f(the)g(program)g(has)g
(stopp)q(ed)h(w)o(orking,)f(along)f(with)h(all)f(of)h(y)o(our)g(w)o
(ordpro)q(cessor,)-1951 57 y(spreadsheet)e(and)f(database)g(programs.)-723 
101 y(It)23 b(is)f(imp)q(ortan)o(t)f(for)h(legal)g(practitio)o(ners)g(to)g
(understand)h(issues)f(of)h(computer)f(securit)o(y)l(,)i(b)q(oth)f(for)f
(the)-1950 57 y(protection)10 b(of)g(their)h(o)o(wn)f(in)o(terests)g(and)h
(the)g(in)o(terests)f(of)g(their)g(clien)o(ts.)18 b(La)o(wy)o(ers)10 b(to)q
(da)o(y)g(m)o(ust)g(automaticall)o(y)-987 124 y(3)-987 b
3 @eop1

4 @bop0
@F8 @sf
[<
FFFE700E700638021C031E010E0107010780038001C001E000E0407040784038201C200E38
0E3FFF>
	 16 20 -1 19 20] 122 @dc
[<
000FC000003820000070180000E0080001C0040001C0020003800200038002000780010007
80010007800100078001000780010007800100078001000780010007800100078001000780
01000780010007800100078001000780010007800100078001000780010007800100078001
0007800100078003800FC007C0FFFC3FF8>
	 29 32 -2 30 34] 85 @dc
[<
003FF800038000038000038000038000038000038000038000038003E3800E13801C0B8038
0780380380780380700380F00380F00380F00380F00380F00380F003807003807803803803
803C07801C058006198003E080>
	 21 29 -2 19 24] 113 @dc
[<
7FE3FF00070070000700700007007000070070000700700007007000070070000700700007
00700007007000070070000700700007007000070070000700700007007000070070000700
7000FFFFFF80070070000700700007007000070070000700700007007000070070000300F0
300380F87801C0787800F06E30001F83E0>
	 29 32 0 31 27] 11 @dc
[<
07FFFE00001F8000000F0000000F0000000F0000000F0000000F0000000F0000000F000000
0F0000000F0000000F0000000F0000000F0000000F0000000F0000000F0000000F0000000F
0000000F0000000F0000800F0010800F0010800F0010800F0010C00F0030400F0020400F00
20600F0060780F01E07FFFFFE0>
	 28 31 -2 30 33] 84 @dc
[<
FFFFF0000F803C0007801F0007800F0007800F8007800780078007C0078007C0078007C007
8007C0078007C00780078007800F8007800F0007801E0007803C0007FFF00007803C000780
1E0007801F0007800F0007800F8007800F8007800F8007800F8007800F8007800F0007801F
0007801E000F803800FFFFE000>
	 26 31 -2 30 32] 66 @dc
[<
3F006180F0C0F0606070007000700070007000700070007000700070007000700070007000
70007000700070007000700070007000F007F0007000000000000000000000000000E001F0
01F001F000E0>
	 12 40 2 30 14] 106 @dc
[<
70F8F8F8700000000000000000000070F8F8F870>
	 5 20 -4 19 13] 58 @dc
[<
381C7C3EFC7EFC7EB85C804080408040402040202010201010080804>
	 15 14 -5 31 23] 92 @dc
[<
402020101008100808040804040204020402743AFC7EFC7EF87C7038>
	 15 14 -2 31 23] 34 @dc
[<
40202010101008080878F8F8F0700000000000000000000070F8F8F870>
	 5 29 -4 19 13] 59 @dc
@F2 @sf
[<
FFFFFF80FFFFFF80FFFFFF807FFFFFC03FFFFFC01FFFFFC00FFFFFC0070001C0038001C001
C001C000E000E0007000E0003C00E0001E0000000F0000000780000003E0000003F0000001
F8000000FC000000FE0000007F0000007F8000003FC000003FC000003FE03C003FE07E001F
E0FF001FE0FF001FE0FF003FE0FF003FC0FE003FC07C007F803800FF001F03FE000FFFFC00
03FFF00000FF8000>
	 27 39 -3 38 34] 50 @dc
[<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>
	 68 41 -1 40 71] 87 @dc
[<
FFFE3FFF80FFFE3FFF80FFFE3FFF800FE003F8000FE003F8000FE003F8000FE003F8000FE0
03F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8000FE003F8
000FE003F8000FE003F8000FE003F8000FE003F8000FF003F8000FF003F8000FF803F8000F
F803F0000FEE03F0000FE787E0000FE1FFC0000FE07F00000FE00000000FE00000000FE000
00000FE00000000FE00000000FE00000000FE00000000FE00000000FE00000000FE0000000
0FE00000000FE0000000FFE0000000FFE0000000FFE0000000>
	 33 42 -3 41 38] 104 @dc
[<
01FC03FC0FFF0FFC3F839FFC7F00DF807E007F80FE003F80FE003F80FE003F80FE003F807F
003F803F003F803F803F800FE03F8007FC3F8000FFFF80000FFF8000003F8000003F800000
3F8007003F800F803F801FC03F001FC07E001FC07E000F81F80007FFF00001FF8000>
	 30 27 -2 26 33] 97 @dc
[<
0E01FC00000F07FF80000F9E07E0000FF803F0000FF001F8000FE000FC000FE000FE000FE0
007F000FE0007F000FE0007F000FE0007F800FE0007F800FE0007F800FE0007F800FE0007F
800FE0007F800FE0007F800FE0007F000FE0007F000FE0007F000FE000FE000FE000FC000F
F000F8000FF801F0000FFE07E0000FE7FF80000FE1FE00000FE00000000FE00000000FE000
00000FE00000000FE00000000FE00000000FE00000000FE00000000FE00000000FE0000000
0FE00000000FE0000000FFE0000000FFE0000000FFE0000000>
	 33 42 -2 41 38] 98 @dc
[<
0001C000000003E000000003E000000007F000000007F00000000FF80000000FF80000000F
F80000001FDC0000001FDC0000003FDE0000003F8E0000007F8F0000007F070000007F0700
0000FE03800000FE03800001FC01C00001FC01C00003FC01E00003F800E00007F800F00007
F000700007F0007000FFFE03FF80FFFE03FF80FFFE03FF80>
	 33 27 -1 26 36] 118 @dc
[<
00700000F80001FC0003FE0003FE0003FE0001FC0000F80000700000000000000000000000
0000000000000000007000007000007000007000007000007000007800003800003800003C
00001E00001F00000F800007C00007F00003F83801FC7C01FEFE01FEFE01FEFE01FEFC01FE
7801FC3801F81E03F00FFFE001FF00>
	 23 42 -4 41 32] 63 @dc

4 @eop0

0 0 4 @bop1 195 w @F8 @sf(recognize)13 b(insecure)g(computer)g(systems)f
(and)h(lax)g(op)q(erating)f(pro)q(cedures)h(in)g(the)g(same)g(w)o(as)f(as)g
(La)o(wy)o(ers)g(no)o(w)-1950 57 y(recognize)j(p)q(o)q(orly)g(written)f
(con)o(tracts.)k(Additionally)l(,)c(as)g(computers)h(b)q(ecome)h(more)f(p)q
(erv)m(asiv)o(e,)f(more)h(legal)-1951 56 y(cases)j(will)f(arise)h(whic)o
(h)g(rev)o(olv)o(e)f(around)h(issues)g(of)g(computer)g(securit)o(y)l(.)29 b
(Unless)18 b(familiar)e(with)i(the)g(basic)-1950 56 y(concepts)e(of)e
(computer)i(securit)o(y)l(,)e(a)h(la)o(wy)o(er)f(will)f(not)i(kno)o(w)g
(ho)o(w)g(to)f(approac)o(h)h(the)g(question.)-1686 102 y(Not)e(b)q(eing)h
(a)g(la)o(wy)o(er,)o 13 x(the)g(author)f(will)f(not)i(attempt)e(to)h
(address)h(the)g(legal)f(asp)q(ects)g(surrounding)h(computer)-1950 56 y
(securit)o(y)l(.)27 b(Instead,)19 b(the)f(goal)f(of)g(this)g(article)g(is)g
(to)h(con)o(v)o(ey)f(to)h(the)f(reader)h(a)g(basic)f(understanding)h(of)g
(the)-1950 57 y(tec)o(hnical)i(issues)h(in)g(the)f(\014eld.)38 b(Ev)o(en)
20 b(a)h(simple)f(understanding)h(of)g(computer)f(securit)o(y)h(will)e
(a\013ord)h(the)-1950 56 y(a)o(v)o(erage)d(la)o(wy)o(er)h(protection)f
(from)h(the)h(acciden)o(tal)f(loss)g(or)g(theft)g(of)g(do)q(cumen)o(ts)h
(and)g(data)f(stored)g(in)h(the)-1950 57 y(\014rm's)g(computer)g(systems,)g
(and)g(allo)o(w)f(the)h(la)o(wy)o(er)e(to)i(b)q(egin)g(to)g(ev)m(aluate)g
(cases)g(in)g(whic)o(h)g(b)o(ypassing)f(of)-1950 56 y(computer)d(securit)o
(y)g(is)f(of)h(primary)f(in)o(terest.)-804 102 y(This)h(article)f
(attempts)h(to)g(broadly)f(co)o(v)o(er)h(questions)g(of)g(computer)h
(securit)o(y)e(in)i(the)f(small)f(business)i(or)f(la)o(w)-1951 56 y(\014rm.)
23 b(Because)17 b(of)f(its)f(ob)s(jectiv)o(es,)g(this)h(article)f(is)h
(not)g(a)g(step-b)o(y-step)g(guide)h(on)f(ho)o(w)g(to)f(mak)o(e)h(a)g(la)o
(w)f(\014rm)-1950 57 y(computer)i(more)f(secure:)23 b(Instead,)17 b(this)f
(article)g(hop)q(es)h(to)f(acquain)o(t)g(the)g(reader)h(with)f(the)h
(issues)f(in)o(v)o(olv)o(ed)-1951 56 y(so)d(that)g(the)h(reader)g(ma)o(y)f
(then)h(b)q(e)g(able)f(to)g(analyze)h(systems)f(on)h(a)f(case-b)o(y-case)h
(basis)f(and)h(recognize)f(when)-1949 56 y(outside)i(assistance)f(is)h
(required.)-589 102 y(Simply)10 b(de\014ned,)j(computer)d(securit)o(y)g
(is)h(the)f(pro)q(cess,)i(pro)q(cedures,)g(or)e(to)q(ols)g(whic)o(h)g
(assure)h(that)f(data)g(en)o(tered)-1950 56 y(in)o(to)i(a)i(computer)f(to)q
(da)o(y)g(will)f(b)q(e)i(retriev)m(able)f(at)g(a)g(later)f(time)h(b)o(y)l
(,)h(and)g(only)f(b)o(y)l(,)g(those)g(authorized)g(to)g(do)h(so.)-1951 57 y
(The)i(pro)q(cedures)h(should)f(additionally)f(include)h(systems)g(b)o(y)g
(whic)o(h)g(computer)g(system)g(managers)f(\(simply)-1951 56 y(\\managemen)o
(t")k(on)h(future)g(references\))h(will)e(b)q(e)i(noti\014ed)f(when)h
(attempts)e(at)h(p)q(enetrating)g(securit)o(y)f(are)-1950 57 y(made.)k
(Securit)o(y)15 b(is)h(violated)f(when)i(some)e(p)q(erson)i(or)f(p)q
(ersons)g(\(the)g(\\sub)o(v)o(erter"\))f(succeedes)i(in)f(retrieving)-1951 
56 y(data)h(without)g(authorizatio)o(n.)27 b(Securit)o(y)17 b(is)h(also)e
(breac)o(hed)j(when)f(the)g(sub)o(v)o(erter)f(manages)g(to)g(destro)o(y)g
(or)-1950 57 y(altering)d(data)g(b)q(elonging)h(to)g(others,)f(making)g
(retriev)m(al)h(of)f(the)i(original)o 14 x(data)f(imp)q(ossible.)-1638 101 y
(Although)g(a)h(substan)o(tial)o 15 x(e\013ort)e(has)i(b)q(een)g(sp)q(en)o
(t)g(in)g(the)g(academic)f(and)h(computer)f(researc)o(h)h(comm)o(unities)
-1951 57 y(exploring)f(issues)h(of)g(computer)g(securit)o(y)l(,)f(little)f
(of)i(what)f(is)h(understo)q(o)q(d)g(has)g(b)q(een)h(put)g(in)o(to)e
(practice)g(on)h(a)-1950 56 y(wide)i(scale.)27 b(Computers)18 b(are)f(not)h
(inheren)o(tly)f(insecure,)i(but)f(there)g(is)f(a)h(great)f(temptation)g
(to)g(build)h(and)-1950 56 y(run)13 b(computers)g(with)g(lax)f(securit)o
(y)g(pro)q(cedures,)i(since)g(this)e(often)h(results)f(in)h(simpler)g(and)g
(faster)f(op)q(eration.)-1951 57 y(If)k(securit)o(y)f(considerations)g
(are)h(built)f(in)o(to)g(a)g(pro)q(duct)i(from)e(the)h(b)q(eginning)g
(they)f(are)h(relativ)o(ely)e(lo)o(w)h(cost;)-1951 56 y(securit)o(y)f
(added)h(as)g(an)g(after-though)o(t)e(is)h(often)h(v)o(ery)f(exp)q(ensiv)o
(e.)20 b(Additionally)l(,)13 b(man)o(y)i(computer)f(users)h(are)-1950 57 y
(simply)f(not)h(a)o(w)o(are)f(of)h(ho)o(w)g(their)f(facilities)g(are)h
(insecure)g(and)g(ho)o(w)g(to)g(rectify)f(the)i(situatio)o(n.)-1686 188 y 
@F2 @sf(2)69 b(Who)24 b(are)f(the)f(sub)n(v)n(erters?)-846 146 y @F8 @sf
(It)12 b(is)f(a)g(mistak)o(e)f(to)h(assume)h(that)f(all)f(p)q(eople)i(b)q
(en)o(t)g(on)g(stealing)e(or)h(destro)o(ying)g(data)g(can)g(b)q(e)i(group)q
(ed)f(together)-1951 57 y(and)i(that)f(simila)o(r)f(defenses)j(are)e
(equally)g(e\013ectiv)o(e)g(against)f(all)g(sub)o(v)o(erters.)19 b(In)14 b
(practice,)f(the)h(are)f(t)o(w)o(o)f(ma)s(jor)-1951 56 y(groups:)25 b
(those)18 b(who)g(w)o(an)o(t)f(to)h(steal)f(data)h(and)g(those)g(who)g
(wish)g(to)f(destro)o(y)h(it.)28 b(The)18 b(\014rst)g(group)g(can)g(b)q(e)
-1949 57 y(called)c(\\spies,")f(the)h(second)h(group)f(can)g(b)q(e)h
(called)e(\\v)m(andals")h(or)f(\\crac)o(k)o(ers.")19 b(Di\013eren)o(t)13 b
(securit)o(y)g(measures)-1950 56 y(are)i(targeted)f(at)h(eac)o(h)g(group.)
-540 102 y(Spies)c(are)e(sometimes)h(exactly)f(that:)17 b(spies,)11 b
(either)f(go)o(v)o(ernmen)o(tal)e(or)i(corp)q(orate)g(who)g(stand)g(to)g
(gain)f(from)h(the)-1950 56 y(p)q(ossession)k(of)h(con\014den)o(tial)f(or)g
(secret)h(data.)k(Other)c(times,)f(spies)g(are)h(emplo)o(y)o(ees)f(of)g
(the)h(organizati)o(on)f(that)-987 154 y(4)-987 b
4 @eop1

5 @bop0
@F8 @sf
[<
FFFFFC>
	 22 1 0 12 23] 123 @dc
[<
000100000003800000038000000380000007C0000007C0000007C000000F2000000F200000
1F3000001E1000001E1000003C0800003C0800003C0800007804000078040000F8060000F0
020000F0020001F0010001E0010001E0010003C0008003C0008003C0008007800040078000
400F8000600F0000601F8000F8FFF003FE>
	 31 32 -1 30 34] 86 @dc
[<
7FE3FE3FF00700700700070070070007007007000700700700070070070007007007000700
70070007007007000700700700070070070007007007000700700700070070070007007007
000700700700070070070007007007000700700700FFFFFFFF000700700000070070000007
007000000700700000070070000007007000000700F00F000300F00F000380F80F0001C07C
060000F04F0400001F81F800>
	 36 32 0 31 38] 14 @dc
@F2 @sf
[<
00FF800007FFF0001FFFFC003F01FE007C007F007E007F80FF007FC0FF003FC0FF003FE0FF
003FE07E003FE03C003FE000003FE000003FE000003FC000003FC000007F8000007F000000
7E000001FC0000FFF00000FFC0000007F0000001F8000001FC000000FE000000FF000000FF
000F007F801F807F803F807F803F807F803F807F803F80FF001F00FF000F81FE0007FFFC00
03FFF000007F8000>
	 27 39 -3 38 34] 51 @dc
[<
007FFFFFE000007FFFFFE000007FFFFFE00000003FC0000000003FC0000000003FC0000000
003FC0000000003FC0000000003FC0000000003FC0000000003FC0000000003FC000000000
3FC0000000003FC0000000003FC0000000003FC0000000003FC0000000003FC0000000003F
C0000000003FC0000000003FC0000000003FC0000000003FC0000000003FC0000000003FC0
0000E0003FC000E0E0003FC000E0E0003FC000E0E0003FC000E0E0003FC000E0F0003FC001
E0F0003FC001E070003FC001C078003FC003C078003FC003C07E003FC007C07F803FC03FC0
7FFFFFFFFFC07FFFFFFFFFC07FFFFFFFFFC0>
	 43 40 -2 39 48] 84 @dc
[<
FFFE1FFFC3FFF8FFFE1FFFC3FFF8FFFE1FFFC3FFF80FE001FC003F800FE001FC003F800FE0
01FC003F800FE001FC003F800FE001FC003F800FE001FC003F800FE001FC003F800FE001FC
003F800FE001FC003F800FE001FC003F800FE001FC003F800FE001FC003F800FE001FC003F
800FE001FC003F800FE001FC003F800FE001FC003F800FF001FE003F800FF001FE003F800F
D801FF003F800FCC01F9803F000FC603F8C07F00FFC383F0707E00FFC1FFE03FFC00FFC07F
800FF000>
	 53 27 -3 26 57] 109 @dc
[<
1C003E007F00FF80FF80FF807F003E001C000000000000000000000000000000000000001C
003E007F00FF80FF80FF807F003E001C00>
	 9 27 -5 26 19] 58 @dc
[<
FFFE000000FFFE000000FFFE0000000FE00000000FE00000000FE00000000FE00000000FE0
0000000FE00000000FE00000000FE00000000FE00000000FE1FC00000FE7FF80000FFE0FE0
000FF803F0000FF001F8000FE001FC000FE000FE000FE000FF000FE000FF000FE0007F000F
E0007F800FE0007F800FE0007F800FE0007F800FE0007F800FE0007F800FE0007F800FE000
7F000FE0007F000FE000FF000FE000FE000FE000FC000FF001F8000FF803F000FFFE07E000
FFE7FF8000FFE1FE0000>
	 33 39 -2 26 38] 112 @dc
[<
007FF00003FFFE000FC01F801F0007C03C0001E07C0001F0F80000F8F80000F8F80000F8F8
0000F87C0001F83E0007F01FFFFFF007FFFFE00FFFFFC01FFFFF801FFFFF003FFFF8003E00
00003C000000380000003800000018FF80001FFFE0000FC1F8001F80FC001F007C003F007E
007F007F007F007F007F007F007F007F007F007F007F007F003F007E101F007C381F80FC7C
0FC1FE7C03FFE7F800FF81F0>
	 30 40 -2 26 34] 103 @dc
[<
0FC00000003FE00000007C78000000FE3C000000FE1E000000FE0E000000FE0F0000007C07
0000003807800000000380000000038000000001C000000001C000000003E000000003E000
000007F000000007F00000000FF80000000FF80000000FF80000001FDC0000001FDC000000
3FDE0000003F8E0000007F8F0000007F070000007F07000000FE03800000FE03800001FC01
C00001FC01C00003FC01E00003F800E00007F800F00007F000700007F0007000FFFE03FF80
FFFE03FF80FFFE03FF80>
	 33 39 -1 26 36] 121 @dc
[<
2000300018000C0006000300030001800180018000C000C01CC07FC07FC0FFC0FFC0FF807F
007F001C00>
	 10 21 -5 8 19] 44 @dc
[<
00078003C00000078003C000000FC007E000000FC007E000000FC007E000001FE00FF00000
1FE00FF000003FF01FF800003FF01FB800003FF01FB800007F783F3C00007F383F1C0000FF
383F1E0000FE1C7E0E0000FE1C7E0E0001FE1EFC0F0001FC0EFC070001FC0EFC070003F807
F8038003F807F8038007F807F803C007F003F001C007F003F001C00FE007E000E0FFFE7FFC
0FFEFFFE7FFC0FFEFFFE7FFC0FFE>
	 47 27 -1 26 50] 119 @dc
@F8 @sf
[<
C000C000C0006000600060003000300030001800180018000C000C000C0006000600060003
000300030001800180018000C000C000C0006000600060003000300030001800180018000C
000C000C000600060006000300030001>
	 16 45 -3 33 23] 47 @dc
[<
FFE01FFE1F8007E0070003C0020007C00100078001800F0000801F0000401E0000603C0000
207C00001078000018F8000009F0000005E0000007E0000003C00000078000000F8000000F
8000001E4000003E4000003C2000007C10000078100000F0080001F00C0001E0040003C002
0007C007000FE00FC07FF83FF8>
	 31 31 -1 30 34] 88 @dc
[<
000FE0000078182000E00460038002E0070001E00F0001E01E0001E01E0001E03C0001E03C
0001E07C0001E0780001E0F80003E0F8007FFCF8000000F8000000F8000000F8000000F800
0000F8000000F8000000780000207C0000203C0000203C0000601E0000601E0000600F0000
E0070001E0038002E000E004E000781860000FE020>
	 30 33 -3 31 36] 71 @dc

5 @eop0

0 0 5 @bop1 195 w @F8 @sf(o)o(wns)16 b(the)i(computer)f({)f(emplo)o(y)o
(ees)h(who)g(seek)g(informatio)o(n)f(in)h(the)g(computer)g(for)g(p)q
(ersonal)f(adv)m(ancemen)o(t)-1949 57 y(or)f(blac)o(kmail.)o -259 101 a
(Crac)o(k)o(ers)20 b(are)h(t)o(ypically)f(adolescen)o(t)h(b)q(o)o(ys)h
(who)f(ha)o(v)o(e)g(a)g(computer)g(and)h(a)f(mo)q(dem.)39 b(They)21 b(are)h
(usually)-1951 56 y(v)o(ery)15 b(in)o(telligen)o(t)f(and)i(break)g(in)o
(to)f(computer)g(systems)h(for)f(the)h(c)o(hallenge.)21 b(They)16 b(comm)o
(unicate)f(with)g(their)-1950 57 y(friends)h(via)g(computer)h(bulletin)f
(b)q(oards,)g(often)g(using)g(stolen)g(A)l(TT)h(credit)f(card)g(or)g(MCI)h
(n)o(um)o(b)q(ers)f(to)g(pa)o(y)-1950 56 y(for)h(the)g(calls.)25 b(On)18 b
(these)f(b)q(oards,)h(crac)o(k)o(ers)e(rep)q(ort)h(phone)h(n)o(um)o(b)q
(ers,)g(user)f(names,)h(passw)o(ords)e(and)h(other)-1950 57 y(informatio)o
(n)h(regarding)h(computer)g(systems)g(they)g(ha)o(v)o(e)g(\\disco)o(v)o
(ered.")31 b(Man)o(y)18 b(crac)o(k)o(ers)h(are)g(a)o(w)o(are)f(that)-1951 
56 y(their)e(actions)f(are)h(illegal)e(and)j(cease)f(them)g(on)h(their)e
(18th)h(birthda)o(y)g(to)f(a)o(v)o(oid)g(criminal)g(liabilit)o -1 x(y)g
(for)g(their)-1950 57 y(actions.)25 b(\\V)l(andals")17 b(describ)q(es)h(a)e
(larger)h(group)g(whic)o(h)g(includes)g(b)q(oth)h(crac)o(k)o(ers)e(and)i
(other)e(p)q(eople)i(lik)o(ely)-1951 56 y(to)d(v)m(andalize)g(data,)f(suc)o
(h)h(as)g(disgrun)o(tled)g(emplo)o(y)o(ees.)-977 102 y(Computer)e(securit)o
(y)f(has)h(t)o(w)o(o)f(sets)g(of)h(m)o(utual)f(goals,)g(eac)o(h)h
(tailored)f(to)g(a)h(particular)f(set)h(of)f(opp)q(onen)o(ts.)20 b(The)-1950 
56 y(\014rst)13 b(goal)g(is)g(to)h(mak)o(e)f(the)h(cost)f(of)h(violati)o
(ng)f(the)g(computer)h(securit)o(y)f(v)m(astly)h(greater)f(than)g(the)h(v)m
(alue)g(of)g(the)-1950 57 y(data)f(whic)o(h)h(migh)o(t)f(b)q(e)i(stolen.)j
(This)c(is)g(designed)g(to)f(deter)h(the)g(spies,)g(who)g(are)g(in)o
(terested)f(in)h(stealing)f(data)-1951 56 y(for)h(its)f(v)m(alue.)20 b
(The)15 b(second)g(goal)e(of)h(securit)o(y)g(is)g(to)g(to)g(mak)o(e)f(it)h
(to)q(o)g(di\016cult)g(for)g(crac)o(k)o(ers)f(to)h(gain)g(access)h(to)-1951 
56 y(a)g(computer)g(system)g(within)f(a)h(w)o(ork)m(able)g(p)q(erio)q(d)g
(of)g(time.)-1055 189 y @F2 @sf(3)69 b(Three)22 b(terms:)31 b(op)r
(erating)24 b(system,)f(accoun)n(ts)g(and)h(passw)n(ords)-1794 146 y @F8 @sf
(The)19 b(program)e(whic)o(h)h(con)o(trols)f(the)h(basic)g(op)q(erations)g
(of)g(a)g(computer)g(is)g(referred)g(to)g(as)g(the)g(computer's)-1950 57 y
(\\op)q(erating)j(system.")41 b(Often)22 b(the)g(same)g(computer)h(can)f
(b)q(e)h(used)g(to)e(run)i(sev)o(eral)e(di\013eren)o(t)h(op)q(erating)-1951 
56 y(systems)f(\(but)h(not)f(sim)o(ultaneously\).)o 38 x(F)l(or)g
(example,)i(the)f(IBM)g(PC/A)l(T)f(can)h(run)g(either)f(the)h(MSDOS)-1950 
56 y(op)q(erating)17 b(system)h(or)f(Xenix,)h(a)g(Unix-based)g(op)q
(erating)g(system.)27 b(Under)19 b(these)f(t)o(w)o(o)f(op)q(erating)g
(systems,)-1951 57 y(the)e(PC/A)l(T)g(has)g(completely)g(di\013eren)o(t)f
(b)q(eha)o(vior.)-916 101 y(If)k(a)f(computer)g(system)g(is)f(in)o(tended)i
(for)f(use)g(b)o(y)h(man)o(y)e(p)q(eople,)i(the)g(op)q(erating)e(system)h
(m)o(ust)g(distinguish)-1951 57 y(b)q(et)o(w)o(een)j(users)g(to)f(prev)o
(en)o(t)h(them)g(from)f(in)o(terfering)f(with)i(eac)o(h)g(other.)33 b(F)l
(or)19 b(example,)i(most)e(m)o(ulti-user)-1951 56 y(op)q(erating)12 b
(systems)h(will)f(not)h(allo)o(w)o 12 x(one)g(user)h(to)e(delete)h(\014les)h
(b)q(elonging)e(to)h(another)g(user)g(unless)g(the)g(second)-1949 57 y
(user)i(ga)o(v)o(e)g(explicitly)f(p)q(ermission.)-621 101 y(T)o(ypically)l
(,)e(eac)o(h)h(user)g(of)g(the)g(computer)g(is)g(assigned)g(an)g(\\accoun)o
(t.")18 b(The)13 b(op)q(erating)g(system)f(then)i(do)q(es)f(not)-1950 57 y
(allo)o(w)i(commands)i(issued)g(b)o(y)g(the)g(user)g(of)g(one)g(accoun)o
(t)g(to)f(mo)q(dify)h(data)f(whic)o(h)h(w)o(as)f(created)h(b)o(y)g
(another)-1950 56 y(accoun)o(t.)i(Accoun)o(ts)13 b(are)f(usually)g(named)h
(with)g(b)q(et)o(w)o(een)g(one)g(and)g(eigh)o(t)f(letters)f(or)i(n)o(um)o
(b)q(ers)g(whic)o(h)f(are)h(also)-1951 57 y(called)k(\\usernames.")27 b(T)o
(ypical)17 b(usernames)h(that)f(the)h(author)f(has)g(had)h(include)g
(\\simsong",)f(\\Gar\014nk)o(el",)o -1951 56 a(\\slg",)d(\\SIMSON")h(and)h
(\\ML1744.)o(")-674 101 y(Most)k(op)q(erating)f(systems)h(require)h(that)f
(a)g(user)h(en)o(ter)f(b)q(oth)h(the)g(accoun)o(t)f(name)h(and)g(a)f
(\\passw)o(ord")f(in)-1950 57 y(order)i(to)g(use)h(the)g(accoun)o(t.)39 b
(Accoun)o(t)21 b(names)h(are)f(generally)g(public)g(kno)o(wledge)h(while)f
(passw)o(ords)f(are)-1950 56 y(secret,)13 b(kno)o(wn)f(only)g(to)g(the)h
(user)g(and)g(the)g(op)q(erating)f(system.)18 b(\(Some)13 b(op)q(erating)e
(systems)i(mak)o(e)f(passw)o(ords)-1951 57 y(a)o(v)m(ailable)17 b(to)g
(system)h(managemen)o(t,)g(an)g(insecure)h(practice)f(whic)o(h)g(will)f(b)q
(e)i(explored)f(in)g(a)g(later)f(section.\))-1951 56 y(Since)i(the)g
(accoun)o(t)g(can)g(not)f(b)q(e)i(used)g(without)d(the)i(passw)o(ord)f
(the)h(name)g(of)g(the)g(accoun)o(t)f(can)h(b)q(e)h(made)-1950 57 y
(public)14 b(kno)o(wledge.)19 b(If)c(a)f(crac)o(k)o(er)f(do)q(es)i(break)f
(in)o(to)f(an)h(accoun)o(t,)g(only)g(the)g(passw)o(ord)g(needs)h(to)e(b)q
(e)i(c)o(hanged.)-1950 56 y(Kno)o(wing)g(a)g(p)q(erson's)g(username)g(is)g
(mandatory)f(in)h(order)g(to)f(exc)o(hange)i(electronic)f(mail.)-647 154 y
(5)-987 b
5 @eop1

6 @bop0
@F2 @sf
[<
007FFFF8007FFFF8007FFFF80000FE000000FE000000FE000000FE000000FE000000FE0000
00FE000000FE00FFFFFFF8FFFFFFF8FFFFFFF8E0007E0070007E0038007E001C007E000E00
7E000E007E0007007E0003807E0001C07E0000E07E0000E07E0000707E0000387E00001C7E
00000E7E00000E7E0000077E000003FE000001FE000000FE000000FE0000007E0000003E00
00001E0000000E00>
	 29 39 -2 38 34] 52 @dc
[<
FFFFF01FFFFEFFFFF01FFFFEFFFFF01FFFFE03FC00007F8003FC00007F8003FC00007F8003
FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC
00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00
007F8003FC00007F8003FFFFFFFF8003FFFFFFFF8003FFFFFFFF8003FC00007F8003FC0000
7F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F
8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F8003FC00007F80
03FC00007F80FFFFF01FFFFEFFFFF01FFFFEFFFFF01FFFFE>
	 47 41 -3 40 54] 72 @dc
@F2 @sf
[<
00FF800003FFF0000FFFF8001F01FE003C007F0078003F8078003F80FC001FC0FE001FC0FE
001FE0FE001FE0FE001FE07C001FE018001FE000001FE000001FE000001FC000001FC00000
1F800C003F000E003E000F80FC000FFFF8000E7FC0000E0000000E0000000E0000000E0000
000E0000000E0000000FFE00000FFFC0000FFFE0000FFFF0000FFFF8000FFFFC000FFFFE00
0F803F000C000300>
	 27 39 -3 38 34] 53 @dc
[<
C01FF000E0FFFE00F3FFFF00FFE01F80FF0007C0FC0003E0F80003F0F00001F0F00001F0E0
0001F8E00001F8E00001F8600001F8000003F8000007F800000FF800007FF00007FFF000FF
FFE003FFFFE007FFFFC00FFFFF801FFFFE003FFFFC007FFFE0007FFE0000FFC00000FF0000
00FE0000E0FE0000E0FC0000E0FC0001E0FC0001E07C0001E07C0003E03E0007E01F001FE0
0F807FE007FFF9E003FFF0E0007F8060>
	 29 41 -4 40 38] 83 @dc
@F8 @sf
[<
03F0000E1C001C0E00180600380700780780700380700380700380F003C0F003C0F003C0F0
03C0F003C0F003C0F003C0F003C0F003C0F003C0F003C0F003C0F003C07003807003807003
807003803807001806001C0E000E1C0003F000>
	 18 31 -2 29 23] 48 @dc

6 @eop0

0 0 6 @bop1 195 w @F2 @sf(4)69 b(Ho)n(w)23 b(m)n(uc)n(h)g(securit)n(y?)-713 
147 y @F8 @sf(In)e(most)f(computer)g(systems,)h(securit)o(y)f(is)g(purc)o
(hased)h(at)f(a)g(cost)g(in)g(system)g(p)q(erformance,)h(ease)g(of)f(use,)
-1950 56 y(complexit)o(y)d(and)h(managemen)o(t)g(time.)28 b(Man)o(y)18 b
(go)o(v)o(ernmen)o(t)f(systems)g(ha)o(v)o(e)h(a)g(full)g(time)f(\\securit)o
(y)g(o\016cer")-1950 56 y(whose)k(job)h(is)f(to)g(sup)q(ervise)h(and)g
(monitor)e(the)h(securit)o(y)g(op)q(erations)g(of)g(the)h(computer)f
(facilit)o(y)l(.)38 b(Man)o(y)-1951 57 y(univ)o(ersities)19 b(are)h(also)g
(extremely)g(concerned)h(ab)q(out)g(securit)o(y)l(,)g(since)f(they)h(are)f
(w)o(ell-mark)o(ed)f(targets)h(for)-1951 56 y(crac)o(k)o(ers)g(in)g(the)h
(surrounding)f(comm)o(unit)o(y)l(.)36 b(Most)19 b(businesses,)j(ho)o(w)o
(ev)o(er,)f(are)f(notoriously)f(lax)h(in)g(their)-1950 57 y(securit)o(y)
15 b(practices,)f(largely)g(out)h(of)f(ignorance)h(and)g(a)g(lac)o(k)g(of)g
(direct)f(exp)q(erience.)-1476 101 y(Securit)o(y)k(exists)g(in)g(man)o(y)g
(forms:)25 b(An)19 b(op)q(erating)f(system)g(ma)o(y)f(b)q(e)j(programmed)d
(to)h(prev)o(en)o(t)g(users)h(from)-1951 57 y(reading)c(data)f(they)i(are)f
(not)g(authorized)g(to)f(access.)21 b(Securit)o(y)15 b(ma)o(y)f(b)q(e)i
(pro)q(cedures)g(follo)o(w)o(ed)e(b)o(y)h(computer)-1950 56 y(users,)f
(suc)o(h)i(as)e(disp)q(osing)g(of)g(all)g(prin)o(touts)g(and)g(un)o
(usable)h(magnetic)f(media)h(in)f(shredders)h(or)g(incinerators.)o -1951 
57 a(Securit)o(y)g(ma)o(y)g(b)q(e)h(in)g(the)f(form)g(of)g(alarms)g(and)g
(logs)g(whic)o(h)g(tell)g(the)h(managemen)o(t)e(when)j(a)e(break-in)g(is)g
(at-)-1950 56 y(tempted)d(and/or)g(successful.)20 b(Securit)o(y)12 b(ma)o
(y)f(b)q(e)i(a)g(function)f(of)g(hiring)f(pro)q(cedures)j(whic)o(h)e
(require)g(extensiv)o(e)-1950 57 y(securit)o(y)i(c)o(hec)o(ks)g(of)g
(emplo)o(y)o(ees)g(b)q(efore)g(allo)o(wing)e(them)j(to)e(access)i(con\014den)o
(tial)e(data.)19 b(Lastly)l(,)14 b(securit)o(y)g(ma)o(y)-1951 56 y(b)q(e)j
(in)f(the)g(form)g(of)g(ph)o(ysical)g(securit)o(y)l(,)f(suc)o(h)i(as)f(lo)q
(c)o(ks)g(on)g(do)q(ors)g(and)g(alarm)f(systems)h(in)o(tended)h(to)e
(protect)-1950 56 y(the)g(equipmen)o(t)g(and)h(media)f(from)f(theft.)-738 
102 y(In)19 b(a)e(secure)i(en)o(vironmen)o(t,)e(the)h(man)o(y)g(t)o(yp)q
(es)g(and)g(la)o(y)o(ers)f(of)g(securit)o(y)g(are)h(used)h(to)e(reinforce)h
(eac)o(h)g(other,)-1951 56 y(with)12 b(the)h(hop)q(e)g(that)g(if)f(one)h
(la)o(y)o(er)e(fails)h(another)g(la)o(y)o(er)g(will)f(prev)o(en)o(t)i(or)f
(minimize)g(the)h(damage.)19 b(Established)-1951 57 y(proto)q(col)11 b
(and)h(judgmen)o(t)f(are)h(required)g(to)f(determine)h(the)g(amoun)o(t)f
(and)h(cost)f(of)h(securit)o(y)f(whic)o(h)h(a)f(particular)-1951 56 y
(organizatio)o(n's)j(data)g(w)o(arran)o(t.)-563 188 y @F2 @sf(5)69 b
(Securit)n(y)23 b(through)h(obscurit)n(y)-910 147 y @F8 @sf(Securit)o(y)
17 b(through)g(obscurit)o(y)g(is)f(the)i(reliance)f(up)q(on)h(little)e
(kno)o(wn)h(and)g(often)g(unc)o(hangeable)h(artifacts)e(for)-1951 56 y
(securit)o(y)l(.)j(Securit)o(y)12 b(through)g(obscurit)o(y)g(is)g(not)g(a)h
(form)f(of)g(securit)o(y)l(,)g(although)g(it)g(is)g(often)g(mistak)o(en)g
(for)g(suc)o(h.)-1950 57 y(Usually)h(no)h(mec)o(hanism)g(informs)f(site)h
(managemen)o(t)f(that)g(the)h(\\securit)o(y")f(has)h(b)q(een)h(circum)o(v)o
(en)o(ted.)20 b(Often)-1950 56 y(in)o(trusions)e(are)g(not)g(detected)i
(un)o(til)e(signi\014can)o(t)f(damage)h(has)h(b)q(een)h(done)f(or)f(the)h
(in)o(truder)f(gets)h(careless.)-1951 57 y(Once)c(damage)f(is)g(detected,)g
(managemen)o(t)g(has)g(little)f(c)o(hoice)h(but)g(to)g(c)o(ho)q(ose)g(a)g
(new)h(securit)o(y)e(system)h(whic)o(h)-1950 56 y(do)q(es)i(not)e(dep)q
(end)q 16 x(on)h(obscurit)o(y)g(for)f(its)h(strength.)-913 102 y(The)20 b
(classic)g(example)g(of)g(securit)o(y)f(through)h(obscurit)o(y)g(is)f(the)i
(family)e(that)g(hides)i(the)f(k)o(ey)g(to)g(the)g(fron)o(t)-1951 56 y(do)q
(or)c(under)i(the)f(\\W)l(elcome")f(mat.)23 b(The)17 b(only)g(thing)f(to)g
(stop)g(a)h(burglar)f(from)g(en)o(tering)g(the)h(house)g(is)f(the)-1950 
57 y(ignorance)i(that)f(there)h(is)g(a)g(hidden)h(k)o(ey)f(and)g(its)f(lo)q
(cation)g({)h(that)f(is,)h(the)g(k)o(ey's)g(obscurit)o(y)l(.)28 b(If)18 b
(the)h(house)-1950 56 y(is)c(burglarized)h(and)g(the)g(burglar)e(returns)i
(the)g(k)o(ey)g(to)f(its)g(original)f(place,)h(the)h(family)f(will)f(ha)o
(v)o(e)i(no)g(w)o(a)o(y)e(of)-1950 56 y(kno)o(wing)i(ho)o(w)g(the)g
(burglar)g(got)f(in.)24 b(If)17 b(the)f(family)g(do)q(es)g(c)o(hange)h
(the)g(lo)q(cation)e(of)h(the)h(hidden)g(k)o(ey)l(,)f(all)g(the)-1950 57 y
(burglar)d(needs)i(to)f(do)g(is)g(to)f(\014nd)i(it)f(again.)k(A)d(higher)f
(lev)o(el)f(of)h(securit)o(y)g(w)o(ould)f(b)q(e)i(ac)o(hiev)o(ed)f(b)o(y)h
(disp)q(osing)e(of)-1950 56 y(the)i(hidden)h(k)o(ey)f(and)h(issuing)e(k)o
(eys)h(to)g(eac)o(h)g(mem)o(b)q(er)g(of)g(the)g(family)l(.)-1243 102 y(F)l
(or)e(an)g(example)g(of)g(securit)o(y)g(through)f(obscurit)o(y)h(on)g(a)g
(computer,)g(imagine)g(the)g(o)o(wner)g(of)g(a)g(small)f(business)-1950 
56 y(who)k(uses)g(her)g(IBM)g(PC)f(for)h(b)q(oth)g(da)o(y-to-da)o(y)f(b)q
(o)q(okk)o(eeping)h(and)g(managemen)o(t)f(of)g(emplo)o(y)o(ee)h(records.)
21 b(In)-1949 57 y(an)15 b(attempt)f(to)h(k)o(eep)g(the)g(emplo)o(y)o(ee)g
(records)g(hidden)g(from)g(his)g(emplo)o(y)o(ees,)f(she)h(lab)q(els)g(the)g
(disk)g(\\DOS)g(1.0)-987 165 y(6)-987 b
6 @eop1

7 @bop0
@F8 @sf
[<
FFF8FFF80F800F8007800F0007800F0007800F0007800F0007800F0007800F0007800F0007
800F0007800F0007800F0007800F0007800F0007800F0007800F0007FFFF0007800F000780
0F0007800F0007800F0007800F0007800F0007800F0007800F0007800F0007800F0007800F
0007800F000F800F80FFF8FFF8>
	 29 31 -2 30 34] 72 @dc
@F2 @sf
[<
003FC00000FFF00003FFFC0007E07E000FC03F001F803F801F801FC03F001FC03F001FE07F
001FE07F001FE07F001FE07F001FE0FF001FE0FF001FE0FF001FE0FF001FC0FF801FC0FF80
1F80FFC03F00FFC03E00FF707C00FF3FF800FF0FC000FF0000007F0000007F0000007F0000
003F8000003F801F001F803F801FC03F800FC03F8007E03F8003F01F8001FC0F0000FFFE00
003FFC000007F000>
	 27 39 -3 38 34] 54 @dc
[<
FFFFF00000FFFFF00000FFFFF0000003FC00000003FC00000003FC00000003FC00000003FC
00000003FC00000003FC00000003FC00000003FC00000003FC00000003FC00000003FC0000
0003FC00000003FC00000003FC00000003FC00000003FFFFFE0003FFFFFF8003FC003FE003
FC000FF003FC0007F803FC0007FC03FC0003FC03FC0003FE03FC0003FE03FC0003FE03FC00
03FE03FC0003FE03FC0003FE03FC0003FE03FC0003FC03FC0007FC03FC0007F803FC000FF0
03FC003FE0FFFFFFFFC0FFFFFFFF00FFFFFFF800>
	 39 41 -3 40 47] 80 @dc
[<
FFFEFFFEFFFE0FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00F
E00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE00FE0
0FE00FE0FFE0FFE0FFE0>
	 15 42 -3 41 19] 108 @dc
@F2 @sf
[<
00380000007C000000FE000000FE000000FE000000FE000000FE000000FE000000FE000000
FE0000007E0000007E0000007E0000007E0000003E0000003E0000003F0000001F0000001F
0000000F0000000F00000007800000078000000380000001C0000000E000E000E000E00070
00E000380070001C0070000E0070000E007FFFFF007FFFFF807FFFFFC07FFFFFE03FFFFFF0
3FFFFFF03FFFFFF03E00000038000000>
	 28 41 -4 40 34] 55 @dc
@F2 @sf
[<
007FC00003FFF8000FFFFC001FC03E003F000F007C0007807C0003C0F80003C0F80003E0F8
0003E0F80003E0F80007E0F80007E078001FE07C007FE03C01FFC01E03FFC00F0FFF8007FF
FF0001FFFE0001FFFC0003FFF80007FFE0000FFFF8001FFE3C001FFC1E003FF01F003FC00F
003F000F803F000F803E000F803E000F801E000F801E001F000F003F0007C07E0003FFFC00
01FFF000003FC000>
	 27 39 -3 38 34] 56 @dc
[<
FFFFFFFE0000FFFFFFFFC000FFFFFFFFF00003F8001FF80003F80007FC0003F80003FE0003
F80001FF0003F80000FF0003F80000FF8003F80000FF8003F80000FF8003F80000FF8003F8
0000FF8003F80000FF8003F80000FF0003F80000FF0003F80001FE0003F80001FE0003F800
03FC0003F80007F00003FFFFFFE00003FFFFFE000003F800FFC00003F8001FE00003F8000F
F00003F80007F80003F80003FC0003F80003FC0003F80003FE0003F80001FE0003F80001FE
0003F80001FE0003F80003FE0003F80003FC0003F80003FC0003F80007FC0003F8000FF800
03F8001FF000FFFFFFFFC000FFFFFFFF8000FFFFFFF80000>
	 41 41 -3 40 49] 66 @dc
[<
FFFC3FFEFFFC3FFEFFFC3FFE0FC00FE00FC00FC00FC01FC00FC03F800FC07F000FC07F000F
C0FE000FC1FC000FE3F8000FF3F8000FFFF0000FFFE0000FEFE0000FE7C0000FE3C0000FE0
E0000FE078000FE03C000FE01E000FE00F000FE007800FE01FFC0FE01FFC0FE01FFC0FE000
000FE000000FE000000FE000000FE000000FE000000FE000000FE000000FE000000FE00000
0FE000000FE00000FFE00000FFE00000FFE00000>
	 31 42 -2 41 36] 107 @dc

7 @eop0

0 0 7 @bop1 195 w @F8 @sf(BA)o(CKUP)18 b(DISK.")g(The)g(o)o(wner's)f(hop)q
(e)i(is)e(that)h(none)g(of)f(the)h(emplo)o(y)o(ees)g(will)e(b)q(e)j(in)o
(terested)e(in)h(the)g(disk)-1950 57 y(after)d(reading)g(the)g(lab)q(el.)
20 b(Although)15 b(the)g(lab)q(el)g(ma)o(y)g(indeed)h(disin)o(terest)e
(inquisitiv)o(e)g(emplo)o(y)o(ees,)h(there)g(are)-1950 56 y(far)g(b)q
(etter)g(w)o(a)o(ys)f(to)g(secure)i(the)f(disk)g(\(suc)o(h)h(as)e(lo)q(c)o
(king)h(it)f(in)h(a)g(\014le)g(cabinet\).)-1396 101 y(In)j(a)e(second)i
(example)f(of)f(securit)o(y)h(through)f(obscurit)o(y)l(,)h(a)f(secretary)h
(stores)f(p)q(ersonal)h(corresp)q(ondence)h(on)-1950 57 y(her)c(o\016ce)g
(w)o(ordpro)q(cessor.)19 b(T)l(o)14 b(hide)g(the)g(do)q(cumen)o(ts')g
(existence,)g(she)h(c)o(ho)q(oses)e(\014lenames)i(for)e(them)h(suc)o(h)g
(as)-1950 56 y(MEMO1,)f(MEMO2,)h(...,)f(and)h(sets)g(the)h(\014rst)f
(three)g(pages)g(of)g(the)h(do)q(cumen)o(ts)f(to)g(b)q(e)h(the)f(actual)g
(text)g(of)g(old,)-1951 57 y(in)o(ter-o\016ce)g(memos.)19 b(Her)c(priv)m
(ate)f(letters)f(are)h(obscurely)h(hidden)g(after)f(the)g(old)g(memos.)19 b
(Once)d(her)e(system)-1950 56 y(is)h(disco)o(v)o(ered,)f(none)i(of)e(her)i
(corresp)q(ondence)g(is)f(secure.)-1013 188 y @F2 @sf(6)69 b(Ph)n(ysical)
24 b(Securit)n(y)-622 147 y @F8 @sf(Ph)o(ysical)15 b(securit)o(y)h(refers)g
(to)f(devices)i(and)f(pro)q(cedures)h(used)g(to)e(protect)h(computer)g
(hardw)o(are)f(and)i(media.)-1951 56 y(Ph)o(ysical)h(securit)o(y)g(is)g
(the)h(most)f(imp)q(ortan)o(t)f(asp)q(ect)i(of)f(computer)h(securit)o(y)l
(.)30 b(Because)20 b(of)e(the)h(similar)o(iti)o(es)-1951 57 y(b)q(et)o(w)o
(een)14 b(computers)g(and)g(other)f(ph)o(ysical)h(ob)s(jects,)f(ph)o
(ysical)g(securit)o(y)g(is)g(the)h(asp)q(ect)g(of)g(computer)g(whic)o(h)f
(is)-1950 56 y(b)q(est)i(understo)q(o)q(d.)-332 102 y(Lik)o(e)i(t)o(yp)q
(ewriters)e(and)i(furniture,)f(o\016ce)h(computers)f(are)h(targets)e(for)h
(theft.)24 b(But)17 b(unlik)o(e)f(t)o(yp)q(ewriters)g(and)-1950 56 y
(furniture,)d(the)h(cost)g(of)f(a)g(computer)h(theft)g(can)g(b)q(e)g(man)o
(y)f(times)g(the)h(dollar)f(v)m(alue)h(of)f(the)h(equipmen)o(t)g(stolen.)
-1951 57 y(Often,)h(the)g(dollar)f(v)m(alue)i(of)f(the)g(data)g(stored)f
(inside)h(a)g(computer)g(far)g(exceeds)h(the)f(v)m(alue)h(of)f(the)g
(computer)-1950 56 y(itself.)25 b(V)l(ery)18 b(strict)e(precautions)h(m)o
(ust)g(b)q(e)h(tak)o(en)e(to)h(insure)g(that)g(computer)g(equipmen)o(t)h
(is)e(not)h(stolen)g(b)o(y)-1950 57 y(casual)e(thiev)o(es.)-287 188 y 
@F2 @sf(7)69 b(Hardw)n(are)-397 146 y @F8 @sf(A)14 b(v)m(ariet)o(y)e(of)i
(devices)f(are)h(a)o(v)m(ailable)e(to)h(ph)o(ysically)f(secure)j
(computers)e(and)h(computer)f(equipmen)o(t)h(in)f(place.)-1950 57 y
(Examples)i(are)h(securit)o(y)f(plates)g(whic)o(h)h(moun)o(t)f(underneath)i
(a)e(computer)h(and)g(attac)o(h)e(it)h(to)h(the)f(table)h(that)-1951 56 y
(it)g(rests)g(on.)24 b(Other)17 b(approac)o(hes)g(include)g(the)f(use)h
(of)g(hea)o(vy-dut)o(y)f(cables)h(threaded)g(through)f(holes)g(in)h(the)
-1950 57 y(computer's)e(cabinet.)21 b(It)15 b(is)g(imp)q(ortan)o(t,)f
(when)i(installing)e(suc)o(h)i(a)f(restraining)f(device,)i(to)f(assure)g
(that)g(they)-1950 56 y(will)h(not)i(damage)f(or)h(in)o(terfere)f(with)g
(the)h(op)q(eration)f(of)g(the)h(computer)g(\(more)f(than)h(one)g
(installa)o(tio)o(n)f(has)-1950 57 y(had)e(w)o(orkmen)g(drill)f(holes)h
(through)g(circuit)f(b)q(oards)h(to)g(b)q(olt)g(them)g(do)o(wn)g(to)f
(tables.\))-1544 188 y @F2 @sf(8)69 b(Bac)n(kups)-353 146 y @F8 @sf(T)l(o)
18 b(\\bac)o(k)h(up")f(information)f(means)i(to)f(mak)o(e)g(a)g(cop)o(y)g
(of)h(it)f(from)f(one)i(place)g(to)f(another.)29 b(The)19 b(cop)o(y)l(,)g
(or)-1950 57 y(\\bac)o(kup,")c(is)f(sa)o(v)o(ed)h(in)g(a)g(safe)g(place.)
20 b(In)c(the)f(ev)o(en)o(t)g(that)f(the)i(original)o 14 x(is)e(lost,)g
(the)i(bac)o(kup)f(can)g(b)q(e)h(used.)-1919 101 y(Bac)o(kups)11 b(should)h
(b)q(e)g(p)q(erformed)f(regularly)f(to)g(protect)h(the)g(user)h(from)e
(loss)h(of)f(data)h(resulting)f(from)h(hardw)o(are)-1951 57 y
(malfunction.)24 b(Impro)o(v)o(ed)16 b(reliabilit)n(y)g(is)g(a)g(kind)h
(of)f(securit)o(y)l(,)h(in)f(that)h(it)f(helps)h(to)f(assure)g(that)g
(data)g(stored)-986 195 y(7)-987 b
7 @eop1

8 @bop0
@F2 @sf
[<
01FE000007FF80000FFFE0001E03F0001F01F8003F807C003F807E003F803F003F803F001F
003F8000003F8000001FC000001FC000001FC000001FE0007E1FE003FF9FE007C1DFE00F80
7FE01F807FE03F003FE07F003FE07F001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001F
C0FF001FC0FF001FC0FF001F807F001F807F003F003F803F001F807E000FE0FC0007FFF800
01FFF000007F8000>
	 27 39 -3 38 34] 57 @dc
[<
FFFFFF00FFFFFF007F007F003F801F003FC00F001FE007000FE007800FF0078007F8038003
F8038001FC038001FE038000FF0000007F0000007F8000003FC000001FC000700FE000700F
F0007007F8007803F8007803FC003801FE003C00FE003F007F003FFFFF803FFFFF80>
	 25 27 -2 26 31] 122 @dc
@F8 @sf
[<
7FE7FE0700E00700E00700E00700E00700E00700E00700E00700E00700E00700E00700E007
00E00700E00700E00700E00700E00700E00700E0FFFFE00700E00700E00700E00700E00700
E00700E00700E00700E00381E001C1E000E0E0003FE0>
	 23 32 0 31 25] 13 @dc

8 @eop0

0 0 8 @bop1 195 w @F8 @sf(to)q(da)o(y)17 b(will)f(b)q(e)h(accessible)h
(tomorro)o -1 x(w.)24 b(The)18 b(sub)o(v)o(erter)f(in)g(suc)o(h)g(an)h(ev)o
(en)o(t)f(migh)o(t)f(b)q(e)i(a)f(the)g(fault)o(y)f(c)o(hip)h(or)-1950 57 y
(p)q(o)o(w)o(er)e(spik)o(e.)k(Bac)o(kups)d(stored)e(o\013)h(site)f(pro)o
(vide)h(insurance)h(against)d(\014re.)-1327 101 y(Bac)o(kups)f(are)g(also)f
(vital)g(in)g(defending)i(against)e(h)o(uman)h(sub)o(v)o(erters.)18 b(If)
12 b(a)g(computer)g(is)g(stolen,)f(the)h(only)g(cop)o(y)-1950 56 y(of)k
(the)h(data)f(it)g(con)o(tained)g(will)f(b)q(e)i(on)g(the)f(bac)o(kup,)h
(whic)o(h)g(can)f(then)h(b)q(e)h(restored)e(on)g(another)g(computer.)-1950 
57 y(If)f(a)g(crac)o(k)o(er)f(breaks)h(in)o(to)f(a)h(computer)g(system)g
(and)g(erases)g(all)f(of)g(the)i(\014les,)e(the)h(bac)o(kups)h(can)f(b)q
(e)h(restored,)-1951 56 y(assuming)e(that)h(the)g(crac)o(k)o(er)g(do)q(es)g
(not)g(ha)o(v)o(e)g(access)g(to)g(or)f(kno)o(wledge)h(of)g(the)g(bac)o
(kups.)-1585 102 y(But)e(bac)o(kups)f(are)h(a)f(p)q(oten)o(tial)f(securit)o
(y)h(problem.)19 b(Bac)o(kups)13 b(are)f(targets)f(for)h(theft)g(b)o(y)h
(spies,)f(since)h(they)g(can)-1950 56 y(con)o(tain)g(exact)h(copies)g(of)g
(con\014den)o(tial)f(information.)18 b(Indeed,)d(bac)o(kups)g(w)o(arran)o
(t)o 13 x(greater)e(ph)o(ysical)h(securit)o(y)-1951 57 y(than)i(the)h
(computer)g(system,)f(since)h(the)f(theft)h(of)f(a)g(bac)o(kup)h(will)e
(not)h(b)q(e)i(noticed)e(as)g(quic)o(kly)g(as)h(the)f(theft)-1950 56 y(of)f
(media)g(con)o(taining)f(w)o(orking)f(data.)-680 102 y(With)i(recognition)g
(of)h(the)g(p)q(oten)o(tial)f(securit)o(y)h(hole)g(of)g(bac)o(kups,)g
(some)g(computer)g(systems)g(allo)o(w)e(users)j(to)-1951 56 y(prev)o(en)o
(t)f(sp)q(eci\014c)i(\014les)e(from)g(b)q(eing)h(bac)o(k)o(ed)f(up)h(at)f
(all.)22 b(Suc)o(h)c(action)d(is)h(justi\014ed)h(when)g(the)f(p)q(oten)o
(tial)f(cost)-1950 57 y(of)g(ha)o(ving)g(a)g(bac)o(kup)h(tap)q(e)g(con)o
(taining)e(the)i(data)f(stolen)g(is)g(greater)g(than)g(the)h(p)q(oten)o
(tial)e(cost)h(of)g(losing)g(the)-1950 56 y(data)i(due)i(to)e(equipmen)o
(t)h(malfunction,)f(or)g(when)i(the)f(data)f(stored)g(on)h(the)g(computer)g
(is)f(itself)g(a)h(cop)o(y)f(of)-1950 56 y(secure)f(master)e(source,)h
(suc)o(h)h(as)e(a)h(tap)q(e)g(in)h(a)e(\014le)i(cabinet.)-1058 189 y @F2 @sf
(9)69 b(Sanitizing)-399 146 y @F8 @sf(Flopp)o(y)13 b(disks)g(and)h(tap)q
(es)g(gro)o(w)e(old)i(and)f(are)h(often)f(discarded.)20 b(Hard)13 b(disks)h
(are)f(remo)o(v)o(ed)g(from)g(service)h(and)-1950 57 y(returned)e(enact)f
(to)g(the)g(man)o(ufacture)g(for)g(repair)f(or)h(p)q(erio)q(dic)h(main)o
(tenance.)18 b(Disk)10 b(pac)o(ks)i(costing)e(thousands)-1950 56 y(of)k
(dollars)e(are)i(remo)o(v)o(ed)g(from)f(equipmen)o(t)h(and)g(resold.)19 b
(If)c(these)f(media)g(ev)o(er)g(con)o(tained)f(con\014den)o(tial)h(data,)
-1951 56 y(sp)q(ecial)i(precautions)g(m)o(ust)f(b)q(e)i(tak)o(en)f(to)g
(ensure)h(that)e(no)h(traces)g(of)g(the)g(data)g(remain)f(on)h(the)h
(media)f(after)-1951 57 y(disp)q(osal.)37 b(This)21 b(pro)q(cess)h(is)f
(called)g(\\sanitizing)o(.")37 b(T)l(o)21 b(understand)h(sanitizing,)o 22 x
(\014rst)f(it)f(is)h(necessary)h(to)-1951 56 y(understand)16 b(ho)o(w)e
(information)g(is)g(recorded)i(on)f(magnetic)g(media:)-1199 102 y(The)e(t)o
(ypical)f(PC)h(\015opp)o(y)g(disk)g(can)g(store)f(appro)o(ximately)f(360)h
(thousand)h(c)o(haracters.)19 b(Eac)o(h)12 b(of)h(these)g(eac)o(h)g(of)-1950 
56 y(these)e(c)o(haracters)f(consists)g(of)g(8)g(binary)h(digits,)f
(called)g(\\bits,")g(whic)o(h)h(can)g(b)q(e)g(set)f(to)g(\\0")g(or)g(\\1.")
18 b(Information)-1951 57 y(on)c(the)f(disk)h(is)f(arranged)g(in)o(to)f
(\014les.)20 b(One)14 b(part)f(of)g(the)h(disk,)f(called)h(the)f
(directory)l(,)g(is)h(used)g(to)f(list)f(the)i(name)-1950 56 y(and)h(lo)q
(cation)f(of)h(ev)o(ery)g(\014le.)-504 102 y(Using)h(the)h(op)q(erating)f
(system's)g(delete-\014le)h(command)g(\(suc)o(h)g(as)f(the)h(MSDOS)g
(\\erase")f(command\))g(is)g(not)-1950 56 y(su\016cien)o(t)21 b(to)g
(insure)g(that)g(data)f(stored)h(cannot)g(b)q(e)h(reco)o(v)o(ered)f(b)o(y)h
(skilled)e(op)q(erators.)37 b(Most)21 b(delete-\014le)-1950 57 y(commands)g
(do)g(not)f(actually)g(erase)h(the)g(target)f(\014le)h(from)f(a)h(disk)o
(ette:)31 b(instead,)21 b(the)g(command)g(merely)-1950 56 y(erases)13 b
(the)g(name)h(of)e(the)i(\014le)f(from)f(the)i(disk)o(ette's)e(directory)l
(.)19 b(This)12 b(action)h(frees)g(the)g(storage)f(area)h(o)q(ccupied)-1949 
56 y(b)o(y)i(the)h(\014le)g(for)f(use)h(but)f(do)q(es)h(not)f(mo)q(dify)g
(the)h(data)f(in)g(an)o(y)h(w)o(a)o(y)l(.)k(The)c(\014le)f(itself)g
(remains)g(in)o(tact)f(and)i(can)-1950 57 y(b)q(e)g(reco)o(v)o(ered)f(at)f
(a)h(later)f(time)g(if)h(it)f(has)h(not)g(b)q(een)h(o)o(v)o(erwrit)o(ten.)j
(Man)o(y)14 b(programs)g(exist)g(on)h(the)h(mark)o(et)e(to)-1951 56 y(do)h
(just)g(this.)-240 102 y(Ev)o(en)j(if)f(the)g(actual)g(\014le)h(con)o(ten)o
(ts)f(are)g(o)o(v)o(erwritt)o(en)g(or)g(erased)h({)f(that)g(is,)g(ev)o(en)h
(if)f(all)g(of)g(the)g(bits)g(used)i(to)-1951 56 y(store)12 b(the)i(con)o
(ten)o(ts)e(of)h(the)g(\014le)g(are)g(set)g(to)f(\\0")h({)f(it)h(is)f
(still)g(p)q(ossible)h(to)f(reco)o(v)o(er)h(the)g(original)e(data,)i
(although)-1951 57 y(not)i(with)f(normal)h(op)q(erating)f(pro)q(cedures.)
196 165 y(8)-987 b
8 @eop1

9 @bop0
@F8 @sf
[<
0F800030E000407000407800F03800F83C00F83C00F83C00203C00003C00003C00003C0000
3C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C
00003C00003C00003C00003C00003C00007C000FFFC0>
	 18 32 -2 30 23] 74 @dc
@F2 @sf
[<
003F800001FFF00007E0FC000FC07E001F803F001F803F003F001F803F001F807F001FC07F
001FC07F001FC07F001FC0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF00
1FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE0FF001FE07F001F
C07F001FC07F001FC07F001FC03F001F803F001F801F803F001F803F000FC07E0007E0FC00
01FFF000003F8000>
	 27 39 -3 38 34] 48 @dc
[<
FFFE001FFFFEFFFE001FFFFEFFFE001FFFFE01C00000FF0001C00000FF0001E00001FF0000
E00001FE0000E00001FE0000700003FC0000700003FC0000780007FC00003FFFFFF800003F
FFFFF800001FFFFFF000001C000FF000001E001FF000000E001FE000000E003FE000000700
3FC0000007003FC0000007807FC0000003807F80000003C0FF80000001C0FF00000001C0FF
00000000E1FE00000000E1FE00000000F3FE0000000073FC0000000073FC000000003FF800
0000003FF8000000003FF8000000001FF0000000001FF0000000000FE0000000000FE00000
00000FE00000000007C00000000007C00000000003800000>
	 47 41 -2 40 52] 65 @dc
@F8 @sf
[<
0FC000107000201800700C00780E0078060030070000070000038000038000038003E3C00E
13C0180BC03807C07007C07007C0F003C0F003C0F003C0F003C0F003C0F00380F003807003
807007003807003806001C0C000E180003F000>
	 18 31 -2 29 23] 57 @dc

9 @eop0

0 0 9 @bop1 195 w @F8 @sf(Imagine)17 b(a)g(blac)o(k)f(and)h(white)g(c)o
(hec)o(k)o(erb)q(oard)g(used)h(for)e(a)h(computer)g(memory)l(.)25 b
(Assume)18 b(that)e(the)h(v)m(alue)g(of)-1950 57 y(an)o(y)h(square)f(on)h
(the)g(c)o(hec)o(k)o(erb)q(oard)g(is)g(prop)q(ortional)e(to)i(the)g
(darkness)g(of)f(the)h(square:)26 b(the)18 b(blac)o(k)f(squares)-1950 56 y
(are)d(1s)f(and)h(the)g(white)g(squares)f(are)h(0s.)19 b(No)o(w)13 b
(consider)h(what)f(happ)q(ens)i(when)g(the)f(c)o(hec)o(k)o(erb)q(oard)g
(is)f(pain)o(ted)-1950 56 y(with)g(one)i(coat)e(of)h(white)g(pain)o(t:)k
(the)c(original)f(c)o(hec)o(k)o(erb)q(oard)h(pattern)f(is)h(still)f
(discernible,)g(but)i(less)f(so.)19 b(The)-1950 57 y(squares)c(whic)o(h)g
(formerly)f(had)i(a)e(v)m(alue)i(of)f(1)g(no)o(w)f(ev)m(aluate)h(to)g(0.1)f
(or)h(0.2.)k(When)c(the)h(computer)f(reads)g(the)-1950 56 y(memory)l(,)e
(the)g(0.1)f(or)h(0.2)f(are)g(rounded)i(to)f(0.)18 b(But)c(an)f(exp)q(ert)g
(with)f(sp)q(ecial)h(equipmen)o(t)g(could)g(easily)g(reco)o(v)o(er)-1951 
57 y(the)i(original)f(pattern.)-403 101 y(Just)f(as)g(the)h(pattern)f(can)g
(b)q(e)h(reco)o(v)o(ered)f(from)g(a)g(c)o(hec)o(k)o(erb)q(oard)g
(uniformly)f(pain)o(ted,)h(data)g(can)g(b)q(e)h(reco)o(v)o(ered)-1950 57 y
(from)d(a)h(\015opp)o(y)h(disk)f(whic)o(h)g(has)g(b)q(een)h(uniformly)e
(erased)h(or)g(reformatted.)18 b(T)o(ypical)11 b(sanitizati)o(on)g(pro)q
(cedures)-1949 56 y(in)o(v)o(olv)o(e)j(writing)g(a)h(1)g(to)g(ev)o(ery)h
(lo)q(cation)e(on)h(the)h(media,)f(then)h(to)f(write)f(a)h(0)h(to)e(ev)o
(ery)i(lo)q(cation,)e(then)i(to)e(\014ll)-1950 57 y(the)g(media)f(with)g
(random)h(data.)k(T)l(o)c(use)g(the)g(c)o(hec)o(k)o(erb)q(oard)f(analogy)l
(,)g(this)g(w)o(ould)g(b)q(e)i(the)e(same)h(as)f(pain)o(ting)-1951 56 y
(the)j(b)q(oard)g(blac)o(k,)f(then)i(white,)e(then)h(with)g(a)f(di\013eren)o
(t)h(c)o(hec)o(k)o(ered)g(pattern.)22 b(The)16 b(original)e(pattern)i
(should)-1950 57 y(then)g(b)q(e)f(undetectable.)21 b(Additional)14 b
(e\013ort)g(migh)o(t)g(b)q(e)i(desired)f(when)h(dealing)e(with)h(v)o(ery)g
(sensitiv)o(e)f(data.)-1906 101 y(Sanitizing)d(is)h(ob)o(viously)f(an)h
(exp)q(ensiv)o(e)h(and)f(time)g(consuming)g(pro)q(cess.)19 b(Ph)o(ysical)
11 b(destruction)h(of)g(the)g(media)-1950 56 y(represen)o(ts)17 b(an)h
(attracti)o(v)o(e)e(alternativ)o(e)g({)h(simply)g(feeding)g(the)h(\015opp)o
(y)f(disk)h(\(or)e(the)i(c)o(hec)o(k)o(erb)q(oard\))f(in)o(to)f(a)-1950 
57 y(pap)q(er)k(shredder)g(do)q(es)g(v)o(ery)g(w)o(ell.)32 b
(Unfortunately)l(,)19 b(ph)o(ysical)g(destruction)g(is)h(not)f
(economically)f(p)q(ossible)-1950 56 y(with)e(exp)q(ensiv)o(e)g(media)g
(whic)o(h)g(m)o(ust)g(b)q(e)h(returned)g(for)e(service)h(or)g(for)g
(resale)f(in)h(order)g(to)g(reco)o(v)o(er)g(costs)f(of)-1950 57 y(purc)o
(hase.)-186 188 y @F2 @sf(10)69 b(Authen)n(tication)-588 146 y @F8 @sf
(Authen)o(tication)17 b(is)g(the)h(pro)q(cess)h(b)o(y)f(whic)o(h)f(the)h
(computer)g(system)g(v)o(eri\014es)g(that)f(a)g(user)i(is)e(who)h(the)g
(user)-1950 57 y(claims)c(to)h(b)q(e,)g(and)h(vice)f(v)o(ersa.)k(Systems)c
(of)g(authen)o(tication)e(are)i(usually)g(classi\014ed)g(as)g(b)q(eing)g
(based)h(on:)-1901 101 y(Something)f(the)g(user)g(has.)20 b(\(k)o(eys\))
-619 102 y(Something)15 b(the)g(user)g(kno)o(ws.)20 b(\(passw)o(ords\))-790 
101 y(Something)15 b(the)g(user)g(is.)20 b(\(\014ngerprin)o(ts\))-726 188 y 
@F2 @sf(11)69 b(P)n(assw)n(ords)-444 147 y @F8 @sf(A)15 b(passw)o(ord)g
(is)g(a)g(secret)g(w)o(ord)g(or)g(phrase)g(whic)o(h)g(should)h(b)q(e)g
(kno)o(wn)f(only)g(to)f(the)i(user)f(and)h(the)f(computer.)-1950 56 y
(When)20 b(the)f(user)g(attempts)f(to)h(use)g(the)h(computer,)f(he)h(m)o
(ust)f(\014rst)f(en)o(ter)h(the)h(passw)o(ord.)31 b(The)19 b(computer)-1950 
57 y(compares)c(the)g(t)o(yp)q(ed)h(passw)o(ord)e(to)h(the)g(stored)g
(passw)o(ord)f(and,)h(if)g(they)g(matc)o(h,)f(allo)o(ws)f(the)j(user)f
(access.)-1906 101 y(Some)22 b(computer)h(systems)f(allo)o(w)o 21 x
(managemen)o(t)g(access)g(to)g(the)h(list)e(of)h(stored)g(passw)o(ords;)i
(doing)e(so)g(is)-1950 57 y(generally)13 b(regarded)g(as)g(an)h(unsound)g
(practice.)19 b(If)14 b(a)g(crac)o(k)o(er)f(gained)g(access)h(to)f(suc)o
(h)h(a)f(list,)f(ev)o(ery)i(passw)o(ord)-1951 56 y(on)j(the)h(computer)f
(system)g(w)o(ould)g(ha)o(v)o(e)g(to)g(b)q(e)h(c)o(hanged.)27 b(Other)18 b
(computers)f(store)g(passw)o(ords)f(after)h(they)-1950 57 y(ha)o(v)o(e)c
(b)q(een)i(pro)q(cessed)g(b)o(y)f(a)f(non-in)o(v)o(ertible)g(mathematical)f
(function.)19 b(The)14 b(user's)g(t)o(yp)q(ed)g(passw)o(ord)f(cannot)-986 
169 y(9)-987 b
9 @eop1

10 @bop0

10 @eop0
0 0 10 @bop1 195 w @F8 @sf(b)q(e)12 b(deriv)o(ed)g(b)o(y)f(the)h(pro)q
(cessed)g(passw)o(ord,)f(eliminating)f(the)h(damage)g(resulting)g(from)f
(the)i(theft)f(of)g(the)h(master)-1951 57 y(passw)o(ord)17 b(list.)26 b
(The)18 b(passw)o(ord)f(that)g(the)h(user)g(t)o(yp)q(es)f(when)i
(attempting)d(to)h(log)g(on)h(is)f(then)h(transformed)-1951 56 y(with)d
(the)g(same)g(mathematical)o 14 x(function)g(and)g(the)h(t)o(w)o(o)e(pro)q
(cessed)i(passw)o(ords)e(are)h(compared)g(for)f(equalit)o(y)l(.)-1950 188 y 
@F2 @sf(12)69 b(What)24 b(mak)n(es)f(a)h(secure)e(passw)n(ord?)-1108 147 y 
@F8 @sf(Insecure)d(passw)o(ords)e(are)g(passw)o(ords)g(whic)o(h)g(are)h
(easy)f(for)g(p)q(eople)i(to)e(guess.)27 b(Examples)17 b(of)h(these)g
(include)-1950 56 y(passw)o(ords)d(whic)o(h)i(are)f(the)g(same)g(as)g
(usernames,)h(common)f(\014rst)g(or)g(last)f(names,)i(passw)o(ords)e(of)h
(four)g(c)o(har-)-1950 57 y(acters)f(or)f(less,)h(and)g(English)g(w)o
(ords)f(\(all)g(english)h(w)o(ords,)f(ev)o(en)h(long)g(ones)g(lik)o(e)f
(\\cinnamon."\).)-1709 101 y(A)20 b(few)g(y)o(ears)f(ago,)h(the)g(t)o
(ypical)f(crac)o(k)o(er)g(w)o(ould)g(sp)q(end)j(man)o(y)d(hours)h(at)f
(his)h(k)o(eyb)q(oard)g(trying)f(passw)o(ord)-1951 56 y(after)14 b(passw)o
(ord.)19 b(T)l(o)q(da)o(y)l(,)14 b(crac)o(k)o(ers)f(ha)o(v)o(e)i
(automated)e(this)h(searc)o(h)g(with)g(p)q(ersonal)g(computers.)20 b(The)
15 b(crac)o(k)o(er)-1951 57 y(can)i(program)e(his)h(computer)g(to)g(try)g
(ev)o(ery)g(w)o(ord)g(in)g(a)g(large)g(\014le.)23 b(T)o(ypically)l(,)15 b
(these)i(\014les)f(consist)g(of)g(thirt)o(y)-1951 56 y(thousand)f(w)o(ord)g
(dictionaries,)o 14 x(lists)f(of)h(\014rst)g(and)g(last)f(names)h(and)h
(easy-to-remem)o(b)q(er)f(k)o(eyb)q(oard)g(patterns.)-1950 102 y(Examples)f
(of)h(secure)g(passw)o(ords)f(include)h(random,)f(unpronounceable)h(com)o
(binations)f(of)g(letters)g(and)h(n)o(um-)-1950 56 y(b)q(ers)21 b(and)f
(sev)o(eral)f(w)o(ords)h(strung)g(together.)34 b(Single)20 b(w)o(ords)f
(sp)q(elled)i(bac)o(kw)o(ards,)f(v)o(ery)g(p)q(opular)g(in)g(some)-1950 
57 y(circles,)14 b(are)h(not)g(secure)h(passw)o(ords)e(since)h(crac)o(k)o
(ers)g(started)f(searc)o(hing)h(for)f(them.)-1478 101 y(The)e(second)f(c)o
(haracteristic)f(of)h(a)g(secure)h(passw)o(ord)e(\(and)i(of)e(a)h(secure)h
(computer\))f(is)g(that)g(it)f(is)h(easily)g(c)o(hanged)-1950 57 y(b)o(y)
16 b(the)g(user.)21 b(Users)16 b(should)g(b)q(e)g(encouraged)g(to)f(c)o
(hange)h(their)g(passw)o(ords)e(frequen)o(tly)i(and)g(whenev)o(er)g(they)
-1950 56 y(b)q(eliev)o(e)d(that)g(someone)g(else)g(has)g(b)q(een)h(using)f
(their)g(accoun)o(t.)19 b(This)13 b(w)o(a)o(y)l(,)f(if)h(a)g(crac)o(k)o
(er)g(do)q(es)g(manage)g(to)f(learn)-1950 57 y(a)j(user's)g(passw)o(ord,)f
(the)h(damage)g(will)f(b)q(e)h(minimized.)-984 101 y(It)h(should)f(go)g
(without)f(sa)o(ying)h(that)g(passw)o(ords)f(should)i(nev)o(er)f(b)q(e)h
(written)f(do)o(wn,)g(told)g(to)f(other)h(p)q(eople)h(or)-1950 56 y(c)o
(hosen)f(according)g(to)g(an)g(easily)f(predicted)i(system.)-943 189 y 
@F2 @sf(13)69 b(Smart)24 b(Cards)-520 146 y @F8 @sf(If)f(the)f(comm)o
(unication)g(link)g(b)q(et)o(w)o(een)g(the)h(user)g(and)f(the)h(computer)f
(is)g(monitored,)h(ev)o(en)g(the)g(longest)-1951 57 y(and)17 b(most)f
(obscure)h(passw)o(ord)g(can)g(b)q(e)g(recorded,)h(giving)d(the)i(ea)o(v)o
(esdropp)q(er)g(access)h(to)e(the)h(accoun)o(t.)25 b(The)-1950 56 y(answ)o
(er,)11 b(some)h(mem)o(b)q(ers)g(of)f(the)h(computer)f(comm)o(unit)o(y)g
(b)q(eliev)o(e,)h(is)f(for)g(users)h(to)f(b)q(e)h(assigned)g(mathematical)o 
-1951 57 a(functions)h(instead)g(of)g(passw)o(ords.)18 b(When)c(the)f
(user)h(attempts)e(to)h(log)f(on,)i(the)f(computer)g(presen)o(ts)h(him)f
(with)-1951 56 y(a)18 b(n)o(um)o(b)q(er.)30 b(The)18 b(user)h(applies)f
(his)g(secret)g(function)h(\(whic)o(h)f(the)g(computer)g(kno)o(ws\))g(to)g
(the)g(n)o(um)o(b)q(er)h(and)-1950 56 y(replies)f(with)f(the)h(result.)29 b
(Since)18 b(the)h(listener)e(nev)o(er)h(sees)h(the)f(function,)g(only)g
(the)g(input)g(and)h(the)f(result,)-1951 57 y(tapping)d(the)g(comm)o
(unications)f(link)g(do)q(es)i(not)f(theoretically)e(giv)o(e)i(one)g
(access)g(to)g(the)g(accoun)o(t.)-1725 101 y(Assume)h(for)g(example,)g
(user)g(P's)f(form)o(ula)g(is)h(\\m)o(ultiply)e(b)o(y)i(2.")22 b(When)17 b
(she)f(tries)f(to)h(log)f(in,)h(the)g(computer)-1950 57 y(prin)o(ts)j(the)h
(n)o(um)o(b)q(er)f(\\1234567.)o(")32 b(She)20 b(t)o(yp)q(es)g(bac)o(k)g
(\\24691)o(34,)o(")f(and)h(the)g(computer)f(lets)g(her)h(log)f(in.)33 b(A)
-1950 56 y(problem)14 b(with)f(this)g(system)g(is)h(that)f(unless)h(v)o
(ery)f(complicated)g(form)o(ulas)g(are)g(used,)i(it)e(is)g(relativ)o(ely)f
(easy)i(for)-1951 57 y(a)h(ea)o(v)o(esdropp)q(er)g(to)g(\014gure)g(out)g
(the)g(form)o(ula.)134 214 y(10)-998 b
10 @eop1

11 @bop0
@F2 @sf
[<
7FFF807FFF807FFF8007F00007F00007F00007F00007F00007F00007F00007F00007F00007
F00007F00007F00007F00007F00007F00007F00007F00007F00007F00007F00007F000FFFF
C0FFFFC0FFFFC007F00007F00007F00007F00007F00007F00007F00007F03E07F07F03F07F
03F87F01F87F00FE3E003FFC0007F0>
	 24 42 -2 41 21] 102 @dc
[<
0FF0003FFC007C3E00FE1F00FE1F80FE0FC0FE0FE07C0FE0000FE0000FE0000FE0000FE000
0FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000F
E0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE0000FE001FFE0
01FFE001FFE0000000000000000000000000000000000000000000000700000F80001FC000
3FE0003FE0003FE0001FC0000F80000700>
	 19 55 4 42 21] 106 @dc
@F8 @sf
[<
70F8F8F8700000000000202020202070707070707070707070F8F8F8F8F8F8F870>
	 5 33 -4 32 13] 33 @dc
[<
007FFE000007C0000003C0000003C0000003C0000003C0000003C0000003C0000003C00000
03C0000003C0000003C0000003C0000007C0000007A000000FB000001F1000001E0800003E
0800003C0400007C040000F8020000F0030001F0010001E0008003E0008007C00040078000
400F8000601F8000F8FFF003FF>
	 32 31 -1 30 34] 89 @dc
@F2 @sf
[<
000001C0000000000003E0000000000003E0000000000007F0000000000007F00000000000
0FF800000000000FF800000000000FF800000000001FFC00000000001FFC00000000003FFE
00000000003FCE00000000007FCF00000000007F870000000000FF878000000000FF038000
000000FF038000000001FF01C000000001FE01C000000003FE01E000000003FC00E0000000
07FC00F000000007F8007000000007F800700000000FF000380000000FF000380000001FF0
001C0000001FE0001C0000003FE0001E0000003FC0000E0000007FC0000F0000007F800007
0000007F800007000000FF000003800000FF000003800001FF000003C00001FE000001C000
03FE000001E000FFFFF0003FFF80FFFFF0003FFF80FFFFF0003FFF80>
	 49 41 -1 40 52] 86 @dc

11 @eop0

0 0 11 @bop1 195 w @F8 @sf(V)l(ery)14 b(complicated)e(form)o(ulas)g(can)h
(b)q(e)h(implemen)o(ted)f(with)g(the)g(\\smart)f(card,")h(whic)o(h)g(is)g
(a)g(small)f(credit-card)-1950 57 y(sized)k(device)g(with)f(an)h(em)o(b)q
(edded)h(computer)f(instead)f(of)h(magnetic)f(strip.)20 b(The)c(host)g
(computer)f(transmits)-1951 56 y(a)g(large)g(\(100)f(digit\))g(n)o(um)o(b)q
(er)i(to)f(the)h(smart)f(card)g(whic)o(h)h(p)q(erforms)f(sev)o(eral)g
(thousand)g(calculations)f(on)i(the)-1950 56 y(n)o(um)o(b)q(er.)j(The)13 b
(smart)e(card)i(then)f(transmits)f(the)i(result)f(bac)o(k)g(to)g(the)g
(host.)19 b(Ob)o(viously)l(,)12 b(dedicated)h(hardw)o(are)-1951 57 y
(consisting)18 b(of)g(the)h(smart)f(cards)g(themselv)o(es)h(and)g(a)f(sp)q
(ecial)h(reader)g(are)f(required.)31 b(Smart)18 b(cards)h(c)o(hange)-1950 
56 y(authen)o(tication)g(from)g(something)g(to)g(user)h(kno)o(ws)g(\(a)f
(passw)o(ord\))g(to)g(something)h(the)g(user)g(has)g(\(a)f(smart)-1951 57 y
(card\).)g(Naturally)l(,)14 b(the)h(theft)g(of)g(a)g(smart-card)f(is)h
(equiv)m(alen)o(t)g(to)f(the)i(disclosure)e(of)h(a)g(passw)o(ord.)-1746 
101 y(Smart)10 b(cards)h(ha)o(v)o(e)g(b)q(een)h(prop)q(osed)g(as)e(a)h
(general)g(replacemen)o(t)g(for)f(man)o(y)h(passw)o(ord)f(applications,)g
(including)-1950 57 y(logon)17 b(for)h(v)o(ery)f(secure)i(computers,)f(v)o
(eri\014cation)f(of)h(credit)g(cards,)g(and)g(A)l(TM)g(cards)g(and)h(iden)o
(tit)o(y)d(cards.)-1950 56 y(Since)h(the)h(cards)e(are)h(authen)o(ticated)f
(b)o(y)h(testing)f(a)h(mathematical)e(function)i(stored)g(inside)f(the)h
(card)g(on)g(a)-1950 57 y(silicon)11 b(computer,)i(rather)f(than)g(a)g(n)o
(um)o(b)q(er)g(stored)g(on)h(a)f(magnetic)f(strip,)h(the)g(cards)h(w)o
(ould)e(b)q(e)i(v)o(ery)f(di\016cult)-1950 56 y(to)j(duplicate)g(or)f
(forge.)19 b(They)d(are)f(also)f(v)o(ery)h(exp)q(ensiv)o(e.)-1025 188 y 
@F2 @sf(14)69 b(Authen)n(tication)23 b(of)g(the)f(computer:)30 b(The)22 b
(T)-6 b(ro)t(jan)24 b(Horse)e(problem)-1949 147 y @F8 @sf(While)13 b(most)g
(computer)g(systems)g(require)g(that)g(the)h(user)f(authen)o(ticate)g
(himself)g(to)g(the)g(computer,)h(v)o(ery)f(few)-1950 56 y(pro)o(vide)i(a)g
(facilit)o(y)f(for)h(the)h(computer)f(to)g(authen)o(ticate)g(itself)g(to)g
(the)g(user!)22 b(Y)l(et,)15 b(computer)h(users)f(face)h(the)-1950 57 y
(same)f(authen)o(tication)f(problems)g(a)h(computer)g(do)q(es.)-950 101 y
(F)l(or)i(example,)g(a)g(user)g(sits)g(do)o(wn)g(at)g(a)g(terminal)f(to)g
(log)h(on)o(to)f(a)h(computer)g(and)h(is)f(prompted)g(to)g(t)o(yp)q(e)g
(his)-1950 57 y(username)d(and)g(his)f(passw)o(ord.)18 b(What)13 b
(assurance)h(do)q(es)g(the)f(user)h(ha)o(v)o(e)f(that)g(the)h(questions)f
(are)g(b)q(eing)h(ask)o(ed)-1950 56 y(b)o(y)i(the)h(op)q(erating)e(system)h
(and)h(not)f(b)o(y)g(a)g(program)f(that)h(has)g(b)q(een)h(left)f(running)h
(on)f(the)g(terminal?)23 b(Suc)o(h)-1949 56 y(a)15 b(program)g({)g(called)g
(a)g(T)l(ro)s(jan)g(Horse)g({)g(can)h(collect)f(h)o(undreds)h(of)f(passw)o
(ords)g(in)g(a)g(v)o(ery)g(short)g(time.)21 b(W)l(ell)-1951 57 y(written)
14 b(tro)s(jan)g(horses)h(can)g(b)q(e)h(exceedingly)g(di\016cult)e(to)h
(detect.)-1178 101 y(Another)j(example)f(of)h(a)f(tro)s(jan)f(horse)i
(program)f(is)g(a)h(program)e(whic)o(h)i(claims)f(to)g(p)q(erforms)g(one)h
(function)-1950 57 y(while)g(actually)f(p)q(erforming)h(another.)29 b(F)l
(or)18 b(example,)g(a)h(program)e(called)h(DSK)o(CA)o(CHE)g(w)o(as)f
(distributed)-1950 56 y(on)22 b(some)g(computer)g(bulletin)g(b)q(oard)g
(systems)g(in)g(the)g(New)h(Y)l(ork)f(in)g(Decem)o(b)q(er)h(1985.)40 b
(The)22 b(program)-1951 57 y(substan)o(tially)12 b(impro)o(v)o(ed)h(disk)h
(i/o)f(p)q(erformance)i(of)e(an)h(IBM)h(P)o(ersonal)e(Computer,)g
(encouraging)h(p)q(eople)h(to)-1951 56 y(use)g(the)f(program)g(and)h(giv)o
(e)e(it)h(to)g(their)g(friends.)19 b(The)c(hidden)h(function)e(of)g(DSK)o
(CA)o(CHE)g(w)o(as)g(to)f(erase)i(the)-1950 57 y(con)o(ten)o(ts)f(of)h
(the)g(computer's)f(disk)h(when)h(it)e(w)o(as)g(run)h(on)g(or)f(after)h
(the)g(trigger)e(date,)i(whic)o(h)f(w)o(as)h(Marc)o(h)f(24,)-1951 56 y
(1986.)-105 102 y(T)l(ro)s(jan)i(horses)g(are)g(p)q(ossible)h(b)q(ecause)h
(reliable)d(w)o(a)o(ys)h(in)g(whic)o(h)h(the)g(computer)f(can)h(authen)o
(ticate)f(itself)g(to)-1951 56 y(the)f(user)h(are)e(not)h(wide)g(spread.)
-579 188 y @F2 @sf(15)69 b(Computer)24 b(Viruses)-688 147 y @F8 @sf(A)18 b
(computer)f(virus)g(is)g(a)g(malicious)f(program)h(whic)o(h)g(can)h(repro)q
(duce)g(itself.)26 b(The)18 b(DSK)o(CA)o(CHE)f(program)-1951 56 y(describ)q
(ed)c(ab)q(o)o(v)o(e)e(is)h(a)f(sort)g(of)h(computer)g(virus)f(that)h
(used)g(h)o(umans)g(to)f(propagate.)18 b(Other)12 b(computer)g(viruses)-1950 
57 y(cop)o(y)g(themselv)o(es)g(automatical)o(ly)f(when)i(they)f(are)g
(executed.)20 b(Viruses)12 b(ha)o(v)o(e)g(b)q(een)h(written)f(whic)o(h)g
(propagate)-999 146 y(11)-998 b
11 @eop1

12 @bop0
/@F3 @newfont
@F3 @sf
[<
7FFFE07FFFE001F80001F80001F80001F80001F80001F80001F80001F80001F80001F80001
F80001F80001F80001F80001F80001F80001F80001F80001F80001F80001F80001F80001F8
0001F80001F800FFF800FFF80001F800007800001800>
	 19 32 -4 31 28] 49 @dc
[<
00FF0003FFC00783E00F00F01E00F83E007C3C007C7C007E7C007E7C007EFC007EFC007EFC
007EFC007EFE007CFE007CFF00F8FD80F0FCFFE0FC7FC0FC08007C00007C00007E00F03E01
F83E01F81F01F80F01F807C0F003F07000FFE0001F80>
	 23 32 -2 31 28] 54 @dc
[<
387CFEFEFE7C38>
	 7 7 -4 6 16] 46 @dc
[<
FFF00600FFFFFFF00F00FFFF06000F0007E006001F8007E006001F8007E006001F8007E006
003FC007E006003FC007E006007E6007E006007E6007E00600FC3007E00600FC3007E00601
F81807E00601F81807E00601F81807E00603F00C07E00603F00C07E00607E00607E00607E0
0607E0060FC00307E0060FC00307E0060FC00307E0061F800187E0061F800187E0063F0000
C7E0063F0000C7E0067E000067E0067E000067E006FC000037E006FC000037E006FC000037
E007F800001FE0FFF800001FFFFFF000000FFF>
	 48 34 -2 33 53] 77 @dc
[<
00FE0007FFC00F83E01F01F03E00F87C007C7C007CFC007EFC007EFC007EFC007EFC007EFC
007EFC007E7C007C7C007C7C007C3E00F81E00F00F83E007FFC000FE00>
	 23 22 -2 21 28] 111 @dc
[<
01FC3FC007FF3FC00F83BE001E00FE003E007E007C003E007C003E00FC003E00FC003E00FC
003E00FC003E00FC003E00FC003E00FC003E00FC003E007C003E007E003E003E003E001F00
7E000F81FE0007FFBE0001FC3E0000003E0000003E0000003E0000003E0000003E0000003E
0000003E0000003E0000003E0000003E0000003E000001FE000001FE00>
	 26 35 -2 34 31] 100 @dc
[<
00FF0003FFC00FC0701F00303E00187E00007C00007C0000FC0000FC0000FC0000FFFFF8FF
FFF8FC00F8FC00F87C00F87C00F03E01F01E01E00F87C007FF8000FE00>
	 21 22 -2 21 26] 101 @dc
[<
FFE0FFE0FFE0FFE0FFE0FFE01F001F001F001F001F001F001F001F001F001F001F001F001F
001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F00
1F001F001F001F001F001F001F001F001F001F001F001F801F801F001F801F801F001F403E
403E001F303E303E00FF1FFC1FFC00FF07F007F000>
	 43 22 -2 21 47] 109 @dc
[<
C7F000EFFC00FC0E00F00700E00380E00380C00380C00780000F8001FF000FFF003FFE007F
F8007FE000FC0000F00300E00300E00300600700781F003FFF000FF300>
	 17 22 -2 21 22] 115 @dc

12 @eop0

0 0 12 @bop1 195 w @F8 @sf(b)o(y)15 b(telephone)h(lines)e(or)h(b)o(y)g
(computer)g(net)o(w)o(orks.)-882 102 y(The)g(computer)g(virus)g(is)g
(another)f(problem)h(of)g(authen)o(tication:)j(Since)e(programs)e(ha)o(v)o
(e)h(no)g(w)o(a)o(y)f(of)g(authen-)-1949 56 y(ticating)g(their)g(actions,)g
(the)h(user)h(m)o(ust)e(pro)q(ceed)i(on)f(blind)g(trust)g(when)g(w)o(e)g
(run)g(them.)20 b(When)c(I)f(use)h(a)e(text)-1950 56 y(editor)i(on)h(m)o
(y)f(computer,)h(I)g(trust)f(that)g(the)h(program)e(will)h(not)g
(maliciously)f(erase)i(all)e(of)i(m)o(y)f(\014les.)25 b(There)-1950 57 y
(are)17 b(times)f(that)g(this)h(trust)f(is)h(misplaced.)25 b(Computer)16 b
(viruses)h(are)g(some)f(of)h(the)g(most)f(e\016cien)o(t)h(programs)-1951 
56 y(at)e(exploiting)e(trust.)-376 102 y(One)18 b(computer)g(virus)f(is)g
(a)g(program)f(whic)o(h)h(when)h(run)g(copies)f(itself)g(o)o(v)o(er)f(a)h
(randomly)g(lo)q(cated)g(program)-1951 56 y(on)d(the)g(hard)h(disk.)k(F)l
(or)14 b(example,)g(the)g(\014rst)g(time)f(the)i(virus)e(is)h(run)h(it)e
(migh)o(t)g(cop)o(y)h(itself)f(on)o(to)h(the)g(installed)-1951 57 y(w)o
(ordpro)q(cessor)i(program.)24 b(Then,)18 b(when)g(either)e(the)i
(original)o 16 x(virus)e(program)g(or)h(the)g(w)o(ordpro)q(cessor)f(pro-)
-1950 56 y(gram)d(are)g(run,)h(another)f(program)f(on)i(the)f(hard)h(disk)f
(will)f(b)q(e)i(corrupted.)20 b(So)q(on)14 b(there)f(will)f(b)q(e)j(no)e
(programs)-1951 57 y(remaining)h(on)h(the)h(disk)f(b)q(esides)g(the)h
(virus.)-794 101 y(A)d(more)g(clea)o(v)o(er)f(virus)h(w)o(ould)g(merely)g
(mo)q(dify)f(the)i(other)f(programs)f(on)h(the)g(disk,)g(inserting)f(a)h
(cop)o(y)g(of)g(itself)-1951 57 y(and)i(then)f(remain)g(dorman)o(t)g(un)o
(til)f(a)h(particular)f(target)g(date)i(w)o(as)e(reac)o(hed.)20 b(The)15 b
(virus)f(migh)o(t)f(then)i(prin)o(t)e(a)-1950 56 y(ransom)h(note)g(and)h
(prev)o(en)o(t)f(use)h(of)f(the)h(infected)g(programs)e(un)o(til)g(a)i(\\k)o
(ey")f(w)o(as)f(purc)o(hased)i(from)f(the)h(virus')-1951 56 y(author.)-145 
102 y(Once)g(a)f(system)f(is)h(infected,)g(the)g(virus)g(is)f(nearly)h
(imp)q(ossible)f(to)h(eradicate.)19 b(The)14 b(real)f(danger)h(of)g
(computer)-1950 56 y(viruses)e(is)g(that)g(they)g(can)h(remain)f(dorman)o
(t)f(for)h(mon)o(ths)g(or)g(y)o(ears,)g(then)h(suddenly)g(strik)o(e,)e
(erasing)h(data)g(and)-1950 57 y(making)g(computer)g(systems)g(useless)g
(\(since)g(all)g(of)g(the)g(computer's)g(programs)f(are)h(infected)h(with)f
(the)g(virus.\))-1951 56 y(Viruses)i(could)g(also)f(b)q(e)i(triggered)e(b)o
(y)i(external)e(ev)o(en)o(ts)h(suc)o(h)h(as)e(phone)i(calls,)e(dep)q(end)q
(ing)i(on)f(the)g(particular)-1951 57 y(computer.)26 b(A)18 b(n)o(um)o(b)q
(er)f(of)g(authors)g(ha)o(v)o(e)g(suggested)g(w)o(a)o(ys)f(of)h(using)g
(computer)g(viruses)g(for)g(in)o(ternational)o -1951 56 a(blac)o(kmail)d
(infecting)h(the)h(nation's)f(banking)g(computers)h(with)f(them.)21 b
(Viruses)16 b(can)g(and)g(ha)o(v)o(e)f(b)q(een)i(placed)-1950 57 y(b)o(y)h
(disgrun)o(tled)g(emplo)o(y)o(ees)g(in)h(soft)o(w)o(a)o(re)e(under)j(dev)o
(elopmen)o(t.)29 b(Suc)o(h)19 b(viruses)f(migh)o(t)g(b)q(e)h(triggered)e
(when)-1949 56 y(the)e(emplo)o(y)o(ee's)g(name)g(is)f(remo)o(v)o(ed)h
(from)g(the)g(business')g(pa)o(yroll.)-1179 102 y(There)k(are)f(sev)o
(eral)g(w)o(a)o(ys)g(to)g(defend)i(against)d(computer)i(viruses.)30 b(The)
19 b(cautious)f(user)h(should)g(nev)o(er)g(use)-1950 56 y(public)i(domain)f
(soft)o(w)o(a)o(re,)g(or)g(only)g(use)h(suc)o(h)g(soft)o(w)o(ar)o(e)e
(after)h(a)g(comp)q(eten)o(t)h(programmer)e(has)h(read)h(the)-1950 56 y
(source-co)q(de)16 b(and)f(recompiled)g(the)h(executable-co)q(de)g(from)e
(scratc)o(h.)-1230 102 y(Computer)f(programs)e(are)i(usually)f(written)g
(in)h(one)g(of)g(sev)o(eral)f(english-lik)o(e)g(languages)g(and)h(then)h
(pro)q(cessed,)-1950 56 y(using)k(a)g(program)g(called)g(a)g(compiler,)g
(in)o(to)f(a)i(form)e(whic)o(h)i(the)f(computer)h(can)f(execute)h
(directly)l(.)30 b(While)-1951 57 y(ev)o(en)20 b(a)f(go)q(o)q(d)h
(programmer)e(w)o(ould)h(ha)o(v)o(e)g(a)g(hard)h(time)f(detecting)g(a)g
(virus)g(if)g(presen)o(ted)h(solely)f(with)g(the)-1950 56 y(executable)c
(co)q(de,)h(they)f(are)g(readily)f(detectable)i(in)f(source-co)q(de.)-1181 
188 y @F2 @sf(16)69 b(T)-6 b(elecomm)n(unications)-743 149 y @F3 @sf(16.1)
56 b(Mo)r(dems)-365 130 y @F8 @sf(The)20 b(w)o(ord)f(MODEM)f(stands)i(for)f
(Mo)q(dulator/D)o(emo)q(dulator)o(.)32 b(A)19 b(mo)q(dem)h(tak)o(es)f(a)g
(stream)g(of)g(data)g(and)-1950 57 y(mo)q(dulates)g(it)g(in)o(to)g(a)g
(series)g(of)g(tones)h(suitable)e(for)h(broadcast)g(o)o(v)o(er)g(standard)g
(telephone)h(lines.)33 b(A)o(t)19 b(the)-1950 56 y(receiving)c(end,)g
(another)g(mo)q(dem)g(demo)q(dulates)h(the)f(tones)g(in)o(to)f(the)h
(original)e(stream)i(of)g(data.)-764 146 y(12)-998 b
12 @eop1

13 @bop0
@F6 @sf
[<
387CFEFEFE7C38>
	 7 7 -4 6 15] 46 @dc

13 @eop0
 0 0 13 @bop1 195 w @F8 @sf(In)16 b(practice,)e(mo)q(dems)i
(are)e(used)i(in)f(t)o(w)o(o)f(distinct)h(w)o(a)o(ys:)j(A\))d(File)f(T)l
(ransfer)h(and)h(B\))f(T)l(elecomputing.)-1826 102 y(When)f(used)f
(strictly)f(for)h(\014le)g(transfer,)g(mo)q(dems)g(are)g(used)h(in)f(a)g
(fashion)f(similar)g(to)g(the)i(w)o(a)o(y)e(that)g(man)o(y)h(la)o(w)-1951 
56 y(\014rms)18 b(no)o(w)f(use)h(telcopier)f(mac)o(hines.)27 b(One)18 b
(computer)g(op)q(erator)f(calls)g(another)g(op)q(erator)g(and)h(they)f
(agree)-1950 56 y(to)h(transfer)g(a)g(\014le.)30 b(Both)19 b(op)q(erators)e
(set)i(up)g(the)g(mo)q(dems,)g(transmit)e(the)i(\014le)f(and)h(then)g(sh)o
(ut)f(do)o(wn)h(the)-1950 57 y(mo)q(dems,)c(usually)f(disconnecting)i
(them)f(from)f(the)h(phone)h(lines.)-1167 101 y(When)i(used)f(in)g(this)g
(manner,)g(the)h(t)o(w)o(o)d(computer)j(op)q(erators)e(are)h(essen)o
(tially)e(authen)o(ticating)h(eac)o(h)h(other)-1950 57 y(o)o(v)o(er)f(the)g
(telephone.)24 b(\(\\Hi,)15 b(Sam?)24 b(This)16 b(is)g(Jean.")24 b(\\Hi)
16 b(Jean.)24 b(I'v)o(e)16 b(got)g(Chris')f(\014le)h(to)g(send.")24 b
(\\Ok,)16 b(send)-1949 56 y(it.)j(Ha)o(v)o(e)13 b(a)g(nice)i(da)o(y)l(."\))j
(If)c(one)g(op)q(erator)f(didn't)h(recognize)g(or)f(had)h(doubts)g(ab)q
(out)g(the)f(other)h(op)q(erator,)f(the)-1950 57 y(transfer)g(w)o(ouldn't)f
(pro)q(ceed)i(un)o(til)f(the)g(questions)g(had)h(b)q(een)h(resolv)o(ed.)j
(This)13 b(system)g(is)g(called)g(attended)h(\014le)-1950 56 y(transfer.)
-167 102 y(Mo)q(dems)d(can)g(also)f(b)q(e)i(used)g(for)f(unattended)g(\014le)h
(transfer,)f(whic)o(h)g(is)f(really)g(a)h(sp)q(ecial)g(case)g(of)g
(telecomputing.)-1951 101 y(In)18 b(telecomputing,)g(one)g(or)f(more)h(of)f
(the)h(mo)q(dems)g(in)o(v)o(olv)o(ed)f(in)g(op)q(erated)h(without)f(h)o
(uman)h(in)o(terv)o(en)o(tion.)o -1951 57 a(In)h(this)e(con\014guration,)g
(a)h(computer)g(is)f(equipp)q(ed)i(with)f(a)f(mo)q(dem)h(capable)g(of)g
(automati)o(cally)e(answ)o(ering)-1951 56 y(a)j(ringing)g(telephone)h
(line.)32 b(Suc)o(h)20 b(mo)q(dems)g(are)f(called)g(AA)h(\(for)e(\\auto)h
(answ)o(er"\))f(mo)q(dems.)33 b(When)20 b(the)-1950 56 y(phone)14 b
(rings,)e(the)i(computer)f(answ)o(ers.)18 b(After)13 b(the)h(mo)q(dem)f
(answ)o(ers)f(the)i(caller)e(is)h(required)g(to)g(authen)o(ticate)-1951 
57 y(himself)h(to)h(the)g(computer)g(system)f(\(at)g(least,)g(this)g(is)h
(the)g(case)g(when)g(a)g(secure)g(computer)g(system)g(is)f(used\),)-1950 
56 y(after)g(whic)o(h)h(the)h(caller)e(is)h(allo)o(w)n(ed)f(to)h(use)h
(the)f(computer)g(system)g(or)f(p)q(erform)h(\014le)h(transfer.)-1678 102 y
(In)i(most)e(con\014gurations,)g(the)h(computer)g(system)f(do)q(es)h(not)g
(authen)o(ticate)f(itself)g(to)g(the)h(caller,)f(creating)g(a)-1950 56 y
(p)q(oten)o(tial)e(for)g(T)l(ro)s(jan)h(horse)g(programs)f(to)g(b)q(e)i
(used)g(b)o(y)f(sub)o(v)o(erters)g(\(see)g(ab)q(o)o(v)o(e\).)-1467 102 y
(AA)g(mo)q(dems)g(answ)o(er)g(the)g(telephone)g(with)f(a)h(distinctiv)o(e)f
(tone.)19 b(If)c(a)g(crac)o(k)o(er)f(dials)g(an)h(AA)g(mo)q(dem,)g(either)
-1950 56 y(b)o(y)c(acciden)o(t)h(or)f(as)g(the)g(result)g(of)g(an)h(delib)q
(erate)f(searc)o(h,)h(the)f(tone)h(is)f(lik)o(e)f(a)h(neon)h(sign)f(in)o
(viting)f(the)i(crac)o(k)o(er)f(to)-1951 57 y(try)i(his)g(luc)o(k.)19 b(F)l
(ortunately)l(,)12 b(most)g(m)o(ulti-user)g(op)q(erating)h(systems)g(are)f
(robust)h(enough)h(to)e(stand)h(up)h(to)f(ev)o(en)-1950 56 y(the)18 b
(most)f(p)q(ersisten)o(t)g(crac)o(k)o(ers.)27 b(Most)17 b(p)q(ersonal)g
(computers)h(are)g(not)f(so)g(robust,)h(although)f(this)g(dep)q(end)q(s)
-1949 57 y(on)d(the)h(particular)e(soft)o(w)o(a)o(re)g(b)q(eing)i(used.)
20 b(Lea)o(ving)14 b(a)g(PC)g(unattended)h(running)f(a)g(\014le-transfer)g
(program)f(is)-1950 56 y(an)i(in)o(vitatio)o(n)f(for)h(an)o(y)g(calling)f
(crac)o(k)o(er)g(to)h(tak)o(e)g(ev)o(ery)g(\014le)g(on)g(the)h(mac)o(hine)f
(he)g(can)h(\014nd,)f(esp)q(ecially)g(if)g(the)-1950 56 y(\014le-transfer)f
(program)f(uses)i(a)f(w)o(ell)g(kno)o(wn)g(proto)q(col)f(and)i(do)q(es)g
(not)f(require)g(the)h(user)g(to)e(t)o(yp)q(e)i(a)f(passw)o(ord.)-1951 57 y
(The)g(only)f(securit)o(y)g(eviden)o(t)g(is)g(the)h(obscurit)o(y)e(of)i
(the)f(telephone)h(n)o(um)o(b)q(er,)g(whic)o(h)f(ma)o(y)g(not)g(b)q(e)h(v)o
(ery)g(obscure)-1950 56 y(at)h(all,)e(and)j(of)e(the)i(\014le)f(transfer)f
(program's)g(proto)q(col.)-981 165 y @F6 @sf(16.1.1)52 b(Call)16 b(bac)o
(k)i(and)g(passw)o(ord)e(mo)q(dems)-933 131 y @F8 @sf(Mo)q(dem)e(man)o
(ufactures)g(ha)o(v)o(e)g(attempted)f(t)o(w)o(o)g(strategies)g(to)h(mak)o
(e)f(AA)i(mo)q(dems)f(more)g(secure:)20 b(passw)o(ords)-1951 57 y(and)15 b
(call)g(bac)o(k.)-276 101 y(When)h(calling)e(a)h(passw)o(ord)g(mo)q(dem,)g
(the)g(user)h(m)o(ust)f(\014rst)g(t)o(yp)q(e)g(a)h(passw)o(ord)e(b)q
(efore)i(the)f(mo)q(dem)h(will)e(pass)-1950 57 y(data)i(to)g(the)h(host)f
(computer.)24 b(The)17 b(issues)f(in)o(v)o(olv)o(ed)f(in)i(breaking)f(in)o
(to)f(a)i(computer)f(system)g(protected)h(b)o(y)-1950 56 y(passw)o(ord)f
(mo)q(dems)i(are)f(the)g(same)g(as)g(in)g(breaking)g(in)o(to)f(a)h
(computer)g(system)g(whic)o(h)g(requires)g(that)g(users)-1950 56 y(en)o
(ter)e(passw)o(ords)f(b)q(efore)i(logging)d(in.)279 216 y(13)-998 b
13 @eop1

14 @bop0
@F3 @sf
[<
FFFFF0FFFFF07FFFF03FFFF01FFFF00FFFF00E003807001803801801C01800E01800700000
3800003E00001F00000F800007C00007E00003F00003F00003F83803F87C01F8FE01F8FE03
F8FE03F8FE03F07C07F07007E03C1FC00FFF0003FC00>
	 21 32 -3 31 28] 50 @dc
[<
0003FE0000001FFFC00000FF00F00001F800380003F0000C0007C00006000F800003001F80
0003003F000003803F000001807F000001807E000001807E00000000FE00000000FE000000
00FE00000000FE00000000FE00000000FE00000000FE00000000FE000000007E000001807E
000001807F000001803F000003803F000003801F800007800F8000078007C0000F8003E000
1F8001F8003F8000FF01E380001FFF81800003FE0080>
	 33 34 -3 33 40] 67 @dc
[<
FFE00000FFE000001F0000001F0000001F0000001F0000001F0000001F0000001F0000001F
0000001F0FC0001F3FF8001FE0FC001FC03E001F803F001F001F801F001F801F000FC01F00
0FC01F000FC01F000FC01F000FC01F000FC01F000FC01F000FC01F001F801F001F801F001F
001F803E001FF07C00FF3FF800FF0FE000>
	 26 32 -2 21 31] 112 @dc
[<
01FC3FC007FF3FC00F81BE001F00FE001F007E001F003E001F003E001F003E001F003E001F
003E001F003E001F003E001F003E001F003E001F003E001F003E001F003E001F003E001F00
3E001F003E00FF01FE00FF01FE00>
	 26 22 -2 21 31] 117 @dc
[<
00F80003FE0007C3000F83000F81800F81800F81800F81800F81800F80000F80000F80000F
80000F80000F80000F80000F80000F80000F80000F8000FFFF00FFFF003F80000F80000780
00078000038000038000018000018000018000018000>
	 17 32 -1 31 22] 116 @dc
[<
FFF000FFF0001F00001F00001F00001F00001F00001F00001F00001F00001F00001F00001F
00001F00001F00001F83C01E87E01E87E01EC7E01E67E0FE3FC0FE1F00>
	 19 22 -2 21 23] 114 @dc
[<
FFF00000C0FFF00001C006000003C006000003C006000007C00600000FC00600001FC00600
003FC00600007FC00600007FC0060000FFC0060001FEC0060003FCC0060007F8C0060007F0
C006000FF0C006001FE0C006003FC0C006007F80C00600FF00C00600FE00C00601FE00C006
03FC00C00607F800C0060FF000C0060FE000C0061FE000C0063FC000C0067F8000C006FF00
00C007FE0000C007FC0000C0FFFC001FFEFFF8001FFE>
	 39 34 -2 33 44] 78 @dc
[<
001800C000003800E000003C01E000007C01F000007E03F000007E03F00000FE03D80000FB
07D80001FB079C0001F38F8C0001F18F0C0003E18F060003E0DF060007E0DE070007C0DE03
0007C07E03000F807C01800F807C01800F807801801F007800C0FFE7FF07F8FFE7FF07F8>
	 37 22 -1 21 40] 119 @dc
[<
FFE0FFC0FFE0FFC01F003C001F007C001F00F8001F01F0001F01E0001F03E0001F07C0001F
0F80001FCF00001FFF00001F7E00001F1C00001F0E00001F0700001F0380001F01C0001F00
60001F0038001F00FF801F00FF801F0000001F0000001F0000001F0000001F0000001F0000
001F0000001F0000001F0000001F0000001F000000FF000000FF000000>
	 26 35 -2 34 30] 107 @dc

14 @eop0

0 0 14 @bop1 195 w @F8 @sf(A)15 b(go)q(o)q(d)h(passw)o(ord)e(mo)q(dem)i
(has)f(a)g(passw)o(ord)g(for)f(ev)o(ery)i(user)f(and)h(records)f(the)h
(times)e(that)h(eac)o(h)g(user)h(calls)-1951 57 y(in,)h(but)g(most)f
(passw)o(ord)g(mo)q(dems)h(only)g(ha)o(v)o(e)f(one)i(passw)o(ord.)24 b(F)l
(or)16 b(most)g(op)q(erating)h(systems)f(a)h(passw)o(ord)-1951 56 y(mo)q
(dem)e(is)g(o)o(v)o(erkill,)o 14 x(since)h(the)f(op)q(erating)g(system)g
(pro)o(vides)f(its)h(o)o(wn)g(passw)o(ord)f(and)i(accoun)o(ting)e
(facilities,)o -1951 56 a(or)i(useless,)h(since,)g(an)o(y)f(functionalit)o
(y)f(whic)o(h)h(a)h(passw)o(ord)e(mo)q(dem)i(pro)o(vides)f(can)h(b)q(e)g
(implemen)o(ted)g(b)q(etter)-1950 57 y(b)o(y)j(programs)g(running)g(on)h
(a)f(computer)g(whic)o(h)g(a)g(non-passw)o(ord)g(mo)q(dem)h(is)f(attac)o
(hed)g(to.)35 b(But)20 b(for)g(an)-1950 56 y(unattended)f(micro)q
(computer)f(p)q(erforming)g(\014le)g(transfer,)g(a)h(passw)o(ord)e(mo)q
(dem)i(ma)o(y)e(b)q(e)j(the)e(only)g(w)o(a)o(y)g(to)-1951 57 y(ac)o(hiev)o
(e)d(a)g(marginal)e(lev)o(el)i(of)g(securit)o(y)l(.)-705 101 y(A)c(call)f
(bac)o(k)g(mo)q(dem)h(is)g(lik)o(e)f(a)g(passw)o(ord)g(mo)q(dem,)i(in)e
(that)g(it)g(requires)h(the)g(caller)f(to)g(t)o(yp)q(e)h(in)g(a)f
(preestablished)-1950 57 y(passw)o(ord.)26 b(The)18 b(di\013erence)g(is)f
(that)g(a)g(call)g(bac)o(k)g(mo)q(dem)h(then)g(hangs)f(up)h(on)g(the)g
(caller)e(and)i(then)g(\\calls)-1951 56 y(bac)o(k")c({)g(the)g(mo)q(dem)h
(dials)e(the)h(phone)h(n)o(um)o(b)q(er)g(asso)q(ciated)e(with)h(the)g
(passw)o(ord.)19 b(The)14 b(idea)h(is)e(that)h(ev)o(en)g(if)-1950 57 y(a)h
(crac)o(k)o(er)f(learns)h(the)g(passw)o(ord,)f(he)i(cannot)f(use)g(the)h
(mo)q(dem)f(b)q(ecause)h(it)f(w)o(on't)f(call)g(him)h(bac)o(k.)-1756 101 y
(In)22 b(practice,)g(shortcomings)e(in)h(the)g(telephone)h(system)e(mak)o
(e)h(call)f(bac)o(k)h(mo)q(dems)h(are)e(no)i(more)e(secure)-1949 57 y
(than)f(passw)o(ord)g(mo)q(dems.)33 b(Most)19 b(telephone)h(exc)o(hanges)g
(are)f(\\caller)f(con)o(trolled,")h(whic)o(h)h(means)f(that)g(a)-1950 56 y
(connection)11 b(is)f(not)g(brok)o(en)g(un)o(til)g(the)g(caller)g(hangs)g
(up.)19 b(If)11 b(the)f(crac)o(k)o(er,)h(after)f(en)o(tering)f(the)i
(correct)f(passw)o(ord,)-1951 56 y(do)q(esn't)j(hang)g(up,)h(the)f(mo)q
(dem)g(will)f(attempt)g(to)h(\\hang)g(up,")g(pic)o(k)g(up)h(the)f(phone,)h
(dial)e(and)i(connect)f(to)g(the)-1950 57 y(crac)o(k)o(er's)i(mo)q(dem)h
(\(since)g(the)g(connection)g(w)o(as)g(nev)o(er)g(dropp)q(ed\).)23 b(A)16 b
(few)g(mo)q(dems)g(will)f(not)h(b)q(eing)g(dialing)-1951 56 y(un)o(til)e
(they)i(hear)f(a)g(dial)f(tone,)h(but)g(this)g(is)f(easily)h(o)o(v)o
(ercome)f(b)o(y)h(pla)o(ying)f(a)h(dial)f(tone)h(in)o(to)g(the)g
(telephone.)-1914 102 y(The)k(idea)f(of)g(call)g(bac)o(k)g(can)h(b)q(e)g
(made)g(substan)o(tiall)o(y)e(more)i(secure)g(b)o(y)f(using)g(t)o(w)o(o)g
(mo)q(dems,)h(so)f(that)g(the)-1950 56 y(returned)f(call)f(is)g(made)g(on)g
(a)h(di\013eren)o(t)e(telephone)i(line)f(than)h(the)f(original)f(call)g
(is)h(receiv)o(ed)h(on.)24 b(Call)15 b(bac)o(k)-1950 57 y(of)h(this)g(t)o
(yp)q(e)h(m)o(ust)e(b)q(e)j(implemen)o(ted)e(b)o(y)g(the)h(op)q(erating)e
(system)i(rather)e(than)i(the)f(mo)q(dem.)24 b(Tw)o(o)16 b(mo)q(dem)-1950 
56 y(call)e(bac)o(k)h(is)g(also)f(defeatable)h(b)o(y)g(use)h(of)f(the)g
(\\ring)f(windo)o(w,")g(explained)h(b)q(elo)o(w:)-1461 102 y(Ho)o(w)j(man)o
(y)h(times)f(ha)o(v)o(e)h(y)o(ou)f(pic)o(k)o(ed)h(up)h(the)f(telephone)g
(to)f(disco)o(v)o(er)g(someone)h(at)f(the)h(other)g(end?)33 b(The)-1950 
56 y(telephone)19 b(system)e(will)g(connect)i(the)f(caller)f(b)q(efore)i
(it)e(rings)h(the)g(called)g(part)o(y's)f(b)q(ell)h(if)g(the)g(telephone)g
(is)-1950 57 y(pic)o(k)o(ed)e(up)g(within)e(a)i(brief)f(p)q(erio)q(d)h(of)f
(time,)f(called)i(the)f(\\ring)g(windo)o(w.")20 b(That)15 b(is)g({)g(when)h
(a)f(computer)h(\(or)-1951 56 y(p)q(erson\))j(pic)o(ks)f(up)h(a)g(silen)o
(t)e(telephone,)j(there)e(is)h(no)f(w)o(a)o(y)g(to)g(guaran)o(tee)g(that)g
(there)g(will)g(b)q(e)h(no)g(part)o(y)f(at)-1951 56 y(the)f(other)g(end)h
(of)f(the)h(line.)26 b(There)17 b(is)g(no)h(theoretical)e(w)o(a)o(y)g
(around)h(the)h(ring)f(windo)o(w)f(problem)h(with)g(the)-1950 57 y(curren)o
(t)i(telephone)g(system,)g(but)g(the)g(problem)g(can)g(b)q(e)g(substan)o
(tially)e(minimized)i(b)o(y)g(programmi)o(ng)f(the)-1950 56 y(dialout-mo)q
(dem)c(to)h(w)o(ait)f(a)h(random)f(amoun)o(t)h(of)g(time)f(b)q(efore)i
(returning)e(the)i(call.)-1492 102 y(The)f(principle)f(adv)m(an)o(tage)f
(of)h(a)g(call)g(bac)o(k)g(mo)q(dem)h(is)e(that)h(it)g(allo)o(w)o(s)f(the)i
(exp)q(ense)g(of)f(the)g(telephone)h(call)f(to)-1951 56 y(b)q(e)j
(incurred)g(at)e(the)i(computer's)e(end,)i(rather)f(than)g(at)g(the)g
(callers)f(end.)24 b(One)17 b(w)o(a)o(y)e(to)h(minimize)f(telecom-)-1950 
57 y(m)o(unication)f(costs)h(migh)o(t)f(b)q(e)i(to)e(install)g(a)h(call)f
(bac)o(k)h(mo)q(dem)g(with)g(a)g(W)-5 b(A)l(TS)15 b(line.)-1490 101 y(In)j
(general,)e(b)q(oth)h(passw)o(ord)f(and)h(call)g(bac)o(k)f(mo)q(dems)h
(represen)o(t)g(exp)q(ensiv)o(e)h(equipmen)o(t)f(with)f(little)g(or)g(no)
-1950 57 y(practical)e(v)m(alue.)21 b(They)15 b(are)g(b)q(ecoming)g(p)q
(opular)h(b)q(ecause)g(mo)q(dem)f(companies,)g(pla)o(ying)f(on)h(p)q
(eople's)h(fears,)-1951 56 y(are)f(making)f(them)h(p)q(opular)g(with)g
(adv)o(ertising.)-856 167 y @F3 @sf(16.2)56 b(Computer)18 b(Net)n(w)n
(orks)-653 131 y @F8 @sf(A)c(net)o(w)o(ork)g(allo)o(w)o(s)f(sev)o(eral)h
(computers)g(to)g(exc)o(hange)g(data)g(and)g(share)g(devices,)h(suc)o(h)g
(as)f(laser)f(prin)o(ters)h(and)-1950 56 y(tap)q(e)c(driv)o(es.)18 b
(Computer)10 b(net)o(w)o(orks)g(can)g(b)q(e)h(small,)f(consisting)f(of)h
(t)o(w)o(o)f(computers)i(connected)g(b)o(y)f(a)g(serial)g(line,)-999 146 y
(14)-998 b
14 @eop1

15 @bop0
@F2 @sf
[<
FFFFFFFFF0FFFFFFFFF0FFFFFFFFF003FC001FF803FC0003F803FC0001F803FC0000F803FC
00007803FC00003803FC00003C03FC00001C03FC00001C03FC00001C03FC01C01C03FC01C0
0E03FC01C00E03FC01C00E03FC03C00003FC03C00003FC0FC00003FFFFC00003FFFFC00003
FFFFC00003FC0FC00003FC03C00003FC03C00003FC01C03803FC01C03803FC01C03803FC01
C07803FC00007003FC00007003FC00007003FC0000F003FC0001F003FC0001F003FC0007F0
03FC001FE0FFFFFFFFE0FFFFFFFFE0FFFFFFFFE0>
	 39 41 -3 40 45] 69 @dc
@F3 @sf
[<
01E00003F00003F00003F00003F00003F00003F00003F00001F00001F00001F00000F00000
F00000F000007800007800003800001800001C00000C00000600C00300C00300C00180E000
C0E000607FFFF07FFFF87FFFF87FFFFC7FFFFE7FFFFE780000600000>
	 23 34 -3 33 28] 55 @dc
[<
0000E0000E00000000E0000E00000000F0001E00000001F0001F00000001F0001F00000003
F8003F80000003F8003F80000003FC007F80000007FC007FC0000007FC007FC000000FF600
FFE000000FE600FE6000000FE600FE6000001FE301FC3000001FC301FC3000001FC383FC30
00003F8183F81800003F8183F81800007F80C7F81C00007F00C7F00C00007F00C7F00C0000
FF006FE0060000FE006FE0060000FE007FE0060001FC003FC0030001FC003FC0030003FC00
3F80038003F8003F80018003F8007F80018007F0007F0000C007F0007F0000C00FF000FF00
00E0FFFF0FFFF01FFEFFFF0FFFF01FFE>
	 55 34 -1 33 58] 87 @dc
[<
FFE1FFC0FFE1FFC01F003E001F003E001F003E001F003E001F003E001F003E001F003E001F
003E001F003E001F003E001F003E001F003E001F003E001F003E001F803E001F803E001F40
3C001F307C001F1FF8001F07E0001F0000001F0000001F0000001F0000001F0000001F0000
001F0000001F0000001F0000001F0000001F000000FF000000FF000000>
	 26 35 -2 34 31] 104 @dc
[<
07E03F1FF87F7E0CF87E02F0FC01F0FC01F0FC01F0FC01F07E01F03F01F01FC1F003FDF000
3FF00001F00001F01E01F03F01F03F01E03F03E03F07C01FFF8007FC00>
	 24 22 -2 21 27] 97 @dc
[<
FFE0FFE01F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F
001F00FF00FF0000000000000000000000000000001C003E007F007F007F003E001C00>
	 11 36 -2 35 16] 105 @dc
[<
FFE1FFC0FFE1FFC01F003E001F003E001F003E001F003E001F003E001F003E001F003E001F
003E001F003E001F003E001F003E001F003E001F003E001F003E001F803E001F803E001F40
3C001F307C00FF1FF800FF07E000>
	 26 22 -2 21 31] 110 @dc
[<
00FE0007FF800FC0E01F00603E00307E00007E00007C0000FC0000FC0000FC0000FC0000FC
0000FC00007C00007C01E07E03F03E03F01F03F00F83F007FFE000FF80>
	 20 22 -2 21 25] 99 @dc
[<
1F0000007F80000069C00000FC600000FC300000FC3800007818000000180000000C000000
0C0000000E0000000E0000001F0000001F0000003F8000003F8000007FC000007CC000007C
C00000F8600000F8600001F0300001F0300003E0180003E0180007E01C0007C00C000FC00E
000F8006000F800600FFE01FE0FFE01FE0>
	 27 32 -1 21 30] 121 @dc
[<
01C00003E00007F00007F00007F00003E00001C00000000000000000000000000000000000
C00000C00000C00000C00000C00000C00000E00000E000007000007800003C00001F00001F
80000FC07807E0FC07E0FC07E0FC07E0F807E07007C0380F801FFF0007FC00>
	 19 35 -3 34 26] 63 @dc
@F8 @sf
[<
000003E0FFFC0F100FC01E0807803E0407807E0407807C0407807C0007807C0007807C0007
8078000780780007807800078070000780F0000780E0000781C00007FF80000780F0000780
780007803C0007801E0007801E0007801F0007801F0007801F0007801F0007801E0007801E
0007803C00078078000F80F000FFFF8000>
	 30 32 -2 30 33] 82 @dc
/@F5 @newfont
@F5 @sf
[<
7F07F0FF8FF87F07F01C01C01C01C00E03800E03800FFF800FFF800FFF8007070007070007
0700070700030600038E00038E00038E00038E00018C0001DC0001DC0001DC0000D80000D8
0000F80000F800007000>
	 21 28 -1 27 24] 65 @dc
[<
FE03F8FE03F8FE03F83800E03800E03800E03800E03800E03800E03870E03870E038F8E038
D8E038D8E039DCE039DCE039DCE0398CE0398CE03B8EE03B8EE03B06E03B06E03B06E03B06
E0FE03F8FE03F8FC01F8>
	 21 28 -1 27 24] 77 @dc
[<
FFFFF8FFFFF8FFFFF81C00381C00381C00381C00381C00381C00001C00001C0E001C0E001C
0E001FFE001FFE001FFE001C0E001C0E001C0E001C00001C00001C00701C00701C00701C00
70FFFFF0FFFFF0FFFFF0>
	 21 28 -1 27 24] 69 @dc
[<
7F00F0FF81F87F01F81C039C1C039C1C039C1C03801C03801C03801C03801C03801C07001C
0F001FFE001FFE001FFF001C0F801C03801C03C01C01C01C01C01C01C01C03C01C03801C0F
807FFF00FFFE007FF800>
	 22 28 -1 27 24] 82 @dc
[<
7FFF00FFFF807FFF0001C00001C00001C00001C00001C00001C00001C00001C00001C00001
C00001C00001C00001C00001C00001C00001C00001C00001C00001C00001C00001C00001C0
007FFF00FFFF807FFF00>
	 17 28 -3 27 24] 73 @dc
[<
00F80003FE0007FF800F07C01E01C03C00E03800E07000E07000E0700000E00000E00000E0
0000E00000E00000E00000E00000E000007000007000E07000E03800E03C01E01E03E00F07
E007FFE003FEE000F8E0>
	 19 28 -2 27 24] 67 @dc

15 @eop0

0 0 15 @bop1 195 w @F8 @sf(or)15 b(v)o(ery)g(large,)f(consisting)g(of)g(h)o
(undreds)j(or)d(thousands)h(of)g(systems.)20 b(One)c(net)o(w)o(ork,)e(the)h
(Arpanet,)g(consists)-1951 57 y(of)i(thousands)h(of)f(computers)h(at)f
(univ)o(ersities,)g(corp)q(orations)f(and)i(go)o(v)o(ernmen)o(t)e
(installati)o(ons)g(all)h(o)o(v)o(er)g(the)-1950 56 y(United)i(States.)30 b
(Among)19 b(other)f(functions,)i(the)f(Arpanet)g(allo)o(w)o(s)f(users)h
(of)f(an)o(y)h(net)o(w)o(ork)o(ed)f(computer)h(to)-1951 56 y(transfer)12 b
(\014les)g(or)g(exc)o(hange)h(electronic)f(mail)f(with)g(users)i(at)f(an)o
(y)g(other)g(net)o(w)o(ork)o(ed)f(computer.)19 b(The)13 b(Arpanet)-1950 
57 y(also)k(pro)o(vides)g(a)g(service\))g(b)o(y)g(whic)o(h)h(a)f(user)h
(of)f(one)g(computer)h(can)g(log)e(on)o(to)h(another)g(computer,)h(ev)o
(en)f(if)-1950 56 y(the)e(other)g(computer)g(is)g(sev)o(eral)f(thousand)i
(miles)e(a)o(w)o(a)o(y)l(.)-1017 102 y(It)j(is)f(utilit)o(y)f(of)h(the)h
(net)o(w)o(ork)f(whic)o(h)g(presen)o(ts)h(p)q(oten)o(tial)e(securit)o(y)h
(problems.)25 b(A)16 b(\014le)h(transfer)f(facilit)o(y)f(can)-1950 56 y(b)q
(e)f(used)g(to)f(steal)g(\014les,)h(remote)f(access)g(can)h(b)q(e)g(used)g
(to)f(steal)g(computer)h(time.)k(A)c(sp)o(y)f(lo)q(oking)g(for)g(a)g(w)o
(a)o(y)g(to)-1951 57 y(remo)o(v)o(e)g(a)h(classi\014ed)g(\014le)g(from)g
(a)g(secure)g(installati)o(on)f(migh)o(t)g(use)h(the)h(net)o(w)o(ork)e(to)g
(\\mail")g(the)h(do)q(cumen)o(t)h(to)-1951 56 y(someb)q(o)q(dy)g(outside)g
(the)g(building.)k(Unrestricted)14 b(remote)h(access)g(to)f(resources)h
(suc)o(h)g(as)f(disks)h(and)g(prin)o(ters)-1951 57 y(places)i(these)g
(devices)g(at)f(the)h(mercy)g(of)f(the)h(other)f(users)h(of)f(the)h(net)o
(w)o(ork.)24 b(A)16 b(substan)o(tial)g(amoun)o(t)f(of)i(the)-1950 56 y
(Arpanet's)12 b(system)g(soft)o(w)o(ar)o(e)f(is)h(dev)o(oted)h(to)f
(enforcing)g(securit)o(y)f(and)i(protecting)e(users)i(of)f(the)g(net)o(w)o
(ork)g(from)-1951 57 y(eac)o(h)j(other.)-219 101 y(In)20 b(general,)f
(computer)g(net)o(w)o(orks)f(can)h(b)q(e)h(divided)f(in)o(to)f(t)o(w)o(o)f
(classes:)28 b(those)18 b(that)h(are)f(ph)o(ysically)g(secure)-1949 56 y
(and)d(those)f(that)h(are)f(not.)19 b(A)c(ph)o(ysically)f(secure)h(net)o
(w)o(ork)f(is)g(a)h(net)o(w)o(ork)e(in)i(whic)o(h)g(the)f(managemen)o(t)g
(kno)o(ws)-1950 57 y(the)i(details)f(of)g(ev)o(ery)h(computer)g(connected)g
(at)g(all)e(times.)21 b(An)c(insecure)f(net)o(w)o(ork)f(is)g(one)h(in)g
(whic)o(h)f(priv)m(ate)-1950 56 y(agen)o(ts,)k(emplo)o(y)o(ees,)h(sab)q
(oteurs)f(and)h(crac)o(k)o(ers)f(are)g(free)h(to)e(add)i(equipmen)o(t.)33 b
(F)l(ew)19 b(net)o(w)o(orks)g(are)g(totall)o(y)-1951 57 y(insecure.)-172 
188 y @F2 @sf(17)69 b(Encryption)-471 148 y @F3 @sf(17.1)56 b(What)18 b
(is)h(encryption?)-658 131 y @F8 @sf(The)j(goal)e(of)h(encryption)h(is)f
(to)g(translate)f(a)h(message)g(\(the)h(\\plain)o(text")o(\))e(in)o(to)h
(a)g(second)h(message)f(\(the)-1950 56 y(\\cyphertext"\))c(whic)o(h)h(is)g
(unreadable)g(without)f(the)h(p)q(ossession)g(of)f(additional)g(informati)o
(on.)27 b(This)17 b(trans-)-1950 57 y(lation)g(is)h(p)q(erformed)g(b)o(y)g
(a)g(mathematical)f(function)h(called)f(the)i(encryption)f(algorit)o(hm.)
28 b(The)18 b(additional)-1951 56 y(informatio)o(n)12 b(is)g(kno)o(wn)g
(as)g(the)g(\\k)o(ey)l(.")19 b(In)13 b(most)f(encryption)g(systems,)g(the)h
(same)f(k)o(ey)g(is)g(used)h(for)f(encryption)-1950 57 y(as)j(for)f
(decryption.)-349 101 y(Encryption)i(allo)o(ws)e(the)i(con)o(ten)o(t)g(of)g
(the)g(message)g(to)f(remain)h(secure)g(ev)o(en)h(if)e(the)i(cyphertext)f
(is)g(stored)f(or)-1950 57 y(transmitted)e(via)g(insecure)h(metho)q(ds)h
(\(or)e(ev)o(en)h(made)g(publicly)g(a)o(v)m(ailable\).)o 19 x(The)g
(securit)o(y)f(in)h(suc)o(h)h(a)e(system)-1950 56 y(resides)j(in)f(the)h
(strength)f(of)g(the)h(encryption)f(system)h(emplo)o(y)o(ed)f(and)h(the)f
(securit)o(y)g(of)h(the)f(k)o(ey)l(.)22 b(In)16 b(an)g(ideal)-1951 57 y
(cryptographic)e(system,)h(the)g(securit)o(y)g(of)f(the)i(message)e
(resides)h(en)o(tirely)g(in)g(the)g(secrecy)h(of)f(the)g(k)o(ey)l(.)-1810 
101 y(When)e(Julius)f(Caeser)g(sen)o(t)h(his)f(rep)q(orts)g(on)g(the)h
(Gallic)e(W)l(ars)h(bac)o(k)g(to)g(Rome,)h(he)g(w)o(an)o(ted)e(the)i(con)o
(ten)o(t)f(of)g(the)-1950 56 y(rep)q(orts)j(to)f(remain)h(secret)g(un)o
(til)f(they)h(reac)o(hed)g(Rome)g(\(where)g(his)g(con\014dan)o(ts)g(w)o
(ould)g(presumably)f(b)q(e)i(able)-1950 57 y(to)f(deco)q(de)i(them.\))k(T)l
(o)15 b(ac)o(hiev)o(e)h(this)f(end,)h(he)g(in)o(v)o(en)o(ted)f(an)h
(encrypted)g(system)g(no)o(w)f(kno)o(wn)g(as)g(the)h(Caeser)-1950 56 y
(Cipher.)k(The)c(Caeser)f(Cipher)g(is)g(a)g(simple)f(substitution)h
(cipher)g(in)g(whic)o(h)g(ev)o(ery)h(letter)e(of)h(the)g(plain)o(text)f
(is)-1950 57 y(substituted)h(with)f(the)i(letter)e(three)h(places)g
(further)g(along)g(in)g(the)g(alphab)q(et.)20 b(Th)o(us,)15 b(the)g(w)o
(ord:)-1720 101 y @F5 @sf(AMERICA)784 191 y @F8 @sf(15)-998 b
15 @eop1

16 @bop0
@F5 @sf
[<
7FF800FFFE007FFF001C0F801C03C01C01C01C01E01C00E01C00E01C00F01C00701C00701C
00701C00701C00701C00701C00701C00701C00F01C00E01C00E01C01E01C03C01C03C01C0F
807FFF00FFFE007FF800>
	 20 28 -1 27 24] 68 @dc
[<
000700000700000F00000E00001E00001C000FFC003FFE007FFF00787F0070F700F0E780E1
E380E1E380E00380E00380E00380E00380E00380E00380E00380E00380E00380E00380E003
80E00380E00380E00380F00780700700780F007FFF003FFE000FF800>
	 17 34 -3 27 24] 81 @dc
[<
7F07F0FF8FF87F07F01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C
01C01FFFC01FFFC01FFFC01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01C01
C07F07F0FF8FF87F07F0>
	 21 28 -1 27 24] 72 @dc
[<
007C0001FF0003FF800783C00F01E00E00E01C00701C00701C00701C00701C00701C00701C
00701C00701C00701C00701C00701C00701C00701C00701C00701C00701C00701C00701C00
70FF83FEFF83FEFF83FE>
	 23 28 0 27 24] 85 @dc
[<
7FFFF0FFFFF07FFFF00E00700E00700E00700E00700E00700E00000E00000E00000E00000E
00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E00
007FE000FFE0007FE000>
	 20 28 -1 27 24] 76 @dc
[<
FFC000FFC000FFC0001C00001C00001C00001C00001C00001C00001C00001C1C001C1C001C
1C001FFC001FFC001FFC001C1C001C1C001C1C001C00001C00001C00E01C00E01C00E01C00
E0FFFFE0FFFFE0FFFFE0>
	 19 28 -2 27 24] 70 @dc

16 @eop0

0 0 16 @bop1 195 w @F8 @sf(encrypts)15 b(as)-224 102 y @F5 @sf(DQHULFD)-168 
101 y @F8 @sf(The)g(\\k)o(ey")g(of)g(the)g(Caeser)g(Cipher)g(is)g(the)g(n)o
(um)o(b)q(er)h(of)f(letters)f(whic)o(h)h(the)h(plain)o(text)e(is)g
(shifted)h(\(three\);)g(the)-1950 56 y(encryption)c(algorithm)f(is)h(the)h
(rule)f(\\shift)g(all)f(letters)h(in)g(the)h(plain)o(text)e(b)o(y)h(the)h
(same)f(n)o(um)o(b)q(er)h(of)f(c)o(haracters.")-1951 57 y(The)i(Caeser)f
(Cipher)g(isn't)f(v)o(ery)h(secure:)19 b(if)12 b(the)g(algorithm)f(is)g
(kno)o(wn,)i(the)f(k)o(ey)g(is)g(deducible)h(b)o(y)g(a)f(few)g(rounds)-1950 
56 y(of)k(trail-and-error.)23 b(Additionally)l(,)o 16 x(the)17 b(algori)o
(thm)e(is)h(readily)g(determinable)g(b)o(y)h(lexigraphical)e(analysis)g
(of)-1950 57 y(the)k(cyphertext.)32 b(Recen)o(tly)l(,)20 b(the)g(author)e
(sen)o(t)h(a)g(p)q(ostcard)g(to)f(a)h(friend)g(whic)o(h)g(w)o(as)f
(encrypted)i(with)f(the)-1950 56 y(Caeser)f(Cipher)f(\(without)g(an)o(y)h
(informati)o(on)f(on)h(the)g(card)g(that)f(it)g(w)o(as)g(encrypted)i(or)e
(whic)o(h)h(system)g(w)o(as)-1951 57 y(used\):)i(the)15 b(p)q(ostcard)g(w)o
(as)g(deco)q(ded)h(in)f(\014v)o(e)h(min)o(utes.)-972 101 y(Mo)q(dern)11 b
(cryptograph)o(y)g(systems)f(assume)h(that)g(b)q(oth)g(the)g(encryption)g
(algorithm)f(and)h(the)g(complete)g(cypher-)-1949 57 y(text)i(are)f
(publicly)h(kno)o(wn.)19 b(Securit)o(y)13 b(of)g(the)g(plain)o(text)f(is)g
(ac)o(hiev)o(ed)h(b)o(y)g(securit)o(y)g(of)g(the)g(k)o(ey)l(.)19 b
(Cryptographic)-1951 56 y(k)o(eys)g(are)f(t)o(ypically)f(v)o(ery)i(large)e
(n)o(um)o(b)q(ers.)31 b(Since)19 b(p)q(eople)h(\014nd)f(it)f(easier)g(to)g
(remem)o(b)q(er)h(sequences)h(of)e(let-)-1950 57 y(ters)d(than)g(n)o(um)o
(b)q(ers,)g(most)f(cryptographic)h(systems)f(allo)o(w)g(the)h(user)h(to)e
(en)o(ter)h(an)g(alphab)q(etic)g(k)o(ey)g(whic)o(h)g(is)-1950 56 y
(translated)f(in)o(ternally)g(in)o(to)g(a)h(v)o(ery)g(large)f(n)o(um)o(b)q
(er.)-924 101 y(Ideally)l(,)i(it)f(should)g(b)q(e)i(imp)q(ossible)e(for)g
(a)h(sp)o(y)f(to)g(translate)g(the)h(cyphertext)g(bac)o(k)f(in)o(to)g
(plain)o(text)g(unless)h(he)-1950 57 y(is)i(in)g(p)q(ossession)g(of)g(the)h
(k)o(ey)l(.)30 b(In)19 b(practice,)f(there)h(are)f(a)g(v)m(ariet)o(y)g(of)g
(metho)q(ds)g(b)o(y)h(whic)o(h)f(cyphertext)h(can)-1950 56 y(b)q(e)f
(decrypted.)25 b(Breaking)17 b(cyphers)g(usually)f(in)o(v)o(olv)o(es)g
(detecting)g(regularities)g(within)g(the)h(cyphertext)g(and)-1950 57 y
(rep)q(eated)11 b(deco)q(ding)g(attempts)f(of)g(the)g(cyphertext)h(with)f
(di\013eren)o(t)g(k)o(eys.)18 b(This)10 b(pro)q(cess)h(requires)f
(considerable)-1950 56 y(amoun)o(ts)15 b(of)h(computer)g(time)g(and)g
(\(frequen)o(tly\))g(a)g(large)f(p)q(ortion)g(of)h(the)h(cyphertext.)23 b
(As)16 b(there)g(are)g(man)o(y)-1950 57 y(excellen)o(t)f(b)q(o)q(oks)g
(written)f(on)i(the)f(sub)s(ject)g(of)g(cryptograph)o(y)l(,)f(it)g(will)g
(not)h(b)q(e)h(explored)f(in)g(depth)h(here.)-1851 166 y @F3 @sf(17.2)56 b
(Wh)n(y)18 b(encryption?)-580 131 y @F8 @sf(Encryption)f(mak)o(es)h(it)f
(more)g(exp)q(ensiv)o(e)h(for)f(spies)h(to)f(steal)g(data,)g(since)h(ev)o
(en)g(after)f(the)h(data)f(is)h(stolen)f(it)-1951 57 y(m)o(ust)g(still)g
(b)q(e)h(decrypted.)29 b(Encryption)18 b(th)o(us)f(pro)o(vides)h(an)g
(additional)e(defense)j(la)o(y)o(er)d(against)h(data)g(theft)-1950 56 y
(after)d(other)h(securit)o(y)g(systems)g(ha)o(v)o(e)f(failed.)-790 102 y
(On)f(computer)e(systems)h(without)f(securit)o(y)l(,)h(suc)o(h)g(as)f
(o\016ce)h(IBM)h(PCs)e(shared)h(b)o(y)g(sev)o(eral)f(p)q(eople,)i
(encryption)-1950 56 y(is)19 b(a)h(means)g(for)f(pro)o(viding)g(priv)m
(acy)h(of)f(data)g(b)q(et)o(w)o(een)h(users.)34 b(Instead)21 b(of)e(cop)o
(ying)g(con\014den)o(tial)h(\014les)g(to)-1951 56 y(remo)o(v)m(able)d
(media,)h(users)f(can)h(simply)f(encrypt)h(their)f(\014les)h(and)g(lea)o
(v)o(e)e(them)i(on)g(the)f(PC's)g(hard)h(disk.)27 b(Of)-1950 57 y(course,)
16 b(the)f(\014les)h(m)o(ust)f(b)q(e)h(decrypted)h(b)q(efore)f(they)g(can)f
(b)q(e)i(used)f(again)f(and)h(encryption)f(of)h(\014les)f(do)q(es)h(not)
-1950 56 y(protect)f(them)g(from)f(deletion.)-550 102 y(Encryption)g(allo)o
(w)o(s)f(con\014den)o(tial)g(data)g(to)g(b)q(e)i(transmitted)e(via)g
(insecure)h(systems,)f(suc)o(h)i(as)e(telephone)h(lines)-1950 56 y(or)h(b)o
(y)h(courier.)21 b(Encryption)15 b(allo)o(ws)f(one)i(to)f(relax)g(other)g
(forms)g(of)h(securit)o(y)f(with)g(the)h(kno)o(wledge)f(that)g(the)-1950 
57 y(encryption)g(system)g(is)g(reasonably)f(secure.)169 428 y(16)-998 b
16 @eop1

17 @bop0
@F3 @sf
[<
01FE000FFFC01E07F07801F87E01FCFF00FCFF00FEFF00FEFF00FE7E00FE3C00FE0000FC00
00FC0001F80001F00007C001FF0001FE00001F800007C00003E00003F01F03F01F03F83F81
F83F81F83F81F83F03F01E03F00F07E007FFC000FE00>
	 23 32 -2 31 28] 51 @dc
[<
7FF8007FF8000F80000F80000F80000F80000F80000F80000F80000F80000F80000F80000F
80000F80000F80000F80000F80000F80000F80000F8000FFFC00FFFC000F80000F80000F80
000F80000F80000F80000F83C00F87E007C7E003C7E001E3E000FFC0003F80>
	 19 35 -1 34 17] 102 @dc
[<
FFFFFFFCFFFFFFFC07F001FC07F0003E07F0001E07F0000E07F0000E07F0000607F0000607
F0000607F0000307F0180307F0180307F0180007F0180007F0380007F0780007FFF80007FF
F80007F0780007F0380007F0180007F0180607F0180607F0180607F0000607F0000E07F000
0E07F0000C07F0001C07F0003C07F000FCFFFFFFFCFFFFFFFC>
	 32 34 -2 33 37] 69 @dc
@F3 @sf
[<
00FFFE00FFFE0007E00007E00007E00007E00007E00007E00007E0FFFFFEFFFFFEE007E070
07E03807E01807E00C07E00E07E00707E00307E00187E001C7E000E7E00077E00037E0001F
E0001FE0000FE00007E00003E00003E00001E00000E0>
	 23 32 -2 31 28] 52 @dc
[<
FFFF83FFFCFFFF83FFFC07F0003FC007F0007F8007F0007F0007F000FF0007F001FE0007F0
01FC0007F003F80007F007F80007F007F00007F00FE00007F01FE00007F01FC00007F83F80
0007FE7F800007F77F000007F3FE000007F1FE000007F0FC000007F038000007F018000007
F00E000007F007000007F003800007F001C00007F000E00007F000300007F000180007F000
0E0007F000070007F0000380FFFF803FFCFFFF803FFC>
	 38 34 -2 33 44] 75 @dc
[<
01FF000FFFE03F01F87C007C78003CF0001EF0001EF0001EF0001E70003E3800FC1FFFFC0F
FFF81FFFF03FFF8038000030000030000013FC001FFF001F0F803E07C03C03C07C03E07C03
E07C03E07C03E07C03E03C03C03E07CF1F0F8F0FFF7F03FC1E>
	 24 33 -2 21 28] 103 @dc
@F3 @sf
[<
03F8000FFF001C1F803007C07007E0FC03F0FC03F0FE03F8FE03F87C03F83803F80003F800
03F80003F00003F01803E01807E01E0FC01FFF0019FC001800001800001800001800001BC0
001FF8001FFE001FFF001FFF801FFFC01E01E0100020>
	 21 32 -3 31 28] 53 @dc

17 @eop0

0 0 17 @bop1 195 w @F3 @sf(17.3)56 b(Costs)19 b(of)g(Encryption)-647 131 y 
@F8 @sf(Encryption)e(is)h(not)f(without)g(its)g(costs.)27 b(Among)17 b
(these)h(are)f(the)h(exp)q(enses)h(of)e(the)h(actual)f(encryption)h(and)
-1950 56 y(decryption,)i(the)f(costs)g(asso)q(ciated)f(with)h(managing)f
(k)o(eys,)i(and)f(the)h(degree)f(of)g(securit)o(y)g(required)g(of)g(the)
-1950 57 y(encryption)c(program.)-407 101 y(Bey)o(ond)h(the)g(cost)f(of)g
(purc)o(hasing)h(the)g(encryption)f(system,)g(there)h(are)f(costs)h(asso)q
(ciated)f(with)g(the)g(emplo)o(y-)-1950 57 y(men)o(t)g(of)f(cryptograph)o
(y)h(as)f(a)h(securit)o(y)g(measure.)k(Encrypting)c(and)g(decrypting)g
(data)g(requires)g(time.)k(Most)-1951 56 y(cryptograph)o(y)14 b(systems)g
(encrypt)i(plain)o(text)d(to)h(cyphertext)i(con)o(taining)d(man)o(y)i(con)o
(trol)e(c)o(haracters:)19 b(sp)q(ecial)-1950 57 y(\014le-transfer)c
(programs)g(m)o(ust)h(b)q(e)g(used)h(to)e(transmit)g(these)h(\014les)g(o)o
(v)o(er)f(telephone)h(lines.)22 b(In)17 b(man)o(y)e(cryptog-)-1950 56 y
(raph)o(y)j(systems,)g(a)g(one)g(c)o(haracter)f(c)o(hange)h(in)g(the)h
(cyphertext)f(will)f(result)g(in)h(the)g(rest)g(of)g(the)g(ciphertext)-1950 
57 y(b)q(eing)d(indecipherable,)f(requiring)g(that)g(100)f(p)q(ercen)o(t)i
(reliable)e(data)h(transmission)f(and)h(storage)f(systems)h(b)q(e)-1949 
56 y(used)i(for)e(encrypted)i(text.)-477 101 y(If)f(the)h(encryption)f
(program)f(is)h(lost)f(or)g(if)h(the)g(k)o(ey)g(is)g(forgotten,)f(an)h
(encrypted)h(message)e(b)q(ecomes)i(useless.)-1950 57 y(This)d(c)o
(haracteristic)f(of)i(cryptograph)o(y)e(encourages)i(man)o(y)f(users)h(to)f
(store)g(b)q(oth)h(an)g(encrypted)g(and)g(a)f(plain-)-1950 56 y(text)f(v)o
(ersion)g(of)h(their)f(message,)g(whic)o(h)h(dramaticall)o(y)f(reduces)h
(the)g(securit)o(y)f(ac)o(hiev)o(ed)h(from)f(the)h(encryption)-1950 57 y
(in)i(the)g(\014rst)g(place.)-339 101 y(An)c(encryption)g(program)f
(should)h(b)q(e)g(the)g(most)f(carefully)g(guarded)h(program)f(on)h(the)g
(system.)18 b(A)11 b(crac)o(k)o(er/sp)o(y)-1951 57 y(migh)o(t)16 b(mo)q
(dify)g(the)g(program)g(so)g(that)g(it)g(records)h(all)e(k)o(eys)i(in)f(a)h
(sp)q(ecial)f(\014le)h(on)f(the)h(system,)f(or)g(so)h(that)f(it)-1951 56 y
(encrypts)j(all)f(\014les)h(with)g(the)g(same)f(k)o(ey)h(\(kno)o(wn)g(to)f
(the)h(crac)o(k)o(er\),)g(or)f(with)g(an)h(easy-to-break)g(algorit)o(hm)
-1951 57 y(rather)g(than)h(the)g(adv)o(ertised)g(one.)34 b(Managemen)o(t)
19 b(should)h(regularly)f(v)o(erify)g(an)h(encryption)g(program)f(to)-1951 
56 y(assure)c(that)f(it)h(is)g(pro)o(viding)f(its)g(exp)q(ected)j
(function,)d(and)i(only)e(its)h(exp)q(ected)h(function.)-1589 167 y @F3 @sf
(17.4)56 b(Key)17 b(Managemen)n(t)-589 131 y @F8 @sf(Key)g(managemen)o(t)f
(is)g(the)g(pro)q(cess)h(b)o(y)g(whic)o(h)f(cryptographic)g(k)o(eys)g(are)g
(decided)i(up)q(on)f(and)f(c)o(hanged.)25 b(F)l(or)-1951 56 y(maxim)o(um)
17 b(securit)o(y)l(,)g(k)o(eys)h(\(lik)o(e)e(passw)o(ords\))h(should)g(b)q
(e)i(randomly)e(c)o(hosen)g(com)o(binations)g(of)g(letters)g(and)-1950 56 y
(n)o(um)o(b)q(ers.)23 b(Keys)16 b(should)g(not)g(b)q(e)h(reused)g(\(that)e
(is,)g(ev)o(ery)h(message)g(should)g(b)q(e)h(encrypted)f(with)g(a)g
(di\013eren)o(t)-1951 57 y(k)o(ey\))g(and)h(no)f(written)f(cop)o(y)i(of)f
(the)g(k)o(ey)g(should)h(exist.)23 b(F)l(ew)16 b(computer)g(users)h(are)f
(able)g(to)g(adhere)h(to)f(suc)o(h)-1950 56 y(demanding)f(proto)q(cols.)
-427 167 y @F3 @sf(17.5)56 b(Encryption)17 b(as)i(a)g(defense)f(against)h
(crac)n(k)n(ers)-1147 131 y @F8 @sf(If)j(a)f(database)g(is)g(stored)g(in)h
(encrypted)g(form,)g(it)f(b)q(ecomes)h(nearly)g(imp)q(ossible)e(for)h(a)h
(sab)q(oture)f(guy)h(to)-1951 56 y(mak)o(e)e(fradulan)o(t)g(en)o(tries)g
(unless)h(the)g(encryption)g(k)o(ey)f(is)h(kno)o(wn.)36 b(This)21 b(pro)o
(vides)f(an)h(excellen)o(t)f(defense)-1949 57 y(against)14 b(crac)o(k)o
(ers)h(and)g(sabatures)g(who)g(v)m(andalize)g(databases)g(b)o(y)g
(creating)g(fraudulen)o(t)g(en)o(tries.)k(On)d(a)f(legal)-1951 56 y
(accoun)o(ting)k(or)f(medical)h(records)g(system,)h(it)e(is)h(far)g(more)f
(damaging)h(to)f(ha)o(v)o(e)h(a)g(database)g(unkno)o(wingly)-1951 57 y(mo)q
(di\014ed)e(than)g(destro)o(y)o(ed.)23 b(A)17 b(destro)o(y)o(ed)f
(database)g(can)h(b)q(e)g(restored)f(from)g(bac)o(kups;)i(mo)q(di\014cations)d
(to)h(a)-1950 56 y(database)i(ma)o(y)g(require)h(w)o(eeks)f(or)g(mon)o
(ths)g(to)g(detect.)31 b(Unfortunately)l(,)18 b(few)h(database)f(programs)f
(on)i(the)-1950 57 y(mark)o(et)14 b(use)i(encryption)f(for)f(stored)h
(\014les.)198 191 y(17)-998 b
17 @eop1

18 @bop0
@F3 @sf
[<
FFFF8000FFFF800007F0000007F0000007F0000007F0000007F0000007F0000007F0000007
F0000007F0000007F0000007F0000007F0000007F0000007FFFF0007FFFFE007F007F007F0
01FC07F000FC07F0007E07F0007E07F0007F07F0007F07F0007F07F0007F07F0007F07F000
7E07F0007E07F000FC07F001FC07F007F0FFFFFFE0FFFFFF00>
	 32 34 -2 33 38] 80 @dc
[<
180FC0001C3FF8001EE07C001FC03E001F801F001F001F801F000F801F000FC01F000FC01F
000FC01F000FC01F000FC01F000FC01F000FC01F000FC01F000F801F000F801F001F001F80
1E001FF07C001F3FF8001F0FE0001F0000001F0000001F0000001F0000001F0000001F0000
001F0000001F0000001F0000001F0000001F000000FF000000FF000000>
	 26 35 -2 34 31] 98 @dc
[<
FFE0FFE01F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F001F
001F001F001F001F001F001F001F001F001F001F001F001F001F001F00FF00FF00>
	 11 35 -2 34 16] 108 @dc
[<
FFFCFFFCFFFCFFFC>
	 14 4 -1 12 19] 45 @dc
@F3 @sf
[<
01FF000FFFC01F01F03C0038780038F8001CF0001CF0001EF0001EF0003EF000FE7801FE78
07FC3C1FFC1E7FF807FFF003FFE007FFC00FFF801FFFC01FF9E03FE0F03F80783F00783E00
783C00781C00781C00F00E00F00703E003FFC000FE00>
	 23 32 -2 31 28] 56 @dc
[<
7FF0FFE07FF0FFE00F801F000F801F000F801F000F801F000F801F000F801F000F801F000F
801F000F801F000F801F000F801F000F801F000F801F000F801F000F801F000F801F000F80
1F000F801F00FFFFFF00FFFFFF000F8000000F8000000F8000000F8000000F800C000F801E
000F803F000F803F0007C03F0003E01F0001F80E00007FFC00000FF000>
	 27 35 -1 34 31] 12 @dc

18 @eop0

0 0 18 @bop1 195 w @F8 @sf(Some)13 b(op)q(erating)e(systems)h(store)g
(user)h(informatio)o(n,)f(suc)o(h)h(as)f(passw)o(ords,)g(encrypted.)20 b
(As)12 b(noted)h(previously)l(,)-1951 57 y(when)19 b(passw)o(ords)e(are)h
(stored)g(with)g(a)g(one-w)o(a)o(y)g(encryption)g(algorithm)f(it)g(is)h
(of)g(little)f(v)m(alue)i(to)e(a)i(crac)o(k)o(er)-1951 56 y(to)d(steal)f
(the)h(\014le)h(whic)o(h)f(con)o(tains)f(user)i(passw)o(ords.)22 b(The)17 b
(UNIX)g(op)q(erating)e(system)h(is)g(so)g(con\014den)o(t)h(in)f(its)-1951 
56 y(encryption)e(system)g(that)f(the)i(passw)o(ord)e(\014le)h(is)g
(readable)g(b)o(y)g(all)f(users)h(of)g(the)g(system;)g(to)g(date,)f(it)h
(do)q(es)g(not)-1950 57 y(app)q(ear)h(that)g(this)f(con\014dence)q 16 x
(is)h(misplaced.)-811 167 y @F3 @sf(17.6)56 b(Encryption)17 b(in)i
(practice)-708 130 y @F8 @sf(In)f(practice,)f(there)h(are)f(sev)o(eral)g
(serviceable)g(cryptograph)o(y)f(systems)h(on)h(the)f(mark)o(et:)24 b
(most)16 b(of)h(them)h(use)-1950 57 y(di\013eren)o(t)j(cryptographic)f
(algorithms,)o 22 x(whic)o(h)h(is)g(b)q(oth)h(adv)m(an)o(tageous)f(and)g
(disadv)m(an)o(tagous)g(to)g(the)g(end)-1949 56 y(user.)j(One)18 b(adv)m
(an)o(tage)e(of)g(the)h(a)o(v)m(ailabili)o(t)o(y)e(of)h(man)o(y)g(di\013eren)o
(t)g(cryptograph)o(y)g(systems)g(is)g(that)g(secrecy)h(of)-1950 57 y(the)i
(encryption)g(system)g(adds)h(to)e(the)i(securit)o(y)e(of)h(the)g(plain)o
(text.)31 b(This)19 b(is)f(a)h(form)g(of)g(securit)o(y)f(through)-1950 56 y
(obscurit)o(y)c(and)i(should)f(not)g(b)q(e)h(relied)e(on,)h(but)h(its)e
(presence)i(will)e(sligh)o(tly)f(strengthen)i(securit)o(y)l(.)-1735 102 y
(A)20 b(disadv)m(an)o(tage)g(of)g(the)g(m)o(ultitude)g(of)g(encryption)g
(systems)g(is)f(that)h(the)g(transmitter)f(of)h(an)g(encrypted)-1949 56 y
(message)13 b(m)o(ust)g(ensure)h(that)f(the)g(prop)q(osed)h(recipien)o(t)f
(kno)o(ws)g(whic)o(h)h(decryption)f(algorithm)f(to)h(use)g(and)h(has)-1950 
57 y(a)h(suitable)f(program,)g(in)h(addition)f(to)h(kno)o(wing)f(the)h
(decryption)h(k)o(ey)l(.)-1250 166 y @F3 @sf(17.7)56 b(Public-k)n(ey)17 b
(encryption)-696 131 y @F8 @sf(In)d(some)e(cryptograph)o(y)g(systems)h(a)f
(di\013eren)o(t)h(k)o(ey)g(is)f(used)i(to)e(encrypt)h(a)g(message)f(than)h
(to)g(decrypt)g(it.)18 b(Suc)o(h)-1949 57 y(systems)e(are)h(called)f
(\\public-k)o(ey")g(systems,)g(b)q(ecause)i(the)f(encrypting)g(k)o(ey)f
(can)h(b)q(e)g(made)g(public)g(without)-1951 56 y(\(in)e(theory\))f
(sacri\014cing)h(the)g(securit)o(y)g(of)f(encrypted)i(messages.)-1145 101 y
(There)e(are)g(sev)o(eral)g(public)g(k)o(ey)g(systems)g(in)g(existence;)g
(all)g(of)f(them)i(ha)o(v)o(e)e(b)q(een)j(brok)o(en)e(with)g(the)g
(exception)-1950 57 y(of)i(system)h(devised)g(b)o(y)f(Riv)o(est,)h(Shamir)f
(and)h(Adlerman)f(called)g(RSA.)i(In)f(RSA,)g(the)g(priv)m(ate)f(k)o(ey)h
(consists)-1951 56 y(of)e(t)o(w)o(o)g(large)f(prime)i(n)o(um)o(b)q(ers)g
(while)f(the)h(public)g(k)o(ey)f(consists)g(of)h(the)f(pro)q(duct)h(of)g
(the)g(t)o(w)o(o)e(n)o(um)o(b)q(ers.)22 b(The)-1950 57 y(system)12 b(is)g
(considered)h(to)f(b)q(e)h(secure)g(b)q(ecause)h(it)d(is)h(not)h(p)q
(ossible,)f(with)g(to)q(da)o(y's)f(computers)i(and)f(algorithms,)o -1951 
56 a(to)i(factor)f(n)o(um)o(b)q(ers)i(sev)o(eral)f(h)o(undred)h(digits)f
(in)g(length.)19 b(The)c(problem)f(with)g(RSA)h(is)f(determining)g(the)h
(size)-1950 57 y(of)g(the)h(prime)f(n)o(um)o(b)q(ers)h(to)f(use:)21 b
(they)15 b(m)o(ust)g(b)q(e)h(large)f(enough)h(so)f(that)g(their)g(pro)q
(duct)h(cannot)f(b)q(e)h(factored)-1950 56 y(within)10 b(a)g(reasonable)g
(amoun)o(t)g(of)g(time,)g(y)o(et)g(small)g(enough)g(to)g(b)q(e)i
(manipulated)e(and)g(transmitted)f(b)o(y)i(existing)-1951 57 y(computers)j
(in)g(a)g(reasonable)g(time)f(frame.)19 b(The)c(problem)f(is)g(comp)q
(ounded)h(b)o(y)f(the)h(fact)e(that)h(new)g(factoring)-1951 56 y(algorit)o
(hm)e(are)g(b)q(eing)h(constan)o(tly)e(dev)o(elop)q(ed,)j(so)e(a)g(n)o(um)o
(b)q(er)h(whic)o(h)f(is)g(long)g(enough)h(to)q(da)o(y)f(ma)o(y)g(not)g(b)q
(e)i(long)-1951 57 y(enough)g(next)f(w)o(eek.)19 b(While)13 b(the)h
(length)f(of)g(the)g(public)h(k)o(ey)f(can)h(alw)o(a)o(ys)e(b)q(e)i
(increased,)f(messages)g(encrypted)-1949 56 y(with)i(to)q(da)o(y's)f
(\\short")g(k)o(eys)h(ma)o(y)f(b)q(e)i(decryptable)f(with)g(tomorro)n(w's)e
(new)j(algorit)o(hms)e(and)h(computers.)-1895 167 y @F3 @sf(17.8)56 b
(Con\014dence)18 b(in)h(the)f(encryption)f(program)-1093 131 y @F8 @sf(A)e
(computer's)g(cryptograph)o(y)g(program)f(is)g(one)i(of)f(the)g(most)g
(rew)o(arding)f(targets)g(for)g(a)h(T)l(ro)s(jan)g(horse.)20 b(The)-1950 
56 y(v)o(ery)15 b(nature)g(of)f(a)h(computer's)g(cryptograph)o(y)f
(program)g(is)g(that)h(it)f(requires)h(absolute)f(faith)h(on)g(the)g(part)f
(of)-1950 56 y(the)k(user)g(that)f(the)h(program)e(is)i(p)q(erforming)f
(exactly)g(the)h(function)f(whic)o(h)h(it)f(claims)g(to,)g(but)h(there)g
(are)f(a)-1950 57 y(n)o(um)o(b)q(er)f(of)e(v)o(ery)h(damaging)f(in)h(whic)o
(h)g(a)g(cryptograph)o(y)f(program)h(can)g(b)q(e)h(mo)q(di\014ed)f
(without)g(notice:)-887 126 y(18)-998 b
18 @eop1

19 @bop0
@F2 @sf
[<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>
	 58 41 -3 40 65] 77 @dc

19 @eop0

0 0 19 @bop1 195 w @F8 @sf(The)15 b(program)f(could)h(mak)o(e)f(a)h(plain)o
(text)f(cop)o(y)g(of)h(ev)o(erything)f(it)g(encrypts)i(or)e(decrypts)h
(without)f(the)h(user's)-1950 57 y(kno)o(wledge.)22 b(This)15 b(cop)o(y)h
(could)g(b)q(e)g(hidden)h(for)e(the)h(later)f(retriev)m(al)g(b)o(y)h(the)g
(crac)o(k)o(er.)22 b(The)16 b(cop)o(y)g(could)g(ev)o(en)-1950 56 y(b)q(e)g
(encrypted)g(with)e(a)h(di\013eren)o(t)g(k)o(ey)l(.)-670 101 y(The)i
(program)e(could)i(k)o(eep)f(a)h(log)e(of)h(ev)o(ery)h(time)e(it)h
(encrypted)h(or)f(decrypted)i(a)e(\014le.)24 b(Included)18 b(in)e(this)g
(log)-1951 57 y(could)f(b)q(e)h(the)f(time,)g(user,)f(\014lename,)h(k)o
(ey)g(and)h(length)f(of)f(the)i(encrypted)g(or)e(decrypted)i(\014le.)-1666 
101 y(The)e(program)e(migh)o(t)g(use)i(an)f(encryption)g(algorit)o(hm)f
(whic)o(h)i(has)f(a)g(hidden)h(\\bac)o(k)f(do)q(or")g({)g(that)f(is,)h(a)g
(secret)-1950 57 y(metho)q(d)i(to)g(decrypt)g(an)o(y)g(cyphertext)h
(message)e(with)h(a)g(second)h(k)o(ey)l(.)-1239 101 y(The)e(program)e
(migh)o(t)h(ha)o(v)o(e)g(a)g(\\time)g(b)q(om)o(b")g(in)g(it)g(so)g(that,)g
(after)g(a)g(particular)f(date,)i(instead)f(of)g(decrypting)-1950 57 y
(cyphertext)g(it)e(prin)o(ts)h(a)g(ransom)g(note.)19 b(The)13 b(user)f(w)o
(ould)g(only)g(b)q(e)h(able)g(to)f(decrypt)g(his)h(\014le)f(after)g
(obtaining)f(a)-1950 56 y(passw)o(ord)i(from)f(the)i(author)e(of)h(the)h
(program,)e(p)q(erhaps)i(at)f(a)g(v)o(ery)g(high)g(cost.)19 b(\(This)12 b
(is)h(a)g(form)g(of)g(computer)-1950 57 y(extortion)h(whic)o(h)h(will)f(b)q
(e)i(further)f(explored)g(under)h(\\sub)o(v)o(ersion."\))o -1222 188 a 
@F2 @sf(18)69 b(Micro)r(computer)24 b(Securit)n(y)f(Issues)-1072 146 y 
@F8 @sf(Bew)o(are)e(of)f(public)i(domain)e(soft)o(w)o(are!)o 37 x
(Although)g(there)i(are)e(man)o(y)h(excellen)o(t)g(programs)f(in)h(the)g
(public)-1950 57 y(domain,)12 b(there)g(is)g(are)g(an)h(increasing)e(n)o
(um)o(b)q(er)i(of)f(malicious)f(T)l(ro)s(jan)g(Horses)h(and)h(computer)f
(viruses.)19 b(Unless)-1950 56 y(the)h(source)g(co)q(de)h(of)f(the)g
(program)f(is)g(carefully)h(examined)g(b)o(y)g(a)g(comp)q(eten)o(t)g
(programmer,)f(it)h(is)f(nearly)-1950 57 y(imp)q(ossible)d(to)h(test)f(a)h
(public)g(domain)f(program)g(for)g(hidden)i(and)f(malicious)f(functions.)
25 b(Ev)o(en)17 b(\\trying)e(a")-1950 56 y(program)h(once)i(ma)o(y)f
(cause)h(signi\014can)o(t)e(data)h(loss)g({)g(esp)q(ecially)g(if)g(the)h
(micro)q(computer)f(is)g(equipp)q(ed)i(with)-1951 57 y(a)f(hard)h(disk.)
30 b(Although)18 b(the)h(v)m(ast)f(ma)s(jorit)o -1 x(y)f(of)h(public)h
(domain)f(soft)o(w)o(are)f(is)h(v)o(ery)g(useful)h(and)g(relativ)o(el)o(y)
-1951 56 y(reliable,)12 b(the)h(risks)f(faced)h(b)o(y)g(the)g(user)f(are)h
(considerable)g(and)g(the)f(trust)h(required)f(in)h(the)g(soft)o(w)o(ar)o
(e)f(absolute.)-1951 56 y(Hobb)o(yists)j(can)h(a\013ord)f(to)g(risk)g
(their)g(data)h(for)f(gains)g(of)g(using)h(some)f(public)h(domain)f(soft)o
(w)o(are;)f(businesses)-1949 57 y(and)h(la)o(w)f(practices)h(cannot)g(b)q
(e)h(so)f(careless.)-790 101 y(The)k(user)f(of)h(a)f(micro)q(computer)g(m)o
(ust)g(bac)o(k)g(up)h(his)f(o)o(wn)g(\014les,)h(not)g(only)f(to)g(protect)g
(against)f(acciden)o(tal)-1951 57 y(deletion)22 b(or)f(loss)h(of)f(data)h
(but)g(also)f(to)h(protect)f(against)g(theft)h(of)g(equipmen)o(t.)40 b
(Although)22 b(no)g(issue)g(in)-1950 56 y(micro)q(computer)d(securit)o(y)g
(is)g(stressed)h(more)f(than)h(bac)o(kups,)g(man)o(y)f(users)h(do)g(not)f
(p)q(erform)g(this)g(routine)-1950 57 y(c)o(hore.)-118 101 y(More)12 b
(than)h(an)o(y)f(other)h(computer)f(system,)h(with)f(a)h(micro)q(computer)f
(ph)o(ysical)g(securit)o(y)g(is)g(vitally)f(imp)q(ortan)o(t)-1951 57 y(b)q
(ecause)j(of)f(the)g(ease)g(of)g(stealing)f(a)g(micro)q(computer)h(and)g
(the)g(ease)h(at)e(whic)o(h)h(it)f(can)i(b)q(e)f(resold.)19 b(\(It)13 b
(is)f(rather)-1950 56 y(di\016cult)i(for)h(a)f(bugler)h(to)f(sell)h(a)f
(stolen)h(mainframe)e(computer\).)20 b(An)o(ti-theft)14 b(devices)h(m)o
(ust)g(b)q(e)g(installed)f(on)-1950 57 y(equipmen)o(t)h(con)o(taining)f
(hard)h(disks,)g(not)g(only)g(for)f(the)i(v)m(alue)f(of)g(the)g(equipmen)o
(t)g(but)h(also)e(for)h(the)g(v)m(alue)g(of)-1950 56 y(the)g(data)g
(stored)g(therein.)-471 101 y(Do)e(not)g(trust)g(the)h(micro)q(computer)f
(or)g(its)g(op)q(erating)g(system)g(to)g(guard)h(con\014den)o(tial)f(do)q
(cumen)o(ts)h(stored)f(on)-1950 57 y(a)j(hard)g(disk.)22 b(If)16 b(a)f(sp)o
(y)h(has)g(ph)o(ysical)f(access)h(to)g(the)g(computer,)g(he)g(can)g(ph)o
(ysically)f(remo)o(v)o(e)g(the)h(hard)g(disk)-1950 56 y(and)h(read)g(its)f
(con)o(ten)o(ts)h(on)g(another)f(mac)o(hine.)26 b(File)16 b(encryption)h
(is)f(another)h(defense)h(against)e(this)g(sort)g(of)-1950 57 y(data)d
(theft,)f(but)i(the)f(installed)f(encryption)h(program)f(should)h(b)q(e)h
(regularly)e(c)o(hec)o(k)o(ed)i(for)e(signs)h(of)g(tamp)q(ering)-1951 56 y
(\(for)h(example,)h(the)g(mo)q(di\014cation)g(date)g(or)f(the)i(size)f(of)f
(the)i(\014le)f(ha)o(ving)f(c)o(hanged\).)-527 222 y(19)-998 b
19 @eop1

20 @bop0

20 @eop0
0 0 20 @bop1 195 w @F8 @sf(Managing)14 b(a)h(secure)g(computer)-572 188 y 
@F2 @sf(19)69 b(Auditing)-402 147 y @F8 @sf(Most)16 b(securit)o
(y-conscious)h(op)q(erating)g(systems)g(pro)o(vide)g(some)g(sort)f(of)h
(auditing)g(system)g(to)g(record)g(ev)o(en)o(ts)-1950 56 y(suc)o(h)d(as)f
(in)o(v)m(alid)g(logon)f(attempts)h(or)f(attempted)h(\014le)h(transfer)f
(of)g(classi\014ed)g(\014les.)19 b(T)o(ypically)l(,)12 b(eac)o(h)i(log)e
(en)o(try)-1950 57 y(consists)f(of)h(a)f(timestamp)g(and)h(a)f
(description)h(of)f(the)h(ev)o(en)o(t.)19 b(One)12 b(of)g(the)g(resp)q
(onsibilit)o(y)e(of)h(site)h(managemen)o(t)-1951 56 y(is)j(to)f(read)h
(these)h(\\securit)o(y)e(logs.")-624 102 y(Most)k(op)q(erating)g(systems)g
(k)o(eep)h(records)g(of)f(the)h(times)g(that)f(eac)o(h)h(user)g(w)o(as)f
(logged)g(on)g(within)g(the)h(past)-1950 56 y(y)o(ear.)k(A)16 b(selectiv)o
(e)g(list)f(of)h(logons)g(b)q(et)o(w)o(een)g(5pm)g(and)h(8am)f(can)g(help)h
(detect)g(unauthorized)f(\\after-hours")-1951 56 y(use)g(of)e(accoun)o(ts)h
(b)o(y)g(crac)o(k)o(ers,)f(esp)q(ecially)h(on)g(computers)g(equipp)q(ed)i
(with)d(mo)q(dems.)-1527 102 y(Some)19 b(op)q(erating)f(systems)g(will)g
(notify)g(a)g(user)h(when)h(he)f(logs)f(in)g(of)h(the)g(last)e(time)i(he)g
(logged)f(in.)31 b(Other)-1950 56 y(systems)14 b(will)g(will)g(notify)g(a)h
(user)g(of)f(ev)o(ery)h(time)g(an)f(unsuccessful)i(login)e(attempt)g(is)h
(made)g(on)g(his)g(accoun)o(t.)-1951 57 y(Presen)o(ted)i(with)f(this)g
(information,)f(it)i(is)f(v)o(ery)g(easy)h(one)g(to)f(disco)o(v)o(er)g
(when)i(crac)o(k)o(ers)e(are)g(attempting)g(\(or)-1951 56 y(ha)o(v)o(e)f
(succeeded\))h(to)f(break)g(in)o(to)f(the)h(system.)-832 102 y(Go)q(o)q(d)g
(auditing)f(systems)h(include)g(the)h(option)e(to)h(set)g(soft)o(w)o(a)o
(re)f(alarms)g(whic)o(h)h(will)f(notify)g(managemen)o(t)g(of)-1950 56 y
(suspicious)g(activit)o(y)l(.)o 19 x(F)l(or)f(example,)h(an)g(alarm)f
(migh)o(t)g(b)q(e)i(sen)o(t)e(to)h(notify)f(managemen)o(t)h(whenev)o(er)g
(someone)-1950 57 y(logs)d(in)o(to)g(the)h(user)g(administratio)o(n)f
(accoun)o(t,)h(or)g(the)g(\014rst)g(time)f(that)h(an)g(accoun)o(t)f(is)h
(accessed)h(o)o(v)o(er)e(a)h(dialup.)-1951 56 y(The)j(securit)o(y)e
(administrator)g(could)h(then)h(v)o(erify)e(that)h(the)g(accoun)o(t)h(w)o
(as)e(used)i(b)o(y)g(those)f(authorized)g(to)g(use)-1950 57 y(it)g(and)i
(not)f(b)o(y)g(crac)o(k)o(ers.)-450 188 y @F2 @sf(20)69 b(Alarms)-353 146 y 
@F8 @sf(Soft)o(w)o(are)13 b(alarms)h(scan)h(for)f(suspicious)h(activit)n
(y)f(and)h(alert)f(managemen)o(t)g(when)h(suc)o(h)g(activit)o(y)e(is)i
(detected.)-1950 57 y(These)k(programs)f(can)h(b)q(e)g(implemen)o(ted)g
(as)f(daily)g(tasks)g(whic)o(h)h(scan)g(the)g(securit)o(y)f(logs)g(and)h
(isolate)e(out)-1950 56 y(questionable)g(o)q(ccurrences.)29 b(Soft)o(w)o
(are)16 b(alarms)g(can)i(b)q(e)h(useful)f(on)f(insecure)i(computers,)e
(suc)o(h)i(as)e(desktop)-1950 57 y(PCs,)d(for)h(altering)f(managemen)o(t)g
(of)h(securit)o(y)g(violat)o(ions)f(whic)o(h)h(the)g(op)q(erating)f
(system)h(cannot)g(prev)o(en)o(t.)-1912 101 y(F)l(or)f(example,)g(it)g(is)g
(p)q(ossible)g(to)g(write)g(a)g(v)o(ery)g(simple)g(program)f(on)i(a)f(PC)g
(that)g(w)o(ould)g(notify)g(managemen)o(t)-1951 57 y(whenev)o(er)j(a)g
(system)f(program,)f(suc)o(h)j(as)e(a)g(text)h(editor,)f(spread)g(sheet)h
(or)g(utilit)n(y)e(program)h(is)g(mo)q(di\014ed)h(or)-1950 56 y(replaced.)
24 b(Suc)o(h)17 b(a)g(program)e(could)h(detect)h(a)f(virus)g(infection)g
(and)h(could)g(b)q(e)g(used)g(to)f(isolate)f(and)i(destro)o(y)-1951 56 y
(the)e(virus)g(b)q(efore)h(it)e(b)q(ecame)i(widespread.)-769 102 y(On)f
(larger)f(computers,)h(alarms)e(can)i(notify)f(managemen)o(t)g(of)h(rep)q
(eated)g(failed)g(logon)e(attempts)h(\(indicating)-1951 56 y(that)g(a)g
(crac)o(k)o(er)g(it)g(attempting)f(to)h(break)g(in)o(to)g(the)g(computer\))h
(or)f(rep)q(eated)h(attempts)e(b)o(y)i(one)f(user)h(to)f(read)-1950 57 y
(another)h(user's)g(\014les.)-383 101 y(It)i(is)f(imp)q(ortan)o(t)f(for)h
(managemen)o(t)f(to)h(test)g(alarms)f(regularly)h(and)g(not)h(to)f(b)q
(ecome)h(dep)q(enden)o(t)h(on)e(alarms)-1951 57 y(to)d(detect)h(attempted)g
(violati)o(ons)f(of)g(securit)o(y;)g(the)h(\014rst)g(action)f(b)o(y)h(an)g
(exp)q(erienced)h(crac)o(k)o(er)e(after)g(breaking)-998 169 y(20)-998 b
20 @eop1

21 @bop0
@F5 @sf
[<
7FC3FCFFE7FE7FC3FC0E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E
00E00E00E00F00E00F80E00FC1C00FFFC00EFF800E3E000E00000E00000E00000E00000E00
007E0000FE00007E0000>
	 23 28 0 27 24] 104 @dc
[<
01FC0007FF001FFF803E03C03801C07001C0700000E00000FFFFC0FFFFC0FFFFC0E001C0E0
01C07003807003803807803E0F001FFE0007FC0001F000>
	 18 20 -3 19 24] 101 @dc
[<
7FFFC0FFFFE07FFFC000E00000E00000E00000E00000E00000E00000E00000E00000E00000
E00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E00000E0
007FE000FFE0007FE000>
	 19 28 -2 27 24] 108 @dc
[<
01F0000FFE001FFF003E0F803C07807803C07001C0F001E0E000E0E000E0E000E0E000E0E0
00E07001C07001C03803803E0F801FFF000FFE0001F000>
	 19 20 -2 19 24] 111 @dc

21 @eop0

0 0 21 @bop1 195 w @F8 @sf(in)o(to)14 b(a)h(system)g(should)g(b)q(e)h(to)e
(disable)h(or)g(reset)g(the)g(soft)o(w)o(are)f(alarms)f(so)i(that)g(the)g
(break)g(in)g(is)g(hidden.)-1865 186 y @F2 @sf(21)69 b(P)n(olicy)24 b(and)g
(Proto)r(col)-734 146 y @F8 @sf(The)16 b(most)f(secure)h(proto)q(col)e(is)i
(useless)f(if)g(p)q(eople)h(do)g(not)f(follo)o(w)f(it.)20 b(A)c(go)q(o)q
(d)g(proto)q(col)e(is)h(one)h(that)f(is)g(easy)l(,)-1950 57 y(if)g(not)f
(automatic,)g(to)g(follo)o(w.)-536 101 y(F)l(or)k(example,)g(man)o(y)g
(univ)o(ersit)o(y)f(computer)h(cen)o(ters)h(ha)o(v)o(e)f(adopted)g(a)g(p)q
(olicy)g(that)g(computer)g(passw)o(ords)-1951 57 y(are)12 b(not)h(giv)o
(en)f(out)g(o)o(v)o(er)g(the)h(telephone)g(under)g(an)o(y)g
(circumstances.)18 b(Suc)o(h)c(a)e(p)q(olicy)l(,)h(if)f(enforced,)h
(eliminates)-1951 56 y(the)19 b(p)q(ossibilit)n(y)e(of)i(a)f(crac)o(k)o
(er)g(telephoning)g(managemen)o(t)g(and,)h(p)q(osing)g(as)f(a)g(sta\013)g
(mem)o(b)q(er,)h(obtaining)e(a)-1950 57 y(user's)e(passw)o(ord.)-322 101 y
(Other)e(p)q(olicies)g(include)g(requiring)g(users)g(to)f(c)o(hange)h
(their)g(passw)o(ords)f(on)h(a)g(regular)f(basis.)19 b(Some)13 b(computer)
-1950 57 y(systems)h(allo)o(w)f(p)q(olicies)h(suc)o(h)h(as)f(this)g(to)g
(b)q(e)i(implemen)o(ted)e(automatical)o(ly:)k(After)c(the)h(same)f(passw)o
(ord)g(has)-1950 56 y(b)q(een)i(used)f(for)f(a)g(giv)o(en)g(p)q(erio)q(d)h
(of)g(time,)e(the)i(computer)g(requires)f(that)g(the)h(user)g(c)o(hange)f
(the)h(passw)o(ord)f(the)-1950 57 y(next)h(time)g(the)g(user)g(logs)g(in.)
-523 185 y @F2 @sf(22)69 b(Sub)n(v)n(ersion)q -462 147 a @F8 @sf(Most)18 b
(inciden)o(ts)g(of)g(data)g(loss)g(are)h(due)g(to)f(emplo)o(y)o(ees)g
(rather)g(than)h(external)f(agen)o(ts.)30 b(Man)o(y)18 b(emplo)o(y)o(ees,)
-1951 56 y(b)o(y)i(virtue)g(of)g(their)g(p)q(osition,)g(are)h(presen)o
(ted)f(with)g(ample)g(opp)q(ortunit)o(y)g(to)f(steal)h(or)g(corrupt)g
(data,)h(use)-1950 57 y(computer)e(resources)g(for)f(p)q(ersonal)g(gain)g
(or)h(the)g(b)q(ene\014t)g(of)g(a)f(third)h(part)o(y)f(and)g(generally)g
(wreak)h(ha)o(v)o(o)q(c.)-1951 56 y(While)14 b(computers)g(mak)o(e)f
(these)i(actions)e(easier,)h(they)g(are)g(merely)g(re\015ections)g(of)g
(concerns)g(already)g(presen)o(t)-1950 57 y(in)j(the)h(businessplace.)26 b
(T)l(raditional)15 b(metho)q(ds)j(of)f(emplo)o(y)o(ee)f(screening)i
(coupled)g(with)e(sophisticated)h(soft-)-1951 56 y(w)o(are)e(alarms)g(and)i
(bac)o(kup)f(systems)g(can)g(b)q(oth)h(minimize)e(the)h(impact)g(of)g(sub)o
(v)o(ersion)f(and)h(aid)g(in)g(its)g(early)-1951 57 y(detection.)-195 186 y 
@F2 @sf(23)69 b(Crac)n(king)-404 146 y @F8 @sf(This)16 b(section)f(is)h
(in)o(tended)g(to)f(giv)o(e)h(some)f(idea)h(of)g(ho)o(w)f(a)h(crac)o(k)o
(er)f(breaks)h(in)o(to)f(a)h(computer.)22 b(The)16 b(in)o(ten)o(t)f(is)-1950 
57 y(that,)i(b)o(y)g(giving)f(a)h(demonstration)f(of)h(ho)o(w)g(a)g(crac)o
(k)o(er)g(breaks)g(in)o(to)f(a)h(computer)h(system,)f(the)g(reader)g(will)
-1951 56 y(gain)f(insigh)o(t)g(in)o(to)g(w)o(a)o(ys)g(of)h(prev)o(en)o
(ting)f(similar)g(actions.)24 b(The)17 b(target)f(system)h(is)g(actually)e
(irrev)o(elen)o(t;)i(the)-1950 56 y(concepts)f(presen)o(ted)f(apply)g(to)g
(man)o(y)g(on)g(the)g(mark)o(et.)-987 102 y(P)o(erhaps)e(as)h(the)g
(result)f(of)g(a)g(random)h(telephone)g(searc)o(h,)f(the)h(crac)o(k)o(er)f
(has)g(found)h(the)g(telephone)g(n)o(um)o(b)q(er)g(of)-1950 56 y(a)h(mo)q
(dem)h(connected)h(to)e(a)g(timesharing)g(computer.)21 b(Up)q(on)c
(calling)d(the)i(computer's)f(mo)q(dem,)h(the)g(crac)o(k)o(er)-1951 57 y
(is)g(prompted)h(to)f(Logon.)25 b(Di\013eren)o(t)15 b(op)q(erating)h
(systems)h(ha)o(v)o(e)f(di\013eren)o(t)g(w)o(a)o(ys)g(of)g(logging)g(in)g
(and)h(p)q(erhaps)-1949 56 y(the)e(crac)o(k)o(er)g(is)g(not)f(familiar)f
(with)i(this)g(one.)20 b(\(The)15 b(crac)o(k)o(er's)f(t)o(yping)g(is)h(lo)o
(w)o(ercase)f(for)g(clarit)o(y)l(.\))k(He)e(starts:)-1896 135 y @F5 @sf
(hello)784 124 y @F8 @sf(21)-998 b
21 @eop1

22 @bop0
@F5 @sf
[<
E7F800FFFE00FFFF80F80780F001C0E001E0E000E06000E00000E00000E00001C00003C000
0F8000FF0007FE001FF0003F0000780000700000E00000E00380E00380E003807007807C0F
803FFF801FFF8003F380>
	 19 28 -2 27 24] 83 @dc
[<
07FF0007FF0007FF0000700000700000700000700000700000700000700000700000700000
7000007000007000007000007000007000007000007000007000E07038E07038E07038E070
38FFFFF8FFFFF87FFFF8>
	 21 28 -1 27 24] 84 @dc
@F5 @sf
[<
7FC000FFE0007FC0000E00000E00000E00000E00000E00000E00000E00000E3E000EFF800F
FFC00FC1E00F80E00F00700F00700E00380E00380E00380E00380E00380E00380E00700F00
700F80E00FC1E07FFFC0FEFF807E3E00>
	 21 30 0 19 24] 112 @dc
[<
01FCFC03FFFE07FFFC0F03E00E01E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E
00E00E00E00E00E00E00E00E00E07E07E0FE0FE07E07E0>
	 23 20 0 19 24] 117 @dc
[<
E7F000FFFC00FFFF00F80F00F00380E00380E00380600780001F0003FE001FFC007FE0007C
0000E00700E00700E00700780F007FFF003FFF0007F700>
	 17 20 -3 19 24] 115 @dc
[<
7FFE00FFFF007FFE0003800003800003800003800003800003800003800003800003800003
C00003C00003E00003F03003F8787FBFF8FF9FF07F87E0>
	 21 20 -1 19 24] 114 @dc
[<
01FC000FFF801FFFC07E03F07800F0E00038E00038E00038E000387000707801F03FFFE01F
FFC01FFE001C000038000039E0001FF8001FFC001E1E001C0E003807003807003807003807
003807001C0E001E1E300FFFF807FFF801E1F0>
	 21 31 -1 19 24] 103 @dc
[<
FFFF00FFFF80FFFF0001C00001C00001C00001C00001C00001C00001C00001C00001C00001
C00001C00001C00001C00001C0007FC000FFC0007FC0000000000000000000000000000380
0007C00007C00007C000038000>
	 17 29 -4 28 24] 105 @dc
[<
7FC3FCFFE7FE7FC3FC0E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E00E
00E00E00E00F00E00F80E00FC1C07FFFC0FEFF807E3E00>
	 23 20 0 19 24] 110 @dc
[<
7F03F0FF87F87F03F01C01C01C03801C03801C07001C07001C0E001C0E001E1C001F1C001F
B8001FB8001DF0001DF0001CF0001C70001C38001C3C001C1E001C0E001C07001C07801C03
C07F07F0FF87F87F07F0>
	 21 28 -1 27 24] 75 @dc
[<
0FF8003FFE007FFF00780F00700700F00780E00380E00380E00380E00380E00380E00380E0
0380E00380E00380E00380E00380E00380E00380E00380E00380E00380F00780700700780F
007FFF003FFE000FF800>
	 17 28 -3 27 24] 79 @dc
[<
01F1C003FDC00FFFC01F0FC01C07C03803C03803C07003C07001C07001C0E00FF0E01FF0E0
0FF0E00000E00000E00000E00000E000007000007001C07001C03801C03803C01C03C01F0F
C00FFFC003FDC001F1C0>
	 20 28 -2 27 24] 71 @dc
[<
01F00007FC000FFE001F1F001C07003803807803C07001C07001C0F001E0E000E0E000E0E0
00E0E000E0E000E0E000E0E000E0E000E0E000E07001C07001C07803C03803801C07001F1F
000FFE0007FC0001F000>
	 19 28 -2 27 24] 48 @dc
[<
7FFFE0FFFFE07FFFE03C00E01E00E00F800007C00001E00000F000007800003C00001E0000
0F000007800003C00001C00001C00000E00000E06000E0F000E0F000E0E001C07003C07C0F
803FFF000FFE0003F000>
	 19 28 -2 27 24] 50 @dc
[<
7F03C0FF87C07F07C01C0DC01C0DC01C0DC01C1DC01C19C01C19C01C39C01C39C01C39C01C
31C01C71C01C71C01C61C01CE1C01CE1C01CE1C01CC1C01CC1C01DC1C01D81C01D81C01D81
C07F07F0FF0FF87E07F0>
	 21 28 -1 27 24] 78 @dc
[<
00700000F80000F80000D80001DC0001DC0001DC00018C00038E00038E00038E00038E0007
07000707000707000707000F07800E03800E03800E03800E03801C01C01C01C01C01C01C01
C0FF07F8FF07F8FF07F8>
	 21 28 -1 27 24] 86 @dc
@F5 @sf
[<
03E3F00FFBF81FFFF03C1F80380F80700780700780E00380E00380E00380E00380E00380E0
0380700380700780380F803C1F801FFF800FFB8003E3800003800003800003800003800003
80001F80003F80001F80>
	 21 28 -2 27 24] 100 @dc
[<
07E1F01FFBF03FFFF0781F00F00F00E00700E00700E007007807007F07001FFF0007FF0000
FF00000700000700300E00781E007FFC003FF8001FE000>
	 20 20 -3 19 24] 97 @dc
[<
00700000F80000F80001DC0001DC0001DC00038E00038E00038E00038E0007070007070007
07000E03800E03800E03801E03C07F8FF0FF8FF87F8FF0>
	 21 20 -1 19 24] 118 @dc
[<
03F0001FFC003FFF007C0F807003C0E001C0F000E0F000E06000E00000E00000E00001C018
03C03C07803FFF003FFE003BF8003800003800003800003800003800003800003800003800
003FFF803FFF801FFF80>
	 19 28 -2 27 24] 53 @dc
[<
03F8001FFE003FFF007C0780F003C0F001C0F000E0F000E00000E00000E00000E00001C000
03C000078003FF0003FE0003FF00000F000003800003C00001C03001C07801C07803C07807
803FFF001FFE0007F800>
	 19 28 -2 27 24] 51 @dc
[<
FF8000FF8000FF80001C00001C00001C00001C00001C00001C00001C00001C00001FFE001F
FF801FFFC01C03C01C01E01C00E01C00701C00701C00701C00701C00701C00E01C01E01C03
C0FFFFC0FFFF80FFFE00>
	 20 28 -1 27 24] 80 @dc
[<
01FC0003FE0001FC0000700000700000700000700000700000700000700000700000700000
F80000F80001DC0001DC0001DC00038E00038E000707000707000F07800E03801E03C01C01
C0FF07F8FF07F8FF07F8>
	 21 28 -1 27 24] 89 @dc
[<
1E00003F00007F80007BC00079E00000E00000F00000700000700000700000780000780000
780000DC0000CC0000CC0001CE0001CE00038E000386000387000707000707000703800E03
800E03800E01C07F8FF0FF8FF87F8FF0>
	 21 30 -1 19 24] 121 @dc
[<
01FC0007FF001FFF803E03C03801C07001C0700000E00000E00000E00000E00000E00000E0
00007000007000003803003E07801FFF8007FF0001FE00>
	 18 20 -3 19 24] 99 @dc
[<
3078FCFC783000000000000000003078FCFC7830>
	 6 20 -9 19 24] 58 @dc
[<
60F87C1E0E071F3F7F7E3E1C>
	 8 12 -8 5 24] 44 @dc
[<
0E03800F07800F07800D05800D8D801D8DC01D8DC01D8DC01D8DC0198CC019DCC019DCC019
DCC039DCE039DCE038F8E038F8E03800E03800E03800E03800E03800E07000707000707000
70FE03F8FE03F8FE03F8>
	 21 28 -1 27 24] 87 @dc
@F5 @sf
[<
7FFF00FFFF80FFFF807FFF00>
	 17 4 -3 15 24] 45 @dc
[<
7FFCFFFE7FFC03800380038003800380038003800380038003800380038003800380038003
804380FB80FF803F800F800780038003800180>
	 15 28 -5 27 24] 49 @dc
[<
007FF000FFF8007FF0000700000700000700000700000700000700FFFFF8FFFFF8FFFFF8F0
07007807003807003C07001E07000E070007070007870003870001C70001E70000E7000077
00007700003F00001F00>
	 21 28 -1 27 24] 52 @dc
[<
00600000F00000F00000F00000F00000F00000F00000F0007FFFC0FFFFE0FFFFE07FFFC000
F00000F00000F00000F00000F00000F00000F000006000>
	 19 20 -2 23 24] 43 @dc
[<
01F80007FE000FFF001E07803C03C03801C07000E07000E07000E0F000E0E000E0F000E0F0
01C0F803C0FE0780FFFF00E7FE00E1F8007000007000003800003801801C03C01E03C00F83
C007FF8001FF00007E00>
	 19 28 -2 27 24] 54 @dc
[<
600000F00000F00000F800007800007C00003C00003C00003E00001E00001F00000F00000F
00000F800007800007C00003C00003C00003E00001E00001F00000F00000F8000078000078
00007C00003C00003E00001E00001E00001F00000F00000F80000780000780000300>
	 17 36 -3 31 24] 47 @dc
[<
03F8000FFE001FFF003E0F807803C07001C0E000E0E000E0E000E0E000E0F001E07001C03C
07801F1F000FFE0007FC001FFF003C07803803807001C07001C07001C07001C03803803E0F
801FFF000FFE0003F800>
	 19 28 -2 27 24] 56 @dc
[<
07C0001FF0003FFC00783E00780F007807803003800001C00001C00001C00000E003F0E00F
FEE01FFFE03C0FE07803E07001E0E001E0E001E0E001C0E001C0E001C07003807807803C0F
001FFE000FFC0003F000>
	 19 28 -2 27 24] 57 @dc
[<
7FFFC0FFFFE0FFFFE0FFFFE0000000000000000000000000FFFFE0FFFFE0FFFFE07FFFC0>
	 19 12 -2 19 24] 61 @dc
[<
600000F00000FC00007E00003F00001FC00007E00003F00001FC00007E00003F00001F8000
1F80003F00007E0001FC0003F00007E0001FC0003F00007E0000FC0000F00000600000>
	 17 24 -3 25 24] 62 @dc

22 @eop0

0 0 22 @bop1 48 195 a @F5 @sf(RESTART)-216 151 y @F8 @sf(The)17 b
(computer)f(prin)o(ts)g(\\REST)l(AR)l(T")h(telling)e(the)i(crac)o(k)o(er)e
(that)h(\\hello")f(is)h(not)g(the)h(prop)q(er)g(w)o(a)o(y)e(to)h(logon)-1951 
57 y(to)d(the)i(computer)f(system.)19 b(Some)14 b(computer)g(systems)f
(pro)o(vide)h(extensiv)o(e)g(help)g(faciliti)o(es)f(in)h(order)g(to)f
(assist)-1951 56 y(no)o(vice)j(users)g(in)h(logging)d(in,)j(whic)o(h)f
(are)g(just)g(as)g(helpful)g(to)g(crac)o(k)o(ers)g(as)g(they)g(are)g(to)g
(no)o(vices.)23 b(F)l(rom)15 b(trial)-1951 57 y(and)g(error,)f(the)i(crac)o
(k)o(er)e(determines)h(the)h(prop)q(er)f(w)o(a)o(y)f(to)h(logon)f(to)h
(the)g(system:)-1404 151 y @F5 @sf(help)-96 56 y(RESTART)-168 57 y(user)
-96 56 y(RESTART)-168 57 y(login)-120 56 y(DMKLOG020E)22 b(USERID)h
(MISSING)g(OR)h(INVALID)-908 152 y @F8 @sf(The)18 b(next)g(task)g(for)f
(the)h(crac)o(k)o(er)f(is)h(to)f(determine)h(a)g(v)m(alid)g(username)g
(and)g(passw)o(ord)f(com)o(bination.)27 b(One)-1949 56 y(w)o(a)o(y)14 b
(to)g(do)g(this)g(is)g(to)g(try)g(a)g(lot)g(of)g(them.)20 b(It)15 b(is)f
(not)g(v)o(ery)g(di\016cult)g(to)g(\014nd)h(a)g(v)m(alid)f(username)h
(from)f(a)g(list)f(of)-1950 56 y(common)i(\014rst)g(and)g(last)f(names:)
-539 152 y @F5 @sf(login)23 b(david)-263 56 y(DMKLOG053E)f(DAVID)h(NOT)h
(IN)f(CP)h(DIRECTORY)-860 57 y(login)f(sally)-263 56 y(DMKLOG053E)f(SALLY)h
(NOT)h(IN)f(CP)h(DIRECTORY)-860 56 y(login)f(cohen)-263 57 y(LOGIN)g
(FORMAT:)g(LOGIN)g(USERNAME,PASSWO)o(RD)-884 56 y(RESTART)-216 152 y @F8 @sf
(Once)16 b(a)f(v)m(alid)g(username)g(is)g(found,)g(the)g(crac)o(k)o(er)g
(tries)f(passw)o(ords)h(un)o(til)f(he)i(\014nd)f(one)h(that)e(w)o(orks:)
-1722 151 y @F5 @sf(login)23 b(cohen,david)-407 56 y(DMKLOG050E)f
(PASSWORD)h(INCORRECT)g(-)g(REINITIATE)g(LOGON)g(PROCEDURE)-1385 57 y
(login)g(cohen,charles)-455 56 y(DMKLOG050E)f(PASSWORD)h(INCORRECT)g(-)g
(REINITIATE)g(LOGON)g(PROCEDURE)-1385 57 y(login)g(cohen,sally)-407 56 y
(LOGMSG)g(-)g(15:40:23)g(+03)h(TUESDAY)f(06/24/86)-908 57 y(WICC)g(CMS)g
(314)h(05/29)f(PRESS)g(ENTER=>)-812 151 y @F8 @sf(The)17 b(basic)f(\015a)o
(w)g(in)h(this)f(op)q(erating)g(system)g(is)g(that)g(it)g(tells)g(the)h
(crac)o(k)o(er)f(the)g(di\013erence)h(b)q(et)o(w)o(een)g(a)g(\(v)m(alid)
-1951 56 y(username,in)o(v)m(alid)e(passw)o(ord\))f(pair)g(and)i(an)f(\(in)o
(v)m(alid)g(username,)g(in)o(v)m(alid)f(passw)o(ord\))h(pair.)k(F)l(or)c
(the)h(in)o(v)m(alid)-1951 57 y(usernames,)g(the)g(system)f(resp)q(onded)i
(with)e(the)h(\\NOT)f(IN)i(CP)e(DIRECTOR)l(Y")i(resp)q(onse,)f(while)f
(for)g(v)m(alid)-1950 56 y(usernames)g(the)h(system)e(ask)o(ed)h(for)g
(the)g(user's)g(P)l(ASSW)o(ORD.)-169 163 y(22)-998 b
22 @eop1

23 @bop0
@F8 @sf
[<
7FFFFFE0FFFFFFF00000000000000000000000000000000000000000000000000000000000
000000FFFFFFF07FFFFFE0>
	 28 12 -3 16 35] 61 @dc
[<
00060000000600000006000000060000000600000006000000060000000600000006000000
0600000006000000060000000600000006000000060000FFFFFFF0FFFFFFF0000600000006
00000006000000060000000600000006000000060000000600000006000000060000000600
0000060000000600000006000000060000>
	 28 32 -3 26 35] 43 @dc

23 @eop0

0 0 23 @bop1 195 w @F8 @sf(Some)16 b(systems)g(systems)g(ask)g(for)g(a)g
(passw)o(ord)g(regardless)g(of)g(whether)g(or)g(not)g(the)h(username)g
(pro)o(vided)f(b)o(y)-1950 57 y(the)g(crac)o(k)o(er)f(is)h(v)m(alid.)22 b
(This)15 b(features)h(enhances)h(securit)o(y)e(dramatically)f(since)i(the)h
(crac)o(k)o(er)e(nev)o(er)h(kno)o(ws)f(if)-1950 56 y(a)g(username)g(he)h
(tries)e(is)h(v)m(alid)g(or)f(not.)-692 101 y(Supp)q(ose)22 b(a)f(crac)o
(k)o(er)f(has)h(to)f(try)h(an)g(a)o(v)o(erage)f(of)g(20,000)g(names)h(or)f
(w)o(ords)g(to)h(\014nd)g(a)g(correct)g(username)-1950 57 y(or)15 b(passw)o
(ord.)21 b(Mathematically)l(,)o 15 x(on)16 b(a)f(system)h(whic)o(h)f(do)q
(es)i(not)e(inform)g(the)h(crac)o(k)o(er)f(when)i(a)e(username)h(is)-1950 
56 y(correct)10 b(the)h(crac)o(k)o(er)f(ma)o(y)g(ha)o(v)o(e)g(to)g(try)g
(up)o(w)o(ards)g(from)g(20,000)o 9 x(x)h(20,000)e(=)h(400,000,0)o(00)f
(username/passw)o(ord)-1951 57 y(com)o(binations.)17 b(On)c(a)e(system)h
(whic)o(h)g(tells)f(the)h(crac)o(k)o(er)f(when)h(he)g(has)g(found)g(a)g(v)m
(alid)g(username)g(the)g(searc)o(h)f(is)-1950 56 y(reduced)j(to)d(total)g
(of)h(20,000)f(+)i(20,000)d(=)j(40,000)e(tries.)18 b(The)13 b(di\013erence)f
(is)g(basically)g(whether)g(the)h(passw)o(ord)-1951 57 y(and)i(the)h
(username)f(can)g(b)q(e)h(guessed)g(sequen)o(tially)e(or)h(m)o(ust)f(b)q
(e)i(guessed)g(together.)-1501 101 y(All)11 b(it)g(tak)o(es)f(is)i
(patience)f(to)g(crac)o(k)g(a)h(system.)18 b(One)12 b(w)o(a)o(y)f(to)g(sp)q
(eed)h(the)g(pro)q(cess)g(is)f(to)g(automate)f(the)i(username)-1950 57 y
(and)k(passw)o(ord)f(searc)o(h:)20 b(essen)o(tially)l(,)15 b(the)g(crac)o
(k)o(er)g(programs)g(his)g(computer)h(to)f(try)g(rep)q(eatedly)h(to)f(log)g
(on)o(to)-1951 56 y(the)i(target)f(system.)26 b(T)l(o)17 b(\014nd)g(a)g
(username,)h(the)f(crac)o(k)o(er)g(can)g(instruct)f(his)h(computer)h(to)e
(cycle)h(through)g(a)-1950 57 y(list)g(of)g(a)g(few)h(thousand)f(\014rst)h
(and)g(last)e(names.)27 b(Once)19 b(a)e(username)h(is)g(found,)g(the)g
(crac)o(k)o(er)f(programs)f(his)-1950 56 y(computer)g(to)g(searc)o(h)h
(for)e(passw)o(ords)h(in)g(a)g(similar)f(fashion.)23 b(The)17 b(crac)o(k)o
(er)f(ma)o(y)f(also)h(ha)o(v)o(e)g(a)g(dictionary)f(of)-1950 56 y(the)g
(30,000)e(most)h(common)h(english)f(w)o(ords,)g(and)h(try)g(eac)o(h)g(of)f
(these)h(as)g(a)g(passw)o(ord.)j(Since)e(p)q(eople)f(tend)h(to)-1951 57 y
(pic)o(k)c(\014rst)h(names,)f(single)g(c)o(haracters,)g(and)h(common)f(w)o
(ords)g(as)g(passw)o(ords,)g(most)f(passw)o(ords)h(can)h(b)q(e)g(brok)o
(en)-1950 56 y(within)i(a)g(few)h(thousand)g(tries.)21 b(If)16 b(the)f
(crac)o(k)o(er's)g(computer)h(can)g(test)f(one)h(passw)o(ord)f(ev)o(ery)g
(5)h(seconds,)g(ten)-1950 57 y(thousand)j(passw)o(ords)f(can)h(b)q(e)h
(tested)f(in)g(under)g(15)g(hours.)31 b(\(Hop)q(efully)19 b(b)o(y)g(this)f
(time)g(a)h(soft)o(w)o(are)e(alarm)-1951 56 y(w)o(ould)g(ha)o(v)o(e)g
(disabled)g(logins)f(from)h(the)h(computer's)f(mo)q(dem,)g(but)h(few)f(op)q
(erating)g(systems)g(con)o(tain)g(suc)o(h)-1950 57 y(pro)o(visions.\))o 
-229 101 a(Finding)c(one)h(v)m(alid)f(username/passw)o(ord)g(com)o
(binatio)o(n)g(on)g(a)h(system)f(do)q(es)h(not)f(place)g(the)h(en)o(tire)f
(computer)-1950 57 y(at)i(the)i(mercy)f(of)f(the)h(crac)o(k)o(er)g
(\(unless)g(it)f(is)h(a)f(privileged)h(accoun)o(t)g(whic)o(h)g(he)g(disco)o
(v)o(ers\),)f(but)h(it)f(do)q(es)i(giv)o(e)-1951 56 y(him)12 b(a)f(v)o
(ery)h(strong)e(basis)i(from)f(whic)o(h)g(to)h(explore)f(and)h(then)g
(crac)o(k)g(the)g(rest)f(of)h(the)g(accoun)o(ts)f(on)h(the)g(system.)-1951 
57 y(Some)j(computers)g(are)g(more)g(resistan)o(t)f(to)g(this)h(sort)f(of)h
(exploration)f(than)h(others.)-1482 101 y(If)i(the)g(crac)o(k)o(er)f(giv)o
(es)g(up)h(trying)f(to)g(p)q(enetrate)h(the)g(login)f(serv)o(er)g(of)g
(the)h(host,)f(there)h(are)g(still)e(man)o(y)h(other)-1950 56 y(w)o(a)o
(ys)j(to)g(crac)o(k)h(the)g(system.)34 b(He)20 b(migh)o(t)f(telephone)h
(the)g(computer)g(op)q(erator)f(and,)i(pretending)f(to)g(b)q(e)g(a)-1950 
57 y(mem)o(b)q(er)13 b(of)g(the)g(computer)g(cen)o(ter's)f(sta\013,)g(ask)h
(for)f(the)h(op)q(erator's)f(passw)o(ord.)18 b(\(Crac)o(k)o(ers)11 b(ha)o
(v)o(e)i(successfully)-1950 56 y(used)j(this)e(metho)q(d)i(to)e(break)h
(in)o(to)g(n)o(umerous)g(computer)g(systems)g(around)g(the)g(coun)o(try)l
(.\))-1619 102 y(Some)21 b(crac)o(k)o(ers)g(use)h(their)f(computers)g(to)g
(searc)o(h)g(for)g(other)g(computers.)38 b(A)22 b(crac)o(k)o(er)f(will)f
(program)g(his)-1950 56 y(computer)h(to)g(randomly)f(dial)g(telephone)i(n)o
(um)o(b)q(ers)f(searc)o(hing)g(for)f(AA)h(mo)q(dems.)38 b(When)22 b(the)f
(crac)o(k)o(er's)-1951 57 y(computer)11 b(\014nds)h(a)f(mo)q(dem)h(answ)o
(ering,)f(the)g(phone)h(n)o(um)o(b)q(er)g(is)f(recorded)g(for)g(later)f
(crac)o(king.)18 b(Automaticall)o(y)-1951 56 y(dialing)e(mo)q(dems)h(can)h
(also)e(b)q(e)i(used)g(to)f(crac)o(k)g(in)o(to)f(long)h(distance)g
(services)g(suc)o(h)h(as)e(MCI)i(and)f(Sprin)o(t)g(b)o(y)-1950 57 y
(trying)d(successiv)o(e)i(accoun)o(t)e(n)o(um)o(b)q(ers.)-694 101 y
(Although)i(it)g(is)g(theoretically)f(p)q(ossible)h(to)g(trac)o(k)g(a)g
(crac)o(k)o(er)g(bac)o(k)g(through)h(his)f(call,)g(suc)o(h)g(action)g
(requires)-1950 57 y(the)g(assistance)f(of)h(the)g(telephone)h(utilit)n(y)l
(.)k(Utilities)15 b(will)f(not)i(trace)g(telephone)g(calls)f(unless)h
(ordered)h(to)e(do)-1950 56 y(so)f(b)o(y)g(p)q(olice)f(who)h(ha)o(v)o(e,)g
(to)f(date,)h(b)q(een)h(v)o(ery)f(hesitan)o(t)f(ab)q(out)g(ordering)h(suc)o
(h)g(action.)19 b(A)o(t)13 b(a)h(recen)o(t)g(massiv)o(e)-1951 56 y
(computer)k(break)f(in)h(at)e(Stanford)i(Univ)o(ersit)o(y)e(one)i(researc)o
(h)f(sta\013er)f(comm)o(unicated)i(with)f(a)g(crac)o(k)o(er)g(o)o(v)o(er)
-1951 57 y(the)d(computer)g(for)f(t)o(w)o(o)f(hours)i(while)f(another)g
(sta\013er)g(in)h(the)g(lab)f(con)o(tacted)g(p)q(olice)h(to)f(arrange)g(a)g
(trace;)h(the)-1950 56 y(p)q(olice)h(refused.)669 218 y(23)-998 b
23 @eop1

24 @bop0
@F2 @sf
[<
00007FF003000003FFFE0F00001FFFFF1F00003FF007BF0000FF8001FF0001FE0000FF0003
F80000FF0007F00000FF000FF00000FF001FE00000FF001FE00000FF003FC00000FF003FC0
0000FF007FC00000FF007F8001FFFFF87F8001FFFFF8FF8001FFFFF8FF8000000000FF8000
000000FF8000000000FF8000000000FF8000000000FF8000000000FF8000000000FF800000
00007F80000000007F80000007007FC0000007003FC0000007003FC000000F001FE000000F
001FE000000F000FF000001F0007F000003F0003F800003F0001FE0000FF0000FF8001FF00
003FF00FFF00001FFFFF0F000003FFFC070000007FE00300>
	 45 41 -4 40 54] 71 @dc

24 @eop0

0 0 24 @bop1 195 w @F2 @sf(24)69 b(Conclusion)-465 147 y @F8 @sf(Computer)
16 b(securit)o(y)f(is)h(a)g(topic)f(to)q(o)h(large)f(to)g(co)o(v)o(er)h
(fully)f(in)h(an)o(y)g(publication,)f(least)g(of)h(all)f(in)h(as)g(short)f
(an)-1950 56 y(in)o(tro)q(duction)h(as)g(this.)24 b(In)18 b(order)e(to)g
(ev)m(aulate)h(a)g(securit)o(y)f(system)g(it)g(is)g(necessary)h(to)g
(think)f(lik)o(e)g(a)h(crac)o(k)o(er)-1951 56 y(or)e(a)g(sub)o(v)o(erter.)k
(After)c(that,)f(most)g(other)h(details)f(follo)o(w.)-1045 189 y @F2 @sf
(25)69 b(Glossary)q -396 146 a @F8 @sf(Bac)o(kup)15 b(\(n.\):)j(A)d(cop)o
(y)f(of)g(informatio)o(n)g(stored)g(in)g(a)g(computer,)g(to)g(b)q(e)h
(used)g(in)f(the)h(ev)o(en)o(t)f(that)f(the)i(original)o -1951 57 a(is)g
(destro)o(y)o(ed.)-248 101 y(Bac)o(k)g(up)h(\(v.\):)i(T)l(o)d(mak)o(e)g(a)g
(bac)o(kup.)-661 101 y(break)i(\(v.\):)23 b(T)l(o)17 b(gain)f(access)i(to)e
(computers)h(or)g(informatio)o(n)f(though)o(t)h(to)f(b)q(e)i(secure.)26 b
(T)l(o)17 b(break)g(a)g(cypher)-1949 57 y(is)h(to)g(b)q(e)h(able)g(to)f
(decrypt)h(an)o(y)f(message)g(encrypted)i(with)e(it.)29 b(T)l(o)19 b
(break)f(a)h(computer)f(is)g(to)g(log)g(on)h(to)f(it)-1951 56 y(without)c
(authorization.)-449 102 y(bit:)19 b(One)d(unit)f(of)g(memory)g(storage.)j
(Either)d(a)g(\\0")f(or)h(a)g(\\1.")-1119 101 y(clien)o(t:)21 b(With)15 b
(reference)i(to)e(a)h(computer)g(net)o(w)o(ork,)f(the)h(computer)g(or)f
(program)g(whic)o(h)h(requests)g(data)g(or)f(a)-1950 57 y(service.)-146 
101 y(Con\014dence:)24 b(The)18 b(lev)o(el)e(of)g(trust)h(whic)o(h)f(can)h
(b)q(e)h(placed)f(in)g(a)f(computer)h(system)g(or)f(program)g(to)g(p)q
(erform)-1950 57 y(the)g(function)g(whic)o(h)g(it)g(is)g(designed)g(to)g
(do.)22 b(Alternativ)o(ely)l(,)15 b(the)h(amoun)o(t)g(of)f(protection)h
(o\013ered)g(b)o(y)g(suc)o(h)g(a)-1950 56 y(system.)-149 102 y(Crac)o(k)o
(er:)j(A)c(p)q(erson)h(who)f(breaks)g(in)o(to)f(computers)h(for)f(fun.)-1078 
101 y(Encryption:)21 b(The)c(pro)q(cess)f(of)f(taking)g(information)g(and)h
(making)f(it)g(unreadable)i(to)e(those)h(who)g(are)f(not)h(in)-1950 56 y
(p)q(ossession)f(of)g(a)g(the)g(decrypting)g(k)o(ey)l(.)-687 102 y(MODEM:)g
(Mo)q(dulator/Demo)q(dulato)o(r.)23 b(A)16 b(device)h(used)g(for)f
(sending)h(computer)f(information)f(o)o(v)o(er)h(a)g(tele-)-1950 56 y
(phone)g(line.)-218 102 y(Public)j(k)o(ey:)27 b(A)19 b(cryptograph)o(y)f
(system)g(whic)o(h)h(uses)g(one)g(k)o(ey)g(to)g(encrypt)g(a)f(message)h
(and)g(a)g(second)g(k)o(ey)-1950 56 y(to)e(decrypt)g(it.)26 b(In)18 b(a)f
(p)q(erfect)h(public-k)o(ey)g(system)e(it)h(is)g(not)g(p)q(ossible)g(to)g
(decrypt)g(a)h(message)e(without)h(the)-1950 57 y(second)f(k)o(ey)l(.)-223 
101 y(RSA:)g(Riv)o(est,)e(Shamir)h(and)g(Adlerman.)20 b(A)15 b(p)q(opular)g
(public-k)o(ey)g(cryptograph)o(y)g(system.)-1611 102 y(T)l(ro)s(jan)i
(Horse:)24 b(A)18 b(program)e(whic)o(h)i(claims)e(to)h(b)q(e)i(p)q
(erforming)e(one)g(function)h(while)f(actually)g(p)q(erforming)-1951 56 y
(another.)-165 102 y(Sanitizing:)29 b(Ensuring)21 b(that)f(con\014den)o
(tial)g(data)f(has)i(b)q(een)h(remo)o(v)o(ed)e(from)f(computer)i(media)f
(b)q(efore)h(the)-1950 56 y(media)15 b(is)g(disp)q(osed)g(of.)539 144 y
(24)-998 b
24 @eop1

25 @bop0
@F2 @sf
[<
FFFFF0003FF0FFFFF001FFF8FFFFF003FE1C03FC0007F80E03FC000FF80703FC001FF80703
FC001FF00703FC001FF00003FC001FF00003FC001FF00003FC001FE00003FC001FE00003FC
001FE00003FC001FE00003FC001FE00003FC001FC00003FC003F800003FC003F800003FC00
7F000003FC00FC000003FFFFF0000003FFFFFE000003FC007FC00003FC001FE00003FC0007
F80003FC0007F80003FC0003FC0003FC0003FE0003FC0003FE0003FC0003FE0003FC0003FE
0003FC0003FE0003FC0003FE0003FC0003FC0003FC0007FC0003FC0007F80003FC000FF000
03FC007FE000FFFFFFFF8000FFFFFFFE0000FFFFFFE00000>
	 48 41 -3 40 52] 82 @dc

25 @eop0

0 0 25 @bop1 195 w @F8 @sf(securit)o(y)15 b(logs:)j(A)e(recording)e(of)h
(all)f(ev)o(en)o(ts)h(of)g(a)g(computer)g(system)g(p)q(ertinen)o(t)g(to)f
(securit)o(y)l(.)-1639 102 y(Securit)o(y)e(through)f(obscurit)o(y:)18 b
(Securit)o(y)11 b(that)g(arises)h(from)f(ignorance)g(of)h(op)q(erating)f
(pro)q(cedures)i(rather)e(than)-1950 56 y(\014rst)k(principles.)-297 101 y
(serv)o(er:)31 b(With)20 b(resp)q(ect)h(to)g(a)f(net)o(w)o(ork,)h(the)g
(computer)g(or)f(program)g(whic)o(h)h(resp)q(onds)h(to)e(requests)h(from)
-1951 57 y(clien)o(ts.)-139 101 y(smart)14 b(card:)20 b(a)15 b
(credit-card)g(sized)g(computer,)g(used)h(for)e(user)i(authen)o(tication.)o 
-1412 102 a(sub)o(v)o(ersion:)j(A)o(ttac)o(ks)13 b(on)i(a)f(computer)g
(system's)g(securit)o(y)g(from)g(trusted)g(individuals)g(within)f(the)i
(organiza-)-1951 56 y(tion)-79 188 y @F2 @sf(26)69 b(References)21 b(and)j
(Credits)-837 147 y @F8 @sf(F)l(or)15 b(more)f(information)g(on)h
(computer)g(securit)o(y)l(,)f(see:)-956 101 y(The)j(Co)q(debreak)o(ers,)f
(b)o(y)g(Da)o(vid)f(Kahn,)i(1973.)22 b(Av)m(ailable)15 b(in)h(abridged)h
(\(b)o(y)e(author\))h(pap)q(erbac)o(k.)23 b(A)17 b(signet)-1951 57 y(Bo)q
(ok)e(from)g(The)g(New)g(American)g(Library)l(,)g(Inc,)g(Bergen\014eld,)h
(NJ)f(07621.)k(ISBN)d(0-451-08967)o(-7.)-1768 101 y(The)f(Hut)h(Six)f
(Story)l(,)f(b)o(y)h(Gordon)g(W)l(elc)o(hman.)-841 102 y(P)o(ersonal)i
(Computer)h(Securit)o(y)g(Considerations,)g(b)o(y)g(the)g(National)f
(Computer)h(Securit)o(y)g(Cen)o(ter,)h(NCSC-)-1950 56 y(W)-5 b(A-002-85,)
13 b(Decem)o(b)q(er)j(1985,)e(from)g(the)h(Go)o(v)o(ernmen)o(t)g(Prin)o
(ting)e(O\016ce.)-1326 102 y(Sp)q(ecial)22 b(Publication)f(500-120)g(-)h
(Securit)o(y)g(of)f(P)o(ersonal)g(Computer)h(Systems:)33 b(A)22 b
(Managemen)o(t)f(Guide,)-1950 56 y(Jan)o(uary)15 b(1985,)f(from)g(the)h
(National)f(Bureau)i(of)e(Standards.)-1088 102 y(Some)20 b(of)f(the)h
(informati)o(on)e(presen)o(ted)j(in)e(this)g(article)g(is)g(the)g(result)h
(of)f(discussions)g(on)h(the)f(ARP)l(ANET)-1949 56 y(net)o(w)o(ork)14 b
(\\Securit)o(y")g(mailing)g(list)g(and)h(the)h(Usenet)f(net)o(w)o(ork)f
(\\net.crypt")h(newsgroup.)-1588 101 y(Multics)f(is)h(a)g(trademark)f(of)h
(Honeyw)o(ell.)-737 102 y(UNIX)h(is)f(a)f(trademark)h(of)f(Bell)h(Lab)q
(oratories.)-847 101 y(VM/CMS)f(is)h(a)g(trademark)f(of)h(In)o
(ternational)f(Business)h(Mac)o(hines)g(\(IBM\).)-414 686 y(25)-998 b
25 @eop1

(\nEND-JOB simson.dvi\n) print flush
restore
DataMuseum.dk

DKUUG/EUUG Conference tapes

⟦eef6f249b⟧ TextFile

Derivation

TextFile
