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    Length: 1714 (0x6b2)
    Types: TextFile
    Notes: UNIX file
    Names: »crypt.3«

└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
    └─⟦28c352965⟧ »/a« UNIX Filesystem
        └─⟦this⟧ »usr/man/man3/crypt.3« 

TextFile

.ig
	@(#)crypt.3	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH CRYPT 3 
.SH NAME
crypt, encrypt \- a one way hashing encryption algorithm
.SH SYNOPSIS
.nf
.B char \(**crypt (key, salt)
.B char \(**key, \(**salt;
.PP
.B void encrypt (block)
.B char \(**block;
.SH DESCRIPTION
.I Crypt\^
is the password encryption function.
It is based on a one way hashing encryption algorithm with
variations intended (among other things) to frustrate use of hardware
implementations of a key search.
.PP
.I Key\^
is a user's typed password.
.I Salt\^
is a two-character string chosen from the
set [\f3a-zA-Z0-9./\fP];
this
string is used to perturb the hashing algorithm in one of 4096
different ways, after which the password is used as the key to
encrypt repeatedly a constant string.
The returned value points to the encrypted password.
The first two characters are the salt itself.
.PP
There is a character array of length 64 containing only the characters
with numerical value 0 and 1.
When this string is divided into groups of 8,
the low-order bit in each group is ignored;
this gives a 56-bit key which is set into the machine by crypt.
.PP
The
.I encrypt\^
entry provides (rather primitive)
access to the actual hashing algorithm.
The argument to the
.I encrypt\^
entry is a character array of length 64 containing only the characters
with numerical value of 0 and 1.
The argument array is modified in place to a similar array
representing the bits of the argument after having been
subjected to the hashing algorithm using the key set by
.IR crypt .
.SH "SEE ALSO"
passwd(1), passwd(5), login(1), getpass(3)
.SH BUGS
The return value
points to static data that are overwritten
by each call.