crypt.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th CRYPT III 4/30/73
.sh NAME
crypt \*- password encoding
.sh SYNOPSIS
.ft B
mov	$key,r0
.br
jsr	pc,crypt
.s3
char *crypt(key)
.br
char *key;
.ft R
.sh DESCRIPTION
On entry, r0 points to a string of
characters terminated by an ASCII NUL.
The routine
performs an operation on the key which is difficult to invert
(i.e. encrypts it) and leaves the resulting eight bytes
of ASCII alphanumerics in a global cell called ``word''.
.s3
From C, the
.it key
argument is a string
and the value returned is a pointer to the eight-character
result.
.s3
This routine is used to encrypt all passwords.
.sh "SEE ALSO"
passwd(I), passwd(V), login(I)
.sh BUGS
Short or otherwise simple passwords can be decrypted
easily by exhaustive search.
Six characters of gibberish is reasonably safe.