CRYPT(3C) (C Programming Language Utilities) CRYPT(3C)
NAME
crypt, setkey, encrypt - generate hashing encryption
SYNOPSIS
char *crypt (key, salt)
char *key, *salt;
void setkey (key)
char *key;
void encrypt (block, ignored)
char *block;
int ignored;
DESCRIPTION
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.
Key is a user's typed password. Salt is a two-character
string chosen from the set [a-zA-Z0-9./]; 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.
The setkey and encrypt entries provide (rather primitive)
access to the actual hashing algorithm. The argument of
setkey is a character array of length 64 containing only the
characters with numerical value 0 and 1. If 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. This is the key that will be used with the hashing
algorithm to encrypt the string block with the function
encrypt.
The argument to the encrypt entry is a character array of
length 64 containing only the characters with numerical
Page 1 May 1989
CRYPT(3C) (C Programming Language Utilities) CRYPT(3C)
value 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 setkey. Ignored is unused by encrypt but it must be
present.
SEE ALSO
getpass(3C), passwd(4).
login(1), passwd(1) in the User's Reference Manual.
CAVEAT
The return value points to static data that are overwritten
by each call.
Page 2 May 1989