term% cat index.txt CRYPT(3) Library Functions Manual CRYPT(3)
NAME
crypt, setkey, encrypt - DES encryption
SYNOPSIS
char *crypt(key, salt)
char *key, *salt;
setkey(key)
char *key;
encrypt(block, edflag)
char *block;
DESCRIPTION
Crypt is the password encryption routine. It is based on the NBS Data
Encryption Standard, with variations intended (among other things) to
frustrate use of hardware implementations of the DES for key search.
The first argument to crypt is a user's typed password. The second is
a 2-character string chosen from the set [a-zA-Z0-9./]. The salt
string is used to perturb the DES 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 pass‐
word, in the same alphabet as the salt. The first two characters are
the salt itself.
The other entries provide (rather primitive) access to the actual DES
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, leading to a 56-bit key which is set into the machine.
The argument to the encrypt entry is likewise a character array of
length 64 containing 0's and 1's. The argument array is modified in
place to a similar array representing the bits of the argument after
having been subjected to the DES algorithm using the key set by setkey.
If edflag is 0, the argument is encrypted; if non-zero, it is de‐
crypted.
SEE ALSO
crypt(1), passwd(1), passwd(5), getpass(3)
BUGS
The return value points to static data whose content is overwritten by
each call.
Crypt and encrypt are not available outside the United States and
Canada.
CRYPT(3)