CRYPT(3C)                                                            CRYPT(3C)


NAME
     crypt, setkey, encrypt - generate hashing encryption

SYNOPSIS
     #include <crypt.h>

     char *crypt(const char *key, const char *salt);

     void setkey(const char *key);

     void encrypt(const 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 the input string to encrypt, for instance, 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 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
     login(1), passwd(1), getpass(3C), passwd(4)

CAVEAT
     The return value points to static data that are overwritten by each call.


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