CRYPT(3C)                            SysV                            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 eight, 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
     by 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 SysV Command Reference.

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