CRYPT(3C)               COMMAND REFERENCE               CRYPT(3C)



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 normally a user's typed
     password.  The second is a two-character string chosen from
     the set a-z, A-Z, 0-9, ., and /.  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 password, 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 eight, 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 zeros and ones.  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 setkeys.  If edflag is 0,
     the argument is encrypted; if nonzero, it is decrypted.

CAVEATS
     The return value points to static data whose content is
     overwritten by each call.

SEE ALSO
     passwd(1), passwd(5), login(1), getpass(3c).







Printed 10/17/86                                                1

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