2.9BSD/usr/man/cat3/crypt.3

CRYPT(3)            UNIX Programmer's 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
     _C_r_y_p_t 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 implemen-
     tations of the DES for key search.

     The first argument to _c_r_y_p_t is a user's typed password.  The
     second is a 2-character string chosen from the set [a-zA-
     Z0-9./].  The _s_a_l_t string is used to perturb the DES algo-
     rithm in one of 4096 different ways, after which the pass-
     word 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 char-
     acters are the salt itself.

     The other entries provide (rather primitive) access to the
     actual DES algorithm.  The argument of _s_e_t_k_e_y 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 _e_n_c_r_y_p_t 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 _s_e_t_k_e_y. If _e_d_f_l_a_g is 0,
     the argument is encrypted; if non-zero, it is decrypted.

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

BUGS
     The return value points to static data whose contents are
     overwritten by each call.

Printed 7/31/83                                                 1