man(1) Manual page archive

     CRYPT(3)                                                 CRYPT(3)

          crypt, setkey, encrypt - DES encryption

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

          char *key;

          encrypt(block, edflag)
          char *block;

          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 implemen-
          tations 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 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 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 decrypted.

          crypt(1), passwd(1), passwd(5), getpass(3)

          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.