crypt(3C)                                               crypt(3C)



     NAME
          crypt, setkey, encrypt - generate DES encryption

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

          void setkey (key)
          char *key;

          void encrypt (block, edflag)
          char *block;
          int edflag;

     DESCRIPTION
          crypt is the password encryption function.  It is based on
          the NBS Data Encryption Standard (DES), with variations
          intended to frustrate use of hardware implementations of the
          DES for key search.

          key is a user's typed password.  is a 2-character string
          chosen from the set [a-zA-Z0-9./]; this string is used to
          perturb the DES algorithm in one of 4,096 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 2 characters are the salt
          itself.

          The setkey and encrypt 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; this gives a 56-bit key which is set into the
          machine.  The 56-bit key is used with the above-mentioned
          algorithm to encrypt or decrypt 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 DES algorithm using the key set
          by setkey.  If edflag is zero, the argument is encrypted; if
          non-zero, it is decrypted.

     SEE ALSO
          login(1), passwd(1), getpass(3C), passwd(4).

     BUGS
          The return value points to static data that is overwritten
          by each call.



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