crypt(1)                   DG/UX 4.30                    crypt(1)



     NAME
          crypt - encode/decode

     SYNOPSIS
          crypt [ password ]

     DESCRIPTION
          Crypt, although documented here, is not distributed outside
          of the United States in accordance with Federal Export
          regulations.  International versions of the DG/UX System do
          not include encryption mechanisms.  Crypt reads from the
          standard input and writes on the standard output.  Password
          is a key that selects a particular transformation.  If no
          password is given, crypt demands a key from the terminal and
          turns off printing while the key is being typed in.  Crypt
          encrypts and decrypts with the same key:

               crypt password <clear >cypher

               crypt password <cypher | pr

          will print the clear.

          Files encrypted by crypt are compatible with those treated
          by the editor ed in encryption mode.

          The security of encrypted files depends on three factors:
          the fundamental method must be hard to solve; direct search
          of the key space must be infeasible; and "sneak paths" by
          which keys or clear text can become visible must be
          minimized.

          Crypt implements a one-rotor machine designed along the
          lines of the German Enigma, but with a 256-element rotor.
          Methods of attack on such machines are known, but not
          widely; moreover, they require a lot of work.

          The transformation of a key into the internal settings of
          the machine is deliberately designed to be expensive, i.e.,
          to take a substantial fraction of a second to compute.
          However, if keys are restricted to (say) three lowercase
          letters, then encrypted files can be read by expending only
          a substantial fraction of five minutes of machine time.

          Since the key is an argument to the crypt command, it is
          potentially visible to users executing ps(1) or a
          derivative.  The choice of keys and key security are the
          most vulnerable aspect of crypt.







     Licensed material--property of copyright holder(s)         Page 1

     crypt(1)                   DG/UX 4.30                    crypt(1)



     EXAMPLES
          $ cat aname
          Don Ho
          $ crypt 24 < aname > encryptedname

          Crypt is passed a key and a file that contains a name to be
          encrypted.  Crypt puts the encrypted name into the file
          encrypted_name.
          $ crypt 24 < encryptedname
          Don Ho

          Crypt decrypts the contents of the encrypted file and
          displays the decrypted results on the screen.

     FILES
          /dev/tty  For typed key

     SEE ALSO
          ed(1), makekey(1), stty(1).

     BUGS
          If output is piped to nroff and the encryption key is not
          given on the command line, crypt can leave terminal modes in
          a strange state (see stty(1)).
          If two or more files encrypted with the same key are
          concatenated and an attempt is made to decrypt the result,
          only the contents of the first of the original files will be
          decrypted correctly.



























     Licensed material--property of copyright holder(s)         Page 2