CRYPT(1)       (Security Administration Utilities)       CRYPT(1)



  NAME
       crypt - encode/decode

  SYNOPSIS
       crypt [ password ]
       crypt [-k]

  DESCRIPTION
       crypt reads from the standard input and writes on the
       standard output.  The password is a key that selects a
       particular transformation.  If no argument is given, crypt
       demands a key from the terminal and turns off printing while
       the key is being typed in.  If the -k option is used, crypt
       will use the key assigned to the environment variable
       CRYPTKEY.  crypt encrypts and decrypts with the same key:

            crypt key <clear >cypher
            crypt key <cypher | pr

       Files encrypted by crypt are compatible with those treated
       by the editors ed(1), edit(1), ex(1), and vi(1) 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; ``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 the amount of work required is likely to be
       large.

       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 lower-case
       letters, then encrypted files can be read by expending only


  Page 1                                                   May 1989

  CRYPT(1)       (Security Administration Utilities)       CRYPT(1)



       a substantial fraction of five minutes of machine time.

       If 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.

  FILES
       /dev/tty  for typed key

  SEE ALSO
       ed(1), edit(1), ex(1), makekey(1), ps(1), stty(1), vi(1).

  WARNING
       This command is provided with the Security Administration
       Utilities, which is only available in the United States.  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.

  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)).

















  Page 2                                                   May 1989