CRYPT(1)                                                 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
          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).



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     CRYPT(1)                                                 CRYPT(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)).

     ORIGIN
          AT&T V.3








































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