


      CRYPT(1)                    (UNIX 5.0)                   CRYPT(1)



      NAME
           crypt - encode/decode

      SYNTAX
           crypt [ password ]

      DESCRIPTION
           Crypt encrypts and decrypts files according to a password.

           Crypt reads from the standard input and writes on the
           standard output.

           The 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 key <clear >cypher
                crypt key <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; ``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.

           To discourage a spy from trying all combination of keywords
           to read your file, the transformation of files is
           deliberately slow.  But a keyword of three lowercase
           characters would be quite easy to crack in a short time, so
           make your keywords longer.

           To prevent your keyword from showing up in the command field
           of the ps(1) output, crypt destroys the record of the
           keyword immediately upon execution.

           The choice of keys and key security are the most vulnerable
           aspect of crypt.

           You may encryt a file twice, with two different keywords.



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      CRYPT(1)                    (UNIX 5.0)                   CRYPT(1)



           According to federal export regulations, crypt is not
           available out of U.S.A.

      FILES
           /dev/tty  for typed key

      SEE ALSO
           ed(1), makekey(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.






































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