CRYPT(1)            RISC/os Reference Manual             CRYPT(1)



NAME
     crypt - encode/decode

SYNOPSIS
     crypt [ password ]
     crypt [-k]

DESCRIPTION
     crypt reads from the standard input and writes on the stan-
     dard output.  The password is a key that selects a particu-
     lar 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 encryp-
     tion 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.  How-
     ever, 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 poten-
     tially 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), nroff(1), pg(1), ps(1),
     stty(1), vi(1).



                        Printed 11/19/92                   Page 1

CRYPT(1)            RISC/os Reference Manual             CRYPT(1)



NOTES
     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 con-
     catenated and an attempt is made to decrypt the result, only
     the contents of the first of the original files will be
     decrypted correctly.

     If output is piped to nroff and the encryption key is not
     given on the command line then do not pipe crypt through
     pg(1) or any other program that changes the tty settings.
     Doing so may cause crypt to leave terminal modes in a
     strange state [see stty(1)].










































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