CRYPT(1)                GENIX Programmer's Manual                CRYPT(1)



      NAME
           crypt - encode/decode

      SYNOPSIS
           crypt [ password ]

      DESCRIPTION
           Crypt reads from the standard input and writes on the standard  out-
           put.   The  password  is a key that selects a particular transforma-
           tion.  If no password is given, crypt demands a key from the  termi-
           nal  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 funda-
           mental  method must be hard to solve; direct search of the key space
           must be infeasible; `sneak paths' by which  keys  or  cleartext  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.

           Since the key is an argument to the crypt command, it is potentially
           visible  to users executing ps(1) or a derivative.  To minimize this
           possibility, crypt takes care to  destroy  any  record  of  the  key
           immediately  upon  entry.  No doubt the choice of keys and key secu-
           rity are the most vulnerable aspect of crypt.

      FILES
           /dev/tty for typed key

      SEE ALSO
           ed(1), makekey(8)

      BUGS
           There is no warranty of merchantability nor any warranty of  fitness



      Printed 11/16/83                                                        1

      CRYPT(1)                GENIX Programmer's Manual                CRYPT(1)



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      Printed 11/16/83                                                        2