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



NAME
     crypt - encode/decode

SYNOPSIS
     crypt [ password ]

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 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 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.  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.

     Since the key is an argument to the crypt command, it is
     potentially visible to users executing ps(1) or a deriva-
     tive.  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 security are the most
     vulnerable aspect of crypt.

FILES
     /dev/tty      for typed key

SEE ALSO
     ed(1).



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



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