CRYPT(1)						 CRYPT(1)

NAME
       crypt - encode/decode

SYNOPSIS
       crypt [ password ]

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 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 min-
       imized.

       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  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), makekey(8)

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CRYPT(1)						 CRYPT(1)

BUGS
       There is no warranty of merchantability nor  any	 warranty
       of  fitness  for	 a  particular purpose nor any other war-
       ranty, either express or implied, as to	the  accuracy  of
       the  enclosed materials or as to their suitability for any
       particular purpose.  Accordingly, Bell Telephone Laborato-
       ries assumes no responsibility for their use by the recip-
       ient.   Further, Bell Laboratories assumes  no  obligation
       to  furnish  any	 assistance of any kind whatsoever, or to
       furnish any additional information or documentation.

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