CRYPT(1)						      General Commands Manual							  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 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  security  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 for a particular purpose nor any other warranty, either express or
       implied, as to the accuracy of the enclosed materials or as to their suitability for any particular purpose.  Accordingly,  Bell  Telephone
       Laboratories  assumes  no  responsibility for their use by the recipient.   Further, Bell Laboratories assumes no obligation to furnish any
       assistance of any kind whatsoever, or to furnish any additional information or documentation.

																	  CRYPT(1)