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Unix Version 7 - man page for crypt (v7 section 1)

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 exe-
       cuting  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 for a particular pur-
       pose 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 Tele-
       phone 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)


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