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CRYPT(1)							      CRYPT(1)

NAME    [Toc]    [Back]

     crypt - encode/decode

SYNOPSIS    [Toc]    [Back]

     crypt [ password ]
     crypt [-k]

DESCRIPTION    [Toc]    [Back]

     crypt reads from the standard input and writes on the standard output.
     The password is a key that	selects	a particular transformation.  If no
     argument is given,	crypt demands a	key from the terminal and turns	off
     printing while the	key is being typed in.	If the -k option is used,
     crypt will	use the	key assigned to	the environment	variable CrYpTkEy.
     crypt encrypts and	decrypts with the same key:

	  crypt	key <clear >cypher
	  crypt	key <cypher | pr

     Files encrypted by	crypt are compatible with those	treated	by the editors
     ed(1), edit(1), ex(1), and	vi(1) 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 clear	text 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.

     If	the key	is an argument to the crypt command, it	is potentially visible
     to	users executing	ps(1) or a derivative.	The choice of keys and key
     security are the most vulnerable aspect of	crypt.

FILES    [Toc]    [Back]

     /dev/tty  for typed key

SEE ALSO    [Toc]    [Back]

     ed(1), edit(1), ex(1), makekey(1),	ps(1), stty(1),	vi(1).

WARNING    [Toc]    [Back]

     If	two or more files encrypted with the same key are concatenated and an
     attempt is	made to	decrypt	the result, only the contents of the first of
     the original files	will be	decrypted correctly.

									Page 1

CRYPT(1)							      CRYPT(1)

BUGS    [Toc]    [Back]

     If	output is piped	to nroff and the encryption key	is not given on	the
     command line, crypt can leave terminal modes in a strange state (see

									PPPPaaaaggggeeee 2222
[ Back ]
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