V10/man/man1/crypt.1

.TH CRYPT 1
.CT 1 misc files secur
.SH NAME
crypt, encrypt, decrypt \- encode/decode
.SH SYNOPSIS
.B /usr/games/crypt
[
.I password
]
.PP
.B /usr/games/encrypt
[
.B -p
] [
.I password
]
.PP
.B /usr/games/decrypt
[
.B -p
] [
.I password
]
.SH DESCRIPTION
These commands read from the standard input and write
on the standard output.
The
.I password
is an enciphering key.
If no password
is given,
one is demanded from the terminal;
echoing is turned off while it is being typed in.
.I Crypt
uses a relatively simple, fast method (rotor machine) for both
enciphering and deciphering.
.I Encrypt
and
.I decrypt
use a more robust, slower method (DES).
Files enciphered by
.I crypt
are not intelligible to
.I encrypt/decrypt,
and vice versa.
.PP
It is prudent to supply the key from the terminal,
not from the command line, and to pick a reasonably obscure and long key
(6 letters for
.I crypt
and much longer for
.IR encrypt ).
.PP
Under option
.B -p
.I encrypt
enciphers into printing characters, which can be sent by
.IR mail (1).
.I Decrypt 
can distinguish ciphertext from clear:
it will work on a full mail message, headers and all.
.SH FILES
.F /dev/tty
for typed key
.SH "SEE ALSO"
.IR ed (1),
.IR makekey (8)
.br
J. A. Reeds and P. J. Weinberger,
`File Security and the Unix Crypt Command,'
.I AT&T Bell Laboratories Technical Journal,
.B 63
(1984) 1673-1684
.SH BUGS
.I Crypt
is breakable by knowledgeable cryptanalysts.
Its only practical use is for mildly private
data transmission.
.I Encrypt/decrypt
gives strong protection for transmission over untrusted
channels between trusted machines.
.br
It is unwise to count on encryption of any sort for
safe storage of documents.