crypt(1)
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crypt Command
encode/decode
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SYNTAX
crypt [ password ]
DESCRIPTION
Crypt, although documented here, is not distributed outside of
the United States in accordance with Federal Export regulations.
International versions of the DG/UX System do not include
encryption mechanisms. Crypt reads from the standard input and
writes on the standard output. 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 password <clear >cypher
crypt password <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; and "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, they
require a lot of work.
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 lowercase 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.
DG/UX 4.00 Page 1
Licensed material--property of copyright holder(s)
crypt(1)
The choice of keys and key security are the most vulnerable
aspect of crypt.
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EXAMPLES
$ cat aname
Don Ho
$ crypt 24 < aname > encryptedname
Crypt is passed a key and a file that contains a name to be
encrypted. Crypt puts the encrypted name into the file
encrypted_name.
$ crypt 24 < encryptedname
Don Ho
Crypt decrypts the contents of the encrypted file and displays
the decrypted results on the screen.
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FILES
/dev/tty For typed key
SEE ALSO
ed(1), makekey(1), stty(1).
BUGS
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 stty(1)).
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.
DG/UX 4.00 Page 2
Licensed material--property of copyright holder(s)