CRYPT(1) — HP-UX
NAME
crypt − encode/decode files
SYNOPSIS
crypt [ password ]
REMARKS
The decryption facilities provided by this software are under control of the United States Government and cannot be exported without special licenses. These capabilities are only available by special arrangement through HP.
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 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 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. The choice of keys and key security are the most vulnerable aspect of crypt.
FILES
/dev/ttyfor typed key
SEE ALSO
BUGS
If output is piped to nroff(1) 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.
Hewlett-Packard Company — Version B.1, May 11, 2021