CRYPT(1) General Commands Manual CRYPT(1)
crypt - encode/decode
crypt [ password ]
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 edi-
tor ed in encryption mode.
The security of encrypted files depends on three factors: the fundamen-
tal method must be hard to solve; direct search of the key space must
be infeasible; `sneak paths' by which keys or cleartext can become vis-
ible 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 executing ps(1) or a derivative. To minimize this
possibility, crypt takes care to destroy any record of the key immedi-
ately upon entry. No doubt the choice of keys and key security are the
most vulnerable aspect of crypt.
/dev/tty for typed key
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