crypt(1)crypt(1)NAMEcrypt - encode/decode
SYNOPSIScrypt key < input.File > output.File
DESCRIPTION
The crypt command reads from the standard input and writes on the stan‐
dard output. You must supply a key which selects a particular transfor‐
mation. If no password is given, crypt demands a key from the terminal
and turns off printing while the key is being typed in. The crypt com‐
mand encrypts and decrypts with the same key.
Files encrypted by crypt are compatible with those treated by the ed,
ex and vi editors 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, and sneak paths by which keys or clear text can become
visible must be minimized.
The crypt command 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, for example, to take a sub‐
stantial fraction of a second to compute. However, if keys are
restricted to three lowercase letters, then encrypted files can be read
by expending only a substantial fraction of five minutes of machine
time.
Since the key you choose is an argument to the crypt command, it is
potentially visible to users executing the ps command or a derivative.
To minimize this possibility, crypt destroys any record of the key
immediately upon entry. The most vulnerable aspect of crypt is the
choice of keys and key security.
EXAMPLES
The following examples use KEY as the key to encrypt and decrypt files.
The first example encrypts the file plain.File, naming the resulting
encrypted file crypt.File. The second example decrypts the file
crypt.File, naming the resulting decrypted file decrypt.File. The third
example prints the encrypted file in clear text. $ crypt KEY <
plain.File > crypt.File
$ crypt KEY < crypt.File > decrypt.File
$ crypt KEY < crypt.File | pr
FILES
for typed key
SEE ALSO
Commands: ed(1), ex(1), vi(1), makekey(8)
Functions: crypt(3)crypt(1)
