crypt - encode or decode a file
The crypt utility encrypts and decrypts the contents of a
file. crypt reads from the standard input and writes on the
standard output. The password is a key that selects a par-
ticular 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:
example% crypt key<clear.file> encrypted.file
example% crypt key<encrypted.file | pr
will print the contents of clear.file.
Files encrypted by crypt are compatible with those treated
by the editors ed(1), ex(1), and vi(1) 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 cleartext 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 widely known, thus
crypt provides minimal security.
The transformation of a key into the internal settings of
the machine is deliberately designed to be expensive, that
is, 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
command. To minimize this possibility, crypt takes care to
destroy any record of the key immediately upon entry. No
doubt the choice of keys and key security are the most
vulnerable aspect of crypt.
for typed key
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWcsu |
des(1), ed(1), ex(1), makekey(1), ps(1), vi(1), attributes
Man(1) output converted with