.\" @(#)crypt.1 6.4 (Berkeley) 4/22/91
.TH CRYPT 1 "April 22, 1991"
This interface is obsoleted by bdes(1).
reads from the standard input and writes
is a key that selects a particular transformation.
demands a key from the terminal and turns
off printing while the key is being typed in.
encrypts and decrypts with the same key:
are compatible with those treated by the editor
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.
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
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
it is potentially visible to users executing
To minimize this possibility,
takes care to destroy any record of the key
No doubt the choice of keys and key security
are the most vulnerable aspect of
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