CRYPT(C) XENIX System V CRYPT(C)
Name
crypt - Encode/decode.
Syntax
crypt [ password ]
crypt [-k]
Description
The crypt command reads from the standard input and writes
to the standard output. The password is a key that selects
a particular transformation. If no argument is given, crypt
demands a key from the terminal and turns off printing while
the key is being typed in. If the -k option is used, crypt
will use the key assigned to the environment variable
CRYPTKEY. The crypt command encrypts and decrypts with the
same key:
crypt key <clear >cypher
crypt key <cypher | pr
Files encrypted by crypt are compatible with those treated
by the editors ed(C), edit(C), ex(C), and vi(C) 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.
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, 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.
If the key is an argument to the crypt command, it is
potentially visible to users executing ps(C) or a
derivative. To minimize this possibility, crypt takes care
to destroy any record of the key immediately upon entry.
The choice of keys and key security are the most vulnerable
aspect of crypt.
Files
/dev/tty for typed key
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CRYPT(C) XENIX System V CRYPT(C)
See Also
ed(C), edit(C), ex(C), makekey(C), ps(C), stty(C), vi(C)
Notes
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.
Distribution of the crypt libraries and utilities is
regulated by the U.S. Government and are not available to
sites outside of the United States and its territories.
Because we cannot control the destination of the software,
these utilities are not included in the standard product.
If your site is within the U.S. or its territories, you can
obtain the crypt software through your product distributor
or reseller.
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