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crypt(1)
NAME
  crypt - encode/decode

SYNOPSIS
  crypt key < input.File > output.File

DESCRIPTION
  The crypt command reads from the standard input and writes on the standard
  output. You must supply a key which 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. The crypt command 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 fundamental
  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 substantial
  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
  /dev/tty
      for typed key

SEE ALSO
  Commands: ed(1), ex(1), vi(1), makekey(8)

  Functions: crypt(3)

Index for Section 1

Alphabetical listing for C

Top of page