32v 1m crypt

CRYPT(1) UNIX Programmer's Manual CRYPT(1)

NAME

    crypt - encode/decode

SYNOPSIS

    crypt [ password ]

DESCRIPTION

    _C_r_y_p_t reads from the standard input and writes on the stan-
    dard output.  The _p_a_s_s_w_o_r_d is a key that selects a particu-
    lar transformation.  If no _p_a_s_s_w_o_r_d is given, _c_r_y_p_t demands
    a key from the terminal and turns off printing while the key
    is being typed in.  _C_r_y_p_t encrypts and decrypts with the
    same key:

         crypt key <clear >cypher
         crypt key <cypher | pr

    will print the clear.

    Files encrypted by _c_r_y_p_t are compatible with those treated
    by the editor _e_d 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.

    _C_r_y_p_t 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.  How-
    ever, 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 _c_r_y_p_t command, it is
    potentially visible to users executing _p_s(1) or a deriva-
    tive.  To minimize this possibility, _c_r_y_p_t 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 _c_r_y_p_t.

FILES

    /dev/tty for typed key

SEE ALSO

    ed(1), makekey(8)

BUGS

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