32v 1m crypt

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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

    There is no warranty of merchantability nor any warranty of
    fitness for a particular purpose nor any other warranty,
    either express or implied, as to the accuracy of the
    enclosed materials or as to their suitability for any par-
    ticular purpose.  Accordingly, Bell Telephone Laboratories
    assumes no responsibility for their use by the recipient.
    Further, Bell Laboratories assumes no obligation to furnish
    any assistance of any kind whatsoever, or to furnish any
    additional information or documentation.