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(* $Id: crypt_3des.mli,v 1.1 1999/06/18 00:23:58 gerd Exp $
* ----------------------------------------------------------------------
* This module is part of the cryptgps package by Gerd Stolpmann.
*)
(* DES, created by the NSA, is a 64 bit block cipher. Triple-DES is a
* variant that applies DES three times to the same input block. More
* precisely, first the block is encrypted with key k1, then decrypted
* with key k2 and then encrypted again with key k3.
* It is best to choose k1,k2,k3 distinct. Sometimes k1=k3.
* This implementation accepts strings with 8, 16, or 24 bytes as keys,
* taking the first 8 bytes as k1, the second as k2, and the third as k3.
* Please note that some bits are used as parity bits, such that the
* effective key length is 56, resp. 112, resp. 168 bits.
*
* Triple-DES is 3 times slower than DES.
*)
module Cryptsystem : Cryptsystem_64.T;;
module Cryptmodes : Cryptmodes_64.T with type key = Cryptsystem.key;;
(* Key management functions:
*
* Although only 56 bits count a DES key is written with 64 bits. The
* extra bits are used for parity checking.
*)
val check_parity : string -> unit
(* Checks that the parity of the key given as string is ok. The string
* must have a length of 8 or 16 or 24 characters.
*)
val set_parity : string -> string
(* Sets the parity bits in the given key and returns a new string. *)
(* - DES has been heavily studied and seems to have a rather good design
* - DES has only 56 bit keys (this means DES should be considered a
* weak algorithm today, but the variant 3DES is still secure)
* - DES has been designed to be implemented in hardware, and software
* implementations are relatively slow
* - DES is an ANSI and (indirectly) an ISO standard.
* - There are very few weak keys.
*)
(* ======================================================================
* History:
*
* $Log: crypt_3des.mli,v $
* Revision 1.1 1999/06/18 00:23:58 gerd
* First release.
*
*)
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