git.distorted.org.uk Git - u/mdw/catacomb/blob - skipjack.h

   1 /* -*-c-*-
   2  *
   3  * $Id: skipjack.h,v 1.3 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * The Skipjack block cipher
   6  *
   7  * (c) 2000 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Notes on the Skipjack block cipher --------------------------------*
  31  *
  32  * Skipjack was designed by the NSA, as a type II algorithm to be used in the
  33  * Clipper system.  It was initially classified, so that it couldn't be used
  34  * without the key escrow feature, though a team of `respectable'
  35  * cryptographers, including Dorothy Denning, had a quick look at it and
  36  * pronounced it `good', as if this was meant to be convincing.  It is
  37  * apparently a particular parameterization of a family which includes type I
  38  * algorithms.  Since declassification, Biham has discovered a miss-in-the-
  39  * middle attack which breaks Skipjack with 31 rounds faster than brute
  40  * force.
  41  *
  42  * This implementation is provided for interest's sake, and possibly for
  43  * interoperability, rather than as a good cipher to use.
  44  */
  45
  46 #ifndef CATACOMB_SKIPJACK_H
  47 #define CATACOMB_SKIPJACK_H
  48
  49 #ifdef __cplusplus
  50   extern "C" {
  51 #endif
  52
  53 /*----- Header files ------------------------------------------------------*/
  54
  55 #include <stddef.h>
  56
  57 #include <mLib/bits.h>
  58
  59 /*----- Magical numbers ---------------------------------------------------*/
  60
  61 #define SKIPJACK_BLKSZ 8
  62 #define SKIPJACK_KEYSZ 10
  63 #define SKIPJACK_CLASS (N, B, 64)
  64
  65 extern const octet skipjack_keysz[];
  66
  67 /*----- Data structures ---------------------------------------------------*/
  68
  69 typedef struct skipjack_ctx {
  70   uint32 ka, kb, kc, kd, ke;
  71 } skipjack_ctx;
  72
  73 /*----- Functions provided ------------------------------------------------*/
  74
  75 /* --- @skipjack_init@ --- *
  76  *
  77  * Arguments:   @skipjack_ctx *k@ = pointer to key block
  78  *              @const void *buf@ = pointer to key buffer
  79  *              @size_t sz@ = size of key material
  80  *
  81  * Returns:     ---
  82  *
  83  * Use:         Initializes a Skipjack key buffer.  The key buffer must be
  84  *              exactly 10 bytes long.
  85  */
  86
  87 extern void skipjack_init(skipjack_ctx */*k*/,
  88                           const void */*buf*/, size_t /*sz*/);
  89
  90 /* --- @skipjack_eblk@, @skipjack_dblk@ --- *
  91  *
  92  * Arguments:   @const skipjack_ctx *k@ = pointer to key block
  93  *              @const uint32 s[2]@ = pointer to source block
  94  *              @uint32 d[2]@ = pointer to skipjacktination block
  95  *
  96  * Returns:     ---
  97  *
  98  * Use:         Low-level block encryption and decryption.
  99  */
 100
 101 extern void skipjack_eblk(const skipjack_ctx */*k*/,
 102                           const uint32 */*s*/, uint32 */*d*/);
 103 extern void skipjack_dblk(const skipjack_ctx */*k*/,
 104                           const uint32 */*s*/, uint32 */*d*/);
 105
 106 /*----- That's all, folks -------------------------------------------------*/
 107
 108 #ifdef __cplusplus
 109   }
 110 #endif
 111
 112 #endif