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

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