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

   1 /* -*-c-*-
   2  *
   3  * $Id: skipjack.h,v 1.1 2000/07/15 15:39:33 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: skipjack.h,v $
  33  * Revision 1.1  2000/07/15 15:39:33  mdw
  34  * The NSA's Skipjack block cipher.
  35  *
  36  */
  37
  38 /*----- Notes on the Skipjack block cipher --------------------------------*
  39  *
  40  * Skipjack was designed by the NSA, as a type II algorithm to be used in the
  41  * Clipper system.  It was initially classified, so that it couldn't be used
  42  * without the key escrow feature, though a team of `respectable'
  43  * cryptographers, including Dorothy Denning, had a quick look at it and
  44  * pronounced it `good', as if this was meant to be convincing.  It is
  45  * apparently a particular parameterization of a family which includes type I
  46  * algorithms.  Since declassification, Biham has discovered a miss-in-the-
  47  * middle attack which breaks Skipjack with 31 rounds faster than brute
  48  * force.
  49  *
  50  * This implementation is provided for interest's sake, and possibly for
  51  * interoperability, rather than as a good cipher to use.
  52  */
  53
  54 #ifndef CATACOMB_SKIPJACK_H
  55 #define CATACOMB_SKIPJACK_H
  56
  57 #ifdef __cplusplus
  58   extern "C" {
  59 #endif
  60
  61 /*----- Header files ------------------------------------------------------*/
  62
  63 #include <stddef.h>
  64
  65 #include <mLib/bits.h>
  66
  67 /*----- Magical numbers ---------------------------------------------------*/
  68
  69 #define SKIPJACK_BLKSZ 8
  70 #define SKIPJACK_KEYSZ 10
  71 #define SKIPJACK_CLASS (N, B, 64)
  72
  73 extern const octet skipjack_keysz[];
  74
  75 /*----- Data structures ---------------------------------------------------*/
  76
  77 typedef struct skipjack_ctx {
  78   octet k[10];
  79 } skipjack_ctx;
  80
  81 /*----- Functions provided ------------------------------------------------*/
  82
  83 /* --- @skipjack_init@ --- *
  84  *
  85  * Arguments:   @skipjack_ctx *k@ = pointer to key block
  86  *              @const void *buf@ = pointer to key buffer
  87  *              @size_t sz@ = size of key material
  88  *
  89  * Returns:     ---
  90  *
  91  * Use:         Initializes a Skipjack key buffer.  The key buffer must be
  92  *              exactly 10 bytes long.
  93  */
  94
  95 extern void skipjack_init(skipjack_ctx */*k*/,
  96                           const void */*buf*/, size_t /*sz*/);
  97
  98 /* --- @skipjack_eblk@, @skipjack_dblk@ --- *
  99  *
 100  * Arguments:   @const skipjack_ctx *k@ = pointer to key block
 101  *              @const uint32 s[2]@ = pointer to source block
 102  *              @uint32 d[2]@ = pointer to skipjacktination block
 103  *
 104  * Returns:     ---
 105  *
 106  * Use:         Low-level block encryption and decryption.
 107  */
 108
 109 extern void skipjack_eblk(const skipjack_ctx */*k*/,
 110                           const uint32 */*s*/, uint32 */*d*/);
 111 extern void skipjack_dblk(const skipjack_ctx */*k*/,
 112                           const uint32 */*s*/, uint32 */*d*/);
 113
 114 /*----- That's all, folks -------------------------------------------------*/
 115
 116 #ifdef __cplusplus
 117   }
 118 #endif
 119
 120 #endif