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

   1 /* -*-c-*-
   2  *
   3  * $Id: skipjack.c,v 1.2 2000/07/15 20:48:45 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.c,v $
  33  * Revision 1.2  2000/07/15 20:48:45  mdw
  34  * Remove some useless tests in the G function.
  35  *
  36  * Revision 1.1  2000/07/15 15:39:33  mdw
  37  * The NSA's Skipjack block cipher.
  38  *
  39  */
  40
  41 /*----- Header files ------------------------------------------------------*/
  42
  43 #include <mLib/bits.h>
  44
  45 #include "blkc.h"
  46 #include "gcipher.h"
  47 #include "skipjack.h"
  48 #include "skipjack-tab.h"
  49
  50 /*----- Global variables --------------------------------------------------*/
  51
  52 const octet skipjack_keysz[] = { KSZ_SET, 10, 0 };
  53
  54 /*----- The Skipjack S-box ------------------------------------------------*/
  55
  56 static octet f[256] = SKIPJACK_S;
  57
  58 /*----- Main code ---------------------------------------------------------*/
  59
  60 /* --- @skipjack_init@ --- *
  61  *
  62  * Arguments:   @skipjack_ctx *k@ = pointer to key block
  63  *              @const void *buf@ = pointer to key buffer
  64  *              @size_t sz@ = size of key material
  65  *
  66  * Returns:     ---
  67  *
  68  * Use:         Initializes a Skipjack key buffer.  The key buffer must be
  69  *              exactly 10 bytes long.
  70  */
  71
  72 void skipjack_init(skipjack_ctx *k, const void *buf, size_t sz)
  73 {
  74   KSZ_ASSERT(skipjack, sz);
  75   memcpy(k->k, buf, sz);
  76 }
  77
  78 /* --- @skipjack_eblk@, @skipjack_dblk@ --- *
  79  *
  80  * Arguments:   @const skipjack_ctx *k@ = pointer to key block
  81  *              @const uint32 s[2]@ = pointer to source block
  82  *              @uint32 d[2]@ = pointer to skipjacktination block
  83  *
  84  * Returns:     ---
  85  *
  86  * Use:         Low-level block encryption and decryption.
  87  */
  88
  89 #define G(x, i) do {                                                    \
  90   octet _x = U8(x >> 8), _y = U8(x);                                    \
  91   _x ^= f[_y ^ k->k[i++]];                                              \
  92   _y ^= f[_x ^ k->k[i++]]; if (i >= 10) i = 0;                          \
  93   _x ^= f[_y ^ k->k[i++]];                                              \
  94   _y ^= f[_x ^ k->k[i++]]; if (i >= 10) i = 0;                          \
  95   x = U16((_x << 8) | _y);                                              \
  96 } while (0)
  97
  98 #define RULE_A(w, x, y, z, n, i) do {                                   \
  99   G(w, i); z ^= w ^ n++;                                                \
 100 } while (0)
 101
 102 #define RULE_B(w, x, y, z, n, i) do {                                   \
 103   x ^= w ^ n++; G(w, i);                                                \
 104 } while (0)
 105
 106 void skipjack_eblk(const skipjack_ctx *k, const uint32 *s, uint32 *d)
 107 {
 108   unsigned i = 0;
 109   unsigned n = 1;
 110   uint16 w = U16(s[0] >> 16), x = U16(s[0]);
 111   uint16 y = U16(s[1] >> 16), z = U16(s[1]);
 112
 113   RULE_A(w, x, y, z, n, i); RULE_A(z, w, x, y, n, i);
 114   RULE_A(y, z, w, x, n, i); RULE_A(x, y, z, w, n, i);
 115   RULE_A(w, x, y, z, n, i); RULE_A(z, w, x, y, n, i);
 116   RULE_A(y, z, w, x, n, i); RULE_A(x, y, z, w, n, i);
 117   RULE_B(w, x, y, z, n, i); RULE_B(z, w, x, y, n, i);
 118   RULE_B(y, z, w, x, n, i); RULE_B(x, y, z, w, n, i);
 119   RULE_B(w, x, y, z, n, i); RULE_B(z, w, x, y, n, i);
 120   RULE_B(y, z, w, x, n, i); RULE_B(x, y, z, w, n, i);
 121   RULE_A(w, x, y, z, n, i); RULE_A(z, w, x, y, n, i);
 122   RULE_A(y, z, w, x, n, i); RULE_A(x, y, z, w, n, i);
 123   RULE_A(w, x, y, z, n, i); RULE_A(z, w, x, y, n, i);
 124   RULE_A(y, z, w, x, n, i); RULE_A(x, y, z, w, n, i);
 125   RULE_B(w, x, y, z, n, i); RULE_B(z, w, x, y, n, i);
 126   RULE_B(y, z, w, x, n, i); RULE_B(x, y, z, w, n, i);
 127   RULE_B(w, x, y, z, n, i); RULE_B(z, w, x, y, n, i);
 128   RULE_B(y, z, w, x, n, i); RULE_B(x, y, z, w, n, i);
 129
 130   d[0] = ((uint32)w << 16) | (uint32)x;
 131   d[1] = ((uint32)y << 16) | (uint32)z;
 132 }
 133
 134 #define G_INV(x, i) do {                                                \
 135   octet _x = U8(x >> 8), _y = U8(x);                                    \
 136   _y ^= f[_x ^ k->k[--i]];                                              \
 137   _x ^= f[_y ^ k->k[--i]]; if (i == 0) i = 10;                          \
 138   _y ^= f[_x ^ k->k[--i]];                                              \
 139   _x ^= f[_y ^ k->k[--i]]; if (i == 0) i = 10;                          \
 140   x = U16((_x << 8) | _y);                                              \
 141 } while (0)
 142
 143 #define RULE_A_INV(w, x, y, z, n, i) do {                               \
 144   w ^= x ^ --n; G_INV(x, i);                                            \
 145 } while (0)
 146
 147 #define RULE_B_INV(w, x, y, z, n, i) do {                               \
 148   G_INV(x, i); y ^= x ^ --n;                                            \
 149 } while (0)
 150
 151 void skipjack_dblk(const skipjack_ctx *k, const uint32 *s, uint32 *d)
 152 {
 153   unsigned i = 8;
 154   unsigned n = 33;
 155   uint16 w = U16(s[0] >> 16), x = U16(s[0]);
 156   uint16 y = U16(s[1] >> 16), z = U16(s[1]);
 157
 158   RULE_B_INV(w, x, y, z, n, i); RULE_B_INV(x, y, z, w, n, i);
 159   RULE_B_INV(y, z, w, x, n, i); RULE_B_INV(z, w, x, y, n, i);
 160   RULE_B_INV(w, x, y, z, n, i); RULE_B_INV(x, y, z, w, n, i);
 161   RULE_B_INV(y, z, w, x, n, i); RULE_B_INV(z, w, x, y, n, i);
 162   RULE_A_INV(w, x, y, z, n, i); RULE_A_INV(x, y, z, w, n, i);
 163   RULE_A_INV(y, z, w, x, n, i); RULE_A_INV(z, w, x, y, n, i);
 164   RULE_A_INV(w, x, y, z, n, i); RULE_A_INV(x, y, z, w, n, i);
 165   RULE_A_INV(y, z, w, x, n, i); RULE_A_INV(z, w, x, y, n, i);
 166   RULE_B_INV(w, x, y, z, n, i); RULE_B_INV(x, y, z, w, n, i);
 167   RULE_B_INV(y, z, w, x, n, i); RULE_B_INV(z, w, x, y, n, i);
 168   RULE_B_INV(w, x, y, z, n, i); RULE_B_INV(x, y, z, w, n, i);
 169   RULE_B_INV(y, z, w, x, n, i); RULE_B_INV(z, w, x, y, n, i);
 170   RULE_A_INV(w, x, y, z, n, i); RULE_A_INV(x, y, z, w, n, i);
 171   RULE_A_INV(y, z, w, x, n, i); RULE_A_INV(z, w, x, y, n, i);
 172   RULE_A_INV(w, x, y, z, n, i); RULE_A_INV(x, y, z, w, n, i);
 173   RULE_A_INV(y, z, w, x, n, i); RULE_A_INV(z, w, x, y, n, i);
 174
 175   d[0] = ((uint32)w << 16) | (uint32)x;
 176   d[1] = ((uint32)y << 16) | (uint32)z;
 177 }
 178
 179 BLKC_TEST(SKIPJACK, skipjack)
 180
 181 /*----- That's all, folks -------------------------------------------------*/