mdw@git.distorted.org.uk Git - catacomb/blob - symm/desx.c

   1 /* -*-c-*-
   2  *
   3  * Implementation of DESX
   4  *
   5  * (c) 2001 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 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <assert.h>
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34
  35 #include <mLib/bits.h>
  36
  37 #include "blkc.h"
  38 #include "des-base.h"
  39 #include "des.h"
  40 #include "desx.h"
  41 #include "gcipher.h"
  42 #include "permute.h"
  43
  44 /*----- Tables ------------------------------------------------------------*/
  45
  46 extern const octet desx_s[256];
  47
  48 /*----- Global variables --------------------------------------------------*/
  49
  50 const octet desx_keysz[] = { KSZ_SET, 23, 7, 8, 15, 16, 24, 0 };
  51
  52 /*----- Main code ---------------------------------------------------------*/
  53
  54 /* --- @desx_init@ --- *
  55  *
  56  * Arguments:   @desx_ctx *k@ = pointer to key block
  57  *              @const void *buf@ = pointer to key buffer
  58  *              @size_t sz@ = size of key material
  59  *
  60  * Returns:     ---
  61  *
  62  * Use:         Initializes a DESX key buffer.  The key buffer contains, in
  63  *              order, a single-DES key (either 7 or 8 bytes), an optional
  64  *              8-byte pre-whitening key, and an optional 8-byte
  65  *              post-whitening key.  If no whitening keys are specified, the
  66  *              algorithm becomes the same as single-DES.
  67  */
  68
  69 static void mangle(octet *b, const octet *p)
  70 {
  71   unsigned i;
  72
  73   for (i = 0; i < 8; i++)
  74     b[i] = *p++ ^ desx_s[b[i] ^ b[(i + 1) & 7u]];
  75 }
  76
  77 void desx_init(desx_ctx *k, const void *buf, size_t sz)
  78 {
  79   const octet *p = buf, *kk = buf;
  80   size_t n;
  81
  82   KSZ_ASSERT(desx, sz);
  83
  84   n = sz % 8 == 7 ? 7 : 8;
  85   des_init(&k->k, p, n);
  86   p += n;
  87   sz -= n;
  88   if (!sz)
  89     k->prea = k->preb = k->posta = k->postb = 0;
  90   else {
  91     const octet *q = p;
  92     k->prea = LOAD32(q + 0);
  93     k->preb = LOAD32(q + 4);
  94     p += 8;
  95     sz -= 8;
  96     if (sz) {
  97       k->posta = LOAD32(p + 0);
  98       k->postb = LOAD32(p + 4);
  99     } else {
 100       octet b[16];
 101       uint32 x, y;
 102
 103       des_expand(kk, n, &x, &y);
 104       STORE32(b + 8, x); STORE32(b + 12, y);
 105       memset(b, 0, 8);
 106       mangle(b, b + 8);
 107       mangle(b, q);
 108       k->posta = LOAD32(b + 0);
 109       k->postb = LOAD32(b + 4);
 110     }
 111   }
 112 }
 113
 114 /* --- @desx_eblk@, @desx_dblk@ --- *
 115  *
 116  * Arguments:   @const desx_ctx *k@ = pointer to key block
 117  *              @const uint32 s[2]@ = pointer to source block
 118  *              @uint32 d[2]@ = pointer to destination block
 119  *
 120  * Returns:     ---
 121  *
 122  * Use:         Low-level block encryption and decryption.
 123  */
 124
 125 void desx_eblk(const desx_ctx *k, const uint32 *s, uint32 *d)
 126 {
 127 #define REGWD 32
 128   typedef uint32 regty;
 129
 130   uint32 x = s[0], y = s[1];
 131   x ^= k->prea; y ^= k->preb;
 132   DES_IP(x, y);
 133   DES_EBLK(k->k.k, x, y, x, y);
 134   DES_IPINV(x, y);
 135   x ^= k->posta; y ^= k->postb;
 136   d[0] = x, d[1] = y;
 137
 138 #undef REGWD
 139 }
 140
 141 void desx_dblk(const desx_ctx *k, const uint32 *s, uint32 *d)
 142 {
 143 #define REGWD 32
 144   typedef uint32 regty;
 145
 146   uint32 x = s[0], y = s[1];
 147   x ^= k->posta; y ^= k->postb;
 148   DES_IP(x, y);
 149   DES_DBLK(k->k.k, x, y, x, y);
 150   DES_IPINV(x, y);
 151   x ^= k->prea; y ^= k->preb;
 152   d[0] = x, d[1] = y;
 153
 154 #undef REGWD
 155 }
 156
 157 BLKC_TEST(DESX, desx)
 158
 159 /*----- That's all, folks -------------------------------------------------*/