linux/crypto/twofish_generic.c
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   1/*
   2 * Twofish for CryptoAPI
   3 *
   4 * Originally Twofish for GPG
   5 * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
   6 * 256-bit key length added March 20, 1999
   7 * Some modifications to reduce the text size by Werner Koch, April, 1998
   8 * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
   9 * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
  10 *
  11 * The original author has disclaimed all copyright interest in this
  12 * code and thus put it in the public domain. The subsequent authors 
  13 * have put this under the GNU General Public License.
  14 *
  15 * This program is free software; you can redistribute it and/or modify
  16 * it under the terms of the GNU General Public License as published by
  17 * the Free Software Foundation; either version 2 of the License, or
  18 * (at your option) any later version.
  19 *
  20 * This program is distributed in the hope that it will be useful,
  21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 * GNU General Public License for more details.
  24 * 
  25 * You should have received a copy of the GNU General Public License
  26 * along with this program; if not, write to the Free Software
  27 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
  28 * USA
  29 *
  30 * This code is a "clean room" implementation, written from the paper
  31 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
  32 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
  33 * through http://www.counterpane.com/twofish.html
  34 *
  35 * For background information on multiplication in finite fields, used for
  36 * the matrix operations in the key schedule, see the book _Contemporary
  37 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
  38 * Third Edition.
  39 */
  40
  41#include <asm/byteorder.h>
  42#include <crypto/twofish.h>
  43#include <linux/module.h>
  44#include <linux/init.h>
  45#include <linux/types.h>
  46#include <linux/errno.h>
  47#include <linux/crypto.h>
  48#include <linux/bitops.h>
  49
  50/* Macros to compute the g() function in the encryption and decryption
  51 * rounds.  G1 is the straight g() function; G2 includes the 8-bit
  52 * rotation for the high 32-bit word. */
  53
  54#define G1(a) \
  55     (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
  56   ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
  57
  58#define G2(b) \
  59     (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
  60   ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
  61
  62/* Encryption and decryption Feistel rounds.  Each one calls the two g()
  63 * macros, does the PHT, and performs the XOR and the appropriate bit
  64 * rotations.  The parameters are the round number (used to select subkeys),
  65 * and the four 32-bit chunks of the text. */
  66
  67#define ENCROUND(n, a, b, c, d) \
  68   x = G1 (a); y = G2 (b); \
  69   x += y; y += x + ctx->k[2 * (n) + 1]; \
  70   (c) ^= x + ctx->k[2 * (n)]; \
  71   (c) = ror32((c), 1); \
  72   (d) = rol32((d), 1) ^ y
  73
  74#define DECROUND(n, a, b, c, d) \
  75   x = G1 (a); y = G2 (b); \
  76   x += y; y += x; \
  77   (d) ^= y + ctx->k[2 * (n) + 1]; \
  78   (d) = ror32((d), 1); \
  79   (c) = rol32((c), 1); \
  80   (c) ^= (x + ctx->k[2 * (n)])
  81
  82/* Encryption and decryption cycles; each one is simply two Feistel rounds
  83 * with the 32-bit chunks re-ordered to simulate the "swap" */
  84
  85#define ENCCYCLE(n) \
  86   ENCROUND (2 * (n), a, b, c, d); \
  87   ENCROUND (2 * (n) + 1, c, d, a, b)
  88
  89#define DECCYCLE(n) \
  90   DECROUND (2 * (n) + 1, c, d, a, b); \
  91   DECROUND (2 * (n), a, b, c, d)
  92
  93/* Macros to convert the input and output bytes into 32-bit words,
  94 * and simultaneously perform the whitening step.  INPACK packs word
  95 * number n into the variable named by x, using whitening subkey number m.
  96 * OUTUNPACK unpacks word number n from the variable named by x, using
  97 * whitening subkey number m. */
  98
  99#define INPACK(n, x, m) \
 100   x = le32_to_cpu(src[n]) ^ ctx->w[m]
 101
 102#define OUTUNPACK(n, x, m) \
 103   x ^= ctx->w[m]; \
 104   dst[n] = cpu_to_le32(x)
 105
 106
 107
 108/* Encrypt one block.  in and out may be the same. */
 109static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 110{
 111        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 112        const __le32 *src = (const __le32 *)in;
 113        __le32 *dst = (__le32 *)out;
 114
 115        /* The four 32-bit chunks of the text. */
 116        u32 a, b, c, d;
 117        
 118        /* Temporaries used by the round function. */
 119        u32 x, y;
 120
 121        /* Input whitening and packing. */
 122        INPACK (0, a, 0);
 123        INPACK (1, b, 1);
 124        INPACK (2, c, 2);
 125        INPACK (3, d, 3);
 126        
 127        /* Encryption Feistel cycles. */
 128        ENCCYCLE (0);
 129        ENCCYCLE (1);
 130        ENCCYCLE (2);
 131        ENCCYCLE (3);
 132        ENCCYCLE (4);
 133        ENCCYCLE (5);
 134        ENCCYCLE (6);
 135        ENCCYCLE (7);
 136        
 137        /* Output whitening and unpacking. */
 138        OUTUNPACK (0, c, 4);
 139        OUTUNPACK (1, d, 5);
 140        OUTUNPACK (2, a, 6);
 141        OUTUNPACK (3, b, 7);
 142        
 143}
 144
 145/* Decrypt one block.  in and out may be the same. */
 146static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 147{
 148        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 149        const __le32 *src = (const __le32 *)in;
 150        __le32 *dst = (__le32 *)out;
 151  
 152        /* The four 32-bit chunks of the text. */
 153        u32 a, b, c, d;
 154        
 155        /* Temporaries used by the round function. */
 156        u32 x, y;
 157        
 158        /* Input whitening and packing. */
 159        INPACK (0, c, 4);
 160        INPACK (1, d, 5);
 161        INPACK (2, a, 6);
 162        INPACK (3, b, 7);
 163        
 164        /* Encryption Feistel cycles. */
 165        DECCYCLE (7);
 166        DECCYCLE (6);
 167        DECCYCLE (5);
 168        DECCYCLE (4);
 169        DECCYCLE (3);
 170        DECCYCLE (2);
 171        DECCYCLE (1);
 172        DECCYCLE (0);
 173
 174        /* Output whitening and unpacking. */
 175        OUTUNPACK (0, a, 0);
 176        OUTUNPACK (1, b, 1);
 177        OUTUNPACK (2, c, 2);
 178        OUTUNPACK (3, d, 3);
 179
 180}
 181
 182static struct crypto_alg alg = {
 183        .cra_name           =   "twofish",
 184        .cra_driver_name    =   "twofish-generic",
 185        .cra_priority       =   100,
 186        .cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
 187        .cra_blocksize      =   TF_BLOCK_SIZE,
 188        .cra_ctxsize        =   sizeof(struct twofish_ctx),
 189        .cra_alignmask      =   3,
 190        .cra_module         =   THIS_MODULE,
 191        .cra_u              =   { .cipher = {
 192        .cia_min_keysize    =   TF_MIN_KEY_SIZE,
 193        .cia_max_keysize    =   TF_MAX_KEY_SIZE,
 194        .cia_setkey         =   twofish_setkey,
 195        .cia_encrypt        =   twofish_encrypt,
 196        .cia_decrypt        =   twofish_decrypt } }
 197};
 198
 199static int __init twofish_mod_init(void)
 200{
 201        return crypto_register_alg(&alg);
 202}
 203
 204static void __exit twofish_mod_fini(void)
 205{
 206        crypto_unregister_alg(&alg);
 207}
 208
 209module_init(twofish_mod_init);
 210module_exit(twofish_mod_fini);
 211
 212MODULE_LICENSE("GPL");
 213MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 214MODULE_ALIAS("twofish");
 215
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