LXR linux/crypto/twofish

   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, see <http://www.gnu.org/licenses/>.
  27 *
  28 *
  29 * This code is a "clean room" implementation, written from the paper
  30 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
  31 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
  32 * through http://www.counterpane.com/twofish.html
  33 *
  34 * For background information on multiplication in finite fields, used for
  35 * the matrix operations in the key schedule, see the book _Contemporary
  36 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
  37 * Third Edition.
  38 */
  39
  40#include <asm/byteorder.h>
  41#include <crypto/twofish.h>
  42#include <linux/module.h>
  43#include <linux/init.h>
  44#include <linux/types.h>
  45#include <linux/errno.h>
  46#include <linux/crypto.h>
  47#include <linux/bitops.h>
  48
  49/* Macros to compute the g() function in the encryption and decryption
  50 * rounds.  G1 is the straight g() function; G2 includes the 8-bit
  51 * rotation for the high 32-bit word. */
  52
  53#define G1(a) \
  54     (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
  55   ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
  56
  57#define G2(b) \
  58     (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
  59   ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
  60
  61/* Encryption and decryption Feistel rounds.  Each one calls the two g()
  62 * macros, does the PHT, and performs the XOR and the appropriate bit
  63 * rotations.  The parameters are the round number (used to select subkeys),
  64 * and the four 32-bit chunks of the text. */
  65
  66#define ENCROUND(n, a, b, c, d) \
  67   x = G1 (a); y = G2 (b); \
  68   x += y; y += x + ctx->k[2 * (n) + 1]; \
  69   (c) ^= x + ctx->k[2 * (n)]; \
  70   (c) = ror32((c), 1); \
  71   (d) = rol32((d), 1) ^ y
  72
  73#define DECROUND(n, a, b, c, d) \
  74   x = G1 (a); y = G2 (b); \
  75   x += y; y += x; \
  76   (d) ^= y + ctx->k[2 * (n) + 1]; \
  77   (d) = ror32((d), 1); \
  78   (c) = rol32((c), 1); \
  79   (c) ^= (x + ctx->k[2 * (n)])
  80
  81/* Encryption and decryption cycles; each one is simply two Feistel rounds
  82 * with the 32-bit chunks re-ordered to simulate the "swap" */
  83
  84#define ENCCYCLE(n) \
  85   ENCROUND (2 * (n), a, b, c, d); \
  86   ENCROUND (2 * (n) + 1, c, d, a, b)
  87
  88#define DECCYCLE(n) \
  89   DECROUND (2 * (n) + 1, c, d, a, b); \
  90   DECROUND (2 * (n), a, b, c, d)
  91
  92/* Macros to convert the input and output bytes into 32-bit words,
  93 * and simultaneously perform the whitening step.  INPACK packs word
  94 * number n into the variable named by x, using whitening subkey number m.
  95 * OUTUNPACK unpacks word number n from the variable named by x, using
  96 * whitening subkey number m. */
  97
  98#define INPACK(n, x, m) \
  99   x = le32_to_cpu(src[n]) ^ ctx->w[m]
 100
 101#define OUTUNPACK(n, x, m) \
 102   x ^= ctx->w[m]; \
 103   dst[n] = cpu_to_le32(x)
 104
 105
 106
 107/* Encrypt one block.  in and out may be the same. */
 108static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 109{
 110        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 111        const __le32 *src = (const __le32 *)in;
 112        __le32 *dst = (__le32 *)out;
 113
 114        /* The four 32-bit chunks of the text. */
 115        u32 a, b, c, d;
 116        
 117        /* Temporaries used by the round function. */
 118        u32 x, y;
 119
 120        /* Input whitening and packing. */
 121        INPACK (0, a, 0);
 122        INPACK (1, b, 1);
 123        INPACK (2, c, 2);
 124        INPACK (3, d, 3);
 125        
 126        /* Encryption Feistel cycles. */
 127        ENCCYCLE (0);
 128        ENCCYCLE (1);
 129        ENCCYCLE (2);
 130        ENCCYCLE (3);
 131        ENCCYCLE (4);
 132        ENCCYCLE (5);
 133        ENCCYCLE (6);
 134        ENCCYCLE (7);
 135        
 136        /* Output whitening and unpacking. */
 137        OUTUNPACK (0, c, 4);
 138        OUTUNPACK (1, d, 5);
 139        OUTUNPACK (2, a, 6);
 140        OUTUNPACK (3, b, 7);
 141        
 142}
 143
 144/* Decrypt one block.  in and out may be the same. */
 145static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 146{
 147        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 148        const __le32 *src = (const __le32 *)in;
 149        __le32 *dst = (__le32 *)out;
 150  
 151        /* The four 32-bit chunks of the text. */
 152        u32 a, b, c, d;
 153        
 154        /* Temporaries used by the round function. */
 155        u32 x, y;
 156        
 157        /* Input whitening and packing. */
 158        INPACK (0, c, 4);
 159        INPACK (1, d, 5);
 160        INPACK (2, a, 6);
 161        INPACK (3, b, 7);
 162        
 163        /* Encryption Feistel cycles. */
 164        DECCYCLE (7);
 165        DECCYCLE (6);
 166        DECCYCLE (5);
 167        DECCYCLE (4);
 168        DECCYCLE (3);
 169        DECCYCLE (2);
 170        DECCYCLE (1);
 171        DECCYCLE (0);
 172
 173        /* Output whitening and unpacking. */
 174        OUTUNPACK (0, a, 0);
 175        OUTUNPACK (1, b, 1);
 176        OUTUNPACK (2, c, 2);
 177        OUTUNPACK (3, d, 3);
 178
 179}
 180
 181static struct crypto_alg alg = {
 182        .cra_name           =   "twofish",
 183        .cra_driver_name    =   "twofish-generic",
 184        .cra_priority       =   100,
 185        .cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
 186        .cra_blocksize      =   TF_BLOCK_SIZE,
 187        .cra_ctxsize        =   sizeof(struct twofish_ctx),
 188        .cra_alignmask      =   3,
 189        .cra_module         =   THIS_MODULE,
 190        .cra_u              =   { .cipher = {
 191        .cia_min_keysize    =   TF_MIN_KEY_SIZE,
 192        .cia_max_keysize    =   TF_MAX_KEY_SIZE,
 193        .cia_setkey         =   twofish_setkey,
 194        .cia_encrypt        =   twofish_encrypt,
 195        .cia_decrypt        =   twofish_decrypt } }
 196};
 197
 198static int __init twofish_mod_init(void)
 199{
 200        return crypto_register_alg(&alg);
 201}
 202
 203static void __exit twofish_mod_fini(void)
 204{
 205        crypto_unregister_alg(&alg);
 206}
 207
 208module_init(twofish_mod_init);
 209module_exit(twofish_mod_fini);
 210
 211MODULE_LICENSE("GPL");
 212MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 213MODULE_ALIAS_CRYPTO("twofish");
 214MODULE_ALIAS_CRYPTO("twofish-generic");
 215