crypto/twofish_generic.c

   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. */
 108 static 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. */
 145 static 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
 181 static 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
 198 static int __init twofish_mod_init(void)
 199 {
 200         return crypto_register_alg(&alg);
 201 }
 202
 203 static void __exit twofish_mod_fini(void)
 204 {
 205         crypto_unregister_alg(&alg);
 206 }
 207
 208 module_init(twofish_mod_init);
 209 module_exit(twofish_mod_fini);
 210
 211 MODULE_LICENSE("GPL");
 212 MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 213 MODULE_ALIAS_CRYPTO("twofish");
 214 MODULE_ALIAS_CRYPTO("twofish-generic");