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, 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. */
 109 static 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. */
 146 static 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
 182 static 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_list           =   LIST_HEAD_INIT(alg.cra_list),
 192         .cra_u              =   { .cipher = {
 193         .cia_min_keysize    =   TF_MIN_KEY_SIZE,
 194         .cia_max_keysize    =   TF_MAX_KEY_SIZE,
 195         .cia_setkey         =   twofish_setkey,
 196         .cia_encrypt        =   twofish_encrypt,
 197         .cia_decrypt        =   twofish_decrypt } }
 198 };
 199
 200 static int __init twofish_mod_init(void)
 201 {
 202         return crypto_register_alg(&alg);
 203 }
 204
 205 static void __exit twofish_mod_fini(void)
 206 {
 207         crypto_unregister_alg(&alg);
 208 }
 209
 210 module_init(twofish_mod_init);
 211 module_exit(twofish_mod_fini);
 212
 213 MODULE_LICENSE("GPL");
 214 MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 215 MODULE_ALIAS("twofish");