twofish.c 6.27 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
/*
 * Twofish for CryptoAPI
 *
 * Originally Twofish for GPG
 * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
 * 256-bit key length added March 20, 1999
 * Some modifications to reduce the text size by Werner Koch, April, 1998
 * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
 * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
 *
 * The original author has disclaimed all copyright interest in this
 * code and thus put it in the public domain. The subsequent authors 
 * have put this under the GNU General Public License.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 * USA
 *
 * This code is a "clean room" implementation, written from the paper
 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
 * through http://www.counterpane.com/twofish.html
 *
 * For background information on multiplication in finite fields, used for
 * the matrix operations in the key schedule, see the book _Contemporary
 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
 * Third Edition.
 */
40 41

#include <asm/byteorder.h>
42
#include <crypto/twofish.h>
Linus Torvalds's avatar
Linus Torvalds committed
43 44 45 46 47
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/crypto.h>
48
#include <linux/bitops.h>
Linus Torvalds's avatar
Linus Torvalds committed
49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

/* Macros to compute the g() function in the encryption and decryption
 * rounds.  G1 is the straight g() function; G2 includes the 8-bit
 * rotation for the high 32-bit word. */

#define G1(a) \
     (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
   ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])

#define G2(b) \
     (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
   ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])

/* Encryption and decryption Feistel rounds.  Each one calls the two g()
 * macros, does the PHT, and performs the XOR and the appropriate bit
 * rotations.  The parameters are the round number (used to select subkeys),
 * and the four 32-bit chunks of the text. */

#define ENCROUND(n, a, b, c, d) \
   x = G1 (a); y = G2 (b); \
   x += y; y += x + ctx->k[2 * (n) + 1]; \
   (c) ^= x + ctx->k[2 * (n)]; \
71 72
   (c) = ror32((c), 1); \
   (d) = rol32((d), 1) ^ y
Linus Torvalds's avatar
Linus Torvalds committed
73 74 75 76 77

#define DECROUND(n, a, b, c, d) \
   x = G1 (a); y = G2 (b); \
   x += y; y += x; \
   (d) ^= y + ctx->k[2 * (n) + 1]; \
78 79
   (d) = ror32((d), 1); \
   (c) = rol32((c), 1); \
Linus Torvalds's avatar
Linus Torvalds committed
80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
   (c) ^= (x + ctx->k[2 * (n)])

/* Encryption and decryption cycles; each one is simply two Feistel rounds
 * with the 32-bit chunks re-ordered to simulate the "swap" */

#define ENCCYCLE(n) \
   ENCROUND (2 * (n), a, b, c, d); \
   ENCROUND (2 * (n) + 1, c, d, a, b)

#define DECCYCLE(n) \
   DECROUND (2 * (n) + 1, c, d, a, b); \
   DECROUND (2 * (n), a, b, c, d)

/* Macros to convert the input and output bytes into 32-bit words,
 * and simultaneously perform the whitening step.  INPACK packs word
 * number n into the variable named by x, using whitening subkey number m.
 * OUTUNPACK unpacks word number n from the variable named by x, using
 * whitening subkey number m. */

#define INPACK(n, x, m) \
100
   x = le32_to_cpu(src[n]) ^ ctx->w[m]
Linus Torvalds's avatar
Linus Torvalds committed
101 102 103

#define OUTUNPACK(n, x, m) \
   x ^= ctx->w[m]; \
104
   dst[n] = cpu_to_le32(x)
Linus Torvalds's avatar
Linus Torvalds committed
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)
Linus Torvalds's avatar
Linus Torvalds committed
110
{
111
	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
112 113
	const __le32 *src = (const __le32 *)in;
	__le32 *dst = (__le32 *)out;
Linus Torvalds's avatar
Linus Torvalds committed
114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145

	/* The four 32-bit chunks of the text. */
	u32 a, b, c, d;
	
	/* Temporaries used by the round function. */
	u32 x, y;

	/* Input whitening and packing. */
	INPACK (0, a, 0);
	INPACK (1, b, 1);
	INPACK (2, c, 2);
	INPACK (3, d, 3);
	
	/* Encryption Feistel cycles. */
	ENCCYCLE (0);
	ENCCYCLE (1);
	ENCCYCLE (2);
	ENCCYCLE (3);
	ENCCYCLE (4);
	ENCCYCLE (5);
	ENCCYCLE (6);
	ENCCYCLE (7);
	
	/* Output whitening and unpacking. */
	OUTUNPACK (0, c, 4);
	OUTUNPACK (1, d, 5);
	OUTUNPACK (2, a, 6);
	OUTUNPACK (3, b, 7);
	
}

/* Decrypt one block.  in and out may be the same. */
146
static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
Linus Torvalds's avatar
Linus Torvalds committed
147
{
148
	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
149 150
	const __le32 *src = (const __le32 *)in;
	__le32 *dst = (__le32 *)out;
Linus Torvalds's avatar
Linus Torvalds committed
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183
  
	/* The four 32-bit chunks of the text. */
	u32 a, b, c, d;
	
	/* Temporaries used by the round function. */
	u32 x, y;
	
	/* Input whitening and packing. */
	INPACK (0, c, 4);
	INPACK (1, d, 5);
	INPACK (2, a, 6);
	INPACK (3, b, 7);
	
	/* Encryption Feistel cycles. */
	DECCYCLE (7);
	DECCYCLE (6);
	DECCYCLE (5);
	DECCYCLE (4);
	DECCYCLE (3);
	DECCYCLE (2);
	DECCYCLE (1);
	DECCYCLE (0);

	/* Output whitening and unpacking. */
	OUTUNPACK (0, a, 0);
	OUTUNPACK (1, b, 1);
	OUTUNPACK (2, c, 2);
	OUTUNPACK (3, d, 3);

}

static struct crypto_alg alg = {
	.cra_name           =   "twofish",
184 185
	.cra_driver_name    =   "twofish-generic",
	.cra_priority       =   100,
Linus Torvalds's avatar
Linus Torvalds committed
186 187 188
	.cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
	.cra_blocksize      =   TF_BLOCK_SIZE,
	.cra_ctxsize        =   sizeof(struct twofish_ctx),
189
	.cra_alignmask      =	3,
Linus Torvalds's avatar
Linus Torvalds committed
190 191 192 193 194 195 196 197 198 199
	.cra_module         =   THIS_MODULE,
	.cra_list           =   LIST_HEAD_INIT(alg.cra_list),
	.cra_u              =   { .cipher = {
	.cia_min_keysize    =   TF_MIN_KEY_SIZE,
	.cia_max_keysize    =   TF_MAX_KEY_SIZE,
	.cia_setkey         =   twofish_setkey,
	.cia_encrypt        =   twofish_encrypt,
	.cia_decrypt        =   twofish_decrypt } }
};

200
static int __init twofish_mod_init(void)
Linus Torvalds's avatar
Linus Torvalds committed
201 202 203 204
{
	return crypto_register_alg(&alg);
}

205
static void __exit twofish_mod_fini(void)
Linus Torvalds's avatar
Linus Torvalds committed
206 207 208 209
{
	crypto_unregister_alg(&alg);
}

210 211
module_init(twofish_mod_init);
module_exit(twofish_mod_fini);
Linus Torvalds's avatar
Linus Torvalds committed
212 213 214

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION ("Twofish Cipher Algorithm");