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/*
* 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, see <http://www.gnu.org/licenses/>.
*
*
* 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.
*/
#include <asm/byteorder.h>
#include <crypto/twofish.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/crypto.h>
#include <linux/bitops.h>
/* 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)]; \
(c) = ror32((c), 1); \
(d) = rol32((d), 1) ^ y
#define DECROUND(n, a, b, c, d) \
x = G1 (a); y = G2 (b); \
x += y; y += x; \
(d) ^= y + ctx->k[2 * (n) + 1]; \
(d) = ror32((d), 1); \
(c) = rol32((c), 1); \
(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) \
x = le32_to_cpu(src[n]) ^ ctx->w[m]
#define OUTUNPACK(n, x, m) \
x ^= ctx->w[m]; \
dst[n] = cpu_to_le32(x)
/* Encrypt one block. in and out may be the same. */
static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
const __le32 *src = (const __le32 *)in;
__le32 *dst = (__le32 *)out;
/* 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. */
static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
const __le32 *src = (const __le32 *)in;
__le32 *dst = (__le32 *)out;
/* 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",
.cra_driver_name = "twofish-generic",
.cra_priority = 100,
.cra_flags = CRYPTO_ALG_TYPE_CIPHER,
.cra_blocksize = TF_BLOCK_SIZE,
.cra_ctxsize = sizeof(struct twofish_ctx),
.cra_alignmask = 3,
.cra_module = THIS_MODULE,
.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 } }
};
static int __init twofish_mod_init(void)
{
return crypto_register_alg(&alg);
}
static void __exit twofish_mod_fini(void)
{
crypto_unregister_alg(&alg);
}
subsys_initcall(twofish_mod_init);
module_exit(twofish_mod_fini);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
MODULE_ALIAS_CRYPTO("twofish");
MODULE_ALIAS_CRYPTO("twofish-generic");
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