215 lines
6.3 KiB
C
215 lines
6.3 KiB
C
/*
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* Twofish for CryptoAPI
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*
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* Originally Twofish for GPG
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* By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
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* 256-bit key length added March 20, 1999
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* Some modifications to reduce the text size by Werner Koch, April, 1998
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* Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
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* Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
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*
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* The original author has disclaimed all copyright interest in this
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* code and thus put it in the public domain. The subsequent authors
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* have put this under the GNU General Public License.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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* USA
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*
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* This code is a "clean room" implementation, written from the paper
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* _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
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* Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
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* through http://www.counterpane.com/twofish.html
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*
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* For background information on multiplication in finite fields, used for
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* the matrix operations in the key schedule, see the book _Contemporary
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* Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
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* Third Edition.
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*/
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#include <asm/byteorder.h>
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#include <crypto/twofish.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/crypto.h>
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#include <linux/bitops.h>
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/* Macros to compute the g() function in the encryption and decryption
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* rounds. G1 is the straight g() function; G2 includes the 8-bit
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* rotation for the high 32-bit word. */
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#define G1(a) \
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(ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
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^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
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#define G2(b) \
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(ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
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^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
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/* Encryption and decryption Feistel rounds. Each one calls the two g()
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* macros, does the PHT, and performs the XOR and the appropriate bit
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* rotations. The parameters are the round number (used to select subkeys),
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* and the four 32-bit chunks of the text. */
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#define ENCROUND(n, a, b, c, d) \
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x = G1 (a); y = G2 (b); \
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x += y; y += x + ctx->k[2 * (n) + 1]; \
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(c) ^= x + ctx->k[2 * (n)]; \
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(c) = ror32((c), 1); \
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(d) = rol32((d), 1) ^ y
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#define DECROUND(n, a, b, c, d) \
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x = G1 (a); y = G2 (b); \
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x += y; y += x; \
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(d) ^= y + ctx->k[2 * (n) + 1]; \
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(d) = ror32((d), 1); \
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(c) = rol32((c), 1); \
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(c) ^= (x + ctx->k[2 * (n)])
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/* Encryption and decryption cycles; each one is simply two Feistel rounds
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* with the 32-bit chunks re-ordered to simulate the "swap" */
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#define ENCCYCLE(n) \
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ENCROUND (2 * (n), a, b, c, d); \
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ENCROUND (2 * (n) + 1, c, d, a, b)
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#define DECCYCLE(n) \
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DECROUND (2 * (n) + 1, c, d, a, b); \
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DECROUND (2 * (n), a, b, c, d)
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/* Macros to convert the input and output bytes into 32-bit words,
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* and simultaneously perform the whitening step. INPACK packs word
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* number n into the variable named by x, using whitening subkey number m.
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* OUTUNPACK unpacks word number n from the variable named by x, using
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* whitening subkey number m. */
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#define INPACK(n, x, m) \
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x = le32_to_cpu(src[n]) ^ ctx->w[m]
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#define OUTUNPACK(n, x, m) \
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x ^= ctx->w[m]; \
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dst[n] = cpu_to_le32(x)
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/* Encrypt one block. in and out may be the same. */
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static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
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{
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struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
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const __le32 *src = (const __le32 *)in;
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__le32 *dst = (__le32 *)out;
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/* The four 32-bit chunks of the text. */
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u32 a, b, c, d;
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/* Temporaries used by the round function. */
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u32 x, y;
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/* Input whitening and packing. */
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INPACK (0, a, 0);
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INPACK (1, b, 1);
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INPACK (2, c, 2);
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INPACK (3, d, 3);
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/* Encryption Feistel cycles. */
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ENCCYCLE (0);
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ENCCYCLE (1);
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ENCCYCLE (2);
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ENCCYCLE (3);
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ENCCYCLE (4);
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ENCCYCLE (5);
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ENCCYCLE (6);
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ENCCYCLE (7);
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/* Output whitening and unpacking. */
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OUTUNPACK (0, c, 4);
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OUTUNPACK (1, d, 5);
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OUTUNPACK (2, a, 6);
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OUTUNPACK (3, b, 7);
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}
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/* Decrypt one block. in and out may be the same. */
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static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
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{
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struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
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const __le32 *src = (const __le32 *)in;
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__le32 *dst = (__le32 *)out;
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/* The four 32-bit chunks of the text. */
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u32 a, b, c, d;
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/* Temporaries used by the round function. */
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u32 x, y;
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/* Input whitening and packing. */
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INPACK (0, c, 4);
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INPACK (1, d, 5);
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INPACK (2, a, 6);
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INPACK (3, b, 7);
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/* Encryption Feistel cycles. */
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DECCYCLE (7);
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DECCYCLE (6);
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DECCYCLE (5);
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DECCYCLE (4);
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DECCYCLE (3);
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DECCYCLE (2);
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DECCYCLE (1);
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DECCYCLE (0);
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/* Output whitening and unpacking. */
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OUTUNPACK (0, a, 0);
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OUTUNPACK (1, b, 1);
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OUTUNPACK (2, c, 2);
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OUTUNPACK (3, d, 3);
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}
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static struct crypto_alg alg = {
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.cra_name = "twofish",
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.cra_driver_name = "twofish-generic",
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.cra_priority = 100,
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.cra_flags = CRYPTO_ALG_TYPE_CIPHER,
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.cra_blocksize = TF_BLOCK_SIZE,
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.cra_ctxsize = sizeof(struct twofish_ctx),
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.cra_alignmask = 3,
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.cra_module = THIS_MODULE,
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.cra_list = LIST_HEAD_INIT(alg.cra_list),
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.cra_u = { .cipher = {
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.cia_min_keysize = TF_MIN_KEY_SIZE,
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.cia_max_keysize = TF_MAX_KEY_SIZE,
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.cia_setkey = twofish_setkey,
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.cia_encrypt = twofish_encrypt,
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.cia_decrypt = twofish_decrypt } }
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};
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static int __init twofish_mod_init(void)
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{
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return crypto_register_alg(&alg);
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}
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static void __exit twofish_mod_fini(void)
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{
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crypto_unregister_alg(&alg);
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}
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module_init(twofish_mod_init);
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module_exit(twofish_mod_fini);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
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