/* * 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. */ #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_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 } } }; static int __init twofish_mod_init(void) { return crypto_register_alg(&alg); } static void __exit twofish_mod_fini(void) { crypto_unregister_alg(&alg); } module_init(twofish_mod_init); module_exit(twofish_mod_fini); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION ("Twofish Cipher Algorithm");