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Diffstat (limited to 'crypto/twofish_generic.c')
| -rw-r--r-- | crypto/twofish_generic.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/crypto/twofish_generic.c b/crypto/twofish_generic.c new file mode 100644 index 00000000..1f07b843 --- /dev/null +++ b/crypto/twofish_generic.c @@ -0,0 +1,215 @@ +/* + * 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"); +MODULE_ALIAS("twofish"); |