1 /* 2 * Twofish for CryptoAPI 3 * 4 * Originally Twofish for GPG 5 * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998 6 * 256-bit key length added March 20, 1999 7 * Some modifications to reduce the text size by Werner Koch, April, 1998 8 * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com> 9 * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net> 10 * 11 * The original author has disclaimed all copyright interest in this 12 * code and thus put it in the public domain. The subsequent authors 13 * have put this under the GNU General Public License. 14 * 15 * This program is free software; you can redistribute it and/or modify 16 * it under the terms of the GNU General Public License as published by 17 * the Free Software Foundation; either version 2 of the License, or 18 * (at your option) any later version. 19 * 20 * This program is distributed in the hope that it will be useful, 21 * but WITHOUT ANY WARRANTY; without even the implied warranty of 22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 23 * GNU General Public License for more details. 24 * 25 * You should have received a copy of the GNU General Public License 26 * along with this program; if not, write to the Free Software 27 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 28 * USA 29 * 30 * This code is a "clean room" implementation, written from the paper 31 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey, 32 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available 33 * through http://www.counterpane.com/twofish.html 34 * 35 * For background information on multiplication in finite fields, used for 36 * the matrix operations in the key schedule, see the book _Contemporary 37 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the 38 * Third Edition. 39 */ 40 41 #include <asm/byteorder.h> 42 #include <crypto/twofish.h> 43 #include <linux/module.h> 44 #include <linux/init.h> 45 #include <linux/types.h> 46 #include <linux/errno.h> 47 #include <linux/crypto.h> 48 #include <linux/bitops.h> 49 50 /* Macros to compute the g() function in the encryption and decryption 51 * rounds. G1 is the straight g() function; G2 includes the 8-bit 52 * rotation for the high 32-bit word. */ 53 54 #define G1(a) \ 55 (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \ 56 ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24]) 57 58 #define G2(b) \ 59 (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \ 60 ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24]) 61 62 /* Encryption and decryption Feistel rounds. Each one calls the two g() 63 * macros, does the PHT, and performs the XOR and the appropriate bit 64 * rotations. The parameters are the round number (used to select subkeys), 65 * and the four 32-bit chunks of the text. */ 66 67 #define ENCROUND(n, a, b, c, d) \ 68 x = G1 (a); y = G2 (b); \ 69 x += y; y += x + ctx->k[2 * (n) + 1]; \ 70 (c) ^= x + ctx->k[2 * (n)]; \ 71 (c) = ror32((c), 1); \ 72 (d) = rol32((d), 1) ^ y 73 74 #define DECROUND(n, a, b, c, d) \ 75 x = G1 (a); y = G2 (b); \ 76 x += y; y += x; \ 77 (d) ^= y + ctx->k[2 * (n) + 1]; \ 78 (d) = ror32((d), 1); \ 79 (c) = rol32((c), 1); \ 80 (c) ^= (x + ctx->k[2 * (n)]) 81 82 /* Encryption and decryption cycles; each one is simply two Feistel rounds 83 * with the 32-bit chunks re-ordered to simulate the "swap" */ 84 85 #define ENCCYCLE(n) \ 86 ENCROUND (2 * (n), a, b, c, d); \ 87 ENCROUND (2 * (n) + 1, c, d, a, b) 88 89 #define DECCYCLE(n) \ 90 DECROUND (2 * (n) + 1, c, d, a, b); \ 91 DECROUND (2 * (n), a, b, c, d) 92 93 /* Macros to convert the input and output bytes into 32-bit words, 94 * and simultaneously perform the whitening step. INPACK packs word 95 * number n into the variable named by x, using whitening subkey number m. 96 * OUTUNPACK unpacks word number n from the variable named by x, using 97 * whitening subkey number m. */ 98 99 #define INPACK(n, x, m) \ 100 x = le32_to_cpu(src[n]) ^ ctx->w[m] 101 102 #define OUTUNPACK(n, x, m) \ 103 x ^= ctx->w[m]; \ 104 dst[n] = cpu_to_le32(x) 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) 110 { 111 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm); 112 const __le32 *src = (const __le32 *)in; 113 __le32 *dst = (__le32 *)out; 114 115 /* The four 32-bit chunks of the text. */ 116 u32 a, b, c, d; 117 118 /* Temporaries used by the round function. */ 119 u32 x, y; 120 121 /* Input whitening and packing. */ 122 INPACK (0, a, 0); 123 INPACK (1, b, 1); 124 INPACK (2, c, 2); 125 INPACK (3, d, 3); 126 127 /* Encryption Feistel cycles. */ 128 ENCCYCLE (0); 129 ENCCYCLE (1); 130 ENCCYCLE (2); 131 ENCCYCLE (3); 132 ENCCYCLE (4); 133 ENCCYCLE (5); 134 ENCCYCLE (6); 135 ENCCYCLE (7); 136 137 /* Output whitening and unpacking. */ 138 OUTUNPACK (0, c, 4); 139 OUTUNPACK (1, d, 5); 140 OUTUNPACK (2, a, 6); 141 OUTUNPACK (3, b, 7); 142 143 } 144 145 /* Decrypt one block. in and out may be the same. */ 146 static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) 147 { 148 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm); 149 const __le32 *src = (const __le32 *)in; 150 __le32 *dst = (__le32 *)out; 151 152 /* The four 32-bit chunks of the text. */ 153 u32 a, b, c, d; 154 155 /* Temporaries used by the round function. */ 156 u32 x, y; 157 158 /* Input whitening and packing. */ 159 INPACK (0, c, 4); 160 INPACK (1, d, 5); 161 INPACK (2, a, 6); 162 INPACK (3, b, 7); 163 164 /* Encryption Feistel cycles. */ 165 DECCYCLE (7); 166 DECCYCLE (6); 167 DECCYCLE (5); 168 DECCYCLE (4); 169 DECCYCLE (3); 170 DECCYCLE (2); 171 DECCYCLE (1); 172 DECCYCLE (0); 173 174 /* Output whitening and unpacking. */ 175 OUTUNPACK (0, a, 0); 176 OUTUNPACK (1, b, 1); 177 OUTUNPACK (2, c, 2); 178 OUTUNPACK (3, d, 3); 179 180 } 181 182 static struct crypto_alg alg = { 183 .cra_name = "twofish", 184 .cra_driver_name = "twofish-generic", 185 .cra_priority = 100, 186 .cra_flags = CRYPTO_ALG_TYPE_CIPHER, 187 .cra_blocksize = TF_BLOCK_SIZE, 188 .cra_ctxsize = sizeof(struct twofish_ctx), 189 .cra_alignmask = 3, 190 .cra_module = THIS_MODULE, 191 .cra_u = { .cipher = { 192 .cia_min_keysize = TF_MIN_KEY_SIZE, 193 .cia_max_keysize = TF_MAX_KEY_SIZE, 194 .cia_setkey = twofish_setkey, 195 .cia_encrypt = twofish_encrypt, 196 .cia_decrypt = twofish_decrypt } } 197 }; 198 199 static int __init twofish_mod_init(void) 200 { 201 return crypto_register_alg(&alg); 202 } 203 204 static void __exit twofish_mod_fini(void) 205 { 206 crypto_unregister_alg(&alg); 207 } 208 209 module_init(twofish_mod_init); 210 module_exit(twofish_mod_fini); 211 212 MODULE_LICENSE("GPL"); 213 MODULE_DESCRIPTION ("Twofish Cipher Algorithm"); 214 MODULE_ALIAS_CRYPTO("twofish"); 215 MODULE_ALIAS_CRYPTO("twofish-generic"); 216