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, see <http://www.gnu.org/licenses/>.
27 *
28 *
29 * This code is a "clean room" implementation, written from the paper
30 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
31 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
32 * through http://www.counterpane.com/twofish.html
33 *
34 * For background information on multiplication in finite fields, used for
35 * the matrix operations in the key schedule, see the book _Contemporary
36 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
37 * Third Edition.
38 */
39
40#include <asm/byteorder.h>
41#include <crypto/twofish.h>
42#include <linux/module.h>
43#include <linux/init.h>
44#include <linux/types.h>
45#include <linux/errno.h>
46#include <linux/crypto.h>
47#include <linux/bitops.h>
48
49/* Macros to compute the g() function in the encryption and decryption
50 * rounds. G1 is the straight g() function; G2 includes the 8-bit
51 * rotation for the high 32-bit word. */
52
53#define G1(a) \
54 (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
55 ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
56
57#define G2(b) \
58 (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
59 ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
60
61/* Encryption and decryption Feistel rounds. Each one calls the two g()
62 * macros, does the PHT, and performs the XOR and the appropriate bit
63 * rotations. The parameters are the round number (used to select subkeys),
64 * and the four 32-bit chunks of the text. */
65
66#define ENCROUND(n, a, b, c, d) \
67 x = G1 (a); y = G2 (b); \
68 x += y; y += x + ctx->k[2 * (n) + 1]; \
69 (c) ^= x + ctx->k[2 * (n)]; \
70 (c) = ror32((c), 1); \
71 (d) = rol32((d), 1) ^ y
72
73#define DECROUND(n, a, b, c, d) \
74 x = G1 (a); y = G2 (b); \
75 x += y; y += x; \
76 (d) ^= y + ctx->k[2 * (n) + 1]; \
77 (d) = ror32((d), 1); \
78 (c) = rol32((c), 1); \
79 (c) ^= (x + ctx->k[2 * (n)])
80
81/* Encryption and decryption cycles; each one is simply two Feistel rounds
82 * with the 32-bit chunks re-ordered to simulate the "swap" */
83
84#define ENCCYCLE(n) \
85 ENCROUND (2 * (n), a, b, c, d); \
86 ENCROUND (2 * (n) + 1, c, d, a, b)
87
88#define DECCYCLE(n) \
89 DECROUND (2 * (n) + 1, c, d, a, b); \
90 DECROUND (2 * (n), a, b, c, d)
91
92/* Macros to convert the input and output bytes into 32-bit words,
93 * and simultaneously perform the whitening step. INPACK packs word
94 * number n into the variable named by x, using whitening subkey number m.
95 * OUTUNPACK unpacks word number n from the variable named by x, using
96 * whitening subkey number m. */
97
98#define INPACK(n, x, m) \
99 x = le32_to_cpu(src[n]) ^ ctx->w[m]
100
101#define OUTUNPACK(n, x, m) \
102 x ^= ctx->w[m]; \
103 dst[n] = cpu_to_le32(x)
104
105
106
107/* Encrypt one block. in and out may be the same. */
108static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
109{
110 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
111 const __le32 *src = (const __le32 *)in;
112 __le32 *dst = (__le32 *)out;
113
114 /* The four 32-bit chunks of the text. */
115 u32 a, b, c, d;
116
117 /* Temporaries used by the round function. */
118 u32 x, y;
119
120 /* Input whitening and packing. */
121 INPACK (0, a, 0);
122 INPACK (1, b, 1);
123 INPACK (2, c, 2);
124 INPACK (3, d, 3);
125
126 /* Encryption Feistel cycles. */
127 ENCCYCLE (0);
128 ENCCYCLE (1);
129 ENCCYCLE (2);
130 ENCCYCLE (3);
131 ENCCYCLE (4);
132 ENCCYCLE (5);
133 ENCCYCLE (6);
134 ENCCYCLE (7);
135
136 /* Output whitening and unpacking. */
137 OUTUNPACK (0, c, 4);
138 OUTUNPACK (1, d, 5);
139 OUTUNPACK (2, a, 6);
140 OUTUNPACK (3, b, 7);
141
142}
143
144/* Decrypt one block. in and out may be the same. */
145static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
146{
147 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
148 const __le32 *src = (const __le32 *)in;
149 __le32 *dst = (__le32 *)out;
150
151 /* The four 32-bit chunks of the text. */
152 u32 a, b, c, d;
153
154 /* Temporaries used by the round function. */
155 u32 x, y;
156
157 /* Input whitening and packing. */
158 INPACK (0, c, 4);
159 INPACK (1, d, 5);
160 INPACK (2, a, 6);
161 INPACK (3, b, 7);
162
163 /* Encryption Feistel cycles. */
164 DECCYCLE (7);
165 DECCYCLE (6);
166 DECCYCLE (5);
167 DECCYCLE (4);
168 DECCYCLE (3);
169 DECCYCLE (2);
170 DECCYCLE (1);
171 DECCYCLE (0);
172
173 /* Output whitening and unpacking. */
174 OUTUNPACK (0, a, 0);
175 OUTUNPACK (1, b, 1);
176 OUTUNPACK (2, c, 2);
177 OUTUNPACK (3, d, 3);
178
179}
180
181static struct crypto_alg alg = {
182 .cra_name = "twofish",
183 .cra_driver_name = "twofish-generic",
184 .cra_priority = 100,
185 .cra_flags = CRYPTO_ALG_TYPE_CIPHER,
186 .cra_blocksize = TF_BLOCK_SIZE,
187 .cra_ctxsize = sizeof(struct twofish_ctx),
188 .cra_alignmask = 3,
189 .cra_module = THIS_MODULE,
190 .cra_u = { .cipher = {
191 .cia_min_keysize = TF_MIN_KEY_SIZE,
192 .cia_max_keysize = TF_MAX_KEY_SIZE,
193 .cia_setkey = twofish_setkey,
194 .cia_encrypt = twofish_encrypt,
195 .cia_decrypt = twofish_decrypt } }
196};
197
198static int __init twofish_mod_init(void)
199{
200 return crypto_register_alg(&alg);
201}
202
203static void __exit twofish_mod_fini(void)
204{
205 crypto_unregister_alg(&alg);
206}
207
208module_init(twofish_mod_init);
209module_exit(twofish_mod_fini);
210
211MODULE_LICENSE("GPL");
212MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
213MODULE_ALIAS_CRYPTO("twofish");
214MODULE_ALIAS_CRYPTO("twofish-generic");
215