Root/crypto/twofish_generic.c

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. */
109static 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. */
146static 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
182static 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
199static int __init twofish_mod_init(void)
200{
201    return crypto_register_alg(&alg);
202}
203
204static void __exit twofish_mod_fini(void)
205{
206    crypto_unregister_alg(&alg);
207}
208
209module_init(twofish_mod_init);
210module_exit(twofish_mod_fini);
211
212MODULE_LICENSE("GPL");
213MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
214MODULE_ALIAS("twofish");
215

Archive Download this file



interactive