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. */
twofish_encrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)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. */
twofish_decrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)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
twofish_mod_init(void)199 static int __init twofish_mod_init(void)
200 {
201 return crypto_register_alg(&alg);
202 }
203
twofish_mod_fini(void)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