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Linux/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. */
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 

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