linux/crypto/twofish_generic.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Twofish for CryptoAPI
   4 *
   5 * Originally Twofish for GPG
   6 * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
   7 * 256-bit key length added March 20, 1999
   8 * Some modifications to reduce the text size by Werner Koch, April, 1998
   9 * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
  10 * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
  11 *
  12 * The original author has disclaimed all copyright interest in this
  13 * code and thus put it in the public domain. The subsequent authors 
  14 * have put this under the GNU General Public License.
  15 *
  16 * This code is a "clean room" implementation, written from the paper
  17 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
  18 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
  19 * through http://www.counterpane.com/twofish.html
  20 *
  21 * For background information on multiplication in finite fields, used for
  22 * the matrix operations in the key schedule, see the book _Contemporary
  23 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
  24 * Third Edition.
  25 */
  26
  27#include <asm/byteorder.h>
  28#include <crypto/twofish.h>
  29#include <linux/module.h>
  30#include <linux/init.h>
  31#include <linux/types.h>
  32#include <linux/errno.h>
  33#include <linux/crypto.h>
  34#include <linux/bitops.h>
  35
  36/* Macros to compute the g() function in the encryption and decryption
  37 * rounds.  G1 is the straight g() function; G2 includes the 8-bit
  38 * rotation for the high 32-bit word. */
  39
  40#define G1(a) \
  41     (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
  42   ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
  43
  44#define G2(b) \
  45     (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
  46   ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
  47
  48/* Encryption and decryption Feistel rounds.  Each one calls the two g()
  49 * macros, does the PHT, and performs the XOR and the appropriate bit
  50 * rotations.  The parameters are the round number (used to select subkeys),
  51 * and the four 32-bit chunks of the text. */
  52
  53#define ENCROUND(n, a, b, c, d) \
  54   x = G1 (a); y = G2 (b); \
  55   x += y; y += x + ctx->k[2 * (n) + 1]; \
  56   (c) ^= x + ctx->k[2 * (n)]; \
  57   (c) = ror32((c), 1); \
  58   (d) = rol32((d), 1) ^ y
  59
  60#define DECROUND(n, a, b, c, d) \
  61   x = G1 (a); y = G2 (b); \
  62   x += y; y += x; \
  63   (d) ^= y + ctx->k[2 * (n) + 1]; \
  64   (d) = ror32((d), 1); \
  65   (c) = rol32((c), 1); \
  66   (c) ^= (x + ctx->k[2 * (n)])
  67
  68/* Encryption and decryption cycles; each one is simply two Feistel rounds
  69 * with the 32-bit chunks re-ordered to simulate the "swap" */
  70
  71#define ENCCYCLE(n) \
  72   ENCROUND (2 * (n), a, b, c, d); \
  73   ENCROUND (2 * (n) + 1, c, d, a, b)
  74
  75#define DECCYCLE(n) \
  76   DECROUND (2 * (n) + 1, c, d, a, b); \
  77   DECROUND (2 * (n), a, b, c, d)
  78
  79/* Macros to convert the input and output bytes into 32-bit words,
  80 * and simultaneously perform the whitening step.  INPACK packs word
  81 * number n into the variable named by x, using whitening subkey number m.
  82 * OUTUNPACK unpacks word number n from the variable named by x, using
  83 * whitening subkey number m. */
  84
  85#define INPACK(n, x, m) \
  86   x = le32_to_cpu(src[n]) ^ ctx->w[m]
  87
  88#define OUTUNPACK(n, x, m) \
  89   x ^= ctx->w[m]; \
  90   dst[n] = cpu_to_le32(x)
  91
  92
  93
  94/* Encrypt one block.  in and out may be the same. */
  95static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
  96{
  97        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
  98        const __le32 *src = (const __le32 *)in;
  99        __le32 *dst = (__le32 *)out;
 100
 101        /* The four 32-bit chunks of the text. */
 102        u32 a, b, c, d;
 103        
 104        /* Temporaries used by the round function. */
 105        u32 x, y;
 106
 107        /* Input whitening and packing. */
 108        INPACK (0, a, 0);
 109        INPACK (1, b, 1);
 110        INPACK (2, c, 2);
 111        INPACK (3, d, 3);
 112        
 113        /* Encryption Feistel cycles. */
 114        ENCCYCLE (0);
 115        ENCCYCLE (1);
 116        ENCCYCLE (2);
 117        ENCCYCLE (3);
 118        ENCCYCLE (4);
 119        ENCCYCLE (5);
 120        ENCCYCLE (6);
 121        ENCCYCLE (7);
 122        
 123        /* Output whitening and unpacking. */
 124        OUTUNPACK (0, c, 4);
 125        OUTUNPACK (1, d, 5);
 126        OUTUNPACK (2, a, 6);
 127        OUTUNPACK (3, b, 7);
 128        
 129}
 130
 131/* Decrypt one block.  in and out may be the same. */
 132static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 133{
 134        struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 135        const __le32 *src = (const __le32 *)in;
 136        __le32 *dst = (__le32 *)out;
 137  
 138        /* The four 32-bit chunks of the text. */
 139        u32 a, b, c, d;
 140        
 141        /* Temporaries used by the round function. */
 142        u32 x, y;
 143        
 144        /* Input whitening and packing. */
 145        INPACK (0, c, 4);
 146        INPACK (1, d, 5);
 147        INPACK (2, a, 6);
 148        INPACK (3, b, 7);
 149        
 150        /* Encryption Feistel cycles. */
 151        DECCYCLE (7);
 152        DECCYCLE (6);
 153        DECCYCLE (5);
 154        DECCYCLE (4);
 155        DECCYCLE (3);
 156        DECCYCLE (2);
 157        DECCYCLE (1);
 158        DECCYCLE (0);
 159
 160        /* Output whitening and unpacking. */
 161        OUTUNPACK (0, a, 0);
 162        OUTUNPACK (1, b, 1);
 163        OUTUNPACK (2, c, 2);
 164        OUTUNPACK (3, d, 3);
 165
 166}
 167
 168static struct crypto_alg alg = {
 169        .cra_name           =   "twofish",
 170        .cra_driver_name    =   "twofish-generic",
 171        .cra_priority       =   100,
 172        .cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
 173        .cra_blocksize      =   TF_BLOCK_SIZE,
 174        .cra_ctxsize        =   sizeof(struct twofish_ctx),
 175        .cra_alignmask      =   3,
 176        .cra_module         =   THIS_MODULE,
 177        .cra_u              =   { .cipher = {
 178        .cia_min_keysize    =   TF_MIN_KEY_SIZE,
 179        .cia_max_keysize    =   TF_MAX_KEY_SIZE,
 180        .cia_setkey         =   twofish_setkey,
 181        .cia_encrypt        =   twofish_encrypt,
 182        .cia_decrypt        =   twofish_decrypt } }
 183};
 184
 185static int __init twofish_mod_init(void)
 186{
 187        return crypto_register_alg(&alg);
 188}
 189
 190static void __exit twofish_mod_fini(void)
 191{
 192        crypto_unregister_alg(&alg);
 193}
 194
 195subsys_initcall(twofish_mod_init);
 196module_exit(twofish_mod_fini);
 197
 198MODULE_LICENSE("GPL");
 199MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 200MODULE_ALIAS_CRYPTO("twofish");
 201MODULE_ALIAS_CRYPTO("twofish-generic");
 202