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41 results

twofish.c

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  • twofish.c 14.30 KiB
    /* twofish.c
     *
     * The twofish block cipher.
     */
    
    /* twofish - An implementation of the twofish cipher.
     * Copyright (C) 1999 Ruud de Rooij <ruud@debian.org>
     *
     * Modifications for lsh, integrated testing
     * Copyright (C) 1999 J.H.M. Dassen (Ray) <jdassen@wi.LeidenUniv.nl>
     *
     * Integrated with the nettle library,
     * Copyright (C) 2001 Niels Möller
     */
    
    /* nettle, low-level cryptographics library
     *
     * The nettle library is free software; you can redistribute it and/or modify
     * it under the terms of the GNU Lesser General Public License as published by
     * the Free Software Foundation; either version 2.1 of the License, or (at your
     * option) any later version.
     * 
     * The nettle Library is distributed in the hope that it will be useful, but
     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     * License for more details.
     * 
     * You should have received a copy of the GNU Lesser General Public License
     * along with the nettle library; see the file COPYING.LIB.  If not, write to
     * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
     * MA 02111-1301, USA.
     */
    
    #if HAVE_CONFIG_H
    # include "config.h"
    #endif
    
    #include <assert.h>
    #include <string.h>
    
    #include "twofish.h"
    
    #include "macros.h"
    
    /* Bitwise rotations on 32-bit words.  These are defined as macros that
     * evaluate their argument twice, so do not apply to any expressions with
     * side effects.
     */
    
    #define rol1(x) (((x) << 1) | (((x) & 0x80000000) >> 31))
    #define rol8(x) (((x) << 8) | (((x) & 0xFF000000) >> 24))
    #define rol9(x) (((x) << 9) | (((x) & 0xFF800000) >> 23))
    #define ror1(x) (((x) >> 1) | (((x) & 0x00000001) << 31))
    
    /* ------------------------------------------------------------------------- */
    
    /* The permutations q0 and q1.  These are fixed permutations on 8-bit values.
     * The permutations have been computed using the program twofish-data,
     * which is distributed along with this file.
     */
    
    static const uint8_t q0[256] = {
      0xA9,0x67,0xB3,0xE8,0x04,0xFD,0xA3,0x76,
      0x9A,0x92,0x80,0x78,0xE4,0xDD,0xD1,0x38,
      0x0D,0xC6,0x35,0x98,0x18,0xF7,0xEC,0x6C,
      0x43,0x75,0x37,0x26,0xFA,0x13,0x94,0x48,
      0xF2,0xD0,0x8B,0x30,0x84,0x54,0xDF,0x23,
      0x19,0x5B,0x3D,0x59,0xF3,0xAE,0xA2,0x82,
      0x63,0x01,0x83,0x2E,0xD9,0x51,0x9B,0x7C,
      0xA6,0xEB,0xA5,0xBE,0x16,0x0C,0xE3,0x61,
      0xC0,0x8C,0x3A,0xF5,0x73,0x2C,0x25,0x0B,
      0xBB,0x4E,0x89,0x6B,0x53,0x6A,0xB4,0xF1,
      0xE1,0xE6,0xBD,0x45,0xE2,0xF4,0xB6,0x66,
      0xCC,0x95,0x03,0x56,0xD4,0x1C,0x1E,0xD7,
      0xFB,0xC3,0x8E,0xB5,0xE9,0xCF,0xBF,0xBA,
      0xEA,0x77,0x39,0xAF,0x33,0xC9,0x62,0x71,
      0x81,0x79,0x09,0xAD,0x24,0xCD,0xF9,0xD8,
      0xE5,0xC5,0xB9,0x4D,0x44,0x08,0x86,0xE7,
      0xA1,0x1D,0xAA,0xED,0x06,0x70,0xB2,0xD2,
      0x41,0x7B,0xA0,0x11,0x31,0xC2,0x27,0x90,
      0x20,0xF6,0x60,0xFF,0x96,0x5C,0xB1,0xAB,
      0x9E,0x9C,0x52,0x1B,0x5F,0x93,0x0A,0xEF,
      0x91,0x85,0x49,0xEE,0x2D,0x4F,0x8F,0x3B,
      0x47,0x87,0x6D,0x46,0xD6,0x3E,0x69,0x64,
      0x2A,0xCE,0xCB,0x2F,0xFC,0x97,0x05,0x7A,
      0xAC,0x7F,0xD5,0x1A,0x4B,0x0E,0xA7,0x5A,
      0x28,0x14,0x3F,0x29,0x88,0x3C,0x4C,0x02,
      0xB8,0xDA,0xB0,0x17,0x55,0x1F,0x8A,0x7D,
      0x57,0xC7,0x8D,0x74,0xB7,0xC4,0x9F,0x72,
      0x7E,0x15,0x22,0x12,0x58,0x07,0x99,0x34,
      0x6E,0x50,0xDE,0x68,0x65,0xBC,0xDB,0xF8,
      0xC8,0xA8,0x2B,0x40,0xDC,0xFE,0x32,0xA4,
      0xCA,0x10,0x21,0xF0,0xD3,0x5D,0x0F,0x00,
      0x6F,0x9D,0x36,0x42,0x4A,0x5E,0xC1,0xE0,
    };
    
    static const uint8_t q1[256] = {
      0x75,0xF3,0xC6,0xF4,0xDB,0x7B,0xFB,0xC8,
      0x4A,0xD3,0xE6,0x6B,0x45,0x7D,0xE8,0x4B,
      0xD6,0x32,0xD8,0xFD,0x37,0x71,0xF1,0xE1,
      0x30,0x0F,0xF8,0x1B,0x87,0xFA,0x06,0x3F,
      0x5E,0xBA,0xAE,0x5B,0x8A,0x00,0xBC,0x9D,
      0x6D,0xC1,0xB1,0x0E,0x80,0x5D,0xD2,0xD5,
      0xA0,0x84,0x07,0x14,0xB5,0x90,0x2C,0xA3,
      0xB2,0x73,0x4C,0x54,0x92,0x74,0x36,0x51,
      0x38,0xB0,0xBD,0x5A,0xFC,0x60,0x62,0x96,
      0x6C,0x42,0xF7,0x10,0x7C,0x28,0x27,0x8C,
      0x13,0x95,0x9C,0xC7,0x24,0x46,0x3B,0x70,
      0xCA,0xE3,0x85,0xCB,0x11,0xD0,0x93,0xB8,
      0xA6,0x83,0x20,0xFF,0x9F,0x77,0xC3,0xCC,
      0x03,0x6F,0x08,0xBF,0x40,0xE7,0x2B,0xE2,
      0x79,0x0C,0xAA,0x82,0x41,0x3A,0xEA,0xB9,
      0xE4,0x9A,0xA4,0x97,0x7E,0xDA,0x7A,0x17,
      0x66,0x94,0xA1,0x1D,0x3D,0xF0,0xDE,0xB3,
      0x0B,0x72,0xA7,0x1C,0xEF,0xD1,0x53,0x3E,
      0x8F,0x33,0x26,0x5F,0xEC,0x76,0x2A,0x49,
      0x81,0x88,0xEE,0x21,0xC4,0x1A,0xEB,0xD9,
      0xC5,0x39,0x99,0xCD,0xAD,0x31,0x8B,0x01,
      0x18,0x23,0xDD,0x1F,0x4E,0x2D,0xF9,0x48,
      0x4F,0xF2,0x65,0x8E,0x78,0x5C,0x58,0x19,
      0x8D,0xE5,0x98,0x57,0x67,0x7F,0x05,0x64,
      0xAF,0x63,0xB6,0xFE,0xF5,0xB7,0x3C,0xA5,
      0xCE,0xE9,0x68,0x44,0xE0,0x4D,0x43,0x69,
      0x29,0x2E,0xAC,0x15,0x59,0xA8,0x0A,0x9E,
      0x6E,0x47,0xDF,0x34,0x35,0x6A,0xCF,0xDC,
      0x22,0xC9,0xC0,0x9B,0x89,0xD4,0xED,0xAB,
      0x12,0xA2,0x0D,0x52,0xBB,0x02,0x2F,0xA9,
      0xD7,0x61,0x1E,0xB4,0x50,0x04,0xF6,0xC2,
      0x16,0x25,0x86,0x56,0x55,0x09,0xBE,0x91,
    };
    
    /* ------------------------------------------------------------------------- */
    
    /* uint8_t gf_multiply(uint8_t p, uint8_t a, uint8_t b)
     *
     * Multiplication in GF(2^8).
     *
     * This function multiplies a times b in the Galois Field GF(2^8) with
     * primitive polynomial p.
     * The representation of the polynomials a, b, and p uses bits with
     * values 2^i to represent the terms x^i.  The polynomial p contains an
     * implicit term x^8.
     *
     * Note that addition and subtraction in GF(2^8) is simply the XOR
     * operation.
     */
    
    static uint8_t
    gf_multiply(uint8_t p, uint8_t a, uint8_t b)
    {
      uint32_t shift  = b;
      uint8_t result = 0;
      while (a)
        {
          if (a & 1) result ^= shift;
          a = a >> 1;
          shift = shift << 1;
          if (shift & 0x100) shift ^= p;
        }
      return result;
    }
    
    /* ------------------------------------------------------------------------- */
    
    /* The matrix RS as specified in section 4.3 the twofish paper. */
    
    static const uint8_t rs_matrix[4][8] = {
        { 0x01, 0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E },
        { 0xA4, 0x56, 0x82, 0xF3, 0x1E, 0xC6, 0x68, 0xE5 },
        { 0x02, 0xA1, 0xFC, 0xC1, 0x47, 0xAE, 0x3D, 0x19 },
        { 0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E, 0x03 } };
    
    /* uint32_t compute_s(uint32_t m1, uint32_t m2);
     *
     * Computes the value RS * M, where M is a byte vector composed of the
     * bytes of m1 and m2.  Arithmetic is done in GF(2^8) with primitive
     * polynomial x^8 + x^6 + x^3 + x^2 + 1.
     *
     * This function is used to compute the sub-keys S which are in turn used
     * to generate the S-boxes.
     */
    
    static uint32_t
    compute_s(uint32_t m1, uint32_t m2)
    {
      uint32_t s = 0;
      int i;
      for (i = 0; i < 4; i++)
        s |=  ((  gf_multiply(0x4D, m1,       rs_matrix[i][0])
    	    ^ gf_multiply(0x4D, m1 >> 8,  rs_matrix[i][1])
    	    ^ gf_multiply(0x4D, m1 >> 16, rs_matrix[i][2])
    	    ^ gf_multiply(0x4D, m1 >> 24, rs_matrix[i][3])
    	    ^ gf_multiply(0x4D, m2,       rs_matrix[i][4])
    	    ^ gf_multiply(0x4D, m2 >> 8,  rs_matrix[i][5])
    	    ^ gf_multiply(0x4D, m2 >> 16, rs_matrix[i][6])
    	    ^ gf_multiply(0x4D, m2 >> 24, rs_matrix[i][7])) << (i*8));
      return s;
    }
    
    /* ------------------------------------------------------------------------- */
    
    /* This table describes which q S-boxes are used for each byte in each stage
     * of the function h, cf. figure 2 of the twofish paper.
     */
    
    static const uint8_t * const q_table[4][5] =
      { { q1, q1, q0, q0, q1 },
        { q0, q1, q1, q0, q0 },
        { q0, q0, q0, q1, q1 },
        { q1, q0, q1, q1, q0 } };
    
    /* The matrix MDS as specified in section 4.3.2 of the twofish paper. */
    
    static const uint8_t mds_matrix[4][4] = { { 0x01, 0xEF, 0x5B, 0x5B },
    				 { 0x5B, 0xEF, 0xEF, 0x01 },
    				 { 0xEF, 0x5B, 0x01, 0xEF },
    				 { 0xEF, 0x01, 0xEF, 0x5B } };
    
    /* uint32_t h_uint8_t(int k, int i, uint8_t x, uint8_t l0, uint8_t l1, uint8_t l2, uint8_t l3);
     *
     * Perform the h function (section 4.3.2) on one byte.  It consists of
     * repeated applications of the q permutation, followed by a XOR with
     * part of a sub-key.  Finally, the value is multiplied by one column of
     * the MDS matrix.  To obtain the result for a full word, the results of
     * h for the individual bytes are XORed.
     *
     * k is the key size (/ 64 bits), i is the byte number (0 = LSB), x is the
     * actual byte to apply the function to; l0, l1, l2, and l3 are the
     * appropriate bytes from the subkey.  Note that only l0..l(k-1) are used.
     */
    
    static uint32_t
    h_byte(int k, int i, uint8_t x, uint8_t l0, uint8_t l1, uint8_t l2, uint8_t l3)
    {
      uint8_t y = q_table[i][4][l0 ^
                q_table[i][3][l1 ^
                  q_table[i][2][k == 2 ? x : l2 ^
                    q_table[i][1][k == 3 ? x : l3 ^ q_table[i][0][x]]]]];
    
      return ( ((uint32_t)gf_multiply(0x69, mds_matrix[0][i], y))
    	   | ((uint32_t)gf_multiply(0x69, mds_matrix[1][i], y) << 8)
    	   | ((uint32_t)gf_multiply(0x69, mds_matrix[2][i], y) << 16)
    	   | ((uint32_t)gf_multiply(0x69, mds_matrix[3][i], y) << 24) );
    }
    
    /* uint32_t h(int k, uint8_t x, uint32_t l0, uint32_t l1, uint32_t l2, uint32_t l3);
     *
     * Perform the function h on a word.  See the description of h_byte() above.
     */
    
    static uint32_t
    h(int k, uint8_t x, uint32_t l0, uint32_t l1, uint32_t l2, uint32_t l3)
    {
      return (  h_byte(k, 0, x, l0,       l1,       l2,       l3)
    	  ^ h_byte(k, 1, x, l0 >> 8,  l1 >> 8,  l2 >> 8,  l3 >> 8)
    	  ^ h_byte(k, 2, x, l0 >> 16, l1 >> 16, l2 >> 16, l3 >> 16)
    	  ^ h_byte(k, 3, x, l0 >> 24, l1 >> 24, l2 >> 24, l3 >> 24) );
    }
    
    
    /* ------------------------------------------------------------------------- */
    
    /* API */
    
    /* Structure which contains the tables containing the subkeys and the
     * key-dependent s-boxes.
     */
    
    
    /* Set up internal tables required for twofish encryption and decryption.
     *
     * The key size is specified in bytes.  Key sizes up to 32 bytes are
     * supported.  Larger key sizes are silently truncated.  
     */
    
    void
    twofish_set_key(struct twofish_ctx *context,
    		size_t keysize, const uint8_t *key)
    {
      uint8_t key_copy[32];
      uint32_t m[8], s[4], t;
      int i, j, k;
    
      /* Extend key as necessary */
    
      assert(keysize <= 32);
    
      /* We do a little more copying than necessary, but that doesn't
       * really matter. */
      memset(key_copy, 0, 32);
      memcpy(key_copy, key, keysize);
    
      for (i = 0; i<8; i++)
        m[i] = LE_READ_UINT32(key_copy + i*4);
      
      if (keysize <= 16)
        k = 2;
      else if (keysize <= 24)
        k = 3;
      else
        k = 4;
    
      /* Compute sub-keys */
    
      for (i = 0; i < 20; i++)
        {
          t = h(k, 2*i+1, m[1], m[3], m[5], m[7]);
          t = rol8(t);
          t += (context->keys[2*i] =
    	    t + h(k, 2*i, m[0], m[2], m[4], m[6]));
          t = rol9(t);
          context->keys[2*i+1] = t;
        }
    
      /* Compute key-dependent S-boxes */
    
      for (i = 0; i < k; i++)
        s[k-1-i] = compute_s(m[2*i], m[2*i+1]);
    
      for (i = 0; i < 4; i++)
        for (j = 0; j < 256; j++)
          context->s_box[i][j] = h_byte(k, i, j,
    				    s[0] >> (i*8),
    				    s[1] >> (i*8),
    				    s[2] >> (i*8),
    				    s[3] >> (i*8));
    }
    
    /* Encrypt blocks of 16 bytes of data with the twofish algorithm.
     *
     * Before this function can be used, twofish_set_key() must be used in order to
     * set up various tables required for the encryption algorithm.
     * 
     * This function always encrypts 16 bytes of plaintext to 16 bytes of
     * ciphertext.  The memory areas of the plaintext and the ciphertext can
     * overlap.
     */
    
    void
    twofish_encrypt(const struct twofish_ctx *context,
    		size_t length,
    		uint8_t *ciphertext,
    		const uint8_t *plaintext)
    {
      const uint32_t * keys        = context->keys;
      const uint32_t (*s_box)[256] = context->s_box;
    
      assert( !(length % TWOFISH_BLOCK_SIZE) );
      for ( ; length; length -= TWOFISH_BLOCK_SIZE)
        {  
          uint32_t words[4];
          uint32_t r0, r1, r2, r3, t0, t1;
          int i;
    
          for (i = 0; i<4; i++, plaintext += 4)
    	words[i] = LE_READ_UINT32(plaintext);
    
          r0 = words[0] ^ keys[0];
          r1 = words[1] ^ keys[1];
          r2 = words[2] ^ keys[2];
          r3 = words[3] ^ keys[3];
      
          for (i = 0; i < 8; i++) {
    	t1 = (  s_box[1][r1 & 0xFF]
    		^ s_box[2][(r1 >> 8) & 0xFF]
    		^ s_box[3][(r1 >> 16) & 0xFF]
    		^ s_box[0][(r1 >> 24) & 0xFF]);
    	t0 = (  s_box[0][r0 & 0xFF]
    		^ s_box[1][(r0 >> 8) & 0xFF]
    		^ s_box[2][(r0 >> 16) & 0xFF]
    		^ s_box[3][(r0 >> 24) & 0xFF]) + t1;
    	r3 = (t1 + t0 + keys[4*i+9]) ^ rol1(r3);
    	r2 = (t0 + keys[4*i+8]) ^ r2;
    	r2 = ror1(r2);
    
    	t1 = (  s_box[1][r3 & 0xFF]
    		^ s_box[2][(r3 >> 8) & 0xFF]
    		^ s_box[3][(r3 >> 16) & 0xFF]
    		^ s_box[0][(r3 >> 24) & 0xFF]);
    	t0 = (  s_box[0][r2 & 0xFF]
    		^ s_box[1][(r2 >> 8) & 0xFF]
    		^ s_box[2][(r2 >> 16) & 0xFF]
    		^ s_box[3][(r2 >> 24) & 0xFF]) + t1;
    	r1 = (t1 + t0 + keys[4*i+11]) ^ rol1(r1);
    	r0 = (t0 + keys[4*i+10]) ^ r0;
    	r0 = ror1(r0);
          }
    
          words[0] = r2 ^ keys[4];
          words[1] = r3 ^ keys[5];
          words[2] = r0 ^ keys[6];
          words[3] = r1 ^ keys[7];
    
          for (i = 0; i<4; i++, ciphertext += 4)
    	LE_WRITE_UINT32(ciphertext, words[i]);
        }
    }
    
    /* Decrypt blocks of 16 bytes of data with the twofish algorithm.
     *
     * Before this function can be used, twofish_set_key() must be used in order to
     * set up various tables required for the decryption algorithm.
     * 
     * This function always decrypts 16 bytes of ciphertext to 16 bytes of
     * plaintext.  The memory areas of the plaintext and the ciphertext can
     * overlap.
     */
    
    void
    twofish_decrypt(const struct twofish_ctx *context,
    		size_t length,
    		uint8_t *plaintext,
    		const uint8_t *ciphertext)
    
    {
      const uint32_t *keys  = context->keys;
      const uint32_t (*s_box)[256] = context->s_box;
    
      assert( !(length % TWOFISH_BLOCK_SIZE) );
      for ( ; length; length -= TWOFISH_BLOCK_SIZE)
        {  
          uint32_t words[4];
          uint32_t r0, r1, r2, r3, t0, t1;
          int i;
    
          for (i = 0; i<4; i++, ciphertext += 4)
    	words[i] = LE_READ_UINT32(ciphertext);
    
          r0 = words[2] ^ keys[6];
          r1 = words[3] ^ keys[7];
          r2 = words[0] ^ keys[4];
          r3 = words[1] ^ keys[5];
    
          for (i = 0; i < 8; i++) {
    	t1 = (  s_box[1][r3 & 0xFF]
    		^ s_box[2][(r3 >> 8) & 0xFF]
    		^ s_box[3][(r3 >> 16) & 0xFF]
    		^ s_box[0][(r3 >> 24) & 0xFF]);
    	t0 = (  s_box[0][r2 & 0xFF]
    		^ s_box[1][(r2 >> 8) & 0xFF]
    		^ s_box[2][(r2 >> 16) & 0xFF]
    		^ s_box[3][(r2 >> 24) & 0xFF]) + t1;
    	r1 = (t1 + t0 + keys[39-4*i]) ^ r1;
    	r1 = ror1(r1);
    	r0 = (t0 + keys[38-4*i]) ^ rol1(r0);
    
    	t1 = (  s_box[1][r1 & 0xFF]
    		^ s_box[2][(r1 >> 8) & 0xFF]
    		^ s_box[3][(r1 >> 16) & 0xFF]
    		^ s_box[0][(r1 >> 24) & 0xFF]);
    	t0 = (  s_box[0][r0 & 0xFF]
    		^ s_box[1][(r0 >> 8) & 0xFF]
    		^ s_box[2][(r0 >> 16) & 0xFF]
    		^ s_box[3][(r0 >> 24) & 0xFF]) + t1;
    	r3 = (t1 + t0 + keys[37-4*i]) ^ r3;
    	r3 = ror1(r3);
    	r2 = (t0 + keys[36-4*i]) ^ rol1(r2);
          }
    
          words[0] = r0 ^ keys[0];
          words[1] = r1 ^ keys[1];
          words[2] = r2 ^ keys[2];
          words[3] = r3 ^ keys[3];
    
          for (i = 0; i<4; i++, plaintext += 4)
    	LE_WRITE_UINT32(plaintext, words[i]);
        }
    }