/* twofish.c * * The twofish block cipher. */ /* twofish - An implementation of the twofish cipher. * Copyright (C) 1999 Ruud de Rooij * * Modifications for lsh, integrated testing * Copyright (C) 1999 J.H.M. Dassen (Ray) * * 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 #include #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, unsigned 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, unsigned 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, unsigned 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]); } }