/* * Copyright (C) 2013 Freie Universität Berlin, Computer Systems & Telematics * * This file is subject to the terms and conditions of the GNU Lesser * General Public License v2.1. See the file LICENSE in the top level * directory for more details. */ /** * @ingroup sys_crypto * @{ * * @file * @brief Headers for the implementation of the TwoFish Cipher-Algorithm * * @author Freie Universitaet Berlin, Computer Systems & Telematics * @author Nicolai Schmittberger * @author Zakaria Kasmi * */ #include #include #include #include #include #include "crypto/ciphers.h" #ifndef TWOFISH_H_ #define TWOFISH_H_ #ifdef __cplusplus extern "C" { #endif #define TWOFISH_BLOCK_SIZE 16 #define TWOFISH_KEY_SIZE 16 //only alternative is 32! #define TWOFISH_CONTEXT_SIZE 20 /** * Macro to perform one column of the RS matrix multiplication. The * parameters a, b, c, and d are the four bytes of output; i is the index * of the key bytes, and w, x, y, and z, are the column of constants from * the RS matrix, preprocessed through the poly_to_exp table. **/ #define CALC_S(a, b, c, d, i, w, x, y, z) \ if (key[i]) { \ tmp = poly_to_exp[key[i] - 1]; \ (a) ^= exp_to_poly[tmp + (w)]; \ (b) ^= exp_to_poly[tmp + (x)]; \ (c) ^= exp_to_poly[tmp + (y)]; \ (d) ^= exp_to_poly[tmp + (z)]; \ } /** * Macros to calculate the key-dependent S-boxes for a 128-bit key using * the S vector from CALC_S. CALC_SB_2 computes a single entry in all * four S-boxes, where i is the index of the entry to compute, and a and b * are the index numbers preprocessed through the q0 and q1 tables * respectively. CALC_SB is simply a convenience to make the code shorter; * it calls CALC_SB_2 four times with consecutive indices from i to i+3, * using the remaining parameters two by two. **/ #define CALC_SB_2(i, a, b) \ ctx->s[0][i] = mds[0][q0[(a) ^ sa] ^ se]; \ ctx->s[1][i] = mds[1][q0[(b) ^ sb] ^ sf]; \ ctx->s[2][i] = mds[2][q1[(a) ^ sc] ^ sg]; \ ctx->s[3][i] = mds[3][q1[(b) ^ sd] ^ sh] #define CALC_SB(i, a, b, c, d, e, f, g, h) \ CALC_SB_2 (i, a, b); CALC_SB_2 ((i)+1, c, d); \ CALC_SB_2 ((i)+2, e, f); CALC_SB_2 ((i)+3, g, h) /* Macros exactly like CALC_SB and CALC_SB_2, but for 256-bit keys. */ #define CALC_SB256_2(i, a, b) \ ctx->s[0][i] = mds[0][q0[q0[q1[(b) ^ sa] ^ se] ^ si] ^ sm]; \ ctx->s[1][i] = mds[1][q0[q1[q1[(a) ^ sb] ^ sf] ^ sj] ^ sn]; \ ctx->s[2][i] = mds[2][q1[q0[q0[(a) ^ sc] ^ sg] ^ sk] ^ so]; \ ctx->s[3][i] = mds[3][q1[q1[q0[(b) ^ sd] ^ sh] ^ sl] ^ sp]; #define CALC_SB256(i, a, b, c, d, e, f, g, h) \ CALC_SB256_2 (i, a, b); CALC_SB256_2 ((i)+1, c, d); \ CALC_SB256_2 ((i)+2, e, f); CALC_SB256_2 ((i)+3, g, h) /** * Macros to calculate the whitening and round subkeys. CALC_K_2 computes the * last two stages of the h() function for a given index (either 2i or 2i+1). * a, b, c, and d are the four bytes going into the last two stages. For * 128-bit keys, this is the entire h() function and a and c are the index * preprocessed through q0 and q1 respectively; for longer keys they are the * output of previous stages. j is the index of the first key byte to use. * CALC_K computes a pair of subkeys for 128-bit Twofish, by calling CALC_K_2 * twice, doing the Psuedo-Hadamard Transform, and doing the necessary * rotations. Its parameters are: a, the array to write the results into, * j, the index of the first output entry, k and l, the preprocessed indices * for index 2i, and m and n, the preprocessed indices for index 2i+1. * CALC_K256_2 expands CALC_K_2 to handle 256-bit keys, by doing two * additional lookup-and-XOR stages. The parameters a and b are the index * preprocessed through q0 and q1 respectively; j is the index of the first * key byte to use. CALC_K256 is identical to CALC_K but for using the * CALC_K256_2 macro instead of CALC_K_2. **/ #define CALC_K_2(a, b, c, d, j) \ mds[0][q0[a ^ key[(j) + 8]] ^ key[j]] \ ^ mds[1][q0[b ^ key[(j) + 9]] ^ key[(j) + 1]] \ ^ mds[2][q1[c ^ key[(j) + 10]] ^ key[(j) + 2]] \ ^ mds[3][q1[d ^ key[(j) + 11]] ^ key[(j) + 3]] #define CALC_K(a, j, k, l, m, n) \ x = CALC_K_2 (k, l, k, l, 0); \ y = CALC_K_2 (m, n, m, n, 4); \ y = (y << 8) + (y >> 24); \ x += y; y += x; ctx->a[j] = x; \ ctx->a[(j) + 1] = (y << 9) + (y >> 23) #define CALC_K256_2(a, b, j) \ CALC_K_2 (q0[q1[b ^ key[(j) + 24]] ^ key[(j) + 16]], \ q1[q1[a ^ key[(j) + 25]] ^ key[(j) + 17]], \ q0[q0[a ^ key[(j) + 26]] ^ key[(j) + 18]], \ q1[q0[b ^ key[(j) + 27]] ^ key[(j) + 19]], j) #define CALC_K256(a, j, k, l, m, n) \ x = CALC_K256_2 (k, l, 0); \ y = CALC_K256_2 (m, n, 4); \ y = (y << 8) + (y >> 24); \ x += y; y += x; ctx->a[j] = x; \ ctx->a[(j) + 1] = (y << 9) + (y >> 23) /** * Macros to compute the g() function in the encryption and decryption * rounds. G1 is the straight g() function; G2 includes the 8-bit * rotation for the high 32-bit word. **/ #define G1(a) \ (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \ ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24]) #define G2(b) \ (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \ ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24]) /** * Encryption and decryption Feistel rounds. Each one calls the two g() * macros, does the PHT, and performs the XOR and the appropriate bit * rotations. The parameters are the round number (used to select subkeys), * and the four 32-bit chunks of the text. **/ #define ENCROUND(n, a, b, c, d) \ x = G1 (a); y = G2 (b); \ x += y; y += x + ctx->k[2 * (n) + 1]; \ (c) ^= x + ctx->k[2 * (n)]; \ (c) = ((c) >> 1) + ((c) << 31); \ (d) = (((d) << 1)+((d) >> 31)) ^ y #define DECROUND(n, a, b, c, d) \ x = G1 (a); y = G2 (b); \ x += y; y += x; \ (d) ^= y + ctx->k[2 * (n) + 1]; \ (d) = ((d) >> 1) + ((d) << 31); \ (c) = (((c) << 1)+((c) >> 31)); \ (c) ^= (x + ctx->k[2 * (n)]) /** * Encryption and decryption cycles; each one is simply two Feistel rounds * with the 32-bit chunks re-ordered to simulate the "swap" **/ #define ENCCYCLE(n) \ ENCROUND (2 * (n), a, b, c, d); \ ENCROUND (2 * (n) + 1, c, d, a, b) #define DECCYCLE(n) \ DECROUND (2 * (n) + 1, c, d, a, b); \ DECROUND (2 * (n), a, b, c, d) /** * Macros to convert the input and output bytes into 32-bit words, * and simultaneously perform the whitening step. INPACK packs word * number n into the variable named by x, using whitening subkey number m. * OUTUNPACK unpacks word number n from the variable named by x, using * whitening subkey number m. **/ #define INPACK(n, x, m) \ x = in[4 * (n)] ^ (in[4 * (n) + 1] << 8) \ ^ ((uint32_t)in[4 * (n) + 2] << 16) ^ ((uint32_t)in[4 * (n) + 3] << 24) ^ ctx->w[m] #define OUTUNPACK(n, x, m) \ x ^= ctx->w[m]; \ out[4 * (n)] = x; out[4 * (n) + 1] = x >> 8; \ out[4 * (n) + 2] = x >> 16; out[4 * (n) + 3] = x >> 24 /** * @brief Structure for an expanded Twofish key. * * Note that k[i] corresponds to what the Twofish paper calls K[i+8]. */ typedef struct { /** contains the key-dependent S-boxes composed with the MDS matrix */ uint32_t s[4][256], /** contains the eight "whitening" subkeys, K[0] through K[7] */ w[8], /** holds the remaining, "round" subkeys */ k[32]; } twofish_context_t; /** * @brief Initialize the TwoFish-BlockCipher context. * * @param context structure to hold the opaque data from this * initialization * call. It should be passed to future invocations of * this module * which use this particular key. * @param key_size key size in bytes * @param key pointer to the key * * @return CIPHER_INIT_SUCCESS if the initialization was successful. * The command may be unsuccessful if the key size is not valid. * CIPHER_ERR_BAD_CONTEXT_SIZE if CIPHER_MAX_CONTEXT_SIZE has not been defined (which means that the cipher has not been included in the build) */ int twofish_init(cipher_context_t *context, const uint8_t *key, uint8_t key_size); /** * @brief Encrypts a single block (of blockSize) using the passed context. * * @param context holds the module specific opaque data related to the * key (perhaps key expansions). * @param in a plaintext block of blockSize * @param out the resulting ciphertext block of blockSize * * @return Whether the encryption was successful. Possible failure reasons * include not calling init(). */ int twofish_encrypt(const cipher_context_t *context, const uint8_t *in, uint8_t *out); /** * @brief Decrypts a single block (of blockSize) using the passed context. * * @param context holds the module specific opaque data related to the * key (perhaps key expansions). * @param in a ciphertext block of blockSize * @param out the resulting plaintext block of blockSize * * @return Whether the decryption was successful. Possible failure reasons * include not calling init() */ int twofish_decrypt(const cipher_context_t *context, const uint8_t *in, uint8_t *out); #ifdef __cplusplus } #endif /** @} */ #endif /* TWOFISH_H_ */