3 This file is part of the Crypto-avr-lib/microcrypt-lib.
4 Copyright (C) 2008 Daniel Otte (daniel.otte@rub.de)
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 * a bitsliced implementation of the serpent cipher for avr microcontrollers
22 * email: daniel.otte@rub.de
27 #include <string.h> /* memset() */
28 #include <avr/pgmspace.h>
31 #include "serpent-sboxes.h"
33 /******************************************************************************/
35 uint32_t rotl32(uint32_t a, uint8_t n){
36 return ((a<<n) | (a>>(32-n)));
40 uint32_t rotr32(uint32_t a, uint8_t n){
41 return ((a>>n) | (a<<(32-n)));
45 #define X0 (((uint32_t*)b)[0])
46 #define X1 (((uint32_t*)b)[1])
47 #define X2 (((uint32_t*)b)[2])
48 #define X3 (((uint32_t*)b)[3])
50 void serpent_lt(uint8_t *b);
52 static void serpent_lt(uint8_t *b){
66 static void serpent_inv_lt(uint8_t *b);
69 static void serpent_inv_lt(uint8_t *b){
83 uint32_t serpent_gen_w(uint32_t * b, uint8_t i);
85 #define GOLDEN_RATIO 0x9e3779b9l
87 static uint32_t serpent_gen_w(uint32_t * b, uint8_t i){
89 ret = b[0] ^ b[3] ^ b[5] ^ b[7] ^ GOLDEN_RATIO ^ (uint32_t)i;
90 ret = rotl32(ret, 11);
95 void serpent_init(const void* key, uint16_t keysize_b, serpent_ctx_t* ctx){
99 /* keysize is less than 256 bit, padding needed */
100 memset(buffer, 0, 32);
101 memcpy(buffer, key, (keysize_b+7)/8);
102 ((uint8_t*)buffer)[keysize_b/8] |= 1<<(keysize_b%8);
104 /* keysize is 256 bit */
105 memcpy(buffer, key, 32);
109 ctx->k[i][j] = serpent_gen_w(buffer, i*4+j);
110 memmove(buffer, &(buffer[1]), 7*4); /* shift buffer one to the "left" */
111 buffer[7] = ctx->k[i][j];
115 sbox128(ctx->k[i],3-i);
120 void serpent_enc(void* buffer, const serpent_ctx_t* ctx){
123 memxor(buffer, ctx->k[i], 16);
125 serpent_lt((uint8_t*)buffer);
127 memxor(buffer, ctx->k[i], 16);
130 memxor(buffer, ctx->k[i], 16);
133 void serpent_dec(void* buffer, const serpent_ctx_t* ctx){
136 memxor(buffer, ctx->k[i], 16);
138 inv_sbox128(buffer, i);
139 memxor((uint8_t*)buffer, ctx->k[i], 16);
142 serpent_inv_lt(buffer);
143 inv_sbox128(buffer, i);
144 memxor(buffer, ctx->k[i], 16);