--- /dev/null
+/* serpent.c */
+/*
+ This file is part of the ARM-Crypto-Lib.
+ Copyright (C) 2006-2010 Daniel Otte (daniel.otte@rub.de)
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+/* serpent.c
+ * a bitsliced implementation of the serpent cipher for avr microcontrollers
+ * author: Daniel Otte
+ * email: daniel.otte@rub.de
+ * license: GPLv3
+ */
+
+#include <stdint.h>
+#include <string.h> /* memset() */
+#include "memxor.h"
+#include "serpent.h"
+#include "serpent-sboxes.h"
+
+/******************************************************************************/
+
+uint32_t rotl32(uint32_t a, uint8_t n){
+ return ((a<<n) | (a>>(32-n)));
+}
+
+
+uint32_t rotr32(uint32_t a, uint8_t n){
+ return ((a>>n) | (a<<(32-n)));
+}
+
+
+#define X0 (((uint32_t*)b)[0])
+#define X1 (((uint32_t*)b)[1])
+#define X2 (((uint32_t*)b)[2])
+#define X3 (((uint32_t*)b)[3])
+
+static void serpent_lt(uint8_t *b){
+ X0 = rotl32(X0, 13);
+ X2 = rotl32(X2, 3);
+ X1 ^= X0 ^ X2;
+ X3 ^= X2 ^ (X0 << 3);
+ X1 = rotl32(X1, 1);
+ X3 = rotl32(X3, 7);
+ X0 ^= X1 ^ X3;
+ X2 ^= X3 ^ (X1 << 7);
+ X0 = rotl32(X0, 5);
+ X2 = rotr32(X2, 10);
+}
+
+static void serpent_inv_lt(uint8_t *b){
+ X2 = rotl32(X2, 10);
+ X0 = rotr32(X0, 5);
+ X2 ^= X3 ^ (X1 << 7);
+ X0 ^= X1 ^ X3;
+ X3 = rotr32(X3, 7);
+ X1 = rotr32(X1, 1);
+ X3 ^= X2 ^ (X0 << 3);
+ X1 ^= X0 ^ X2;
+ X2 = rotr32(X2, 3);
+ X0 = rotr32(X0, 13);
+}
+
+#define GOLDEN_RATIO 0x9e3779b9l
+
+static uint32_t serpent_gen_w(uint32_t * b, uint8_t i){
+ uint32_t ret;
+ ret = b[0] ^ b[3] ^ b[5] ^ b[7] ^ GOLDEN_RATIO ^ (uint32_t)i;
+ ret = rotl32(ret, 11);
+ return ret;
+}
+
+void serpent_init(const void* key, uint16_t keysize_b, serpent_ctx_t* ctx){
+ uint32_t buffer[8];
+ uint8_t i,j;
+ if(keysize_b<256){
+ /* keysize is less than 256 bit, padding needed */
+ memset(buffer, 0, 32);
+ memcpy(buffer, key, (keysize_b+7)/8);
+ ((uint8_t*)buffer)[keysize_b/8] |= 1<<(keysize_b%8);
+ } else {
+ /* keysize is 256 bit */
+ memcpy((void*)buffer, key, 32);
+ }
+ for(i=0; i<33; ++i){
+ for(j=0; j<4; ++j){
+ ctx->k[i][j] = serpent_gen_w(buffer, i*4+j);
+ memmove(buffer, &(buffer[1]), 7*4); /* shift buffer one to the "left" */
+ buffer[7] = ctx->k[i][j];
+ }
+ }
+ for(i=0; i<33; ++i){
+ sbox128(ctx->k[i],3-i);
+ }
+}
+
+void serpent_enc(void* buffer, const serpent_ctx_t* ctx){
+ uint8_t i;
+ for(i=0; i<31; ++i){
+ memxor(buffer, ctx->k[i], 16);
+ sbox128(buffer, i);
+ serpent_lt((uint8_t*)buffer);
+ }
+ memxor(buffer, ctx->k[i], 16);
+ sbox128(buffer, i);
+ ++i;
+ memxor(buffer, ctx->k[i], 16);
+}
+
+void serpent_dec(void* buffer, const serpent_ctx_t* ctx){
+ int8_t i=32;
+
+ memxor(buffer, ctx->k[i], 16);
+ --i;
+ inv_sbox128(buffer, i);
+ memxor((uint8_t*)buffer, ctx->k[i], 16);
+ --i;
+ for(; i>=0; --i){
+ serpent_inv_lt(buffer);
+ inv_sbox128(buffer, i);
+ memxor(buffer, ctx->k[i], 16);
+ }
+}
+
+
+
+
+