modified structure

[avr-crypto-lib.git] / serpent / serpent.c

diff --git a/serpent/serpent.c b/serpent/serpent.c
new file mode 100644 (file)
index 0000000..40ccecd
--- /dev/null
+++ b/serpent/serpent.c
@@ -0,0 +1,140 @@
+/* serpent.c */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2008  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 <avr/pgmspace.h>
+#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(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);
+       }
+}
+
+
+
+
+