2 * a bitsliced implementation of the serpent cipher for avr microcontrollers
4 * email: daniel.otte@rub.de
9 #include <string.h> /* memset() */
10 #include <avr/pgmspace.h>
13 uint8_t sbox[] PROGMEM = {
14 0x38, 0xF1, 0xA6, 0x5B, 0xED, 0x42, 0x70, 0x9C,
15 0xFC, 0x27, 0x90, 0x5A, 0x1B, 0xE8, 0x6D, 0x34,
16 0x86, 0x79, 0x3C, 0xAF, 0xD1, 0xE4, 0x0B, 0x52,
17 0x0F, 0xB8, 0xC9, 0x63, 0xD1, 0x24, 0xA7, 0x5E,
18 0x1F, 0x83, 0xC0, 0xB6, 0x25, 0x4A, 0x9E, 0x7D,
19 0xF5, 0x2B, 0x4A, 0x9C, 0x03, 0xE8, 0xD6, 0x71,
20 0x72, 0xC5, 0x84, 0x6B, 0xE9, 0x1F, 0xD3, 0xA0,
21 0x1D, 0xF0, 0xE8, 0x2B, 0x74, 0xCA, 0x93, 0x56,
22 /* now the inverted sboxes */
23 0xD3, 0xB0, 0xA6, 0x5C, 0x1E, 0x47, 0xF9, 0x82,
24 0x58, 0x2E, 0xF6, 0xC3, 0xB4, 0x79, 0x1D, 0xA0,
25 0xC9, 0xF4, 0xBE, 0x12, 0x03, 0x6D, 0x58, 0xA7,
26 0x09, 0xA7, 0xBE, 0x6D, 0x35, 0xC2, 0x48, 0xF1,
27 0x50, 0x83, 0xA9, 0x7E, 0x2C, 0xB6, 0x4F, 0xD1,
28 0x8F, 0x29, 0x41, 0xDE, 0xB6, 0x53, 0x7C, 0xA0,
29 0xFA, 0x1D, 0x53, 0x60, 0x49, 0xE7, 0x2C, 0x8B,
30 0x30, 0x6D, 0x9E, 0xF8, 0x5C, 0xB7, 0xA1, 0x42
34 #define SHR_O(a) c=(a)&1; ((a) = (a)>>1)
35 #define SHR_I(a) ((a) = (c?0x80:0x00)| ((a)>>1))
37 static void ip(uint8_t *o, uint32_t *i){
56 #define SHR_I(a) ((a) = (c?0x80000000L:0x00L)| ((a)>>1)) /* we use 32-bit words here */
59 static void fp(uint32_t *o, uint32_t *i){
77 /******************************************************************************/
79 static void sbox128x(uint8_t box, void* w){
85 t = pgm_read_byte(sbox + box*8 + i);
102 static void sbox128(void * w, uint8_t box){
103 sbox128x(box&0x7, w);
106 static void inv_sbox128(void * w, uint8_t box){
107 sbox128x(((box&0x7)|0x8), w);
110 /******************************************************************************/
112 void memxor(void * dest, void * src, uint8_t size){
114 *((uint8_t*)dest) ^= *((uint8_t*)src);
115 dest = (uint8_t*)dest +1;
116 src = (uint8_t*)src +1;
120 /******************************************************************************/
122 uint32_t rotl32(uint32_t a, uint8_t n){
123 return ((a<<n) | (a>>(32-n)));
127 uint32_t rotr32(uint32_t a, uint8_t n){
128 return ((a>>n) | (a<<(32-n)));
132 #define X0 (((uint32_t*)b)[0])
133 #define X1 (((uint32_t*)b)[1])
134 #define X2 (((uint32_t*)b)[2])
135 #define X3 (((uint32_t*)b)[3])
137 static void lt(uint8_t *b){
141 X3 ^= X2 ^ (X0 << 3);
145 X2 ^= X3 ^ (X1 << 7);
150 static void inv_lt(uint8_t *b){
153 X2 ^= X3 ^ (X1 << 7);
157 X3 ^= X2 ^ (X0 << 3);
163 #define GOLDEN_RATIO 0x9e3779b9l
165 static uint32_t gen_w(uint32_t * b, uint8_t i){
167 ret = b[0] ^ b[3] ^ b[5] ^ b[7] ^ GOLDEN_RATIO ^ (uint32_t)i;
168 ret = rotl32(ret, 11);
172 /* key must be 256bit (32 byte) large! */
173 void serpent_genctx(void * key, serpent_ctx_t * ctx){
176 memcpy(buffer, key, 32);
179 ctx->k[i][j] = gen_w(buffer, i*4+j);
180 memmove(buffer, &(buffer[1]), 7*4); /* shift buffer one to the "left" */
181 buffer[7] = ctx->k[i][j];
185 sbox128(ctx->k[i],3-i);
190 void serpent_enc(void* buffer, serpent_ctx_t * ctx){
193 memxor((uint8_t*)buffer, ctx->k[i], 16);
195 lt((uint8_t*)buffer);
197 memxor((uint8_t*)buffer, ctx->k[i], 16);
200 memxor((uint8_t*)buffer, ctx->k[i], 16);
203 void serpent_dec(void* buffer, serpent_ctx_t * ctx){
206 memxor((uint8_t*)buffer, ctx->k[i], 16);
208 inv_sbox128(buffer, i);
209 memxor((uint8_t*)buffer, ctx->k[i], 16);
212 inv_lt((uint8_t*)buffer);
213 inv_sbox128(buffer, i);
214 memxor((uint8_t*)buffer, ctx->k[i], 16);