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/*
Implementation of the Lilliput-AE tweakable block cipher.
Author: Kévin Le Gouguec, 2019.
For more information, feedback or questions, refer to our website:
https://paclido.fr/lilliput-ae
To the extent possible under law, the implementer has waived all copyright
and related or neighboring rights to the source code in this file.
http://creativecommons.org/publicdomain/zero/1.0/
---
This file provides an implementation of Lilliput-TBC's tweakey schedule,
where multiplications by matrices M and M_R to the power n are performed
by functions expressing the exponentiated matrices with shifts and XORs.
*/
#include <stdint.h>
#include <string.h>
#include "constants.h"
#include "tweakey.h"
#define LANE_BITS 64
#define LANE_BYTES (LANE_BITS/8)
#define LANES_NB (TWEAKEY_BYTES/LANE_BYTES)
void tweakey_state_init(
uint8_t TK[TWEAKEY_BYTES],
const uint8_t key[KEY_BYTES],
const uint8_t tweak[TWEAK_BYTES]
)
{
memcpy(TK, tweak, TWEAK_BYTES);
memcpy(TK+TWEAK_BYTES, key, KEY_BYTES);
}
void tweakey_state_extract(
const uint8_t TK[TWEAKEY_BYTES],
uint8_t round_constant,
uint8_t round_tweakey[ROUND_TWEAKEY_BYTES]
)
{
memset(round_tweakey, 0, ROUND_TWEAKEY_BYTES);
for (size_t j=0; j<LANES_NB; j++)
{
const uint8_t *TKj = TK + j*LANE_BYTES;
for (size_t k=0; k<LANE_BYTES; k++)
{
round_tweakey[k] ^= TKj[k];
}
}
round_tweakey[0] ^= round_constant;
}
static uint8_t _M1(uint8_t x)
{
return x<<3 ^ x>>3;
}
static uint8_t _M3(uint8_t x)
{
return (uint8_t)(x<<3) >> 3;
}
static uint8_t _M4(uint8_t x)
{
return (uint8_t)(x<<2) >> 3;
}
static void _multiply_M(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
y[7] = x[6];
y[6] = x[5];
y[5] = x[5]<<3 ^ x[4];
y[4] = x[4]>>3 ^ x[3];
y[3] = x[2];
y[2] = x[6]<<2 ^ x[1];
y[1] = x[0];
y[0] = x[7];
}
static void _multiply_M2(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
uint8_t x_M_5 = x[5]<<3 ^ x[4];
uint8_t x_M_4 = x[4]>>3 ^ x[3];
y[7] = x[5];
y[6] = x_M_5;
y[5] = x_M_5<<3 ^ x_M_4;
y[4] = x_M_4>>3 ^ x[2];
y[3] = x[6]<<2 ^ x[1];
y[2] = x[5]<<2 ^ x[0];
y[1] = x[7];
y[0] = x[6];
}
static void _multiply_M3(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
uint8_t x_M_5 = x[5]<<3 ^ x[4];
uint8_t x_M_4 = x[4]>>3 ^ x[3];
uint8_t x_M2_5 = x_M_5<<3 ^ x_M_4;
uint8_t x_M2_4 = x_M_4>>3 ^ x[2];
y[7] = x_M_5;
y[6] = x_M2_5;
y[5] = x_M2_5<<3 ^ x_M2_4;
y[4] = x_M2_4>>3 ^ x[6]<<2 ^ x[1];
y[3] = x[5]<<2 ^ x[0];
y[2] = x_M_5<<2 ^ x[7];
y[1] = x[6];
y[0] = x[5];
}
static void _multiply_MR(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
y[0] = x[1];
y[1] = x[2];
y[2] = x[3] ^ x[4]>>3;
y[3] = x[4];
y[4] = x[5] ^ x[6]<<3;
y[5] = x[3]<<2 ^ x[6];
y[6] = x[7];
y[7] = x[0];
}
static void _multiply_MR2(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
y[0] = x[2];
y[1] = x[3] ^ x[4]>>3;
y[2] = x[4] ^ x[5]>>3 ^ _M3(x[6]);
y[3] = x[5] ^ x[6]<<3;
y[4] = x[3]<<2 ^ x[6] ^ x[7]<<3;
y[5] = x[4]<<2 ^ x[7];
y[6] = x[0];
y[7] = x[1];
}
static void _multiply_MR3(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
{
y[0] = x[3] ^ x[4]>>3;
y[1] = x[4] ^ x[5]>>3 ^ _M3(x[6]);
y[2] = _M4(x[3]) ^ x[5] ^ _M1(x[6]) ^ _M3(x[7]);
y[3] = x[3]<<2 ^ x[6] ^ x[7]<<3;
y[4] = x[0]<<3 ^ x[4]<<2 ^ x[7];
y[5] = x[0] ^ x[5]<<2 ^ x[6]<<5;
y[6] = x[1];
y[7] = x[2];
}
typedef void (*matrix_multiplication)(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES]);
static const matrix_multiplication ALPHAS[6] = {
_multiply_M,
_multiply_M2,
_multiply_M3,
_multiply_MR,
_multiply_MR2,
_multiply_MR3
};
void tweakey_state_update(uint8_t TK[TWEAKEY_BYTES])
{
/* Skip lane 0, as it is multiplied by the identity matrix. */
for (size_t j=1; j<LANES_NB; j++)
{
uint8_t *TKj = TK + j*LANE_BYTES;
uint8_t TKj_old[LANE_BYTES];
memcpy(TKj_old, TKj, LANE_BYTES);
ALPHAS[j-1](TKj_old, TKj);
}
}
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