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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 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 M_X[LANE_BYTES];
_multiply_M(X, M_X);
_multiply_M(M_X, Y);
}
static void _multiply_M3(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
{
uint8_t M_X[LANE_BYTES];
uint8_t M2_X[LANE_BYTES];
_multiply_M(X, M_X);
_multiply_M(M_X, M2_X);
_multiply_M(M2_X, Y);
}
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])
{
uint8_t MR_X[LANE_BYTES];
_multiply_MR(X, MR_X);
_multiply_MR(MR_X, Y);
}
static void _multiply_MR3(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
{
uint8_t MR_X[LANE_BYTES];
uint8_t MR2_X[LANE_BYTES];
_multiply_MR(X, MR_X);
_multiply_MR(MR_X, MR2_X);
_multiply_MR(MR2_X, Y);
}
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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