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skinny-64-192.cpp
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skinny-64-192.cpp
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/*
* C++ implementation of Skinny-64-192
* Date: March 8, 2020
* Author: Hosein Hadipour
* Contact: [email protected]
*/
//Skinny-64-192: 40 rounds
#include <stdio.h>
#include <stdint.h>
#include <string>
#include <iostream>
using namespace std;
// 4-bit Sbox
const uint8_t S[16] = {0xc, 0x6, 0x9, 0x0, 0x1, 0xa, 0x2, 0xb, 0x3, 0x8, 0x5, 0xd, 0x4, 0xe, 0x7, 0xf};
// 4-bit Sbox Inverse
const uint8_t Sinv[16] = {0x3, 0x4, 0x6, 0x8, 0xc, 0xa, 0x1, 0xe, 0x9, 0x2, 0x5, 0x7, 0x0, 0xb, 0xd, 0xf};
// Permutation
const uint8_t P[16] = {0x0, 0x1, 0x2, 0x3, 0x7, 0x4, 0x5, 0x6, 0xa, 0xb, 0x8, 0x9, 0xd, 0xe, 0xf, 0xc};
const uint8_t Pinv[16] = {0x0, 0x1, 0x2, 0x3, 0x5, 0x6, 0x7, 0x4, 0xa, 0xb, 0x8, 0x9, 0xf, 0xc, 0xd, 0xe};
// Tweakey Permutation
const uint8_t Q[16] = {0x9, 0xf, 0x8, 0xd, 0xa, 0xe, 0xc, 0xb, 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7};
// const uint8_t Qinv[16] = {0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf, 0x2, 0x0, 0x4, 0x7, 0x6, 0x3, 0x5, 0x1};
// Round Constants
const unsigned char RC[62] = {0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3E, 0x3D, 0x3B, 0x37, 0x2F,
0x1E, 0x3C, 0x39, 0x33, 0x27, 0x0E, 0x1D, 0x3A, 0x35, 0x2B,
0x16, 0x2C, 0x18, 0x30, 0x21, 0x02, 0x05, 0x0B, 0x17, 0x2E,
0x1C, 0x38, 0x31, 0x23, 0x06, 0x0D, 0x1B, 0x36, 0x2D, 0x1A,
0x34, 0x29, 0x12, 0x24, 0x08, 0x11, 0x22, 0x04, 0x09, 0x13,
0x26, 0x0c, 0x19, 0x32, 0x25, 0x0a, 0x15, 0x2a, 0x14, 0x28,
0x10, 0x20};
void print_state(uint8_t state[16]);
void convert_hexstr_to_statearray(string hex_str, uint8_t int_array[16], bool reversed);
uint8_t tweak_tk2_lfsr(uint8_t x);
uint8_t tweak_tk3_lfsr(uint8_t x);
void mix_columns(uint8_t state[16]);
void inv_mix_columns(uint8_t state[16]);
void tweakey_schedule(int rounds, uint8_t tk1[][16], uint8_t tk2[][16], uint8_t tk3[][16], uint8_t round_tweakey[][8]);
void enc(int R, uint8_t plaintext[16], uint8_t ciphertext[16], uint8_t tk[][8]);
void dec(int R, uint8_t plaintext[16], uint8_t ciphertext[16], uint8_t tk[][8]);
void print_state(uint8_t state[16])
{
for (int i = 0; i < 16; i++)
printf("%01x", state[i]);
printf("\n");
}
void convert_hexstr_to_statearray(string hex_str, uint8_t int_array[16], bool reversed = false)
{
if (reversed == true)
for (int i = 15; i > -1; i--)
int_array[15 - i] = static_cast<uint8_t> (stoi(hex_str.substr(i, 1), 0, 16) & 0xf);
else
for (int i = 0; i < 16; i++)
int_array[i] = static_cast<uint8_t> (stoi(hex_str.substr(i, 1), 0, 16) & 0xf);
}
uint8_t tweak_tk2_lfsr(uint8_t x)
{
x = (x << 1) ^ ((x >> 3) & 0x1) ^ ((x >> 2) & 0x1);
x = x & 0xf;
return x;
}
uint8_t tweak_tk3_lfsr(uint8_t x)
{
x = (x >> 1) ^ (((x & 0x1) ^ ((x >> 3) & 0x1)) << 3);
x = x & 0xf;
return x;
}
void mix_columns(uint8_t state[16])
{
uint8_t tmp;
for (uint8_t j = 0; j < 4; j++)
{
state[j + 4 * 1] ^= state[j + 4 * 2];
state[j + 4 * 2] ^= state[j + 4 * 0];
state[j + 4 * 3] ^= state[j + 4 * 2];
tmp = state[j + 4 * 3];
state[j + 4 * 3] = state[j + 4 * 2];
state[j + 4 * 2] = state[j + 4 * 1];
state[j + 4 * 1] = state[j + 4 * 0];
state[j + 4 * 0] = tmp;
}
}
void inv_mix_columns(uint8_t state[16])
{
uint8_t tmp;
for (uint8_t j = 0; j < 4; j++)
{
tmp = state[j + 4 * 3];
state[j + 4 * 3] = state[j + 4 * 0];
state[j + 4 * 0] = state[j + 4 * 1];
state[j + 4 * 1] = state[j + 4 * 2];
state[j + 4 * 2] = tmp;
state[j + 4 * 3] ^= state[j + 4 * 2];
state[j + 4 * 2] ^= state[j + 4 * 0];
state[j + 4 * 1] ^= state[j + 4 * 2];
}
}
void tweakey_schedule(int rounds, uint8_t tk1[][16], uint8_t tk2[][16], uint8_t tk3[][16], uint8_t round_tweakey[][8])
{
// Declare tweakey after permutation
uint8_t tkp1[rounds - 1][16];
uint8_t tkp2[rounds - 1][16];
uint8_t tkp3[rounds - 1][16];
for (uint8_t i = 0; i < 16; i++)
tk1[0][i] = (tk1[0][i] & 0xf);
for (uint8_t i = 0; i < 16; i++)
tk2[0][i] = (tk2[0][i] & 0xf);
for (uint8_t i = 0; i < 16; i++)
tk3[0][i] = (tk3[0][i] & 0xf);
for (uint8_t i = 0; i < 8; i++)
round_tweakey[0][i] = (tk1[0][i] ^ tk2[0][i] ^ tk3[0][i]);
for (int r = 1; r < rounds; r++)
{
// Apply tweakey permutation on TK1, TK2, and TK3
for (int i = 0; i < 16; i++)
{
tkp1[r - 1][i] = tk1[r - 1][Q[i]];
tkp2[r - 1][i] = tk2[r - 1][Q[i]];
tkp3[r - 1][i] = tk3[r - 1][Q[i]];
}
// Apply LFSR on two upper rows of TK2, and TK3
for (int i = 0; i < 16; i++)
{
// LFSRs are not performed on TK1 at all
tk1[r][i] = tkp1[r - 1][i];
if (i < 8)
{
tk2[r][i] = tweak_tk2_lfsr(tkp2[r - 1][i]);
tk3[r][i] = tweak_tk3_lfsr(tkp3[r - 1][i]);
}
else
{
tk2[r][i] = tkp2[r - 1][i];
tk3[r][i] = tkp3[r - 1][i];
}
}
// Update round-tweakey
for (int i = 0; i < 8; i++)
round_tweakey[r][i] = (tk1[r][i] ^ tk2[r][i] ^ tk3[r][i]);
// printf("\ntweakeys: ");
// print_state(round_tweakey[r]);
}
}
void enc(int R, uint8_t plaintext[16], uint8_t ciphertext[16], uint8_t tk[][8])
{
for (uint8_t i = 0; i < 16; i++)
{
ciphertext[i] = plaintext[i] & 0xf;
}
for (uint8_t r = 0; r < R; r++)
{
// SBox
for (uint8_t i = 0; i < 16; i++)
ciphertext[i] = S[ciphertext[i]];
// Add constants (constants only affects on three upper cells of the first column)
ciphertext[0] ^= (RC[r] & 0xf);
ciphertext[4] ^= ((RC[r] >> 4) & 0x3);
ciphertext[8] ^= 0x2;
// Add round tweakey (tweakey only exclusive-ored with two upper rows of the state)
for (uint8_t i = 0; i < 8; i++)
ciphertext[i] ^= tk[r][i];
// Permute nibbles
uint8_t temp[16];
for (uint8_t i = 0; i < 16; i++)
temp[i] = ciphertext[i];
for (uint8_t i = 0; i < 16; i++)
ciphertext[i] = temp[P[i]];
// MixColumn
mix_columns(ciphertext);
// Print state
// printf("\nR%02d : ", r + 1);
// print_state(ciphertext);
}
}
void dec(int R, uint8_t plaintext[16], uint8_t ciphertext[16], uint8_t tk[][8])
{
for (uint8_t i = 0; i < 16; i++)
{
plaintext[i] = ciphertext[i] & 0xf;
}
int ind;
uint8_t temp[16];
for (int r = 0; r < R; r++)
{
// MixColumn inverse
inv_mix_columns(plaintext);
// Permute nibble inverse
for (uint8_t i = 0; i < 16; i++)
temp[i] = plaintext[i];
for (uint8_t i = 0; i < 16; i++)
plaintext[i] = temp[Pinv[i]];
//temp[P[i]] = plaintext[i];
// Add tweakey
ind = R - r - 1;
for (uint8_t i = 0; i < 8; i++)
plaintext[i] ^= tk[ind][i];
// Add constants
plaintext[0] ^= (RC[ind] & 0xf);
plaintext[4] ^= ((RC[ind] >> 4) & 0x3);
plaintext[8] ^= 0x2;
// SBox inverse
for (uint8_t i = 0; i < 16; i++)
plaintext[i] = Sinv[plaintext[i]];
// Print state
// printf("\nR%02d : ", r + 1);
// print_state(plaintext);
}
}
int main()
{
uint8_t plaintext[16];
uint8_t ciphertext[16];
int R = 40;
uint8_t tk1[R][16];
uint8_t tk2[R][16];
uint8_t tk3[R][16];
uint8_t rtk[R][8];
uint8_t tweakey1[16];
uint8_t tweakey2[16];
uint8_t tweakey3[16];
// Test vectors
string tk1_str = "ed00c85b120d6861";
string tk2_str = "8753e24bfd908f60";
string tk3_str = "b2dbb41b422dfcd0";
string plain_str = "530c61d35e8663c3";
string cipher_str = "dd2cf1a8f330303c";
bool reversed = false;
convert_hexstr_to_statearray(tk1_str, tweakey1, reversed);
convert_hexstr_to_statearray(tk2_str, tweakey2, reversed);
convert_hexstr_to_statearray(tk3_str, tweakey3, reversed);
convert_hexstr_to_statearray(plain_str, plaintext, reversed);
for (uint8_t i = 0; i < 16; i++)
{
tk1[0][i] = tweakey1[i];
tk2[0][i] = tweakey2[i];
tk3[0][i] = tweakey3[i];
}
tweakey_schedule(R, tk1, tk2, tk3, rtk);
printf("%-30s", "plaintext before encryption:");
print_state(plaintext);
enc(R, plaintext, ciphertext, rtk);
printf("%-30s", "ciphertext:");
print_state(ciphertext);
printf("%-30s", "expected ciphertext:");
printf("%s\n", cipher_str.c_str());
dec(R, plaintext, ciphertext, rtk);
printf("%-30s", "plaintext after decryption:");
print_state(plaintext);
printf("Press Enter to exit ...\n");
getchar();
return 0;
}