skinny_round.c

/*
 * Date: January 2019
 * Contact: Toon Purnal
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

#include "skinny_round.h"
#include "helpers.h"

//#define DEBUG_SKINNY

/* === Print intermediate results for debugging purposes === */
void print_cells(unsigned char s[4][4], int i){
    #ifdef DEBUG_SKINNY
    int j,k;
    printf("\nAfter round %i: ", i);
    for (j = 0; j < 4; j++)
        for (k = 0; k < 4; k++)
            printf("%02x ", s[j][k]);
    #endif
}

// Packing of data is done as follows (state[i][j] stands for row i and column j):
// 0  1  2  3
// 4  5  6  7
// 8  9 10 11
//12 13 14 15

/* SBox */
#ifdef CRYPTO_BLOCKSIZE_8
const unsigned char sbox[16] = {12,6,9,0,1,10,2,11,3,8,5,13,4,14,7,15};
const unsigned char sbox_inv[16] = {3,4,6,8,12,10,1,14,9,2,5,7,0,11,13,15};
#endif

#ifdef CRYPTO_BLOCKSIZE_16
const unsigned char sbox[256] = {0x65, 0x4c, 0x6a, 0x42, 0x4b, 0x63, 0x43, 0x6b, 0x55, 0x75, 0x5a, 0x7a, 0x53, 0x73, 0x5b, 0x7b,0x35, 0x8c, 0x3a, 0x81, 0x89, 0x33, 0x80, 0x3b, 0x95, 0x25, 0x98, 0x2a, 0x90, 0x23, 0x99, 0x2b,0xe5, 0xcc, 0xe8, 0xc1, 0xc9, 0xe0, 0xc0, 0xe9, 0xd5, 0xf5, 0xd8, 0xf8, 0xd0, 0xf0, 0xd9, 0xf9,0xa5, 0x1c, 0xa8, 0x12, 0x1b, 0xa0, 0x13, 0xa9, 0x05, 0xb5, 0x0a, 0xb8, 0x03, 0xb0, 0x0b, 0xb9,0x32, 0x88, 0x3c, 0x85, 0x8d, 0x34, 0x84, 0x3d, 0x91, 0x22, 0x9c, 0x2c, 0x94, 0x24, 0x9d, 0x2d,0x62, 0x4a, 0x6c, 0x45, 0x4d, 0x64, 0x44, 0x6d, 0x52, 0x72, 0x5c, 0x7c, 0x54, 0x74, 0x5d, 0x7d,0xa1, 0x1a, 0xac, 0x15, 0x1d, 0xa4, 0x14, 0xad, 0x02, 0xb1, 0x0c, 0xbc, 0x04, 0xb4, 0x0d, 0xbd,0xe1, 0xc8, 0xec, 0xc5, 0xcd, 0xe4, 0xc4, 0xed, 0xd1, 0xf1, 0xdc, 0xfc, 0xd4, 0xf4, 0xdd, 0xfd,0x36, 0x8e, 0x38, 0x82, 0x8b, 0x30, 0x83, 0x39, 0x96, 0x26, 0x9a, 0x28, 0x93, 0x20, 0x9b, 0x29,0x66, 0x4e, 0x68, 0x41, 0x49, 0x60, 0x40, 0x69, 0x56, 0x76, 0x58, 0x78, 0x50, 0x70, 0x59, 0x79,0xa6, 0x1e, 0xaa, 0x11, 0x19, 0xa3, 0x10, 0xab, 0x06, 0xb6, 0x08, 0xba, 0x00, 0xb3, 0x09, 0xbb,0xe6, 0xce, 0xea, 0xc2, 0xcb, 0xe3, 0xc3, 0xeb, 0xd6, 0xf6, 0xda, 0xfa, 0xd3, 0xf3, 0xdb, 0xfb,0x31, 0x8a, 0x3e, 0x86, 0x8f, 0x37, 0x87, 0x3f, 0x92, 0x21, 0x9e, 0x2e, 0x97, 0x27, 0x9f, 0x2f,0x61, 0x48, 0x6e, 0x46, 0x4f, 0x67, 0x47, 0x6f, 0x51, 0x71, 0x5e, 0x7e, 0x57, 0x77, 0x5f, 0x7f,0xa2, 0x18, 0xae, 0x16, 0x1f, 0xa7, 0x17, 0xaf, 0x01, 0xb2, 0x0e, 0xbe, 0x07, 0xb7, 0x0f, 0xbf,0xe2, 0xca, 0xee, 0xc6, 0xcf, 0xe7, 0xc7, 0xef, 0xd2, 0xf2, 0xde, 0xfe, 0xd7, 0xf7, 0xdf, 0xff};
const unsigned char sbox_inv[256] = {0xac, 0xe8, 0x68, 0x3c, 0x6c, 0x38, 0xa8, 0xec, 0xaa, 0xae, 0x3a, 0x3e, 0x6a, 0x6e, 0xea, 0xee,0xa6, 0xa3, 0x33, 0x36, 0x66, 0x63, 0xe3, 0xe6, 0xe1, 0xa4, 0x61, 0x34, 0x31, 0x64, 0xa1, 0xe4,0x8d, 0xc9, 0x49, 0x1d, 0x4d, 0x19, 0x89, 0xcd, 0x8b, 0x8f, 0x1b, 0x1f, 0x4b, 0x4f, 0xcb, 0xcf,0x85, 0xc0, 0x40, 0x15, 0x45, 0x10, 0x80, 0xc5, 0x82, 0x87, 0x12, 0x17, 0x42, 0x47, 0xc2, 0xc7,0x96, 0x93, 0x03, 0x06, 0x56, 0x53, 0xd3, 0xd6, 0xd1, 0x94, 0x51, 0x04, 0x01, 0x54, 0x91, 0xd4,0x9c, 0xd8, 0x58, 0x0c, 0x5c, 0x08, 0x98, 0xdc, 0x9a, 0x9e, 0x0a, 0x0e, 0x5a, 0x5e, 0xda, 0xde,0x95, 0xd0, 0x50, 0x05, 0x55, 0x00, 0x90, 0xd5, 0x92, 0x97, 0x02, 0x07, 0x52, 0x57, 0xd2, 0xd7,0x9d, 0xd9, 0x59, 0x0d, 0x5d, 0x09, 0x99, 0xdd, 0x9b, 0x9f, 0x0b, 0x0f, 0x5b, 0x5f, 0xdb, 0xdf,0x16, 0x13, 0x83, 0x86, 0x46, 0x43, 0xc3, 0xc6, 0x41, 0x14, 0xc1, 0x84, 0x11, 0x44, 0x81, 0xc4,0x1c, 0x48, 0xc8, 0x8c, 0x4c, 0x18, 0x88, 0xcc, 0x1a, 0x1e, 0x8a, 0x8e, 0x4a, 0x4e, 0xca, 0xce,0x35, 0x60, 0xe0, 0xa5, 0x65, 0x30, 0xa0, 0xe5, 0x32, 0x37, 0xa2, 0xa7, 0x62, 0x67, 0xe2, 0xe7,0x3d, 0x69, 0xe9, 0xad, 0x6d, 0x39, 0xa9, 0xed, 0x3b, 0x3f, 0xab, 0xaf, 0x6b, 0x6f, 0xeb, 0xef,0x26, 0x23, 0xb3, 0xb6, 0x76, 0x73, 0xf3, 0xf6, 0x71, 0x24, 0xf1, 0xb4, 0x21, 0x74, 0xb1, 0xf4,0x2c, 0x78, 0xf8, 0xbc, 0x7c, 0x28, 0xb8, 0xfc, 0x2a, 0x2e, 0xba, 0xbe, 0x7a, 0x7e, 0xfa, 0xfe,0x25, 0x70, 0xf0, 0xb5, 0x75, 0x20, 0xb0, 0xf5, 0x22, 0x27, 0xb2, 0xb7, 0x72, 0x77, 0xf2, 0xf7,0x2d, 0x79, 0xf9, 0xbd, 0x7d, 0x29, 0xb9, 0xfd, 0x2b, 0x2f, 0xbb, 0xbf, 0x7b, 0x7f, 0xfb, 0xff};
#endif

/* ShiftRows and TweakeySchedule permutations */
const unsigned char P[16] = {0,1,2,3,7,4,5,6,10,11,8,9,13,14,15,12};
const unsigned char TWEAKEY_P[16] = {9,15,8,13,10,14,12,11,0,1,2,3,4,5,6,7};

/* 7-bit round constant */
const unsigned char RC[87] = {0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7e, 0x7d, 0x7b, 0x77, 0x6f, 0x5f, 0x3e, 0x7c, 0x79, 0x73, 0x67, 0x4f, 0x1e, 0x3d, 0x7a, 0x75, 0x6b, 0x57, 0x2e, 0x5c, 0x38, 0x70, 0x61, 0x43, 0x06, 0x0d, 0x1b, 0x37, 0x6e, 0x5d, 0x3a, 0x74, 0x69, 0x53, 0x26, 0x4c, 0x18, 0x31, 0x62, 0x45, 0x0a, 0x15, 0x2b, 0x56, 0x2c, 0x58, 0x30, 0x60, 0x41, 0x02, 0x05, 0x0b, 0x17, 0x2f, 0x5e, 0x3c, 0x78, 0x71, 0x63, 0x47, 0x0e, 0x1d, 0x3b, 0x76, 0x6d, 0x5b, 0x36, 0x6c, 0x59, 0x32, 0x64, 0x49, 0x12, 0x25, 0x4a, 0x14, 0x29, 0x52, 0x24, 0x48, 0x10};



void AddConstants(unsigned char state[4][4], int i){
	state[0][0] ^= (RC[i] & 0xf); // 4-3-2-1
	state[1][0] ^= ((RC[i]>>4) & 0x7); // 7-6-5
	state[2][0] ^= 0x2;

    /* Indicate tweak material */
    state[0][2] ^= 0x2;
}

void SubCell(unsigned char state[4][4]){
    int i,j;
    for(i = 0; i < 4; i++)
        for(j = 0; j <  4; j++)
            state[i][j] = sbox[state[i][j]];
}

void SubCell_inv(unsigned char state[4][4]){
    int i,j;
    for(i = 0; i < 4; i++)
        for(j = 0; j <  4; j++)
            state[i][j] = sbox_inv[state[i][j]];
}

void ShiftRows(unsigned char state[4][4]){
	int i, j, pos;
	unsigned char state_tmp[4][4];

    for(i = 0; i < 4; i++)
        for(j = 0; j < 4; j++){
            pos=P[j+4*i];
            state_tmp[i][j]=state[pos>>2][pos&0x3];
        }
    stateCopy(state, state_tmp);
}

void ShiftRows_inv(unsigned char state[4][4]){
	int i, j, pos;
	unsigned char state_tmp[4][4];

    for(i = 0; i < 4; i++)
        for(j = 0; j < 4; j++){
            pos=P[j+4*i];
            state_tmp[pos>>2][pos&0x3]=state[i][j];
        }
    stateCopy(state, state_tmp);
}

void MixColumn(unsigned char state[4][4]){
	int j;
    unsigned char temp;

	for(j = 0; j < 4; j++){
        state[1][j]^=state[2][j];
        state[2][j]^=state[0][j];
        state[3][j]^=state[2][j];
        temp=state[3][j];

        state[3][j]=state[2][j];
        state[2][j]=state[1][j];
        state[1][j]=state[0][j];
        state[0][j]=temp;
	}
}

void MixColumn_inv(unsigned char state[4][4]){
	int j;
    unsigned char temp;

	for(j = 0; j < 4; j++){
        temp=state[3][j];
        state[3][j]=state[0][j];
        state[0][j]=state[1][j];
        state[1][j]=state[2][j];
        state[2][j]=temp;

        state[3][j]^=state[2][j];
        state[2][j]^=state[0][j];
        state[1][j]^=state[2][j];
	}
}



/* ADVANCE THE KEY SCHEDULE ONCE */
void advanceKeySchedule(unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4])
{
    /* Declarations */
	int i, j, k;
	unsigned char pos;
	unsigned char keyCells_tmp[TWEAKEY_BLOCKSIZE_RATIO][4][4];

    // update the subtweakey states with the permutation
    for(k = 0; k < TWEAKEY_BLOCKSIZE_RATIO; k++){
        for(i = 0; i < 4; i++){ 
            for(j = 0; j < 4; j++){
                pos=TWEAKEY_P[j+4*i];
                keyCells_tmp[k][i][j]=keyCells[k][pos>>2][pos&0x3];
            }
        }
    }

    // update the subtweakey states with the LFSRs
    for(k = 1; k < TWEAKEY_BLOCKSIZE_RATIO; k++)
        for(i = 0; i < 2; i++) // LFSR only on upper two rows
            for(j = 0; j < 4; j++){
                if (k==1){ // TK2
                    #ifdef CRYPTO_BLOCKSIZE_8
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]<<1)&0xE)^((keyCells_tmp[k][i][j]>>3)&0x1)^((keyCells_tmp[k][i][j]>>2)&0x1);
                    #else 
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]<<1)&0xFE)^((keyCells_tmp[k][i][j]>>7)&0x01)^((keyCells_tmp[k][i][j]>>5)&0x01);
                    #endif 
                }
                else if (k==2){ // TK3
                    #ifdef CRYPTO_BLOCKSIZE_8
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]>>1)&0x7)^((keyCells_tmp[k][i][j])&0x8)^((keyCells_tmp[k][i][j]<<3)&0x8);
                    #else 
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]>>1)&0x7F)^((keyCells_tmp[k][i][j]<<7)&0x80)^((keyCells_tmp[k][i][j]<<1)&0x80);
                    #endif 
                }
            }

    tweakeyCopy(keyCells, keyCells_tmp);

}

/* REVERSE THE KEY SCHEDULE ONCE (used in decryption and reconstruction) */
void reverseKeySchedule(unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4]){
	unsigned char keyCells_tmp[TWEAKEY_BLOCKSIZE_RATIO][4][4];
	int i, j, k;
	unsigned char pos;

    // update the subtweakey states with the permutation
    for(k = 0; k <TWEAKEY_BLOCKSIZE_RATIO; k++)
        for(i = 0; i < 4; i++)
            for(j = 0; j < 4; j++){
                // application of the inverse TWEAKEY permutation
                pos=TWEAKEY_P[j+4*i];
                keyCells_tmp[k][pos>>2][pos&0x3]=keyCells[k][i][j];
            }

    // update the subtweakey states with the LFSRs
    for(k = 1; k <TWEAKEY_BLOCKSIZE_RATIO; k++)
        for(i = 2; i < 4; i++)
            for(j = 0; j < 4; j++){
                if (k==1){
                    #ifdef CRYPTO_BLOCKSIZE_8
                    if (CRYPTO_BLOCKSIZE == 8)
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]>>1)&0x7)^((keyCells_tmp[k][i][j]<<3)&0x8)^((keyCells_tmp[k][i][j])&0x8);
                    #else
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]>>1)&0x7F)^((keyCells_tmp[k][i][j]<<7)&0x80)^((keyCells_tmp[k][i][j]<<1)&0x80);
                    #endif
                }
                else if (k==2){
                    #ifdef CRYPTO_BLOCKSIZE_8
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]<<1)&0xE)^((keyCells_tmp[k][i][j]>>3)&0x1)^((keyCells_tmp[k][i][j]>>2)&0x1);
                    #else
                        keyCells_tmp[k][i][j]=((keyCells_tmp[k][i][j]<<1)&0xFE)^((keyCells_tmp[k][i][j]>>7)&0x01)^((keyCells_tmp[k][i][j]>>5)&0x01);
                    #endif
                }
            }
    tweakeyCopy(keyCells, keyCells_tmp);
}


// Extract and apply the subtweakey to the internal state (must be the two top rows XORed together), then update the tweakey state
void AddKey(unsigned char state[4][4], unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4]){

	int i, j, k;
    for (k = 0; k < TWEAKEY_BLOCKSIZE_RATIO; k++) 
        for(i = 0; i < 2; i++) // Row i (two rows only)
            for(j = 0; j < 4; j++) // Cell j in row i
                state[i][j] ^= keyCells[k][i][j]; 

    advanceKeySchedule(keyCells);
}

// Extract and apply the subtweakey to the internal state (must be the two top rows XORed together), then update the tweakey state (inverse function}
void AddKey_inv(unsigned char state[4][4], unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4]){

    int i,j,k;
    reverseKeySchedule(keyCells);

    for (k = 0; k < TWEAKEY_BLOCKSIZE_RATIO; k++)  // For every TKi
        for(i = 0; i < 2; i++) // Row i (two rows only)
            for(j = 0; j < 4; j++) // Cell j in row i
                state[i][j] ^= keyCells[k][i][j]; 
}

void skinny_round(unsigned char state[4][4], unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4], int i){

    SubCell(state);
    AddConstants(state, i);
    AddKey(state, keyCells);
    ShiftRows(state);
    MixColumn(state);

    print_cells(state, i);
}

void skinny_round_inv(unsigned char state[4][4], unsigned char keyCells[TWEAKEY_BLOCKSIZE_RATIO][4][4], int i){

    MixColumn_inv(state);
    ShiftRows_inv(state);
    AddKey_inv(state, keyCells);
    AddConstants(state, i);
    SubCell_inv(state);

    print_cells(state, i);
}