/*
 * aes128.c
 *
 * Created: 27.11.2017 13:33:29
 *  Author: Matthias
 */ 

#include <aes128.h>

/* the expanded keySize */
#define EXPANDED_KEY_SIZE 176
//int expandedKeySize;

/* the expanded key */
//unsigned char expandedKey[EXPANDED_KEY_SIZE];

/* the cipher key */
//unsigned char key[16];

/* the cipher key size */

enum keySize{
	SIZE_16 = 16,
	SIZE_24 = 24,
	SIZE_32 = 32
};

//enum keySize size;

unsigned char sbox[256] =   {
	//0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
	0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, //0
	0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, //1
	0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, //2
	0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, //3
	0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, //4
	0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, //5
	0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, //6
	0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, //7
	0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, //8
	0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, //9
	0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, //A
	0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, //B
	0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, //C
	0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, //D
	0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, //E
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; //F

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

unsigned char Rcon[256] = {

	0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
	0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
	0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
	0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d,
	0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab,
	0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d,
	0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25,
	0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01,
	0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d,
	0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa,
	0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a,
	0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02,
	0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
	0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
	0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
	0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
	0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f,
	0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5,
	0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33,
0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d};

void aes_init() {
	//UINT uitemp = 0;
	/* the expanded keySize */
	//expandedKeySize = EXPANDED_KEY_SIZE;

	/* the cipher key */
	//for (uitemp = 0; uitemp < 16; ++uitemp)
		//key[uitemp] = 0x00;

	/* the cipher key size */
	//size = SIZE_16;
}

unsigned char getSBoxValue(unsigned char num)
{
	return sbox[num];
}

unsigned char getSBoxInvert(unsigned char num)
{
	return rsbox[num];
}

//Key generation

/* Rijndael's key schedule rotate operation
 * rotate the word eight bits to the left
 *
 * rotate(1d2c3a4f) = 2c3a4f1d
 *
 * word is an char array of size 4 (32 bit)
 */
void rotate(unsigned char *word)
{
    unsigned char c;
    int i;

    c = word[0];
    for (i = 0; i < 3; i++)
        word[i] = word[i+1];
    word[3] = c;
}

unsigned char getRconValue(unsigned char num)
{
	return Rcon[num];
}

void core(unsigned char *word, int iteration)
{
	int i;

	/* rotate the 32-bit word 8 bits to the left */
	rotate(word);

	/* apply S-Box substitution on all 4 parts of the 32-bit word */
	for (i = 0; i < 4; ++i)
	{
		word[i] = getSBoxValue(word[i]);
	}

	/* XOR the output of the rcon operation with i to the first part (leftmost) only */
	word[0] = word[0]^getRconValue(((unsigned char) iteration));
}

/* Rijndael's key expansion
 * expands an 128,192,256 key into an 176,208,240 bytes key
 *
 * expandedKey is a pointer to an char array of large enough size
 * key is a pointer to a non-expanded key
 */

void expandKey(unsigned char *expandedKey,
               unsigned char *key,
               enum keySize size,
               /*size_t*/ unsigned int expandedKeySize)
{
    /* current expanded keySize, in bytes */
    int currentSize = 0;
    int rconIteration = 1;
    int i;
    unsigned char t[4] = {0,0,0,0};   // temporary 4-byte variable

    /* set the 16,24,32 bytes of the expanded key to the input key */
    for (i = 0; i < size; i++)
        expandedKey[i] = key[i];
    currentSize += size;

    while (currentSize < expandedKeySize)
    {
        /* assign the previous 4 bytes to the temporary value t */
        for (i = 0; i < 4; i++)
        {
            t[i] = expandedKey[(currentSize - 4) + i];
        }

        /* every 16,24,32 bytes we apply the core schedule to t
         * and increment rconIteration afterwards
         */
        if(currentSize % size == 0)
        {
            core(t, rconIteration++);
        }

        /* For 256-bit keys, we add an extra sbox to the calculation */
        if(size == SIZE_32 && ((currentSize % size) == 16)) {
            for(i = 0; i < 4; i++)
                t[i] = getSBoxValue(t[i]);
        }

        /* We XOR t with the four-byte block 16,24,32 bytes before the new expanded key.
         * This becomes the next four bytes in the expanded key.
         */
        for(i = 0; i < 4; i++) {
            expandedKey[currentSize] = expandedKey[currentSize - size] ^ t[i];
            currentSize++;
        }
    }
}

//Encrypt

void subBytes(unsigned char *state)
{
    int i;
    /* substitute all the values from the state with the value in the SBox
     * using the state value as index for the SBox
     */
    for (i = 0; i < 16; i++)
        state[i] = getSBoxValue(state[i]);
}

void shiftRow(unsigned char *state, unsigned char nbr)
{
	int i, j;
	unsigned char tmp;
	/* each iteration shifts the row to the left by 1 */
	for (i = 0; i < nbr; i++)
	{
		tmp = state[0];
		for (j = 0; j < 3; j++)
		state[j] = state[j+1];
		state[3] = tmp;
	}
}

void shiftRows(unsigned char *state)
{
	int i;
	/* iterate over the 4 rows and call shiftRow() with that row */
	for (i = 0; i < 4; i++)
	shiftRow(state+i*4, i);
}

void addRoundKey(unsigned char *state, unsigned char *roundKey)
{
	int i;
	for (i = 0; i < 16; i++)
	state[i] = state[i] ^ roundKey[i] ;
}

unsigned char galois_multiplication(unsigned char a, unsigned char b)
{
	unsigned char p = 0;
	unsigned char counter;
	unsigned char hi_bit_set;
	for(counter = 0; counter < 8; counter++) {
		if((b & 1) == 1)
			p ^= a;
		hi_bit_set = (a & 0x80);
		a <<= 1;
		if(hi_bit_set == 0x80)
			a ^= 0x1b;
		b >>= 1;
	}
	return p;
}

void mixColumn(unsigned char *column)
{
	unsigned char cpy[4];
	int i;
	for(i = 0; i < 4; i++)
	{
		cpy[i] = column[i];
	}
	column[0] = galois_multiplication(cpy[0],2) ^
	galois_multiplication(cpy[3],1) ^
	galois_multiplication(cpy[2],1) ^
	galois_multiplication(cpy[1],3);

	column[1] = galois_multiplication(cpy[1],2) ^
	galois_multiplication(cpy[0],1) ^
	galois_multiplication(cpy[3],1) ^
	galois_multiplication(cpy[2],3);

	column[2] = galois_multiplication(cpy[2],2) ^
	galois_multiplication(cpy[1],1) ^
	galois_multiplication(cpy[0],1) ^
	galois_multiplication(cpy[3],3);

	column[3] = galois_multiplication(cpy[3],2) ^
	galois_multiplication(cpy[2],1) ^
	galois_multiplication(cpy[1],1) ^
	galois_multiplication(cpy[0],3);
}

void mixColumns(unsigned char *state)
{
	int i, j;
	unsigned char column[4];

	/* iterate over the 4 columns */
	for (i = 0; i < 4; i++)
	{
		/* construct one column by iterating over the 4 rows */
		for (j = 0; j < 4; j++)
		{
			column[j] = state[(j*4)+i];
		}

		/* apply the mixColumn on one column */
		mixColumn(column);

		/* put the values back into the state */
		for (j = 0; j < 4; j++)
		{
			state[(j*4)+i] = column[j];
		}
	}
}

void aes_round(unsigned char *state, unsigned char *roundKey)
{
	subBytes(state);
	shiftRows(state);
	mixColumns(state);
	addRoundKey(state, roundKey);
}

void createRoundKey(unsigned char *expandedKey, unsigned char *roundKey)
{
	int i,j;
	/* iterate over the columns */
	for (i = 0; i < 4; i++)
	{
		/* iterate over the rows */
		for (j = 0; j < 4; j++)
		roundKey[(i+(j*4))] = expandedKey[(i*4)+j];
	}
}

void aes_main(unsigned char *state, unsigned char *expandedKey, int nbrRounds)
{
	int i = 0;

	unsigned char roundKey[16];

	createRoundKey(expandedKey, roundKey);
	addRoundKey(state, roundKey);

	for (i = 1; i < nbrRounds; i++) {
		createRoundKey(expandedKey + 16*i, roundKey);
		aes_round(state, roundKey);
	}

	createRoundKey(expandedKey + 16*nbrRounds, roundKey);
	subBytes(state);
	shiftRows(state);
	addRoundKey(state, roundKey);
}

char aes_encrypt(unsigned char *input,
                 unsigned char *output,
                 unsigned char *key
                 /*, enum keySize size*/)
{
	enum keySize size = SIZE_16;
    /* the expanded keySize */
    int expandedKeySize;

    /* the number of rounds */
    int nbrRounds = 10;	//NOTE: modded

    /* the expanded key */
    //NOTE: modded: unsigned char *expandedKey = 0x00;
	//unsigned char expandedKey[(16*(nbrRounds+1))];
	unsigned char expandedKey[176];

    /* the 128 bit block to encode */
    unsigned char block[16];

    int i,j;

    /* set the number of rounds */
    /*switch (size)
    {
        case SIZE_16:
            nbrRounds = 10;
            break;
        case SIZE_24:
            nbrRounds = 12;
            break;
        case SIZE_32:
            nbrRounds = 14;
            break;
        default:
            return 1; //UNKNOWN_KEYSIZE;
            break;
    }*/ //NOTE: modded

    expandedKeySize = (16*(nbrRounds+1));
    /*if ((expandedKey = malloc(expandedKeySize * sizeof(char))) == NULL)
    {
        return MEMORY_ALLOCATION_PROBLEM;
    }*/

    /* Set the block values, for the block:
     * a0,0 a0,1 a0,2 a0,3
     * a1,0 a1,1 a1,2 a1,3
     * a2,0 a2,1 a2,2 a2,3
     * a3,0 a3,1 a3,2 a3,3
     * the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
     */

    /* iterate over the columns */
    for (i = 0; i < 4; i++)
    {
        /* iterate over the rows */
        for (j = 0; j < 4; j++)
            block[(i+(j*4))] = input[(i*4)+j];
    }

    /* expand the key into an 176, 208, 240 bytes key */
    expandKey(expandedKey, key, size, expandedKeySize);

    /* encrypt the block using the expandedKey */
    aes_main(block, expandedKey, nbrRounds);

    /* unmap the block again into the output */
    for (i = 0; i < 4; i++)
    {
        /* iterate over the rows */
        for (j = 0; j < 4; j++)
            output[(i*4)+j] = block[(i+(j*4))];
    }
    return 0;
}

//Decrypt
void invSubBytes(unsigned char *state)
{
    int i;
    /* substitute all the values from the state with the value in the SBox
     * using the state value as index for the SBox
     */
    for (i = 0; i < 16; i++)
        state[i] = getSBoxInvert(state[i]);
}

void invShiftRow(unsigned char *state, unsigned char nbr)
{
	int i, j;
	unsigned char tmp;
	/* each iteration shifts the row to the right by 1 */
	for (i = 0; i < nbr; i++)
	{
		tmp = state[3];
		for (j = 3; j > 0; j--)
		state[j] = state[j-1];
		state[0] = tmp;
	}
}

void invShiftRows(unsigned char *state)
{
    int i;
    /* iterate over the 4 rows and call invShiftRow() with that row */
    for (i = 0; i < 4; i++)
        invShiftRow(state+i*4, i);
}

void invMixColumn(unsigned char *column)
{
	unsigned char cpy[4];
	int i;
	for(i = 0; i < 4; i++)
	{
		cpy[i] = column[i];
	}
	column[0] = galois_multiplication(cpy[0],14) ^
	galois_multiplication(cpy[3],9) ^
	galois_multiplication(cpy[2],13) ^
	galois_multiplication(cpy[1],11);
	column[1] = galois_multiplication(cpy[1],14) ^
	galois_multiplication(cpy[0],9) ^
	galois_multiplication(cpy[3],13) ^
	galois_multiplication(cpy[2],11);
	column[2] = galois_multiplication(cpy[2],14) ^
	galois_multiplication(cpy[1],9) ^
	galois_multiplication(cpy[0],13) ^
	galois_multiplication(cpy[3],11);
	column[3] = galois_multiplication(cpy[3],14) ^
	galois_multiplication(cpy[2],9) ^
	galois_multiplication(cpy[1],13) ^
	galois_multiplication(cpy[0],11);
}

void invMixColumns(unsigned char *state)
{
	int i, j;
	unsigned char column[4];

	/* iterate over the 4 columns */
	for (i = 0; i < 4; i++)
	{
		/* construct one column by iterating over the 4 rows */
		for (j = 0; j < 4; j++)
		{
			column[j] = state[(j*4)+i];
		}

		/* apply the invMixColumn on one column */
		invMixColumn(column);

		/* put the values back into the state */
		for (j = 0; j < 4; j++)
		{
			state[(j*4)+i] = column[j];
		}
	}
}

void aes_invRound(unsigned char *state, unsigned char *roundKey)
{

	invShiftRows(state);
	invSubBytes(state);
	addRoundKey(state, roundKey);
	invMixColumns(state);
}

void aes_invMain(unsigned char *state, unsigned char *expandedKey, int nbrRounds)
{
	int i = 0;

	unsigned char roundKey[16];

	createRoundKey(expandedKey + 16*nbrRounds, roundKey);
	addRoundKey(state, roundKey);

	for (i = nbrRounds-1; i > 0; i--) {
		createRoundKey(expandedKey + 16*i, roundKey);
		aes_invRound(state, roundKey);
	}

	createRoundKey(expandedKey, roundKey);
	invShiftRows(state);
	invSubBytes(state);
	addRoundKey(state, roundKey);
}

char aes_decrypt(unsigned char *input,
                 unsigned char *output,
                 unsigned char *key
                 /*´, enum keySize size*/)
{
	enum keySize size = SIZE_16;
    /* the expanded keySize */
    int expandedKeySize;

    /* the number of rounds */
    int nbrRounds;

    /* the expanded key */
    unsigned char *expandedKey = 0x00;

    /* the 128 bit block to decode */
    unsigned char block[16];

    int i,j;

    /* set the number of rounds */
    switch (size)
    {
        case SIZE_16:
            nbrRounds = 10;
            break;
        case SIZE_24:
            nbrRounds = 12;
            break;
        case SIZE_32:
            nbrRounds = 14;
            break;
        default:
            return 1; //UNKNOWN_KEYSIZE;
            break;
    }

    expandedKeySize = (16*(nbrRounds+1));
    /*if ((expandedKey = malloc(expandedKeySize * sizeof(char))) == NULL)
    {
        return MEMORY_ALLOCATION_PROBLEM;
    }*/

    /* Set the block values, for the block:
     * a0,0 a0,1 a0,2 a0,3
     * a1,0 a1,1 a1,2 a1,3
     * a2,0 a2,1 a2,2 a2,3
     * a3,0 a3,1 a3,2 a3,3
     * the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3
     */

    /* iterate over the columns */
    for (i = 0; i < 4; i++)
    {
        /* iterate over the rows */
        for (j = 0; j < 4; j++)
            block[(i+(j*4))] = input[(i*4)+j];
    }

    /* expand the key into an 176, 208, 240 bytes key */
    expandKey(expandedKey, key, size, expandedKeySize);

    /* decrypt the block using the expandedKey */
    aes_invMain(block, expandedKey, nbrRounds);

    /* unmap the block again into the output */
    for (i = 0; i < 4; i++)
    {
        /* iterate over the rows */
        for (j = 0; j < 4; j++)
            output[(i*4)+j] = block[(i+(j*4))];
    }
    return 0;
}