aes.cpp

/*
https://raw.githubusercontent.com/reality-boy/miniMover/master/miniMoverLib/aes.cpp
This is an implementation of the AES algorithm, specifically ECB and CBC mode.
Block size can be chosen in aes.h - available choices are AES128 and AES256.

The implementation is verified against the test vectors in:
  National Institute of Standards and Technology Special Publication 800-38A 2001 ED

ECB-AES128
----------

  plain-text:
    6bc1bee22e409f96e93d7e117393172a
    ae2d8a571e03ac9c9eb76fac45af8e51
    30c81c46a35ce411e5fbc1191a0a52ef
    f69f2445df4f9b17ad2b417be66c3710

  key:
    2b7e151628aed2a6abf7158809cf4f3c

  resulting cipher
    3ad77bb40d7a3660a89ecaf32466ef97 
    f5d3d58503b9699de785895a96fdbaaf 
    43b1cd7f598ece23881b00e3ed030688 
    7b0c785e27e8ad3f8223207104725dd4 


NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
        You should pad the end of the string with zeros if this is not the case.
        For AES256 the key size is proportionally larger.

*/


/*****************************************************************************/
/* Includes:                                                                 */
/*****************************************************************************/
#include <stdint.h>
#include <string.h> // CBC mode, for memset
#include <stdio.h>

#include "aes.h"

/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
typedef uint8_t state_t[4][4];


// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM - 
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t 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,
  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };

static const uint8_t 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 };

// The round constant word array, Rcon[i], contains the values given by 
// x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
static const uint8_t Rcon[11] = {
  0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };

/*****************************************************************************/
/* Private functions:                                                        */
/*****************************************************************************/
#define getSBoxValue(num) (sbox[(num)])
#define getSBoxInvert(num) (rsbox[(num)])

// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states. 
static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key, bool isAES256)
{
	const unsigned int Nb = 4;						// The number of columns comprising a state in AES. This is a constant in AES. Value=4
	const unsigned int Nk = (isAES256) ? 8 : 4;		// The number of 32 bit words in a key.
	const unsigned int Nr = (isAES256) ? 14 : 10;		// The number of rounds in AES Cipher.

	unsigned i, j, k;
	uint8_t tempa[4]; // Used for the column/row operations

	// The first round key is the key itself.
	memcpy(RoundKey, Key, (isAES256) ? AES_256_keyExpSize : AES_128_keyExpSize);

	// All other round keys are found from the previous round keys.
	for (i = Nk; i < Nb * (Nr + 1); ++i)
	{
		k = (i - 1) * 4;
		tempa[0]=RoundKey[k + 0];
		tempa[1]=RoundKey[k + 1];
		tempa[2]=RoundKey[k + 2];
		tempa[3]=RoundKey[k + 3];

		if (i % Nk == 0)
		{
			// This function shifts the 4 bytes in a word to the left once.
			// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

			// Function RotWord()
			k = tempa[0];
			tempa[0] = tempa[1];
			tempa[1] = tempa[2];
			tempa[2] = tempa[3];
			tempa[3] = (uint8_t)k;

			// SubWord() is a function that takes a four-byte input word and 
			// applies the S-box to each of the four bytes to produce an output word.

			// Function Subword()
			tempa[0] = getSBoxValue(tempa[0]);
			tempa[1] = getSBoxValue(tempa[1]);
			tempa[2] = getSBoxValue(tempa[2]);
			tempa[3] = getSBoxValue(tempa[3]);

			tempa[0] = tempa[0] ^ Rcon[i/Nk];
		}

		if(isAES256)
		{
			if (i % Nk == 4)
			{
				// Function Subword()
				tempa[0] = getSBoxValue(tempa[0]);
				tempa[1] = getSBoxValue(tempa[1]);
				tempa[2] = getSBoxValue(tempa[2]);
				tempa[3] = getSBoxValue(tempa[3]);
			}
		}

		j = i * 4; k=(i - Nk) * 4;
		RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
		RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
		RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
		RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
	}
}

void AES_init_ctx(struct AES_ctx* ctx, const char* key)
{
	if(key)
	{
		int c = strlen(key);
		if(c == AES_128_KEYLEN)
			ctx->isAES256 = false;
		else if(c == AES_256_KEYLEN)
			ctx->isAES256 = true;
		// else blow up!
		KeyExpansion(ctx->RoundKey, (const uint8_t*)key, ctx->isAES256);
	}
	// else blow up!
}

void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv)
{
	memcpy (ctx->Iv, iv, AES_BLOCKLEN);
}

void AES_init_ctx_iv(struct AES_ctx* ctx, const char* key, const uint8_t* iv)
{
	AES_init_ctx(ctx, key);
	AES_ctx_set_iv(ctx, iv);
}

// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey(uint8_t round, state_t* state, uint8_t* RoundKey, bool isAES256)
{
	const int Nb = 4;						// The number of columns comprising a state in AES. This is a constant in AES. Value=4
	const int Nk = (isAES256) ? 8 : 4;		// The number of 32 bit words in a key.
	const int Nr = (isAES256) ? 14 : 10;	// The number of rounds in AES Cipher.
	(void)Nk;
	(void)Nr;

	int offset = round * Nb * 4;
	int k = 0;
	for (int i = 0; i < 4; ++i)
	{
		(*state)[i][0] ^= RoundKey[offset + k + 0];
		(*state)[i][1] ^= RoundKey[offset + k + 1];
		(*state)[i][2] ^= RoundKey[offset + k + 2];
		(*state)[i][3] ^= RoundKey[offset + k + 3];
		k += Nb;
	}
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes(state_t* state)
{
	for (int i = 0; i < 4; ++i)
	{
		(*state)[0][i] = getSBoxValue((*state)[0][i]);
		(*state)[1][i] = getSBoxValue((*state)[1][i]);
		(*state)[2][i] = getSBoxValue((*state)[2][i]);
		(*state)[3][i] = getSBoxValue((*state)[3][i]);
	}
}

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows(state_t* state)
{
	uint8_t temp;

	// Rotate first row 1 columns to left  
	temp           = (*state)[0][1];
	(*state)[0][1] = (*state)[1][1];
	(*state)[1][1] = (*state)[2][1];
	(*state)[2][1] = (*state)[3][1];
	(*state)[3][1] = temp;

	// Rotate second row 2 columns to left  
	temp           = (*state)[0][2];
	(*state)[0][2] = (*state)[2][2];
	(*state)[2][2] = temp;

	temp           = (*state)[1][2];
	(*state)[1][2] = (*state)[3][2];
	(*state)[3][2] = temp;

	// Rotate third row 3 columns to left
	temp           = (*state)[0][3];
	(*state)[0][3] = (*state)[3][3];
	(*state)[3][3] = (*state)[2][3];
	(*state)[2][3] = (*state)[1][3];
	(*state)[1][3] = temp;
}

#define xtime(x) (((x)<<1) ^ ((((x)>>7) & 1) * 0x1b))

// MixColumns function mixes the columns of the state matrix
// highly optimized, actually faster than lookup table
// don't try to make sense of this :)
static void MixColumns(state_t* state)
{
	uint8_t Tmp;
	uint8_t a, b, c, d;
	for (int i = 0; i < 4; ++i)
	{  
		a = (*state)[i][0];
		b = (*state)[i][1];
		c = (*state)[i][2];
		d = (*state)[i][3];

		Tmp = a ^ b ^ c ^ d ;

		(*state)[i][0] ^= xtime(a ^ b) ^ Tmp ;
		(*state)[i][1] ^= xtime(b ^ c) ^ Tmp ;
		(*state)[i][2] ^= xtime(c ^ d) ^ Tmp ;
		(*state)[i][3] ^= xtime(d ^ a) ^ Tmp ;
	}
}

#if 0 // old, very slow in debug

static uint8_t Multiply(uint8_t x, uint8_t y)
{
	uint8_t xn[5];
	xn[0] = x;
	xn[1] = xtime(xn[0]);
	xn[2] = xtime(xn[1]);
	xn[3] = xtime(xn[2]);
	xn[4] = xtime(xn[3]);

	return 
		((y    & 1) * xn[0]) ^
		((y>>1 & 1) * xn[1]) ^
		((y>>2 & 1) * xn[2]) ^
		((y>>3 & 1) * xn[3]) ^
		((y>>4 & 1) * xn[4]);
}

static void InvMixColumns(state_t* state)
{
	uint8_t a, b, c, d;
	for (int i = 0; i < 4; ++i)
	{ 
		a = (*state)[i][0];
		b = (*state)[i][1];
		c = (*state)[i][2];
		d = (*state)[i][3];

		(*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
		(*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
		(*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
		(*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
	}
}

#else

// new but much larger lookup table multiplication
static void InvMixColumns(state_t* state)
{
	const static uint8_t mul_9[] = {
		0x00,0x09,0x12,0x1b,0x24,0x2d,0x36,0x3f,0x48,0x41,0x5a,0x53,0x6c,0x65,0x7e,0x77,
		0x90,0x99,0x82,0x8b,0xb4,0xbd,0xa6,0xaf,0xd8,0xd1,0xca,0xc3,0xfc,0xf5,0xee,0xe7,
		0x3b,0x32,0x29,0x20,0x1f,0x16,0x0d,0x04,0x73,0x7a,0x61,0x68,0x57,0x5e,0x45,0x4c,
		0xab,0xa2,0xb9,0xb0,0x8f,0x86,0x9d,0x94,0xe3,0xea,0xf1,0xf8,0xc7,0xce,0xd5,0xdc,
		0x76,0x7f,0x64,0x6d,0x52,0x5b,0x40,0x49,0x3e,0x37,0x2c,0x25,0x1a,0x13,0x08,0x01,
		0xe6,0xef,0xf4,0xfd,0xc2,0xcb,0xd0,0xd9,0xae,0xa7,0xbc,0xb5,0x8a,0x83,0x98,0x91,
		0x4d,0x44,0x5f,0x56,0x69,0x60,0x7b,0x72,0x05,0x0c,0x17,0x1e,0x21,0x28,0x33,0x3a,
		0xdd,0xd4,0xcf,0xc6,0xf9,0xf0,0xeb,0xe2,0x95,0x9c,0x87,0x8e,0xb1,0xb8,0xa3,0xaa,
		0xec,0xe5,0xfe,0xf7,0xc8,0xc1,0xda,0xd3,0xa4,0xad,0xb6,0xbf,0x80,0x89,0x92,0x9b,
		0x7c,0x75,0x6e,0x67,0x58,0x51,0x4a,0x43,0x34,0x3d,0x26,0x2f,0x10,0x19,0x02,0x0b,
		0xd7,0xde,0xc5,0xcc,0xf3,0xfa,0xe1,0xe8,0x9f,0x96,0x8d,0x84,0xbb,0xb2,0xa9,0xa0,
		0x47,0x4e,0x55,0x5c,0x63,0x6a,0x71,0x78,0x0f,0x06,0x1d,0x14,0x2b,0x22,0x39,0x30,
		0x9a,0x93,0x88,0x81,0xbe,0xb7,0xac,0xa5,0xd2,0xdb,0xc0,0xc9,0xf6,0xff,0xe4,0xed,
		0x0a,0x03,0x18,0x11,0x2e,0x27,0x3c,0x35,0x42,0x4b,0x50,0x59,0x66,0x6f,0x74,0x7d,
		0xa1,0xa8,0xb3,0xba,0x85,0x8c,0x97,0x9e,0xe9,0xe0,0xfb,0xf2,0xcd,0xc4,0xdf,0xd6,
		0x31,0x38,0x23,0x2a,0x15,0x1c,0x07,0x0e,0x79,0x70,0x6b,0x62,0x5d,0x54,0x4f,0x46};

	const static uint8_t mul_11[] = {
		0x00,0x0b,0x16,0x1d,0x2c,0x27,0x3a,0x31,0x58,0x53,0x4e,0x45,0x74,0x7f,0x62,0x69,
		0xb0,0xbb,0xa6,0xad,0x9c,0x97,0x8a,0x81,0xe8,0xe3,0xfe,0xf5,0xc4,0xcf,0xd2,0xd9,
		0x7b,0x70,0x6d,0x66,0x57,0x5c,0x41,0x4a,0x23,0x28,0x35,0x3e,0x0f,0x04,0x19,0x12,
		0xcb,0xc0,0xdd,0xd6,0xe7,0xec,0xf1,0xfa,0x93,0x98,0x85,0x8e,0xbf,0xb4,0xa9,0xa2,
		0xf6,0xfd,0xe0,0xeb,0xda,0xd1,0xcc,0xc7,0xae,0xa5,0xb8,0xb3,0x82,0x89,0x94,0x9f,
		0x46,0x4d,0x50,0x5b,0x6a,0x61,0x7c,0x77,0x1e,0x15,0x08,0x03,0x32,0x39,0x24,0x2f,
		0x8d,0x86,0x9b,0x90,0xa1,0xaa,0xb7,0xbc,0xd5,0xde,0xc3,0xc8,0xf9,0xf2,0xef,0xe4,
		0x3d,0x36,0x2b,0x20,0x11,0x1a,0x07,0x0c,0x65,0x6e,0x73,0x78,0x49,0x42,0x5f,0x54,
		0xf7,0xfc,0xe1,0xea,0xdb,0xd0,0xcd,0xc6,0xaf,0xa4,0xb9,0xb2,0x83,0x88,0x95,0x9e,
		0x47,0x4c,0x51,0x5a,0x6b,0x60,0x7d,0x76,0x1f,0x14,0x09,0x02,0x33,0x38,0x25,0x2e,
		0x8c,0x87,0x9a,0x91,0xa0,0xab,0xb6,0xbd,0xd4,0xdf,0xc2,0xc9,0xf8,0xf3,0xee,0xe5,
		0x3c,0x37,0x2a,0x21,0x10,0x1b,0x06,0x0d,0x64,0x6f,0x72,0x79,0x48,0x43,0x5e,0x55,
		0x01,0x0a,0x17,0x1c,0x2d,0x26,0x3b,0x30,0x59,0x52,0x4f,0x44,0x75,0x7e,0x63,0x68,
		0xb1,0xba,0xa7,0xac,0x9d,0x96,0x8b,0x80,0xe9,0xe2,0xff,0xf4,0xc5,0xce,0xd3,0xd8,
		0x7a,0x71,0x6c,0x67,0x56,0x5d,0x40,0x4b,0x22,0x29,0x34,0x3f,0x0e,0x05,0x18,0x13,
		0xca,0xc1,0xdc,0xd7,0xe6,0xed,0xf0,0xfb,0x92,0x99,0x84,0x8f,0xbe,0xb5,0xa8,0xa3};

	const static uint8_t mul_13[] = {
		0x00,0x0d,0x1a,0x17,0x34,0x39,0x2e,0x23,0x68,0x65,0x72,0x7f,0x5c,0x51,0x46,0x4b,
		0xd0,0xdd,0xca,0xc7,0xe4,0xe9,0xfe,0xf3,0xb8,0xb5,0xa2,0xaf,0x8c,0x81,0x96,0x9b,
		0xbb,0xb6,0xa1,0xac,0x8f,0x82,0x95,0x98,0xd3,0xde,0xc9,0xc4,0xe7,0xea,0xfd,0xf0,
		0x6b,0x66,0x71,0x7c,0x5f,0x52,0x45,0x48,0x03,0x0e,0x19,0x14,0x37,0x3a,0x2d,0x20,
		0x6d,0x60,0x77,0x7a,0x59,0x54,0x43,0x4e,0x05,0x08,0x1f,0x12,0x31,0x3c,0x2b,0x26,
		0xbd,0xb0,0xa7,0xaa,0x89,0x84,0x93,0x9e,0xd5,0xd8,0xcf,0xc2,0xe1,0xec,0xfb,0xf6,
		0xd6,0xdb,0xcc,0xc1,0xe2,0xef,0xf8,0xf5,0xbe,0xb3,0xa4,0xa9,0x8a,0x87,0x90,0x9d,
		0x06,0x0b,0x1c,0x11,0x32,0x3f,0x28,0x25,0x6e,0x63,0x74,0x79,0x5a,0x57,0x40,0x4d,
		0xda,0xd7,0xc0,0xcd,0xee,0xe3,0xf4,0xf9,0xb2,0xbf,0xa8,0xa5,0x86,0x8b,0x9c,0x91,
		0x0a,0x07,0x10,0x1d,0x3e,0x33,0x24,0x29,0x62,0x6f,0x78,0x75,0x56,0x5b,0x4c,0x41,
		0x61,0x6c,0x7b,0x76,0x55,0x58,0x4f,0x42,0x09,0x04,0x13,0x1e,0x3d,0x30,0x27,0x2a,
		0xb1,0xbc,0xab,0xa6,0x85,0x88,0x9f,0x92,0xd9,0xd4,0xc3,0xce,0xed,0xe0,0xf7,0xfa,
		0xb7,0xba,0xad,0xa0,0x83,0x8e,0x99,0x94,0xdf,0xd2,0xc5,0xc8,0xeb,0xe6,0xf1,0xfc,
		0x67,0x6a,0x7d,0x70,0x53,0x5e,0x49,0x44,0x0f,0x02,0x15,0x18,0x3b,0x36,0x21,0x2c,
		0x0c,0x01,0x16,0x1b,0x38,0x35,0x22,0x2f,0x64,0x69,0x7e,0x73,0x50,0x5d,0x4a,0x47,
		0xdc,0xd1,0xc6,0xcb,0xe8,0xe5,0xf2,0xff,0xb4,0xb9,0xae,0xa3,0x80,0x8d,0x9a,0x97};

	const static uint8_t mul_14[] = {
		0x00,0x0e,0x1c,0x12,0x38,0x36,0x24,0x2a,0x70,0x7e,0x6c,0x62,0x48,0x46,0x54,0x5a,
		0xe0,0xee,0xfc,0xf2,0xd8,0xd6,0xc4,0xca,0x90,0x9e,0x8c,0x82,0xa8,0xa6,0xb4,0xba,
		0xdb,0xd5,0xc7,0xc9,0xe3,0xed,0xff,0xf1,0xab,0xa5,0xb7,0xb9,0x93,0x9d,0x8f,0x81,
		0x3b,0x35,0x27,0x29,0x03,0x0d,0x1f,0x11,0x4b,0x45,0x57,0x59,0x73,0x7d,0x6f,0x61,
		0xad,0xa3,0xb1,0xbf,0x95,0x9b,0x89,0x87,0xdd,0xd3,0xc1,0xcf,0xe5,0xeb,0xf9,0xf7,
		0x4d,0x43,0x51,0x5f,0x75,0x7b,0x69,0x67,0x3d,0x33,0x21,0x2f,0x05,0x0b,0x19,0x17,
		0x76,0x78,0x6a,0x64,0x4e,0x40,0x52,0x5c,0x06,0x08,0x1a,0x14,0x3e,0x30,0x22,0x2c,
		0x96,0x98,0x8a,0x84,0xae,0xa0,0xb2,0xbc,0xe6,0xe8,0xfa,0xf4,0xde,0xd0,0xc2,0xcc,
		0x41,0x4f,0x5d,0x53,0x79,0x77,0x65,0x6b,0x31,0x3f,0x2d,0x23,0x09,0x07,0x15,0x1b,
		0xa1,0xaf,0xbd,0xb3,0x99,0x97,0x85,0x8b,0xd1,0xdf,0xcd,0xc3,0xe9,0xe7,0xf5,0xfb,
		0x9a,0x94,0x86,0x88,0xa2,0xac,0xbe,0xb0,0xea,0xe4,0xf6,0xf8,0xd2,0xdc,0xce,0xc0,
		0x7a,0x74,0x66,0x68,0x42,0x4c,0x5e,0x50,0x0a,0x04,0x16,0x18,0x32,0x3c,0x2e,0x20,
		0xec,0xe2,0xf0,0xfe,0xd4,0xda,0xc8,0xc6,0x9c,0x92,0x80,0x8e,0xa4,0xaa,0xb8,0xb6,
		0x0c,0x02,0x10,0x1e,0x34,0x3a,0x28,0x26,0x7c,0x72,0x60,0x6e,0x44,0x4a,0x58,0x56,
		0x37,0x39,0x2b,0x25,0x0f,0x01,0x13,0x1d,0x47,0x49,0x5b,0x55,0x7f,0x71,0x63,0x6d,
		0xd7,0xd9,0xcb,0xc5,0xef,0xe1,0xf3,0xfd,0xa7,0xa9,0xbb,0xb5,0x9f,0x91,0x83,0x8d};

	uint8_t a, b, c, d;
	for (int i = 0; i < 4; ++i)
	{ 
		a = (*state)[i][0];
		b = (*state)[i][1];
		c = (*state)[i][2];
		d = (*state)[i][3];

		(*state)[i][0] = mul_14[a] ^ mul_11[b] ^ mul_13[c] ^  mul_9[d];
		(*state)[i][1] =  mul_9[a] ^ mul_14[b] ^ mul_11[c] ^ mul_13[d];
		(*state)[i][2] = mul_13[a] ^  mul_9[b] ^ mul_14[c] ^ mul_11[d];
		(*state)[i][3] = mul_11[a] ^ mul_13[b] ^  mul_9[c] ^ mul_14[d];
	}
}

#endif

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void InvSubBytes(state_t* state)
{
	for (int i = 0; i < 4; ++i)
	{
		(*state)[0][i] = getSBoxInvert((*state)[0][i]);
		(*state)[1][i] = getSBoxInvert((*state)[1][i]);
		(*state)[2][i] = getSBoxInvert((*state)[2][i]);
		(*state)[3][i] = getSBoxInvert((*state)[3][i]);
	}
}

static void InvShiftRows(state_t* state)
{
	uint8_t temp;

	// Rotate first row 1 columns to right  
	temp = (*state)[3][1];
	(*state)[3][1] = (*state)[2][1];
	(*state)[2][1] = (*state)[1][1];
	(*state)[1][1] = (*state)[0][1];
	(*state)[0][1] = temp;

	// Rotate second row 2 columns to right 
	temp = (*state)[0][2];
	(*state)[0][2] = (*state)[2][2];
	(*state)[2][2] = temp;

	temp = (*state)[1][2];
	(*state)[1][2] = (*state)[3][2];
	(*state)[3][2] = temp;

	// Rotate third row 3 columns to right
	temp = (*state)[0][3];
	(*state)[0][3] = (*state)[1][3];
	(*state)[1][3] = (*state)[2][3];
	(*state)[2][3] = (*state)[3][3];
	(*state)[3][3] = temp;
}


// Cipher is the main function that encrypts the PlainText.
static void Cipher(state_t* state, uint8_t* RoundKey, bool isAES256)
{
	const unsigned int Nb = 4;						// The number of columns comprising a state in AES. This is a constant in AES. Value=4
	const unsigned int Nk = (isAES256) ? 8 : 4;		// The number of 32 bit words in a key.
	const unsigned int Nr = (isAES256) ? 14 : 10;	// The number of rounds in AES Cipher.
	(void)Nb;
	(void)Nk;

	uint8_t round = 0;

	// Add the First round key to the state before starting the rounds.
	AddRoundKey(0, state, RoundKey, isAES256); 

	// There will be Nr rounds.
	// The first Nr-1 rounds are identical.
	// These Nr-1 rounds are executed in the loop below.
	for (round = 1; round < Nr; ++round)
	{
		SubBytes(state);
		ShiftRows(state);
		MixColumns(state);
		AddRoundKey(round, state, RoundKey, isAES256);
	}

	// The last round is given below.
	// The MixColumns function is not here in the last round.
	SubBytes(state);
	ShiftRows(state);
	AddRoundKey(Nr, state, RoundKey, isAES256);
}

static void InvCipher(state_t* state, uint8_t* RoundKey, bool isAES256)
{
	const unsigned int Nb = 4;						// The number of columns comprising a state in AES. This is a constant in AES. Value=4
	const unsigned int Nk = (isAES256) ? 8 : 4;		// The number of 32 bit words in a key.
	const unsigned int Nr = (isAES256) ? 14 : 10;	// The number of rounds in AES Cipher.
	(void)Nb;
	(void)Nk;

	uint8_t round = 0;

	// Add the First round key to the state before starting the rounds.
	AddRoundKey(Nr, state, RoundKey, isAES256); 

	// There will be Nr rounds.
	// The first Nr-1 rounds are identical.
	// These Nr-1 rounds are executed in the loop below.
	for (round = (Nr - 1); round > 0; --round)
	{
		InvShiftRows(state);
		InvSubBytes(state);
		AddRoundKey(round, state, RoundKey, isAES256);
		InvMixColumns(state);
	}

	// The last round is given below.
	// The MixColumns function is not here in the last round.
	InvShiftRows(state);
	InvSubBytes(state);
	AddRoundKey(0, state, RoundKey, isAES256);
}

static void XorWithIv(uint8_t* buf, uint8_t* Iv)
{
	for (int i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
	{
		buf[i] ^= Iv[i];
	}
}

/*****************************************************************************/
/* Public functions:                                                         */
/*****************************************************************************/

void AES_ECB_encrypt_buffer(struct AES_ctx *ctx,const uint8_t* buf, uint32_t length)
{
	uintptr_t i;

	for (i = 0; i < length; i += AES_BLOCKLEN)
	{
		Cipher((state_t*)buf, ctx->RoundKey, ctx->isAES256);
		buf += AES_BLOCKLEN;
	}
}

void AES_ECB_decrypt_buffer(struct AES_ctx* ctx,const uint8_t* buf, uint32_t length)
{
	uintptr_t i;

	for (i = 0; i < length; i += AES_BLOCKLEN)
	{
		InvCipher((state_t*)buf, ctx->RoundKey, ctx->isAES256);
		buf += AES_BLOCKLEN;
	}
}

void AES_CBC_encrypt_buffer(struct AES_ctx *ctx, uint8_t* buf, uint32_t length)
{
	uintptr_t i;
	uint8_t *Iv = ctx->Iv;
	for (i = 0; i < length; i += AES_BLOCKLEN)
	{
		XorWithIv(buf, Iv);
		Cipher((state_t*)buf, ctx->RoundKey, ctx->isAES256);
		Iv = buf;
		buf += AES_BLOCKLEN;
	}
	/* store Iv in ctx for next call */
	memcpy(ctx->Iv, Iv, AES_BLOCKLEN);
}

void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length)
{
	uintptr_t i;
	uint8_t storeNextIv[AES_BLOCKLEN];
	for (i = 0; i < length; i += AES_BLOCKLEN)
	{
		memcpy(storeNextIv, buf, AES_BLOCKLEN);
		InvCipher((state_t*)buf, ctx->RoundKey, ctx->isAES256);
		XorWithIv(buf, ctx->Iv);
		memcpy(ctx->Iv, storeNextIv, AES_BLOCKLEN);
		buf += AES_BLOCKLEN;
	}
}