AES

AES是一种分组加密算法，明文分组大小为128位，密钥长度有128、192、256位三种。

分组密码也就是把明文分成一组一组的，每组长度相等，每次加密一组数据，直到加密完整个明文。在AES标准规范中，分组长度只能是128位，也就是说，每个分组为16个字节（每个字节8位）。密钥的长度可以使用128位、192位或256位。密钥的长度不同，推荐加密轮数也不同，如下表所示：

AES 密钥长度（32位比特字) 分组长度(32位比特字) 加密轮数
AES-128 4 4 10
AES-192 6 4 12
AES-256 8 4 14
轮数在下面介绍，这里实现的是AES-128，也就是密钥的长度为128位，加密轮数为10轮。
上面说到，AES的加密公式为C = E(K,P)，在加密函数E中，会执行一个轮函数，并且执行10次这个轮函数，这个轮函数的前9次执行的操作是一样的，只有第10次有所不同。也就是说，一个明文分组会被加密10轮。AES的核心就是实现一轮中的所有操作。
AES的处理单位是字节，128位的输入明文分组P和输入密钥K都被分成16个字节，分别记为P = P0 P1 … P15 和 K = K0 K1 … K15。如，明文分组为P = abcdefghijklmnop,其中的字符a对应P0，p对应P15。一般地，明文分组用字节为单位的正方形矩阵描述，称为状态矩阵。在算法的每一轮中，状态矩阵的内容不断发生变化，最后的结果作为密文输出。该矩阵中字节的排列顺序为从上到下、从左至右依次排列，如下图所示：

AES特征：

1、注意循环次数以及循环过程，例如AES-128进行10次循环，前9次相同

2、加密的第1轮到第9轮的轮函数一样，包括4个操作：字节代换、行位移、列混合和轮密钥加。最后一轮迭代不执行列混合。另外，在第一轮迭代之前，先将明文和原始密钥进行一次异或加密操作。

3、明文大小为128位，16字节

4、留意是否有S盒或逆S盒

#include <iostream>
#include <cstdlib>
#include <stdio.h>
using namespace std;
typedef unsigned char byte;
struct word
{
	byte wordKey[4];
};

class AES
{
public:
	AES(){
		initRcon();
	};
	// ~AES();
	void setCipherKey(byte key[]);
	void setPlainText(byte plain[]);

	//
	void keyExpansion(byte key[], word w[]);
	word rotWord(word w);
	word subWord(word w);
	word wordXOR(word w1, word w2);
	//functions in encryption and decryption
	void encryption();
	void processEncryption();
	void addRoundKey(word in[], int round);
	void subByte(word in[]);
	void shiftRows(word in[]);
	void mixColumn(word in[]);
	byte GFMultiplyByte(byte L, byte R);
	void decryption();
	void processDecryption();
	void invShiftRows(word in[]);
	void invSubByte(word in[]);
	void invMixColumn(word in[]);
	void initRcon();
	void showWord(word w[], int len);
	void showMesage();
private:
	byte cipherKey[16];
	word plainText[4];
	word cipherText[4];
	word deCipherText[4];
	static const int Nb=4, Nk=4, Nr=10;
	word Rcon[11];
	word wordKey[44];
	static const byte SBox[16][16];
	static const byte invSBox[16][16];
	static const byte mixColumnMatrix[4][4];
	static const byte invmixColumnMatrix[4][4];
};

void AES::showWord(word w[], int len){
	int i,j;
	for(i=0; i<len; i++){
		for(j=0; j<4; j++){
			printf("%x ", w[i].wordKey[j]);
		}
	}
	cout<<endl;
}

void AES::showMesage(){
	cout<<"plainText:"<<endl;
	showWord(plainText, 4);
	cout<<"wordKey:"<<endl;
	showWord(wordKey, Nb*(Nr+1));
	cout<<"cipherText:"<<endl;
	showWord(cipherText, 4);
	cout<<"deCipherText:"<<endl;
	showWord(deCipherText, 4);
}
// initialize the plainText--trans plaintext from vector to state_matrix
void AES::setPlainText(byte plain[]){
	int i;
	for(i=0; i<16; i++){
		plainText[i/4].wordKey[i%4] = plain[i];
	}
}

//initialize the key--from vector to state_matrix
void AES::setCipherKey(byte key[]){
	int i;
	for(i=0; i<16; i++){
		cipherKey[i] = key[i];
	}
	keyExpansion(cipherKey, wordKey);
}

//initialize the Rcon
void AES::initRcon(){
	int i,j;
	for(i=0; i<4; i++)
		for(j=0; j<4; j++){
			Rcon[i].wordKey[j] = 0x0;
		}
	Rcon[1].wordKey[0] = 0x01;
	Rcon[2].wordKey[0] = 0x02;
	Rcon[3].wordKey[0] = 0x04;
	Rcon[4].wordKey[0] = 0x08;
	Rcon[5].wordKey[0] = 0x10;
	Rcon[6].wordKey[0] = 0x20;
	Rcon[7].wordKey[0] = 0x40;
	Rcon[8].wordKey[0] = 0x80;
	Rcon[9].wordKey[0] = 0x1b;
	Rcon[10].wordKey[0] = 0x36;
}

//initialize the const of mixColumn and invMixColumn
const byte AES::mixColumnMatrix[4][4] = {
	{0x02, 0x03, 0x01, 0x01},
	{0x01, 0x02, 0x03, 0x01},
	{0x01, 0x01, 0x02, 0x03},
	{0x03, 0x01, 0x01, 0x02}
};
const byte AES::invmixColumnMatrix[4][4] = {
	{0x0e, 0x0b, 0x0d, 0x09},
	{0x09, 0x0e, 0x0b, 0x0d},
	{0x0d, 0x09, 0x0e, 0x0b},
	{0x0b, 0x0d, 0x09, 0x0e}
};

//initialize SBox
const byte AES::SBox[16][16] = {
	{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}
};
const byte AES::invSBox[16][16] = {
	0x31, 0x52, 0x5A, 0xC8, 0x0B, 0xAC, 0xF3, 0x3A, 0x8B, 0x54, 
  0x27, 0x9B, 0xAB, 0x95, 0xDE, 0x83, 0x60, 0xCB, 0x53, 0x7F, 
  0xC4, 0xE3, 0x0A, 0x97, 0xE0, 0x29, 0xD5, 0x68, 0xC5, 0xDF, 
  0xF4, 0x7B, 0xAA, 0xD6, 0x42, 0x78, 0x6C, 0xE9, 0x70, 0x17, 
  0xD7, 0x37, 0x24, 0x49, 0x75, 0xA9, 0x89, 0x67, 0x03, 0xFA, 
  0xD9, 0x91, 0xB4, 0x5B, 0xC2, 0x4E, 0x92, 0xFC, 0x46, 0xB1, 
  0x73, 0x08, 0xC7, 0x74, 0x09, 0xAF, 0xEC, 0xF5, 0x4D, 0x2D, 
  0xEA, 0xA5, 0xDA, 0xEF, 0xA6, 0x2B, 0x7E, 0x0C, 0x8F, 0xB0, 
  0x04, 0x06, 0x62, 0x84, 0x15, 0x8E, 0x12, 0x1D, 0x44, 0xC0, 
  0xE2, 0x38, 0xD4, 0x47, 0x28, 0x45, 0x6E, 0x9D, 0x63, 0xCF, 
  0xE6, 0x8C, 0x18, 0x82, 0x1B, 0x2C, 0xEE, 0x87, 0x94, 0x10, 
  0xC1, 0x20, 0x07, 0x4A, 0xA4, 0xEB, 0x77, 0xBC, 0xD3, 0xE1, 
  0x66, 0x2A, 0x6B, 0xE7, 0x79, 0xCC, 0x86, 0x16, 0xD0, 0xD1, 
  0x19, 0x55, 0x3C, 0x9F, 0xFB, 0x30, 0x98, 0xBD, 0xB8, 0xF1, 
  0x9E, 0x61, 0xCD, 0x90, 0xCE, 0x7C, 0x8D, 0x57, 0xAE, 0x6A, 
  0xB3, 0x3D, 0x76, 0xA7, 0x71, 0x88, 0xA2, 0xBA, 0x4F, 0x3E, 
  0x40, 0x64, 0x0F, 0x48, 0x21, 0x35, 0x36, 0x2F, 0xE8, 0x14, 
  0x5D, 0x51, 0xD8, 0xB5, 0xFE, 0xD2, 0x96, 0x93, 0xA1, 0xB6, 
  0x43, 0x0D, 0x4C, 0x80, 0xC9, 0xFF, 0xA3, 0xDD, 0x72, 0x05, 
  0x59, 0xBF, 0x0E, 0x26, 0x34, 0x1F, 0x13, 0xE5, 0xDC, 0xF2, 
  0xC6, 0x50, 0x1E, 0xE4, 0x85, 0xB7, 0x39, 0x8A, 0xCA, 0xED, 
  0x9C, 0xBB, 0x56, 0x23, 0x1A, 0xF0, 0x32, 0x58, 0xB2, 0x65, 
  0x33, 0x6F, 0x41, 0xBE, 0x3F, 0x6D, 0x11, 0x00, 0xAD, 0x5F, 
  0xC3, 0x81, 0x25, 0xA8, 0xA0, 0x9A, 0xF6, 0xF7, 0x5E, 0x99, 
  0x22, 0x2E, 0x4B, 0xF9, 0x3B, 0x02, 0x7A, 0xB9, 0x5C, 0x69, 
  0xF8, 0x1C, 0xDB, 0x01, 0x7D, 0xFD
};

//keyExpansion-get the round key
void AES::keyExpansion(byte key[], word w[]){
	int i=0;
	int j,k;
	word temp;
	while(i < Nk){
		for(j=0; j<4; j++){
			w[j].wordKey[i] = key[j+4*i];
		}
		i++;
	}
	i = Nk;
	while(i < Nb*(Nr+1)){
		temp = w[i-1];
		if((i%Nk) == 0){
			temp = rotWord(temp);
			temp = subWord(temp);
			temp = wordXOR(temp, Rcon[i / Nk]);
		}
		else if(Nk > 6 && (i%Nk) == 4){
			temp = subWord(temp);
		}
		w[i] = wordXOR(w[i - Nk], temp);
		i++;
	}
}

// some sector in keyExpansion
word AES::rotWord(word w){
	int i;
	word temp;
	for(i=0; i<4; i++){
		temp.wordKey[(i+3) % 4] = w.wordKey[i];
	}
	return temp;
}

word AES::subWord(word w){
	int i;
	byte L, R;
	for(i=0; i<4; i++){
		L = w.wordKey[i] >> 4;
		R = w.wordKey[i] & 0x0f;
		w.wordKey[i] = SBox[L][R];
	}
	return w;
}

word AES::wordXOR(word w1, word w2){
	int i;
	word temp;
	for(i=0; i<4; i++){
		temp.wordKey[i] = w1.wordKey[i] ^ w2.wordKey[i];
	}
	return temp;
}

//encryption
void AES::encryption(){
	int i, j ,k;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			cipherText[i].wordKey[j] = plainText[i].wordKey[j];
		}
	}
	// round function
	addRoundKey(cipherText, 0);
	for(i=1; i<10; i++){
		subByte(cipherText);
		shiftRows(cipherText);
		mixColumn(cipherText);
		addRoundKey(cipherText, i);
	}
	subByte(cipherText);
	shiftRows(cipherText);
	addRoundKey(cipherText, 10);
}

void AES::subByte(word in[]){
	int i,j;
	byte L, R;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			L = in[i].wordKey[j] >> 4;
			R = in[i].wordKey[j] & 0x0f;
			in[i].wordKey[j] = SBox[L][R];
		}
	}
}

void AES::shiftRows(word in[]){
	int i,j;
	word temp[4];
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			temp[i].wordKey[j] = in[(i+j)%4].wordKey[j];
		}
	}
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			in[i].wordKey[j] = temp[i].wordKey[j];
		}
	}
}

void AES::mixColumn(word in[]){
	word result[4];
	int i, j, k;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			result[i].wordKey[j] = GFMultiplyByte(mixColumnMatrix[j][0], in[i].wordKey[0]);
			for(k=1; k<4; k++){
				result[i].wordKey[j] ^= GFMultiplyByte(mixColumnMatrix[j][k], in[i].wordKey[k]);
			}
		}
	}
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			in[i].wordKey[j] = result[i].wordKey[j];
		}
	}
}

//forexample: 0xaf * 0x25
byte AES::GFMultiplyByte(byte L, byte R){
	byte temp[8];
	byte result = 0x00;
	temp[0] = L;
	int i;
    // temp[0] = L, temp[1] = L*x(modm(x)), temp[2] = L*x^2(mod(m(x))), temp[3] = L*x^3(mod(m(x)))...
	//先计算，再存起来，后面根据R的实际情况选用需要的
	for(i=1; i<8; i++){
		if(temp[i-1] >= 0x80){
			temp[i] = (temp[i-1] << 1) ^ 0x1b;
		}else{
			temp[i] = temp[i-1] << 1;
		}
	}
	for(i=0; i<8; i++){
		if(int((R >> i) & 0x01) == 1){
			result ^= temp[i];
		}
	}
	return result;
}

void AES::addRoundKey(word in[], int round){
	int i, j;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			in[i].wordKey[j] ^= wordKey[i+4*round].wordKey[j];
		}
	}
}

//decryption
void AES::decryption(){
	int i, j, k;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			deCipherText[i].wordKey[j] = cipherText[i].wordKey[j];
		}
	}
	addRoundKey(deCipherText, 10);
	for(i=9; i>0; i--){
		invShiftRows(deCipherText);
		invSubByte(deCipherText);
		addRoundKey(deCipherText, i);
		invMixColumn(deCipherText);
	}
	invShiftRows(deCipherText);
	invSubByte(deCipherText);
	addRoundKey(deCipherText, 0);
}

void AES::invShiftRows(word in[]){
	int i,j;
	word temp[4];
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			temp[i].wordKey[j] = in[(i-j+4)%4].wordKey[j];
		}
	}
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			in[i].wordKey[j] = temp[i].wordKey[j];
		}
	}
}

void AES::invSubByte(word in[]){
	int i,j;
	byte L, R;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			L = in[i].wordKey[j] >> 4;
			R = in[i].wordKey[j] & 0x0f;
			in[i].wordKey[j] = invSBox[L][R];
		}
	}
}

void AES::invMixColumn(word in[]){
	word result[4];
	int i, j, k;
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			result[i].wordKey[j] = GFMultiplyByte(invmixColumnMatrix[j][0], in[i].wordKey[0]);
			for(k=1; k<4; k++){
				result[i].wordKey[j] ^= GFMultiplyByte(invmixColumnMatrix[j][k], in[i].wordKey[k]);
			}
		}
	}
	for(i=0; i<4; i++){
		for(j=0; j<4; j++){
			in[i].wordKey[j] = result[i].wordKey[j];
		}
	}
}

int main(int argc, char const *argv[])
{
	int i;
    //设置明文和密钥
	byte plain[16], key[16];
	for(i=0; i<16; i++){
		plain[i] = byte(i);
		key[i] = 0x01;
	}
	AES aes;
	aes.setPlainText(plain);
	aes.setCipherKey(key);
	aes.encryption();
	aes.decryption();
	aes.showMesage();
	return 0;
}