AES.cpp

#include <iostream>
#include <bitset>
#include <string>
using namespace std;
typedef bitset<8> byte;
typedef bitset<32> word;

const int Nr = 10;  // AES-128需要 10 轮加密
const int Nk = 4;   // Nk 表示输入密钥的 word 个数

byte S_Box[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}
};

byte Inv_S_Box[16][16] = {
        {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}
};

// 轮常数，密钥扩展中用到。（AES-128只需要10轮）
word Rcon[10] = {0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000,
                 0x20000000, 0x40000000, 0x80000000, 0x1b000000, 0x36000000};

/**********************************************************************/
/*                                                                    */
/*                              AES算法实现                           */
/*                                                                    */
/**********************************************************************/

/******************************下面是加密的变换函数**********************/
/**
 *  S盒变换 - 前4位为行号，后4位为列号
 */
void SubBytes(byte mtx[4*4])
{
    for(int i=0; i<16; ++i)
    {
        int row = mtx[i][7]*8 + mtx[i][6]*4 + mtx[i][5]*2 + mtx[i][4];
        int col = mtx[i][3]*8 + mtx[i][2]*4 + mtx[i][1]*2 + mtx[i][0];
        mtx[i] = S_Box[row][col];
    }
}

/**
 *  行变换 - 按字节循环移位
 */
void ShiftRows(byte mtx[4*4])
{
    // 第二行循环左移一位
    byte temp = mtx[4];
    for(int i=0; i<3; ++i)
        mtx[i+4] = mtx[i+5];
    mtx[7] = temp;
    // 第三行循环左移两位
    for(int i=0; i<2; ++i)
    {
        temp = mtx[i+8];
        mtx[i+8] = mtx[i+10];
        mtx[i+10] = temp;
    }
    // 第四行循环左移三位
    temp = mtx[15];
    for(int i=3; i>0; --i)
        mtx[i+12] = mtx[i+11];
    mtx[12] = temp;
}

/**
 *  有限域上的乘法 GF(2^8)
 */
byte GFMul(byte a, byte b) {
    byte p = 0;
    byte hi_bit_set;
    for (int counter = 0; counter < 8; counter++) {
        if ((b & byte(1)) != 0) {
            p ^= a;
        }
        hi_bit_set = (byte) (a & byte(0x80));
        a <<= 1;
        if (hi_bit_set != 0) {
            a ^= 0x1b; /* x^8 + x^4 + x^3 + x + 1 */
        }
        b >>= 1;
    }
    return p;
}

/**
 *  列变换
 */
void MixColumns(byte mtx[4*4])
{
    byte arr[4];
    for(int i=0; i<4; ++i)
    {
        for(int j=0; j<4; ++j)
            arr[j] = mtx[i+j*4];

        mtx[i] = GFMul(0x02, arr[0]) ^ GFMul(0x03, arr[1]) ^ arr[2] ^ arr[3];
        mtx[i+4] = arr[0] ^ GFMul(0x02, arr[1]) ^ GFMul(0x03, arr[2]) ^ arr[3];
        mtx[i+8] = arr[0] ^ arr[1] ^ GFMul(0x02, arr[2]) ^ GFMul(0x03, arr[3]);
        mtx[i+12] = GFMul(0x03, arr[0]) ^ arr[1] ^ arr[2] ^ GFMul(0x02, arr[3]);
    }
}

/**
 *  轮密钥加变换 - 将每一列与扩展密钥进行异或
 */
void AddRoundKey(byte mtx[4*4], word k[4])
{
    for(int i=0; i<4; ++i)
    {
        word k1 = k[i] >> 24;
        word k2 = (k[i] << 8) >> 24;
        word k3 = (k[i] << 16) >> 24;
        word k4 = (k[i] << 24) >> 24;

        mtx[i] = mtx[i] ^ byte(k1.to_ulong());
        mtx[i+4] = mtx[i+4] ^ byte(k2.to_ulong());
        mtx[i+8] = mtx[i+8] ^ byte(k3.to_ulong());
        mtx[i+12] = mtx[i+12] ^ byte(k4.to_ulong());
    }
}

/**************************下面是解密的逆变换函数***********************/
/**
 *  逆S盒变换
 */
void InvSubBytes(byte mtx[4*4])
{
    for(int i=0; i<16; ++i)
    {
        int row = mtx[i][7]*8 + mtx[i][6]*4 + mtx[i][5]*2 + mtx[i][4];
        int col = mtx[i][3]*8 + mtx[i][2]*4 + mtx[i][1]*2 + mtx[i][0];
        mtx[i] = Inv_S_Box[row][col];
    }
}

/**
 *  逆行变换 - 以字节为单位循环右移
 */
void InvShiftRows(byte mtx[4*4])
{
    // 第二行循环右移一位
    byte temp = mtx[7];
    for(int i=3; i>0; --i)
        mtx[i+4] = mtx[i+3];
    mtx[4] = temp;
    // 第三行循环右移两位
    for(int i=0; i<2; ++i)
    {
        temp = mtx[i+8];
        mtx[i+8] = mtx[i+10];
        mtx[i+10] = temp;
    }
    // 第四行循环右移三位
    temp = mtx[12];
    for(int i=0; i<3; ++i)
        mtx[i+12] = mtx[i+13];
    mtx[15] = temp;
}

void InvMixColumns(byte mtx[4*4])
{
    byte arr[4];
    for(int i=0; i<4; ++i)
    {
        for(int j=0; j<4; ++j)
            arr[j] = mtx[i+j*4];

        mtx[i] = GFMul(0x0e, arr[0]) ^ GFMul(0x0b, arr[1])
                 ^ GFMul(0x0d, arr[2]) ^ GFMul(0x09, arr[3]);
        mtx[i+4] = GFMul(0x09, arr[0]) ^ GFMul(0x0e, arr[1])
                   ^ GFMul(0x0b, arr[2]) ^ GFMul(0x0d, arr[3]);
        mtx[i+8] = GFMul(0x0d, arr[0]) ^ GFMul(0x09, arr[1])
                   ^ GFMul(0x0e, arr[2]) ^ GFMul(0x0b, arr[3]);
        mtx[i+12] = GFMul(0x0b, arr[0]) ^ GFMul(0x0d, arr[1])
                    ^ GFMul(0x09, arr[2]) ^ GFMul(0x0e, arr[3]);
    }
}

/******************************下面是密钥扩展部分***********************/
/**
 * 将4个 byte 转换为一个 word.
 */
word Word(byte& k1, byte& k2, byte& k3, byte& k4)
{
    word result(0x00000000);
    word temp;
    temp = k1.to_ulong();  // K1
    temp <<= 24;
    result |= temp;
    temp = k2.to_ulong();  // K2
    temp <<= 16;
    result |= temp;
    temp = k3.to_ulong();  // K3
    temp <<= 8;
    result |= temp;
    temp = k4.to_ulong();  // K4
    result |= temp;
    return result;
}

/**
 *  按字节 循环左移一位
 *  即把[a0, a1, a2, a3]变成[a1, a2, a3, a0]
 */
word RotWord(word& rw)
{
    word high = rw << 8;
    word low = rw >> 24;
    return high | low;
}

/**
 *  对输入word中的每一个字节进行S-盒变换
 */
word SubWord(word& sw)
{
    word temp;
    for(int i=0; i<32; i+=8)
    {
        int row = sw[i+7]*8 + sw[i+6]*4 + sw[i+5]*2 + sw[i+4];
        int col = sw[i+3]*8 + sw[i+2]*4 + sw[i+1]*2 + sw[i];
        byte val = S_Box[row][col];
        for(int j=0; j<8; ++j)
            temp[i+j] = val[j];
    }
    return temp;
}

/**
 *  密钥扩展函数 - 对128位密钥进行扩展得到 w[4*(Nr+1)]
 */
void KeyExpansion(byte key[4*Nk], word w[4*(Nr+1)])
{
    word temp;
    int i = 0;
    // w[]的前4个就是输入的key
    while(i < Nk)
    {
        w[i] = Word(key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]);
        ++i;
    }

    i = Nk;

    while(i < 4*(Nr+1))
    {
        temp = w[i-1]; // 记录前一个word
        if(i % Nk == 0) {
            word rotres = RotWord(temp);
            w[i] = w[i - Nk] ^ SubWord(rotres) ^ Rcon[i / Nk - 1];
        }else {
            w[i] = w[i - Nk] ^ temp;
        }
        ++i;
    }
}

/******************************下面是加密和解密函数**************************/
/**
 *  加密
 */
void encrypt(byte in[4*4], word w[4*(Nr+1)])
{
    word key[4];
    for(int i=0; i<4; ++i)
        key[i] = w[i];
    AddRoundKey(in, key);

    for(int round=1; round<Nr; ++round)
    {
        SubBytes(in);
        ShiftRows(in);
        MixColumns(in);
        for(int i=0; i<4; ++i)
            key[i] = w[4*round+i];
        AddRoundKey(in, key);
    }

    SubBytes(in);
    ShiftRows(in);
    for(int i=0; i<4; ++i)
        key[i] = w[4*Nr+i];
    AddRoundKey(in, key);
}

/**
 *  解密
 */
void decrypt(byte in[4*4], word w[4*(Nr+1)])
{
    word key[4];
    for(int i=0; i<4; ++i)
        key[i] = w[4*Nr+i];
    AddRoundKey(in, key);

    for(int round=Nr-1; round>0; --round)
    {
        InvShiftRows(in);
        InvSubBytes(in);
        for(int i=0; i<4; ++i)
            key[i] = w[4*round+i];
        AddRoundKey(in, key);
        InvMixColumns(in);
    }

    InvShiftRows(in);
    InvSubBytes(in);
    for(int i=0; i<4; ++i)
        key[i] = w[i];
    AddRoundKey(in, key);
}

/**********************************************************************/
/*                                                                    */
/*                              测试                                  */
/*                                                                    */
/**********************************************************************/
int main()
{
    byte key[16] = {0x2b, 0x7e, 0x15, 0x16,
                    0x28, 0xae, 0xd2, 0xa6,
                    0xab, 0xf7, 0x15, 0x88,
                    0x09, 0xcf, 0x4f, 0x3c};

    byte plain[16] = {0x32, 0x88, 0x31, 0xe0,
                      0x43, 0x5a, 0x31, 0x37,
                      0xf6, 0x30, 0x98, 0x07,
                      0xa8, 0x8d, 0xa2, 0x34};
    // 输出密钥
    cout << "密钥是：";
    for(int i=0; i<16; ++i)
        cout << hex << key[i].to_ulong() << " ";
    cout << endl;

    word w[4*(Nr+1)];
    KeyExpansion(key, w);

    // 输出待加密的明文
    cout << endl << "待加密的明文："<<endl;
    for(int i=0; i<16; ++i)
    {
        cout << hex << plain[i].to_ulong() << " ";
        if((i+1)%4 == 0)
            cout << endl;
    }
    cout << endl;

    // 加密，输出密文
    encrypt(plain, w);
    cout << "加密后的密文："<<endl;
    for(int i=0; i<16; ++i)
    {
        cout << hex << plain[i].to_ulong() << " ";
        if((i+1)%4 == 0)
            cout << endl;
    }
    cout << endl;

    // 解密，输出明文
    decrypt(plain, w);
    cout << "解密后的明文："<<endl;
    for(int i=0; i<16; ++i)
    {
        cout << hex << plain[i].to_ulong() << " ";
        if((i+1)%4 == 0)
            cout << endl;
    }
    cout << endl;
    return 0;
}