C++实现DES密码算法

下面是一个简单的C++实现DES密码算法的示例代码。由于DES算法中使用了大量的位运算，因此代码可能看起来比较复杂。

#include <iostream>
#include <bitset>
#include <cstring>

using namespace std;

// 初始置换表IP
int IP_Table[64] = {
    58, 50, 42, 34, 26, 18, 10, 2,
    60, 52, 44, 36, 28, 20, 12, 4,
    62, 54, 46, 38, 30, 22, 14, 6,
    64, 56, 48, 40, 32, 24, 16, 8,
    57, 49, 41, 33, 25, 17, 9, 1,
    59, 51, 43, 35, 27, 19, 11, 3,
    61, 53, 45, 37, 29, 21, 13, 5,
    63, 55, 47, 39, 31, 23, 15, 7
};

// 逆置换表IP^-1
int IP_1_Table[64] = {
    40, 8, 48, 16, 56, 24, 64, 32,
    39, 7, 47, 15, 55, 23, 63, 31,
    38, 6, 46, 14, 54, 22, 62, 30,
    37, 5, 45, 13, 53, 21, 61, 29,
    36, 4, 44, 12, 52, 20, 60, 28,
    35, 3, 43, 11, 51, 19, 59, 27,
    34, 2, 42, 10, 50, 18, 58, 26,
    33, 1, 41, 9, 49, 17, 57, 25
};

// 扩展置换表E
int E_Table[48] = {
    32, 1, 2, 3, 4, 5, 4, 5,
    6, 7, 8, 9, 8, 9, 10, 11,
    12, 13, 12, 13, 14, 15, 16, 17,
    16, 17, 18, 19, 20, 21, 20, 21,
    22, 23, 24, 25, 24, 25, 26, 27,
    28, 29, 28, 29, 30, 31, 32, 1
};

// S盒
int S_Box[8][4][16] = {
    {
        // S1
        {14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7},
        {0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8},
        {4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0},
        {15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13}
    },
    {
        // S2
        {15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10},
        {3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5},
        {0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15},
        {13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9}
    },
    {
        // S3
        {10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8},
        {13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1},
        {13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7},
        {1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12}
    },
    {
        // S4
        {7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15},
        {13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9},
        {10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4},
        {3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14}
    },
    {
        // S5
        {2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9},
        {14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6},
        {4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14},
        {11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3}
    },
    {
        // S6
        {12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11},
        {10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8},
        {9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6},
        {4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13}
    },
    {
        // S7
        {4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1},
        {13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6},
        {1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2},
        {6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12}
    },
    {
        // S8
        {13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7},
        {1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2},
        {7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8},
        {2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11}
    }
};

// 置换函数P
int P_Table[32] = {
    16, 7, 20, 21, 29, 12, 28, 17,
    1, 15, 23, 26, 5, 18, 31, 10,
    2, 8, 24, 14, 32, 27, 3, 9,
    19, 13, 30, 6, 22, 11, 4, 25
};

// 左移位数表
int Shift_Table[16] = {
    1, 1, 2, 2, 2, 2, 2, 2,
    1, 2, 2, 2, 2, 2, 2, 1
};

// 密钥置换表PC-1
int PC_1_Table[56] = {
    57, 49, 41, 33, 25, 17, 9,
    1, 58, 50, 42, 34, 26, 18,
    10, 2, 59, 51, 43, 35, 27,
    19, 11, 3, 60, 52, 44, 36,
    63, 55, 47, 39, 31, 23, 15,
    7, 62, 54, 46, 38, 30, 22,
    14, 6, 61, 53, 45, 37, 29,
    21, 13, 5, 28, 20, 12, 4
};

// 密钥置换表PC-2
int PC_2_Table[48] = {
    14, 17, 11, 24, 1, 5, 3, 28,
    15, 6, 21, 10, 23, 19, 12, 4,
    26, 8, 16, 7, 27, 20, 13, 2,
    41, 52, 31, 37, 47, 55, 30, 40,
    51, 45, 33, 48, 44, 49, 39, 56,
    34, 53, 46, 42, 50, 36, 29, 32
};

// 子密钥数组
int SubKey[16][48];

// 将64位的明文或密文进行初始置换IP
void IP_Transform(bool* data)
{
    bool temp[64];
    for (int i = 0; i < 64; i++) {
        temp[i] = data[IP_Table[i] - 1];
    }
    memcpy(data, temp, sizeof(temp));
}

// 将64位的明文或密文进行逆置换IP^-1
void IP_1_Transform(bool* data)
{
    bool temp[64];
    for (int i = 0; i < 64; i++) {
        temp[i] = data[IP_1_Table[i] - 1];
    }
    memcpy(data, temp, sizeof(temp));
}

// 将32位的数据左移shift位
void Shift_Left(bool* data, int shift)
{
    bool temp[256];
    memcpy(temp, data, sizeof(temp));
    for (int i = 0; i < 32; i++) {
        data[i] = temp[(i + shift) % 32];
    }
}

// 将64位密钥进行PC-1置换
void PC_1_Transform(bool* key)
{
    bool temp[56];
    for (int i = 0; i < 56; i++) {
        temp[i] = key[PC_1_Table[i] - 1];
    }
    memcpy(key, temp, sizeof(temp));
}

// 将56位密钥进行PC-2置换，生成48位的子密钥
void PC_2_Transform(bool* key, int index)
{
    bool temp[48];
    for (int i = 0; i < 48; i++) {
        temp[i] = key[PC_2_Table[i] - 1];
    }
    memcpy(SubKey[index], temp, sizeof(temp));
}

// 将48位数据进行扩展，扩展为64位
void E_Transform(bool* data)
{
    bool temp[64];
    for (int i = 0; i < 48; i++) {
        temp[i] = data[E_Table[i] - 1];
    }
    memcpy(data, temp, sizeof(temp));
}

// S盒代替函数
void S_Box_Transform(bool* data)
{
    int index;
    for (int i = 0, j = 0; i < 8; i++, j += 6) {
        int x = (data[j] << 1) + data[j + 5];
        int y = (data[j + 1] << 3) + (data[j + 2] << 2) + (data[j + 3] << 1) + data[j + 4];
        index = (i << 2) + y;
        int value = S_Box[i][x][y];
        for (int k = 0; k < 4; k++) {
            data[j + 3 - k] = (value >> k) & 1;
        }
    }
}

// P置换
void P_Transform(bool* data)
{
    bool temp[32];
    for (int i = 0; i < 32; i++) {
        temp[i] = data[P_Table[i] - 1];
    }
    memcpy(data, temp, sizeof(temp));
}

// 生成子密钥
void Generate_SubKey(bool* key)
{
    bool temp[64];
    PC_1_Transform(key);
    for (int i = 0; i < 16; i++) {
        memcpy(temp, key, sizeof(temp));
        Shift_Left(temp, Shift_Table[i]);
        PC_2_Transform(temp, i);
    }
}

// 加密单个64位分组
void Encrypt_One_Block(bool* block)
{
    IP_Transform(block);
    for (int i = 0; i < 16; i++) {
        bool L[32];
        bool R[32];
        bool temp[32];
        memcpy(L, block, 32);
        memcpy(R, block + 32, 32);
        memcpy(temp, R, 32);
        E_Transform(temp);
        for (int j = 0; j < 48; j++) {
            temp[j] ^= SubKey[i][j];
        }
        S_Box_Transform(temp);
        P_Transform(temp);
        for (int j = 0; j < 32; j++) {
            R[j] ^= temp[j];
        }
        memcpy(block, L, 32);
        memcpy(block + 32, R, 32);
    }
    IP_1_Transform(block);
}

// 加密函数
void Encrypt(bool* data, int len, bool* key)
{
    Generate_SubKey(key);
    for (int i = 0; i < len; i += 8) {
        Encrypt_One_Block(data + i);
    }
}

// 测试
int main()
{
    // 明文
    bool data[64] = {
        1, 0, 1, 0, 0, 0, 1, 1,
        0, 1, 1, 1, 1, 0,