des密码c语言

DES算法是一种对称加密算法，它的核心是轮函数和密钥编排。在C语言中实现DES算法的代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define ENCRYPT 1
#define DECRYPT 0

typedef unsigned char BYTE;
typedef unsigned long DWORD;

// 初始置换表
BYTE 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 };

// 逆初始置换表
BYTE IPR_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 };

// 扩充置换表
BYTE 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 };

// P置换表
BYTE 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 };

// S盒
BYTE 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,
};

// 密钥置换表
BYTE PC1_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 };

// 压缩置换表
BYTE PC2_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 };

// 每轮移动位数
BYTE Move_Table[16] = { 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1 };

// 轮函数
void F_func(BYTE* in, BYTE* subkey, BYTE* out)
{
    BYTE expand[48];
    memset(expand, 0, sizeof(expand));
    for (int i = 0; i < 48; ++i)
    {
        expand[i] = in[E_Table[i] - 1] ^ subkey[i];
    }

    for (int i = 0; i < 8; ++i)
    {
        int row = (expand[i * 6] << 1) + expand[i * 6 + 5];
        int col = (expand[i * 6 + 1] << 3) + (expand[i * 6 + 2] << 2) + (expand[i * 6 + 3] << 1) + expand[i * 6 + 4];
        BYTE val = S_Box[i][row][col];

        out[i * 4] = (val & 0x08) >> 3;
        out[i * 4 + 1] = (val & 0x04) >> 2;
        out[i * 4 + 2] = (val & 0x02) >> 1;
        out[i * 4 + 3] = val & 0x01;
    }

    BYTE pval[32];
    for (int i = 0; i < 32; ++i)
    {
        pval[i] = out[P_Table[i] - 1];
    }
    memcpy(out, pval, sizeof(pval));
}

// 生成子密钥
void Generate_Subkey(BYTE* key, BYTE subkey[16][48])
{
    BYTE pc1[56];
    BYTE pc2[48];
    memset(pc1, 0, sizeof(pc1));
    memset(pc2, 0, sizeof(pc2));

    // PC-1置换
    for (int i = 0; i < 56; ++i)
    {
        pc1[i] = key[PC1_Table[i] - 1];
    }

    BYTE left[28], right[28];
    for (int i = 0; i < 28; ++i)
    {
        left[i] = pc1[i];
        right[i] = pc1[i + 28];
    }

    // 生成子密钥
    for (int i = 0; i < 16; ++i)
    {
        // 移位
        for (int j = 0; j < Move_Table[i]; ++j)
        {
            BYTE tmp = left[0];
            for (int k = 0; k < 27; ++k)
            {
                left[k] = left[k + 1];
            }
            left[27] = tmp;

            tmp = right[0];
            for (int k = 0; k < 27; ++k)
            {
                right[k] = right[k + 1];
            }
            right[27] = tmp;
        }

        // PC-2置换
        for (int j = 0; j < 48; ++j)
        {
            pc2[j] = (j < 24) ? left[PC2_Table[j] - 1] : right[PC2_Table[j] - 28];
        }
        memcpy(subkey[i], pc2, sizeof(pc2));
    }
}

// 初始置换
void IP_Transform(BYTE* in, BYTE* out)
{
    for (int i = 0; i < 64; ++i)
    {
        out[i] = in[IP_Table[i] - 1];
    }
}

// 逆初始置换
void IPR_Transform(BYTE* in, BYTE* out)
{
    for (int i = 0; i < 64; ++i)
    {
        out[i] = in[IPR_Table[i] - 1];
    }
}

// DES加密或解密
void DES(BYTE* input, BYTE* output, BYTE subkey[16][48], int type)
{
    BYTE data[64];
    BYTE tmp[32];
    memset(data, 0, sizeof(data));
    memset(tmp, 0, sizeof(tmp));

    // 初始置换
    IP_Transform(input, data);

    // 加密或解密
    for (int i = 0; i < 16; ++i)
    {
        memcpy(tmp, data + 32, 32);
        F_func(data + 32, subkey[type ? i : 15 - i], data + 32);
        for (int j = 0; j < 32; ++j)
        {
            data[j + 32] = data[j] ^ data[j + 32];
            data[j] = tmp[j];
        }
    }

    // 逆初始置换
    IPR_Transform(data, output);
}

// 加密
void Encrypt(BYTE* data, BYTE* key, BYTE* result)
{
    BYTE subkey[16][48];
    memset(subkey, 0, sizeof(subkey));

    Generate_Subkey(key, subkey);
    DES(data, result, subkey, ENCRYPT);
}

// 解密
void Decrypt(BYTE* data, BYTE* key, BYTE* result)
{
    BYTE subkey[16][48];
    memset(subkey, 0, sizeof(subkey));

    Generate_Subkey(key, subkey);
    DES(data, result, subkey, DECRYPT);
}

int main(int argc, char* argv[])
{
    BYTE data[] = "Hello World!";
    BYTE key[] = "12345678";
    BYTE result[64];

    Encrypt(data, key, result);
    printf("Encrypted: ");
    for (int i = 0; i < 8; ++i)
    {
        printf("%02X", result[i]);
    }
    printf("\n");

    Decrypt(result, key, result);
    printf("Decrypted: ");
    for (int i = 0; i < 8; ++i)
    {
        printf("%c", result[i]);
    }
    printf("\n");

    return 0;
}

说明：

- `IP_Table`和`IPR_Table`分别表示初始置换表和逆初始置换表。
- `E_Table`、`P_Table`和`S_Box`分别表示扩充置换表、P置换表和S盒。
- `PC1_Table`和`PC2_Table`分别表示密钥置换表和压缩置换表。
- `Move_Table`表示每轮移动位数。
- `F_func`函数表示DES算法的轮函数。
- `Generate_Subkey`函数用于生成子密钥。
- `IP_Transform`和`IPR_Transform`函数分别表示初始置换和逆初始置换。
- `DES`函数表示DES算法加密或解密函数。
- `Encrypt`和`Decrypt`函数分别表示DES算法的加密和解密函数。
- 在`main`函数中，我们对字符串"Hello World!"进行加密和解密，并输出结果。