c语言实现DES加密算法

以下是使用C语言实现DES加密算法的代码示例：

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

#define ENCRYPT 1
#define DECRYPT 0

typedef unsigned char BYTE;
typedef unsigned int UINT;

// 初始置换表IP
const 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IP^-1
const 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 };

// 扩展置换表E
const 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 };

// 置换函数P
const 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
const 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
};

// 置换选择1
const 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 };

// 置换选择2
const 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 };

// 循环左移位数表
const BYTE Move_Table[16] = { 1, 1, 2, 2,
                              2, 2, 2, 2,
                              1, 2, 2, 2,
                              2, 2, 2, 1 };

// 子密钥
BYTE SubKey[16][48];

// 16轮变换中的数据
BYTE Li[32], Ri[32], Mi[64];

// 初始置换IP
void DES_IP(BYTE *In, BYTE *Out)
{
    int i;
    for (i = 0; i < 64; i++)
    {
        Out[i] = (In[IP_Table[i] - 1] & 0x80) >> (i % 8);
    }
}

// 逆初始置换IP^-1
void DES_IPR(BYTE *In, BYTE *Out)
{
    int i;
    for (i = 0; i < 64; i++)
    {
        Out[i] = (In[IPR_Table[i] - 1] & 0x80) >> (i % 8);
    }
}

// 扩展置换E
void DES_E(BYTE *In, BYTE *Out)
{
    int i;
    for (i = 0; i < 48; i++)