DES算法C语言实现

以下是DES算法的C语言实现代码：

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

/* Initial Permutation Table */
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 };

/* Inverse Initial Permutation Table */
int IP_Table_Inverse[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 };

/* Expansion Table */
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 };

/* Permutation Table */
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 };

/* S-Box Table */
int S_Box[8][4][16] = {
    // S1
    {
        {14, 0, 4, 15, 13, 7, 1, 4, 2, 14, 15, 2, 11, 13, 8, 1, 3, 10, 10, 6, 6, 12, 12, 11, 5, 9, 9, 5, 0, 3, 7, 8, 4, 15, 1, 12, 14, 8, 8, 2, 13, 4, 4, 6, 9, 2, 1, 11, 7, 15, 5, 12, 11, 9, 3, 7, 14, 3, 10, 10, 0, 5, 6, 0, 13},
        {15, 3, 1, 13, 8, 4, 14, 7, 6, 15, 11, 2, 3, 8, 4, 14, 9, 12, 7, 0, 2, 1, 13, 10, 12, 6, 0, 9, 5, 11, 10, 5, 0, 13, 14, 8, 7, 10, 11, 1, 10, 3, 4, 15, 13, 4, 1, 2, 5, 11, 8, 6, 12, 7, 6, 12, 9, 0, 3, 5, 2, 14, 15},
        {10, 13, 0, 7, 9, 0, 14, 9, 6, 3, 3, 4, 15, 6, 5, 10, 1, 2, 13, 11, 8, 12, 5, 2, 11, 14, 12, 4, 7, 8, 5, 6, 15, 1, 12, 10, 3, 11, 14, 4, 1, 7, 9, 4, 12, 2, 10, 15, 13, 0, 14, 3, 7, 1, 10, 13, 0, 6, 9, 8, 6, 15, 9, 3},
        {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, 9, 6, 7, 12, 0, 5, 14, 11, 2, 8, 13, 4, 0, 6, 12, 1, 10, 7, 9, 5, 3, 15, 2, 12, 8, 1, 14, 4, 11, 7, 13, 10, 6, 0, 9, 3, 5}
    },
    // 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, 9, 7, 5, 12, 6, 0},
        {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, 13, 4, 9, 1, 6, 15, 3, 2, 7, 11, 8, 14, 5, 10, 12},
        {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},
        {1, 7, 14, 13, 0, 5, 8, 3, 4, 15, 10, 6, 9, 12, 11, 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, 10, 15, 5, 2, 6, 12, 11, 9, 4, 14, 1, 7, 8, 13, 0, 3}
    },
    // S3
    {
        {15, 13, 8, 10, 11, 5, 6, 2, 4, 3, 14, 7, 1, 9, 4, 12, 7, 2, 1, 11, 10, 13, 0, 6, 12, 8, 5, 3, 15, 9, 14, 6, 11, 9, 7, 13, 12, 15, 5, 0, 3, 4, 10, 14, 1, 2, 8, 5, 6, 2, 12, 10, 11, 9, 1, 13, 14, 0, 3, 4, 7, 8, 15},
        {9, 6, 3, 5, 2, 12, 10, 11, 1, 14, 7, 4, 0, 15, 13, 8, 4, 15, 2, 5, 11, 8, 1, 14, 10, 7, 9, 12, 6, 3, 13, 0, 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12, 2, 13, 6, 15, 9, 11, 0, 4, 5, 8, 12, 3, 7, 10, 1},
        {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},
        {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, 12, 3, 10, 6, 9, 0, 15, 8, 5, 2, 1, 13, 4, 11, 7}
    },
    // S4
    {
        {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},
        {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},
        {1, 7, 14, 13, 0, 5, 8, 3, 4, 15, 10, 6, 9, 12, 11, 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, 10, 15, 5, 2, 6, 12, 11, 9, 4, 14, 1, 7, 8, 13, 0, 3},
        {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, 9, 6, 7, 12, 0, 5, 14, 11, 2, 8, 13, 4, 0, 6, 12, 1, 10, 7, 9, 5, 3, 15, 2, 12, 8, 1, 14, 4, 11, 7, 13, 10, 6, 0, 9, 3, 5}
    },
    // 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,