DES算法解析

jopen 9年前

DES算法 
美国国家标准局1973年开始研究除国防部外的其它部门的计算机系统的数据加密标准,于1973年5月15日和1974年8月27日先后两次向公众发出了征求加密算法的公告。 1977年1月,美国政府颁布:采纳IBM公司设计的方案作为非机密数据的正式数据加密标准(DES,Data Encryption Standard)。

一、DES算法 

美国国家标准局1973年开始研究除国防部外的其它部门的计算机系统的数据加密标准,于1973年5月15日和1974年8月27日先后两次向公众发出了征求加密算法的公告。加密算法要达到的目的(通常称为DES 密码算法要求)主要为以下四点: ☆提供高质量的数据保护,防止数据未经授权的泄露和未被察觉的修改; 

☆具有相当高的复杂性,使得破译的开销超过可能获得的利益,同时又要便于理解和掌握; 

☆DES密码体制的安全性应该不依赖于算法的保密,其安全性仅以加密密钥的保密为基础; 

☆实现经济,运行有效,并且适用于多种完全不同的应用。 

1977年1月,美国政府颁布:采纳IBM公司设计的方案作为非机密数据的正式数据加密标准(DES,Data Encryption Standard)。 

目前在国内,随着三金工程尤其是金卡工程的启动,DES算法在POS、ATM、磁卡及智能卡(IC卡)、加油站、高速公路收费站等领域被广泛应用,以此来实现关键数据的保密,如信用卡持卡人的PIN的加密传输,IC卡与POS间的双向认证、金融交易数据包的MAC校验等,均用到DES算法。 
DES算法的入口参数有三个:Key、Data、Mode。其中Key为8个字节共64位,是DES算法的工作密钥;Data也为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。 
DES算法是这样工作的:如Mode为加密,则用Key 去把数据Data进行加密, 生成Data的密码形式(64位)作为DES的输出结果;如Mode为解密,则用Key去把密码形式的数据Data解密,还原为Data的明码形式(64位)作为DES的输出结果。在通信网络的两端,双方约定一致的Key,在通信的源点用Key对核心数据进行DES加密,然后以密码形式在公共通信网(如电话网)中传输到通信网络的终点,数据到达目的地后,用同样的Key对密码数据进行解密,便再现了明码形式的核心数据。这样,便保证了核心数据(如PIN、MAC等)在公共通信网中传输的安全性和可靠性。 
通过定期在通信网络的源端和目的端同时改用新的Key,便能更进一步提高数据的保密性,这正是现在金融交易网络的流行做法。 
DES算法详述 
DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是64位,整个算法的主流程图如下: 
其功能是把输入的64位数据块按位重新组合,并把输出分为L0、R0两部分,每部分各长32位,其置换规则见下表: 
       58,50,12,34,26,18,10,2,60,52,44,36,28,20,12,4, 
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, 
即将输入的第58位换到第一位,第50位换到第2位,…,依此类推,最后一位是原来的第7位。L0、R0则是换位输出后的两部分,L0是输出的左32位,R0 是右32位,例:设置换前的输入值为D1D2D3……D64,则经过初始置换后的结果为:L0=D58D50…D8;R0=D57D49…D7。 
经过16次迭代运算后。得到L16、R16,将此作为输入,进行逆置换,即得到密文输出。逆置换正好是初始置的逆运算,例如,第1位经过初始置换后,处于第40位,而通过逆置换,又将第40位换回到第1位,其逆置换规则如下表所示: 
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, 
放大换位表 
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, 
单纯换位表 
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, 
在f(Ri,Ki)算法描述图中,S1,S2…S8为选择函数,其功能是把6bit数据变为4bit数据。下面给出选择函数Si(i=1,2……的功能表: 
选择函数Si 
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, 
在此以S1为例说明其功能,我们可以看到:在S1中,共有4行数据,命名为0,1、2、3行;每行有16列,命名为0、1、2、3,……,14、15列。 
现设输入为: D=D1D2D3D4D5D6 
令:列=D2D3D4D5 
行=D1D6 
然后在S1表中查得对应的数,以4位二进制表示,此即为选择函数S1的输出。下面给出子密钥Ki(48bit)的生成算法 
从子密钥Ki的生成算法描述图中我们可以看到:初始Key值为64位,但DES算法规定,其中第8、16、……64位是奇偶校验位,不参与DES运算。故Key 实际可用位数便只有56位。即:经过缩小选择换位表1的变换后,Key 的位数由64 位变成了56位,此56位分为C0、D0两部分,各28位,然后分别进行第1次循环左移,得到C1、D1,将C1(28位)、D1(28位)合并得到56位,再经过缩小选择换位2,从而便得到了密钥K0(48位)。依此类推,便可得到K1、K2、……、K15,不过需要注意的是,16次循环左移对应的左移位数要依据下述规则进行: 
       循环左移位数 
1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1 
以上介绍了DES算法的加密过程。DES算法的解密过程是一样的,区别仅仅在于第一次迭代时用子密钥K15,第二次K14、……,最后一次用K0,算法本身并没有任何变化。 

二、DES算法的应用误区  

DES算法具有极高安全性,到目前为止,除了用穷举搜索法对DES算法进行攻击外,还没有发现更有效的办法。而56位长的密钥的穷举空间为256,这意味着如果一台计算机的速度是每一秒种检测一百万个密钥,则它搜索完全部密钥就需要将近2285年的时间,可见,这是难以实现的,当然,随着科学技术的发展,当出现超高速计算机后,我们可考虑把DES密钥的长度再增长一些,以此来达到更高的保密程度。 
由上述DES算法介绍我们可以看到:DES算法中只用到64位密钥中的其中56位,而第8、16、24、……64位8个位并未参与DES运算,这一点,向我们提出了一个应用上的要求,即DES的安全性是基于除了8,16,24,……64位外的其余56位的组合变化256才得以保证的。因此,在实际应用中,我们应避开使用第8,16,24,……64位作为有效数据位,而使用其它的56位作为有效数据位,才能保证DES算法安全可靠地发挥作用。如果不了解这一点,把密钥Key的8,16,24,….. .64位作为有效数据使用,将不能保证DES加密数据的安全性,对运用DES来达到保密作用的系统产生数据被破译的危险,这正是DES算法在应用上的误区,留下了被人攻击、被人破译的极大隐患。

 

源码:

//初始置换表IP     int IP_Table[64] = {  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,                                      56,48,40,32,24,16,8,0,                                      58,50,42,34,26,18,10,2,                                      60,52,44,36,28,20,12,4,                                      62,54,46,38,30,22,14,6};      //逆初始置换表IP^-1     int IP_1_Table[64] = {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,                32,0,40,8,48,16,56,24};         //扩充置换表E     int E_Table[48] = {31, 0, 1, 2, 3, 4,                       3,  4, 5, 6, 7, 8,                       7,  8,9,10,11,12,                       11,12,13,14,15,16,                       15,16,17,18,19,20,                       19,20,21,22,23,24,                       23,24,25,26,27,28,                       27,28,29,30,31, 0};         //置换函数P     int P_Table[32] = {15,6,19,20,28,11,27,16,                       0,14,22,25,4,17,30,9,                       1,7,23,13,31,26,2,8,                       18,12,29,5,21,10,3,24};         //S盒     int S[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     int PC_1[56] = {56,48,40,32,24,16,8,                   0,57,49,41,33,25,17,                   9,1,58,50,42,34,26,                   18,10,2,59,51,43,35,                   62,54,46,38,30,22,14,                   6,61,53,45,37,29,21,                   13,5,60,52,44,36,28,                   20,12,4,27,19,11,3};         //置换选择2     int PC_2[48] = {13,16,10,23,0,4,2,27,                   14,5,20,9,22,18,11,3,                   25,7,15,6,26,19,12,1,                   40,51,30,36,46,54,29,39,                   50,44,32,46,43,48,38,55,                   33,52,45,41,49,35,28,31};         //对左移次数的规定     int MOVE_TIMES[16] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};       //初始置换表IP  int IP_Table[64] = {  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,                                   56,48,40,32,24,16,8,0,                                   58,50,42,34,26,18,10,2,                                   60,52,44,36,28,20,12,4,                                   62,54,46,38,30,22,14,6};   //逆初始置换表IP^-1  int IP_1_Table[64] = {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,       32,0,40,8,48,16,56,24};    //扩充置换表E  int E_Table[48] = {31, 0, 1, 2, 3, 4,                 3,  4, 5, 6, 7, 8,                 7,  8,9,10,11,12,                 11,12,13,14,15,16,                 15,16,17,18,19,20,                 19,20,21,22,23,24,                 23,24,25,26,27,28,                 27,28,29,30,31, 0};    //置换函数P  int P_Table[32] = {15,6,19,20,28,11,27,16,        0,14,22,25,4,17,30,9,        1,7,23,13,31,26,2,8,        18,12,29,5,21,10,3,24};    //S盒  int S[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  int PC_1[56] = {56,48,40,32,24,16,8,             0,57,49,41,33,25,17,             9,1,58,50,42,34,26,             18,10,2,59,51,43,35,             62,54,46,38,30,22,14,             6,61,53,45,37,29,21,             13,5,60,52,44,36,28,             20,12,4,27,19,11,3};    //置换选择2  int PC_2[48] = {13,16,10,23,0,4,2,27,             14,5,20,9,22,18,11,3,             25,7,15,6,26,19,12,1,             40,51,30,36,46,54,29,39,             50,44,32,46,43,48,38,55,             33,52,45,41,49,35,28,31};    //对左移次数的规定  int MOVE_TIMES[16] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};

int ByteToBit(ElemType ch,ElemType bit[8]);     int BitToByte(ElemType bit[8],ElemType *ch);     int Char8ToBit64(ElemType ch[8],ElemType bit[64]);     int Bit64ToChar8(ElemType bit[64],ElemType ch[8]);     int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]);     int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]);     int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]);     int DES_ROL(ElemType data[56], int time);     int DES_IP_Transform(ElemType data[64]);     int DES_IP_1_Transform(ElemType data[64]);     int DES_E_Transform(ElemType data[48]);     int DES_P_Transform(ElemType data[32]);     int DES_SBOX(ElemType data[48]);     int DES_XOR(ElemType R[48], ElemType L[48],int count);     int DES_Swap(ElemType left[32],ElemType right[32]);     int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]);     int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48], ElemType plainBlock[8]);     int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile);     int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile);      int ByteToBit(ElemType ch,ElemType bit[8]);  int BitToByte(ElemType bit[8],ElemType *ch);  int Char8ToBit64(ElemType ch[8],ElemType bit[64]);  int Bit64ToChar8(ElemType bit[64],ElemType ch[8]);  int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]);  int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]);  int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]);  int DES_ROL(ElemType data[56], int time);  int DES_IP_Transform(ElemType data[64]);  int DES_IP_1_Transform(ElemType data[64]);  int DES_E_Transform(ElemType data[48]);  int DES_P_Transform(ElemType data[32]);  int DES_SBOX(ElemType data[48]);  int DES_XOR(ElemType R[48], ElemType L[48],int count);  int DES_Swap(ElemType left[32],ElemType right[32]);  int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]);  int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48], ElemType plainBlock[8]);  int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile);  int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile);

//字节转换成二进制     int ByteToBit(ElemType ch, ElemType bit[8]){         int cnt;         for(cnt = 0;cnt < 8; cnt++){             *(bit+cnt) = (ch>>cnt)&1;         }         return 0;     }         //二进制转换成字节     int BitToByte(ElemType bit[8],ElemType *ch){         int cnt;         for(cnt = 0;cnt < 8; cnt++){             *ch |= *(bit + cnt)<<cnt;         }         return 0;     }         //将长度为8的字符串转为二进制位串     int Char8ToBit64(ElemType ch[8],ElemType bit[64]){         int cnt;         for(cnt = 0; cnt < 8; cnt++){                     ByteToBit(*(ch+cnt),bit+(cnt<<3));         }         return 0;     }         //将二进制位串转为长度为8的字符串     int Bit64ToChar8(ElemType bit[64],ElemType ch[8]){         int cnt;         memset(ch,0,8);         for(cnt = 0; cnt < 8; cnt++){             BitToByte(bit+(cnt<<3),ch+cnt);         }         return 0;     }         //生成子密钥     int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]){         ElemType temp[56];         int cnt;         DES_PC1_Transform(key,temp);//PC1置换         for(cnt = 0; cnt < 16; cnt++){//16轮跌代,产生16个子密钥             DES_ROL(temp,MOVE_TIMES[cnt]);//循环左移             DES_PC2_Transform(temp,subKeys[cnt]);//PC2置换,产生子密钥         }         return 0;     }         //密钥置换1     int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]){         int cnt;             for(cnt = 0; cnt < 56; cnt++){             tempbts[cnt] = key[PC_1[cnt]];         }         return 0;     }         //密钥置换2     int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]){         int cnt;         for(cnt = 0; cnt < 48; cnt++){             tempbts[cnt] = key[PC_2[cnt]];         }         return 0;     }         //循环左移     int DES_ROL(ElemType data[56], int time){            ElemType temp[56];             //保存将要循环移动到右边的位         memcpy(temp,data,time);         memcpy(temp+time,data+28,time);                  //前28位移动         memcpy(data,data+time,28-time);         memcpy(data+28-time,temp,time);             //后28位移动         memcpy(data+28,data+28+time,28-time);         memcpy(data+56-time,temp+time,time);                 return 0;     }         //IP置换     int DES_IP_Transform(ElemType data[64]){         int cnt;         ElemType temp[64];         for(cnt = 0; cnt < 64; cnt++){             temp[cnt] = data[IP_Table[cnt]];         }         memcpy(data,temp,64);         return 0;     }         //IP逆置换     int DES_IP_1_Transform(ElemType data[64]){         int cnt;         ElemType temp[64];         for(cnt = 0; cnt < 64; cnt++){             temp[cnt] = data[IP_1_Table[cnt]];         }         memcpy(data,temp,64);         return 0;     }         //扩展置换     int DES_E_Transform(ElemType data[48]){         int cnt;         ElemType temp[48];         for(cnt = 0; cnt < 48; cnt++){             temp[cnt] = data[E_Table[cnt]];         }            memcpy(data,temp,48);         return 0;     }         //P置换     int DES_P_Transform(ElemType data[32]){         int cnt;         ElemType temp[32];         for(cnt = 0; cnt < 32; cnt++){             temp[cnt] = data[P_Table[cnt]];         }            memcpy(data,temp,32);         return 0;     }         //异或     int DES_XOR(ElemType R[48], ElemType L[48] ,int count){         int cnt;         for(cnt = 0; cnt < count; cnt++){             R[cnt] ^= L[cnt];         }         return 0;     }         //S盒置换     int DES_SBOX(ElemType data[48]){         int cnt;         int line,row,output;         int cur1,cur2;         for(cnt = 0; cnt < 8; cnt++){             cur1 = cnt*6;             cur2 = cnt<<2;                          //计算在S盒中的行与列             line = (data[cur1]<<1) + data[cur1+5];             row = (data[cur1+1]<<3) + (data[cur1+2]<<2)                 + (data[cur1+3]<<1) + data[cur1+4];             output = S[cnt][line][row];                 //化为2进制             data[cur2] = (output&0X08)>>3;             data[cur2+1] = (output&0X04)>>2;             data[cur2+2] = (output&0X02)>>1;             data[cur2+3] = output&0x01;         }            return 0;     }         //交换     int DES_Swap(ElemType left[32], ElemType right[32]){         ElemType temp[32];         memcpy(temp,left,32);            memcpy(left,right,32);           memcpy(right,temp,32);         return 0;     }         //加密单个分组     int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]){         ElemType plainBits[64];         ElemType copyRight[48];         int cnt;             Char8ToBit64(plainBlock,plainBits);              //初始置换(IP置换)         DES_IP_Transform(plainBits);             //16轮迭代         for(cnt = 0; cnt < 16; cnt++){                    memcpy(copyRight,plainBits+32,32);             //将右半部分进行扩展置换,从32位扩展到48位             DES_E_Transform(copyRight);             //将右半部分与子密钥进行异或操作             DES_XOR(copyRight,subKeys[cnt],48);              //异或结果进入S盒,输出32位结果             DES_SBOX(copyRight);             //P置换             DES_P_Transform(copyRight);             //将明文左半部分与右半部分进行异或             DES_XOR(plainBits,copyRight,32);             if(cnt != 15){                 //最终完成左右部的交换                 DES_Swap(plainBits,plainBits+32);             }         }         //逆初始置换(IP^1置换)         DES_IP_1_Transform(plainBits);         Bit64ToChar8(plainBits,cipherBlock);         return 0;     }         //解密单个分组     int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48],ElemType plainBlock[8]){         ElemType cipherBits[64];         ElemType copyRight[48];         int cnt;             Char8ToBit64(cipherBlock,cipherBits);                //初始置换(IP置换)         DES_IP_Transform(cipherBits);                  //16轮迭代         for(cnt = 15; cnt >= 0; cnt--){                   memcpy(copyRight,cipherBits+32,32);             //将右半部分进行扩展置换,从32位扩展到48位             DES_E_Transform(copyRight);             //将右半部分与子密钥进行异或操作             DES_XOR(copyRight,subKeys[cnt],48);                  //异或结果进入S盒,输出32位结果             DES_SBOX(copyRight);             //P置换             DES_P_Transform(copyRight);                  //将明文左半部分与右半部分进行异或             DES_XOR(cipherBits,copyRight,32);             if(cnt != 0){                 //最终完成左右部的交换                 DES_Swap(cipherBits,cipherBits+32);             }         }         //逆初始置换(IP^1置换)         DES_IP_1_Transform(cipherBits);         Bit64ToChar8(cipherBits,plainBlock);         return 0;     }         //加密文件     int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile){         FILE *plain,*cipher;         int count;         ElemType plainBlock[8],cipherBlock[8],keyBlock[8];         ElemType bKey[64];         ElemType subKeys[16][48];         if((plain = fopen(plainFile,"rb")) == NULL){             return PLAIN_FILE_OPEN_ERROR;         }            if((cipher = fopen(cipherFile,"wb")) == NULL){             return CIPHER_FILE_OPEN_ERROR;         }         //设置密钥         memcpy(keyBlock,keyStr,8);         //将密钥转换为二进制流         Char8ToBit64(keyBlock,bKey);         //生成子密钥         DES_MakeSubKeys(bKey,subKeys);                  while(!feof(plain)){             //每次读8个字节,并返回成功读取的字节数             if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){                 DES_EncryptBlock(plainBlock,subKeys,cipherBlock);                 fwrite(cipherBlock,sizeof(char),8,cipher);               }         }         if(count){             //填充             memset(plainBlock + count,'\0',7 - count);             //最后一个字符保存包括最后一个字符在内的所填充的字符数量             plainBlock[7] = 8 - count;             DES_EncryptBlock(plainBlock,subKeys,cipherBlock);             fwrite(cipherBlock,sizeof(char),8,cipher);         }         fclose(plain);         fclose(cipher);         return OK;     }         //解密文件     int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile){         FILE *plain, *cipher;         int count,times = 0;         long fileLen;         ElemType plainBlock[8],cipherBlock[8],keyBlock[8];         ElemType bKey[64];         ElemType subKeys[16][48];         if((cipher = fopen(cipherFile,"rb")) == NULL){             return CIPHER_FILE_OPEN_ERROR;         }         if((plain = fopen(plainFile,"wb")) == NULL){             return PLAIN_FILE_OPEN_ERROR;         }             //设置密钥         memcpy(keyBlock,keyStr,8);         //将密钥转换为二进制流         Char8ToBit64(keyBlock,bKey);         //生成子密钥         DES_MakeSubKeys(bKey,subKeys);             //取文件长度          fseek(cipher,0,SEEK_END);   //将文件指针置尾         fileLen = ftell(cipher);    //取文件指针当前位置         rewind(cipher);             //将文件指针重指向文件头         while(1){             //密文的字节数一定是8的整数倍             fread(cipherBlock,sizeof(char),8,cipher);             DES_DecryptBlock(cipherBlock,subKeys,plainBlock);                                    times += 8;             if(times < fileLen){                 fwrite(plainBlock,sizeof(char),8,plain);             }             else{                 break;             }         }         //判断末尾是否被填充         if(plainBlock[7] < 8){             for(count = 8 - plainBlock[7]; count < 7; count++){                 if(plainBlock[count] != '\0'){                     break;                 }             }         }            if(count == 7){//有填充             fwrite(plainBlock,sizeof(char),8 - plainBlock[7],plain);         }         else{//无填充             fwrite(plainBlock,sizeof(char),8,plain);         }             fclose(plain);         fclose(cipher);         return OK;     }      //字节转换成二进制  int ByteToBit(ElemType ch, ElemType bit[8]){   int cnt;   for(cnt = 0;cnt < 8; cnt++){    *(bit+cnt) = (ch>>cnt)&1;   }   return 0;  }    //二进制转换成字节  int BitToByte(ElemType bit[8],ElemType *ch){   int cnt;   for(cnt = 0;cnt < 8; cnt++){    *ch |= *(bit + cnt)<<cnt;   }   return 0;  }    //将长度为8的字符串转为二进制位串  int Char8ToBit64(ElemType ch[8],ElemType bit[64]){   int cnt;   for(cnt = 0; cnt < 8; cnt++){      ByteToBit(*(ch+cnt),bit+(cnt<<3));   }   return 0;  }    //将二进制位串转为长度为8的字符串  int Bit64ToChar8(ElemType bit[64],ElemType ch[8]){   int cnt;   memset(ch,0,8);   for(cnt = 0; cnt < 8; cnt++){    BitToByte(bit+(cnt<<3),ch+cnt);   }   return 0;  }    //生成子密钥  int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]){   ElemType temp[56];   int cnt;   DES_PC1_Transform(key,temp);//PC1置换   for(cnt = 0; cnt < 16; cnt++){//16轮跌代,产生16个子密钥    DES_ROL(temp,MOVE_TIMES[cnt]);//循环左移    DES_PC2_Transform(temp,subKeys[cnt]);//PC2置换,产生子密钥   }   return 0;  }    //密钥置换1  int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]){   int cnt;    for(cnt = 0; cnt < 56; cnt++){    tempbts[cnt] = key[PC_1[cnt]];   }   return 0;  }    //密钥置换2  int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]){   int cnt;   for(cnt = 0; cnt < 48; cnt++){    tempbts[cnt] = key[PC_2[cnt]];   }   return 0;  }    //循环左移  int DES_ROL(ElemType data[56], int time){    ElemType temp[56];     //保存将要循环移动到右边的位   memcpy(temp,data,time);   memcpy(temp+time,data+28,time);      //前28位移动   memcpy(data,data+time,28-time);   memcpy(data+28-time,temp,time);     //后28位移动   memcpy(data+28,data+28+time,28-time);   memcpy(data+56-time,temp+time,time);      return 0;  }    //IP置换  int DES_IP_Transform(ElemType data[64]){   int cnt;   ElemType temp[64];   for(cnt = 0; cnt < 64; cnt++){    temp[cnt] = data[IP_Table[cnt]];   }   memcpy(data,temp,64);   return 0;  }    //IP逆置换  int DES_IP_1_Transform(ElemType data[64]){   int cnt;   ElemType temp[64];   for(cnt = 0; cnt < 64; cnt++){    temp[cnt] = data[IP_1_Table[cnt]];   }   memcpy(data,temp,64);   return 0;  }    //扩展置换  int DES_E_Transform(ElemType data[48]){   int cnt;   ElemType temp[48];   for(cnt = 0; cnt < 48; cnt++){    temp[cnt] = data[E_Table[cnt]];   }    memcpy(data,temp,48);   return 0;  }    //P置换  int DES_P_Transform(ElemType data[32]){   int cnt;   ElemType temp[32];   for(cnt = 0; cnt < 32; cnt++){    temp[cnt] = data[P_Table[cnt]];   }    memcpy(data,temp,32);   return 0;  }    //异或  int DES_XOR(ElemType R[48], ElemType L[48] ,int count){   int cnt;   for(cnt = 0; cnt < count; cnt++){    R[cnt] ^= L[cnt];   }   return 0;  }    //S盒置换  int DES_SBOX(ElemType data[48]){   int cnt;   int line,row,output;   int cur1,cur2;   for(cnt = 0; cnt < 8; cnt++){    cur1 = cnt*6;    cur2 = cnt<<2;        //计算在S盒中的行与列    line = (data[cur1]<<1) + data[cur1+5];    row = (data[cur1+1]<<3) + (data[cur1+2]<<2)     + (data[cur1+3]<<1) + data[cur1+4];    output = S[cnt][line][row];      //化为2进制    data[cur2] = (output&0X08)>>3;    data[cur2+1] = (output&0X04)>>2;    data[cur2+2] = (output&0X02)>>1;    data[cur2+3] = output&0x01;   }    return 0;  }    //交换  int DES_Swap(ElemType left[32], ElemType right[32]){   ElemType temp[32];   memcpy(temp,left,32);    memcpy(left,right,32);    memcpy(right,temp,32);   return 0;  }    //加密单个分组  int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]){   ElemType plainBits[64];   ElemType copyRight[48];   int cnt;     Char8ToBit64(plainBlock,plainBits);     //初始置换(IP置换)   DES_IP_Transform(plainBits);     //16轮迭代   for(cnt = 0; cnt < 16; cnt++){      memcpy(copyRight,plainBits+32,32);    //将右半部分进行扩展置换,从32位扩展到48位    DES_E_Transform(copyRight);    //将右半部分与子密钥进行异或操作    DES_XOR(copyRight,subKeys[cnt],48);     //异或结果进入S盒,输出32位结果    DES_SBOX(copyRight);    //P置换    DES_P_Transform(copyRight);    //将明文左半部分与右半部分进行异或    DES_XOR(plainBits,copyRight,32);    if(cnt != 15){     //最终完成左右部的交换     DES_Swap(plainBits,plainBits+32);    }   }   //逆初始置换(IP^1置换)   DES_IP_1_Transform(plainBits);   Bit64ToChar8(plainBits,cipherBlock);   return 0;  }    //解密单个分组  int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48],ElemType plainBlock[8]){   ElemType cipherBits[64];   ElemType copyRight[48];   int cnt;     Char8ToBit64(cipherBlock,cipherBits);     //初始置换(IP置换)   DES_IP_Transform(cipherBits);      //16轮迭代   for(cnt = 15; cnt >= 0; cnt--){      memcpy(copyRight,cipherBits+32,32);    //将右半部分进行扩展置换,从32位扩展到48位    DES_E_Transform(copyRight);    //将右半部分与子密钥进行异或操作    DES_XOR(copyRight,subKeys[cnt],48);      //异或结果进入S盒,输出32位结果    DES_SBOX(copyRight);    //P置换    DES_P_Transform(copyRight);      //将明文左半部分与右半部分进行异或    DES_XOR(cipherBits,copyRight,32);    if(cnt != 0){     //最终完成左右部的交换     DES_Swap(cipherBits,cipherBits+32);    }   }   //逆初始置换(IP^1置换)   DES_IP_1_Transform(cipherBits);   Bit64ToChar8(cipherBits,plainBlock);   return 0;  }    //加密文件  int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile){   FILE *plain,*cipher;   int count;   ElemType plainBlock[8],cipherBlock[8],keyBlock[8];   ElemType bKey[64];   ElemType subKeys[16][48];   if((plain = fopen(plainFile,"rb")) == NULL){    return PLAIN_FILE_OPEN_ERROR;   }    if((cipher = fopen(cipherFile,"wb")) == NULL){    return CIPHER_FILE_OPEN_ERROR;   }   //设置密钥   memcpy(keyBlock,keyStr,8);   //将密钥转换为二进制流   Char8ToBit64(keyBlock,bKey);   //生成子密钥   DES_MakeSubKeys(bKey,subKeys);      while(!feof(plain)){    //每次读8个字节,并返回成功读取的字节数    if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){     DES_EncryptBlock(plainBlock,subKeys,cipherBlock);     fwrite(cipherBlock,sizeof(char),8,cipher);     }   }   if(count){    //填充    memset(plainBlock + count,'\0',7 - count);    //最后一个字符保存包括最后一个字符在内的所填充的字符数量    plainBlock[7] = 8 - count;    DES_EncryptBlock(plainBlock,subKeys,cipherBlock);    fwrite(cipherBlock,sizeof(char),8,cipher);   }   fclose(plain);   fclose(cipher);   return OK;  }    //解密文件  int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile){   FILE *plain, *cipher;   int count,times = 0;   long fileLen;   ElemType plainBlock[8],cipherBlock[8],keyBlock[8];   ElemType bKey[64];   ElemType subKeys[16][48];   if((cipher = fopen(cipherFile,"rb")) == NULL){    return CIPHER_FILE_OPEN_ERROR;   }   if((plain = fopen(plainFile,"wb")) == NULL){    return PLAIN_FILE_OPEN_ERROR;   }     //设置密钥   memcpy(keyBlock,keyStr,8);   //将密钥转换为二进制流   Char8ToBit64(keyBlock,bKey);   //生成子密钥   DES_MakeSubKeys(bKey,subKeys);     //取文件长度    fseek(cipher,0,SEEK_END); //将文件指针置尾   fileLen = ftell(cipher); //取文件指针当前位置   rewind(cipher);    //将文件指针重指向文件头   while(1){    //密文的字节数一定是8的整数倍    fread(cipherBlock,sizeof(char),8,cipher);    DES_DecryptBlock(cipherBlock,subKeys,plainBlock);          times += 8;    if(times < fileLen){     fwrite(plainBlock,sizeof(char),8,plain);    }    else{     break;    }   }   //判断末尾是否被填充   if(plainBlock[7] < 8){    for(count = 8 - plainBlock[7]; count < 7; count++){     if(plainBlock[count] != '\0'){      break;     }    }   }    if(count == 7){//有填充    fwrite(plainBlock,sizeof(char),8 - plainBlock[7],plain);   }   else{//无填充    fwrite(plainBlock,sizeof(char),8,plain);   }     fclose(plain);   fclose(cipher);   return OK;  }    最后,写一个简单的main函数来检验它:        C代码   int main()     {            clock_t a,b;         a = clock();         DES_Encrypt("1.txt","key.txt","2.txt");         b = clock();         printf("加密消耗%d毫秒\n",b-a);                  system("pause");         a = clock();         DES_Decrypt("2.txt","key.txt","3.txt");         b = clock();         printf("解密消耗%d毫秒\n",b-a);         getchar();         return 0;     }

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来自: http://www.cnblogs.com/chars/p/4984269.html