DES算法解析
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; }