📄 des算法详述.htm
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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：<br>
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：<br>
58,50,12,34,26,18,10,2,60,52,44,36,28,20,12,4,<br>
62,54,46,38,30,22,14,6,64,56,48,40,32,24,16,8,<br>
57,49,41,33,25,17, 9,1,59,51,43,35,27,19,11,3,<br>
61,53,45,37,29,21,13,5,63,55,47,39,31,23,15,7,<br>
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。<br>
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：<br>
40,8,48,16,56,24,64,32,39,7,47,15,55,23,63,31,<br>
38,6,46,14,54,22,62,30,37,5,45,13,53,21,61,29,<br>
36,4,44,12,52,20,60,28,35,3,43,11,51,19,59,27,<br>
34,2,42,10,50,18,58 26,33,1,41, 9,49,17,57,25,<br>
放大换位表<br>
32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10,11,<br>
12,13,12,13,14,15,16,17,16,17,18,19,20,21,20,21,<br>
22,23,24,25,24,25,26,27,28,29,28,29,30,31,32, 1,<br>
单纯换位表<br>
16,7,20,21,29,12,28,17, 1,15,23,26, 5,18,31,10,<br>
2,8,24,14,32,27, 3, 9,19,13,30, 6,22,11, 4,25,<br>
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......8)的功能表：<br>
选择函数Si<br>
S1:<br>
14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7,<br>
0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8,<br>
4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0,<br>
15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13,<br>
S2:<br>
15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10,<br>
3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5,<br>
0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15,<br>
13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9,<br>
S3:<br>
10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8,<br>
13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1,<br>
13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7,<br>
1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12,<br>
S4:<br>
7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15,<br>
13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9,<br>
10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4,<br>
3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14,<br>
S5:<br>
2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9,<br>
14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6,<br>
4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14,<br>
11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3,<br>
S6:<br>
12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11,<br>
10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8,<br>
9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6,<br>
4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13,<br>
S7:<br>
4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1,<br>
13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6,<br>
1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2,<br>
6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12,<br>
S8:<br>
13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7,<br>
1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2,<br>
7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8,<br>
2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11,<br>
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。<br>
现设输入为： D＝D1D2D3D4D5D6<br>
令：列＝D2D3D4D5<br>
行＝D1D6<br>
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<br>
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：<br>
循环左移位数<br>
1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1<br>
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。<br>
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DES 算法网络上很多，给你们一个<br>
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/* ================================================================<br>
des()<br>
Description: DES algorithm,do encript or descript.<br>
================================================================ */<br>
int des(unsigned char *source,unsigned char * dest,unsigned char * inkey,
int flg)<br>
{<br>
unsigned char bufout[64],<br>
kwork[56], worka[48], kn[48], buffer[64], key[64],<br>
nbrofshift, temp1, temp2;<br>
int valindex;<br>
register i, j, k, iter;<br>
<br>
/* INITIALIZE THE TABLES */<br>
/* Table - s1 */<br>
static unsigned char s1[4][16] = {<br>
14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,<br>
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,<br>
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,<br>
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 };<br>
<br>
/* Table - s2 */<br>
static unsigned char s2[4][16] = {<br>
15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,<br>
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,<br>
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,<br>
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 };<br>
<br>
/* Table - s3 */<br>
static unsigned char s3[4][16] = {<br>
10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,<br>
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,<br>
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,<br>
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 };<br>
<br>
/* Table - s4 */<br>
static unsigned char s4[4][16] = {<br>
7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,<br>
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,<br>
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,<br>
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 };<br>
<br>
/* Table - s5 */<br>
static unsigned char s5[4][16] = {<br>
2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,<br>
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,<br>
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,<br>
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 };<br>
<br>
/* Table - s6 */<br>
static unsigned char s6[4][16] = {<br>
12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,<br>
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,<br>
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,<br>
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 };<br>
<br>
/* Table - s7 */<br>
static unsigned char s7[4][16] = {<br>
4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,<br>
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,<br>
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,<br>
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 };<br>
<br>
/* Table - s8 */<br>
static unsigned char s8[4][16] = {<br>
13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,<br>
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,<br>
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,<br>
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 };<br>
<br>
<br>
/* Table - Shift */<br>
static unsigned char shift[16] = {<br>
1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };<br>
<br>
<br>
/* Table - Binary */<br>
static unsigned char binary[64] = {<br>
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1,<br>
0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1,<br>
1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1,<br>
1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1 };<br>
<br>
/* MAIN PROCESS */<br>
/* Convert from 64-bit key into 64-byte key */<br>
for (i = 0; i < 8; i++) {<br>
key[8*i] = ((j = *(inkey + i)) / 128) % 2;<br>
key[8*i+1] = (j / 64) % 2;<br>
key[8*i+2] = (j / 32) % 2;<br>
key[8*i+3] = (j / 16) % 2;<br>
key[8*i+4] = (j / 8) % 2;<br>
key[8*i+5] = (j / 4) % 2;<br>
key[8*i+6] = (j / 2) % 2;<br>
key[8*i+7] = j % 2;<br>
}<br>
<br>
/* Convert from 64-bit data into 64-byte data */<br>
for (i = 0; i < 8; i++) {<br>
buffer[8*i] = ((j = *(source + i)) / 128) % 2;<br>
buffer[8*i+1] = (j / 64) % 2;<br>
buffer[8*i+2] = (j / 32) % 2;<br>
buffer[8*i+3] = (j / 16) % 2;<br>
buffer[8*i+4] = (j / 8) % 2;<br>
buffer[8*i+5] = (j / 4) % 2;<br>
buffer[8*i+6] = (j / 2) % 2;<br>
buffer[8*i+7] = j % 2;<br>
}<br>
<br>
/* Initial Permutation of Data */<br>
bufout[ 0] = buffer[57];<br>
bufout[ 1] = buffer[49];<br>
bufout[ 2] = buffer[41];<br>
bufout[ 3] = buffer[33];<br>
bufout[ 4] = buffer[25];<br>
bufout[ 5] = buffer[17];<br>
bufout[ 6] = buffer[ 9];<br>
bufout[ 7] = buffer[ 1];<br>
bufout[ 8] = buffer[59];<br>
bufout[ 9] = buffer[51];<br>
bufout[10] = buffer[43];<br>
bufout[11] = buffer[35];<br>
bufout[12] = buffer[27];<br>
bufout[13] = buffer[19];<br>
bufout[14] = buffer[11];<br>
bufout[15] = buffer[ 3];<br>
bufout[16] = buffer[61];<br>
bufout[17] = buffer[53];<br>
bufout[18] = buffer[45];<br>
bufout[19] = buffer[37];<br>
bufout[20] = buffer[29];<br>
bufout[21] = buffer[21];<br>
bufout[22] = buffer[13];<br>
bufout[23] = buffer[ 5];<br>
bufout[24] = buffer[63];<br>
bufout[25] = buffer[55];<br>
bufout[26] = buffer[47];<br>
bufout[27] = buffer[39];<br>
bufout[28] = buffer[31];<br>
bufout[29] = buffer[23];<br>
bufout[30] = buffer[15];<br>
bufout[31] = buffer[ 7];<br>
bufout[32] = buffer[56];<br>
bufout[33] = buffer[48];<br>
bufout[34] = buffer[40];<br>
bufout[35] = buffer[32];<br>
bufout[36] = buffer[24];<br>
bufout[37] = buffer[16];<br>
bufout[38] = buffer[ 8];<br>
bufout[39] = buffer[ 0];<br>
bufout[40] = buffer[58];<br>
bufout[41] = buffer[50];<br>
bufout[42] = buffer[42];<br>
bufout[43] = buffer[34];<br>
bufout[44] = buffer[26];<br>
bufout[45] = buffer[18];<br>
bufout[46] = buffer[10];<br>
bufout[47] = buffer[ 2];<br>
bufout[48] = buffer[60];<br>
bufout[49] = buffer[52];<br>
bufout[50] = buffer[44];<br>
bufout[51] = buffer[36];<br>
bufout[52] = buffer[28];<br>
bufout[53] = buffer[20];<br>
bufout[54] = buffer[12];<br>
bufout[55] = buffer[ 4];<br>
bufout[56] = buffer[62];<br>
bufout[57] = buffer[54];<br>
bufout[58] = buffer[46];<br>
bufout[59] = buffer[38];<br>
bufout[60] = buffer[30];<br>
bufout[61] = buffer[22];<br>
bufout[62] = buffer[14];<br>
bufout[63] = buffer[ 6];<br>
<br>
/* Initial Permutation of Key */<br>
kwork[ 0] = key[56];<br>
kwork[ 1] = key[48];<br>
kwork[ 2] = key[40];<br>
kwork[ 3] = key[32];<br>
kwork[ 4] = key[24];<br>
kwork[ 5] = key[16];<br>
kwork[ 6] = key[ 8];<br>
kwork[ 7] = key[ 0];<br>
kwork[ 8] = key[57];<br>
kwork[ 9] = key[49];<br>
kwork[10] = key[41];<br>
kwork[11] = key[33];<br>
kwork[12] = key[25];<br>
kwork[13] = key[17];<br>
kwork[14] = key[ 9];<br>
kwork[15] = key[ 1];<br>
kwork[16] = key[58];<br>
kwork[17] = key[50];<br>
kwork[18] = key[42];<br>
kwork[19] = key[34];<br>
kwork[20] = key[26];<br>
kwork[21] = key[18];<br>
kwork[22] = key[10];<br>
kwork[23] = key[ 2];<br>
kwork[24] = key[59];<br>
kwork[25] = key[51];<br>
kwork[26] = key[43];<br>
kwork[27] = key[35];<br>
kwork[28] = key[62];<br>
kwork[29] = key[54];<br>
kwork[30] = key[46];<br>
kwork[31] = key[38];<br>
kwork[32] = key[30];<br>
kwork[33] = key[22];<br>
kwork[34] = key[14];<br>
kwork[35] = key[ 6];<br>
kwork[36] = key[61];<br>
kwork[37] = key[53];<br>
kwork[38] = key[45];<br>
kwork[39] = key[37];<br>
kwork[40] = key[29];<br>
kwork[41] = key[21];<br>
kwork[42] = key[13];<br>
kwork[43] = key[ 5];<br>
kwork[44] = key[60];<br>
kwork[45] = key[52];<br>
kwork[46] = key[44];<br>
kwork[47] = key[36];<br>
kwork[48] = key[28];<br>
kwork[49] = key[20];<br>
kwork[50] = key[12];<br>
kwork[51] = key[ 4];<br>
kwork[52] = key[27];<br>
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