📄 des算法详述.htm
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<P class=p3><FONT
size=2> 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><BR><BR>DES
算法网络上很多，给你们一个<BR><BR><BR>/*
================================================================<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>kwork[53] =
key[19];<BR>kwork[54] = key[11];<BR>kwork[55] = key[ 3];<BR><BR>/* 16
Iterations */<BR>for (iter = 1; iter < 17; iter++) {<BR>for (i = 0; i
< 32; i++)<BR>buffer[i] = bufout[32+i];<BR><BR>/* Calculation of F(R,
K) */<BR>/* Permute - E */<BR>worka[ 0] = buffer[31];<BR>worka[ 1] =
buffer[ 0];<BR>worka[ 2] = buffer[ 1];<BR>worka[ 3] = buffer[
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