des算法的主要流程 DES算法的原理及演讲过程
\u6c42\u6559des\u7b97\u6cd5\u7684\u8be6\u7ec6\u8fc7\u7a0b\u56fe\u4e3a\u6700\u8be6\u7ec6\u7684\u6d41\u7a0b
\u4e0b\u9644\u4e0a\u5b8c\u6574C\u7a0b\u5e8f\uff0c\u6211\u81ea\u5df1\u505a\u7684\uff0c\u4f60\u770b\u770b\u3002
#include "stdio.h"
#include "memory.h"
#include "time.h"
#include "stdlib.h"
#define PLAIN_FILE_OPEN_ERROR -1
#define KEY_FILE_OPEN_ERROR -2
#define CIPHER_FILE_OPEN_ERROR -3
#define OK 1
typedef char ElemType;
/*\u521d\u59cb\u7f6e\u6362\u8868IP*/
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};
/*\u9006\u521d\u59cb\u7f6e\u6362\u8868IP^-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};
/*\u6269\u5145\u7f6e\u6362\u8868E*/
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};
/*\u7f6e\u6362\u51fd\u6570P*/
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\u76d2*/
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}}};
/*\u7f6e\u6362\u9009\u62e91*/
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};
/*\u7f6e\u6362\u9009\u62e92*/
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};
/*\u5bf9\u5de6\u79fb\u6b21\u6570\u7684\u89c4\u5b9a*/
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);
/*\u5b57\u8282\u8f6c\u6362\u6210\u4e8c\u8fdb\u5236*/
int ByteToBit(ElemType ch, ElemType bit[8]){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*(bit+cnt) = (ch>>cnt)&1;
}
return 0;
}
/*\u4e8c\u8fdb\u5236\u8f6c\u6362\u6210\u5b57\u8282*/
int BitToByte(ElemType bit[8],ElemType *ch){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*ch |= *(bit + cnt)<<cnt;
}
return 0;
}
/*\u5c06\u957f\u5ea6\u4e3a8\u7684\u5b57\u7b26\u4e32\u8f6c\u4e3a\u4e8c\u8fdb\u5236\u4f4d\u4e32*/
int Char8ToBit64(ElemType ch[8],ElemType bit[64]){
int cnt;
for(cnt = 0; cnt < 8; cnt++){
ByteToBit(*(ch+cnt),bit+(cnt<<3));
}
return 0;
}
/*\u5c06\u4e8c\u8fdb\u5236\u4f4d\u4e32\u8f6c\u4e3a\u957f\u5ea6\u4e3a8\u7684\u5b57\u7b26\u4e32*/
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;
}
/*\u751f\u6210\u5b50\u5bc6\u94a5*/
int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]){
ElemType temp[56];
int cnt;
DES_PC1_Transform(key,temp);/*PC1\u7f6e\u6362*/
for(cnt = 0; cnt < 16; cnt++){/*16\u8f6e\u8dcc\u4ee3\uff0c\u4ea7\u751f16\u4e2a\u5b50\u5bc6\u94a5*/
DES_ROL(temp,MOVE_TIMES[cnt]);/*\u5faa\u73af\u5de6\u79fb*/
DES_PC2_Transform(temp,subKeys[cnt]);/*PC2\u7f6e\u6362\uff0c\u4ea7\u751f\u5b50\u5bc6\u94a5*/
}
return 0;
}
/*\u5bc6\u94a5\u7f6e\u63621*/
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;
}
/*\u5bc6\u94a5\u7f6e\u63622*/
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;
}
/*\u5faa\u73af\u5de6\u79fb*/
int DES_ROL(ElemType data[56], int time){
ElemType temp[56];
/*\u4fdd\u5b58\u5c06\u8981\u5faa\u73af\u79fb\u52a8\u5230\u53f3\u8fb9\u7684\u4f4d*/
memcpy(temp,data,time);
memcpy(temp+time,data+28,time);
/*\u524d28\u4f4d\u79fb\u52a8*/
memcpy(data,data+time,28-time);
memcpy(data+28-time,temp,time);
/*\u540e28\u4f4d\u79fb\u52a8*/
memcpy(data+28,data+28+time,28-time);
memcpy(data+56-time,temp+time,time);
return 0;
}
/*IP\u7f6e\u6362*/
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\u9006\u7f6e\u6362*/
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;
}
/*\u6269\u5c55\u7f6e\u6362*/
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\u7f6e\u6362*/
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;
}
/*\u5f02\u6216*/
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\u76d2\u7f6e\u6362*/
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;
/*\u8ba1\u7b97\u5728S\u76d2\u4e2d\u7684\u884c\u4e0e\u5217*/
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];
/*\u5316\u4e3a2\u8fdb\u5236*/
data[cur2] = (output&0X08)>>3;
data[cur2+1] = (output&0X04)>>2;
data[cur2+2] = (output&0X02)>>1;
data[cur2+3] = output&0x01;
}
return 0;
}
/*\u4ea4\u6362*/
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;
}
/*\u52a0\u5bc6\u5355\u4e2a\u5206\u7ec4*/
int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]){
ElemType plainBits[64];
ElemType copyRight[48];
int cnt;
Char8ToBit64(plainBlock,plainBits);
/*\u521d\u59cb\u7f6e\u6362\uff08IP\u7f6e\u6362\uff09*/
DES_IP_Transform(plainBits);
/*16\u8f6e\u8fed\u4ee3*/
for(cnt = 0; cnt < 16; cnt++){
memcpy(copyRight,plainBits+32,32);
/*\u5c06\u53f3\u534a\u90e8\u5206\u8fdb\u884c\u6269\u5c55\u7f6e\u6362\uff0c\u4ece32\u4f4d\u6269\u5c55\u523048\u4f4d*/
DES_E_Transform(copyRight);
/*\u5c06\u53f3\u534a\u90e8\u5206\u4e0e\u5b50\u5bc6\u94a5\u8fdb\u884c\u5f02\u6216\u64cd\u4f5c*/
DES_XOR(copyRight,subKeys[cnt],48);
/*\u5f02\u6216\u7ed3\u679c\u8fdb\u5165S\u76d2\uff0c\u8f93\u51fa32\u4f4d\u7ed3\u679c*/
DES_SBOX(copyRight);
/*P\u7f6e\u6362*/
DES_P_Transform(copyRight);
/*\u5c06\u660e\u6587\u5de6\u534a\u90e8\u5206\u4e0e\u53f3\u534a\u90e8\u5206\u8fdb\u884c\u5f02\u6216*/
DES_XOR(plainBits,copyRight,32);
if(cnt != 15){
/*\u6700\u7ec8\u5b8c\u6210\u5de6\u53f3\u90e8\u7684\u4ea4\u6362*/
DES_Swap(plainBits,plainBits+32);
}
}
/*\u9006\u521d\u59cb\u7f6e\u6362\uff08IP^1\u7f6e\u6362\uff09*/
DES_IP_1_Transform(plainBits);
Bit64ToChar8(plainBits,cipherBlock);
return 0;
}
/*\u89e3\u5bc6\u5355\u4e2a\u5206\u7ec4*/
int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48],ElemType plainBlock[8]){
ElemType cipherBits[64];
ElemType copyRight[48];
int cnt;
Char8ToBit64(cipherBlock,cipherBits);
/*\u521d\u59cb\u7f6e\u6362\uff08IP\u7f6e\u6362\uff09*/
DES_IP_Transform(cipherBits);
/*16\u8f6e\u8fed\u4ee3*/
for(cnt = 15; cnt >= 0; cnt--){
memcpy(copyRight,cipherBits+32,32);
/*\u5c06\u53f3\u534a\u90e8\u5206\u8fdb\u884c\u6269\u5c55\u7f6e\u6362\uff0c\u4ece32\u4f4d\u6269\u5c55\u523048\u4f4d*/
DES_E_Transform(copyRight);
/*\u5c06\u53f3\u534a\u90e8\u5206\u4e0e\u5b50\u5bc6\u94a5\u8fdb\u884c\u5f02\u6216\u64cd\u4f5c*/
DES_XOR(copyRight,subKeys[cnt],48);
/*\u5f02\u6216\u7ed3\u679c\u8fdb\u5165S\u76d2\uff0c\u8f93\u51fa32\u4f4d\u7ed3\u679c*/
DES_SBOX(copyRight);
/*P\u7f6e\u6362*/
DES_P_Transform(copyRight);
/*\u5c06\u660e\u6587\u5de6\u534a\u90e8\u5206\u4e0e\u53f3\u534a\u90e8\u5206\u8fdb\u884c\u5f02\u6216*/
DES_XOR(cipherBits,copyRight,32);
if(cnt != 0){
/*\u6700\u7ec8\u5b8c\u6210\u5de6\u53f3\u90e8\u7684\u4ea4\u6362*/
DES_Swap(cipherBits,cipherBits+32);
}
}
/*\u9006\u521d\u59cb\u7f6e\u6362\uff08IP^1\u7f6e\u6362\uff09*/
DES_IP_1_Transform(cipherBits);
Bit64ToChar8(cipherBits,plainBlock);
return 0;
}
/*\u52a0\u5bc6\u6587\u4ef6*/
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;
}
/*\u8bbe\u7f6e\u5bc6\u94a5*/
memcpy(keyBlock,keyStr,8);
/*\u5c06\u5bc6\u94a5\u8f6c\u6362\u4e3a\u4e8c\u8fdb\u5236\u6d41*/
Char8ToBit64(keyBlock,bKey);
/*\u751f\u6210\u5b50\u5bc6\u94a5*/
DES_MakeSubKeys(bKey,subKeys);
while(!feof(plain)){
/*\u6bcf\u6b21\u8bfb8\u4e2a\u5b57\u8282\uff0c\u5e76\u8fd4\u56de\u6210\u529f\u8bfb\u53d6\u7684\u5b57\u8282\u6570*/
if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
}
if(count){
/*\u586b\u5145*/
memset(plainBlock + count,'\0',7 - count);
/*\u6700\u540e\u4e00\u4e2a\u5b57\u7b26\u4fdd\u5b58\u5305\u62ec\u6700\u540e\u4e00\u4e2a\u5b57\u7b26\u5728\u5185\u7684\u6240\u586b\u5145\u7684\u5b57\u7b26\u6570\u91cf*/
plainBlock[7] = 8 - count;
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
fclose(plain);
fclose(cipher);
return OK;
}
/*\u89e3\u5bc6\u6587\u4ef6*/
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;
}
/*\u8bbe\u7f6e\u5bc6\u94a5*/
memcpy(keyBlock,keyStr,8);
/*\u5c06\u5bc6\u94a5\u8f6c\u6362\u4e3a\u4e8c\u8fdb\u5236\u6d41*/
Char8ToBit64(keyBlock,bKey);
/*\u751f\u6210\u5b50\u5bc6\u94a5*/
DES_MakeSubKeys(bKey,subKeys);
/*\u53d6\u6587\u4ef6\u957f\u5ea6 */
fseek(cipher,0,SEEK_END);/*\u5c06\u6587\u4ef6\u6307\u9488\u7f6e\u5c3e*/
fileLen = ftell(cipher); /*\u53d6\u6587\u4ef6\u6307\u9488\u5f53\u524d\u4f4d\u7f6e*/
rewind(cipher); /*\u5c06\u6587\u4ef6\u6307\u9488\u91cd\u6307\u5411\u6587\u4ef6\u5934*/
while(1){
/*\u5bc6\u6587\u7684\u5b57\u8282\u6570\u4e00\u5b9a\u662f8\u7684\u6574\u6570\u500d*/
fread(cipherBlock,sizeof(char),8,cipher);
DES_DecryptBlock(cipherBlock,subKeys,plainBlock);
times += 8;
if(times < fileLen){
fwrite(plainBlock,sizeof(char),8,plain);
}
else{
break;
}
}
/*\u5224\u65ad\u672b\u5c3e\u662f\u5426\u88ab\u586b\u5145*/
if(plainBlock[7] < 8){
for(count = 8 - plainBlock[7]; count < 7; count++){
if(plainBlock[count] != '\0'){
break;
}
}
}
if(count == 7){/*\u6709\u586b\u5145*/
fwrite(plainBlock,sizeof(char),8 - plainBlock[7],plain);
}
else{/*\u65e0\u586b\u5145*/
fwrite(plainBlock,sizeof(char),8,plain);
}
fclose(plain);
fclose(cipher);
return OK;
}
int main()
{
clock_t a,b;
a = clock();
DES_Encrypt("1.txt","key.txt","2.txt");
b = clock();
printf("\u52a0\u5bc6\u6d88\u8017%d\u6beb\u79d2\n",b-a);
system("pause");
a = clock();
DES_Decrypt("2.txt","key.txt","3.txt");
b = clock();
printf("\u89e3\u5bc6\u6d88\u8017%d\u6beb\u79d2\n",b-a);
getchar();
return 0;
}
DES\u7b97\u6cd5\u4e3a\u5bc6\u7801\u4f53\u5236\u4e2d\u7684\u5bf9\u79f0\u5bc6\u7801\u4f53\u5236\uff0c\u53c8\u88ab\u79f0\u4e3a\u7f8e\u56fd\u6570\u636e\u52a0\u5bc6\u6807\u51c6\uff0c\u662f1972\u5e74\u7f8e\u56fdIBM\u516c\u53f8\u7814\u5236\u7684\u5bf9\u79f0\u5bc6\u7801\u4f53\u5236\u52a0\u5bc6\u7b97\u6cd5\u3002 \u660e\u6587\u630964\u4f4d\u8fdb\u884c\u5206\u7ec4\uff0c\u5bc6\u94a5\u957f64\u4f4d\uff0c\u5bc6\u94a5\u4e8b\u5b9e\u4e0a\u662f56\u4f4d\u53c2\u4e0eDES\u8fd0\u7b97\uff08\u7b2c8\u300116\u300124\u300132\u300140\u300148\u300156\u300164\u4f4d\u662f\u6821\u9a8c\u4f4d\uff0c \u4f7f\u5f97\u6bcf\u4e2a\u5bc6\u94a5\u90fd\u6709\u5947\u6570\u4e2a1\uff09\u5206\u7ec4\u540e\u7684\u660e\u6587\u7ec4\u548c56\u4f4d\u7684\u5bc6\u94a5\u6309\u4f4d\u66ff\u4ee3\u6216\u4ea4\u6362\u7684\u65b9\u6cd5\u5f62\u6210\u5bc6\u6587\u7ec4\u7684\u52a0\u5bc6\u65b9\u6cd5\u3002
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：
58,50,42,34,26,18,10,2,60,52,44,36,28,20,12,4,
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,
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换的逆运算。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, 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, 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48bit数据变为32bit数据。下面给出选择函数Si(i=1,2......8）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 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。
绛旓細5)閫嗗垵濮嬬疆鎹;6)杈撳嚭銆
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