DES是一个分组加密算法，它以64位为分组对数据加密。同时DES也是一个对称算法：加密和解密用的是同一个算法。DES是一个包含16个阶段的“替换--置换”的分组加密算法，64位的分组明文序列作为加密算法的输入，经过16轮加密得到64位的密文序列。 理论的概述总是枯燥的，而且也不好描述，直接上图，算法原理看下图：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
原理浅析
DES算法主要分为3部分：加解密运算、f函数的处理、轮子密钥的生成，从右往左分别简单介绍一下。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
轮子密钥的生成
数据表1文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
//PC-1
private int[] PC1={57,49,41,33,25,17,9,
1,58,50,42,34,26,18,
10,2,59,51,43,35,27,
19,11,3,60,52,44,36,
63,55,47,39,31,23,15,
7,62,54,46,38,30,22,
14,6,61,53,45,37,29,
21,13,5,28,20,12,4};
//PC-2
private int[] PC2={14,17,11,24,1,5,3,28,
15,6,21,10,23,19,12,4,
26,8,16,7,27,20,13,2,
41,52,31,37,47,55,30,40,
51,45,33,48,44,49,39,56,
34,53,46,42,50,36,29,32};
//Schedule of Left Shifts
private int[] LFT={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};
复制代码16个子密钥的生成主要是利用了数据表1中的数表，首先将64位的初始密钥利用PC1压缩置换位56位的密钥，然后将其一分为二，这里记为C0和D0。这里28位的C0和28位的D0分别根据LET数组相应位置的值进行左移位得到C1和D1。这是将C1和D1合并根据PC2进行压缩置换得到48位的子密钥，而且注意C1和D1作为下轮的输入以用来产生下一个子密钥。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
f函数的运算
数据表2文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
//E扩展
private int[] E={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};
//P置换
private int[] P={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};
private static final int[][][] S_Box = {//S-盒
{// S_Box[1]
{ 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 } },
{ // S_Box[2]
{ 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 } },
{ // S_Box[3]
{ 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 } },
{ // S_Box[4]
{ 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 } },
{ // S_Box[5]
{ 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 } },
{ // S_Box[6]
{ 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 } },
{ // S_Box[7]
{ 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 } },
{ // S_Box[8]
{ 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 } }
};
复制代码从原理图中可以看到，f函数的输入是明文分组的右半分组记为R和子密钥记为K。32位的R首先要利用数据表2中的E进行E盒扩展变换得到48位的数据，这里记为RE。然后将RE与K进行异或运算并将异或结果利用数据表2中的S_BOX进行S盒替换，得到48位的运算结果记为RS。再将RS利用数据表2中的P进行P盒替换，得到32位的最终结果，记为RF。到这里f函数的运算任务就完成了。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
加解密运算
//初始置换
private int[] IP={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};
//逆初始置换
private int[] IP_1={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};
复制代码关于IP和IP-1 的置换运算就不说了，我只要说一下一轮的加密过程，在第一轮中将64位的明文分为L0和R0,则加密运算如下：
L1=R0
R1=L0⊕f(R0,K0)
然后按此公式进行16轮的运算。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
代码实现
package com.general.encryanddecode;
import org.omg.PortableInterceptor.SYSTEM_EXCEPTION;
import java.util.Arrays;
/**
* @author generalandroid
*
* 根据DES算法原理实现DES加密算法，主要是为了更加深入地理解DES算法
* **/
public class CustomDES {
//初始置换
private int[] IP={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};
//逆初始置换
private int[] IP_1={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};//手残，数组数据没写全
//E扩展
private int[] E={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};
//P置换
private int[] P={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};
private static final int[][][] S_Box = {
{
{ 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 } },
{
{ 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 } },
{
{ 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 } },
{
{ 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 } },
{
{ 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 } },
{
{ 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 } },
{
{ 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 } },
{
{ 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 } }
};
//PC-1
private int[] PC1={57,49,41,33,25,17,9,
1,58,50,42,34,26,18,
10,2,59,51,43,35,27,
19,11,3,60,52,44,36,
63,55,47,39,31,23,15,
7,62,54,46,38,30,22,
14,6,61,53,45,37,29,
21,13,5,28,20,12,4};
//PC-2
private int[] PC2={14,17,11,24,1,5,3,28,
15,6,21,10,23,19,12,4,
26,8,16,7,27,20,13,2,
41,52,31,37,47,55,30,40,
51,45,33,48,44,49,39,56,
34,53,46,42,50,36,29,32};
//Schedule of Left Shifts
private int[] LFT={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};
/**加密轮数**/
private static final int LOOP_NUM=16;
private String [] keys=new String[LOOP_NUM];
private String [] pContent;
private String [] cContent;
private int origin_length;
/**16个子密钥**/
private int[][] sub_key=new int[16][48];
private String content;
private int p_origin_length;
public CustomDES(String key,String content){
this.content=content;
p_origin_length=content.getBytes().length;
generateKeys(key);
}
public static void main(String[] args){
String origin="Android将军->GeneralAndroid->主博客地址：https://blog.csdn.net/android_jiangjun";
System.out.println("原文：\n"+origin);
CustomDES customDES=new CustomDES("密码学专栏",origin);
byte[] c=customDES.deal(origin.getBytes(),1);
System.out.println("密文：\n"+new String(c));
byte[]p=customDES.deal(c,0);
byte[] p_d=new byte[origin.getBytes().length];
System.arraycopy(p,0,p_d,0,origin.getBytes().length);
System.out.println("明文：\n"+new String(p));
}
/***代码运行结果：
*
原文：
Android将军->GeneralAndroid->主博客地址：https://blog.csdn.net/android_jiangjun
密文：
��Lm����=��� 4�zf4�����zj� ��}���~Dͪn�B��t���Du��U*e �VxC�̃Ynh\@NH ˙P�Ka�1y~4
明文：
Android将军->GeneralAndroid->主博客地址：https://blog.csdn.net/android_jiangjun
*
* **/
/****拆分分组****/
public byte[] deal(byte[] p ,int flag){
origin_length=p.length;
int g_num;
int r_num;
g_num=origin_length/8;
r_num=8-(origin_length-g_num*8);//8不填充
byte[] p_padding;
/****填充********/
if (r_num<8){
p_padding=new byte[origin_length+r_num];
System.arraycopy(p,0,p_padding,0,origin_length);
for(int i=0;i<r_num;i++){
p_padding[origin_length+i]=(byte)r_num;
}
}else{
p_padding=p;
}
g_num=p_padding.length/8;
byte[] f_p=new byte[8];
byte[] result_data=new byte[p_padding.length];
for(int i=0;i<g_num;i++){
System.arraycopy(p_padding,i*8,f_p,0,8);
System.arraycopy(descryUnit(f_p,sub_key,flag),0,result_data,i*8,8);
}
if (flag==0){//解密
byte[] p_result_data=new byte[p_origin_length];
System.arraycopy(result_data,0,p_result_data,0,p_origin_length);
return p_result_data;
}
return result_data;
}
/**加密**/
public byte[] descryUnit(byte[] p,int k[][],int flag){
int[] p_bit=new int[64];
StringBuilder stringBuilder=new StringBuilder();
for(int i=0;i<8;i++){
String p_b=Integer.toBinaryString(p[i]&0xff);
while (p_b.length()%8!=0){
p_b="0"+p_b;
}
stringBuilder.append(p_b);
}
String p_str=stringBuilder.toString();
for(int i=0;i<64;i++){
int p_t=Integer.valueOf(p_str.charAt(i));
if(p_t==48){
p_t=0;
}else if(p_t==49){
p_t=1;
}else{
System.out.println("To bit error!");
}
p_bit[i]=p_t;
}
/***IP置换***/
int [] p_IP=new int[64];
for (int i=0;i<64;i++){
p_IP[i]=p_bit[IP[i]-1];
}
if (flag == 1) { // 加密
for (int i = 0; i < 16; i++) {
L(p_IP, i, flag, k[i]);
}
} else if (flag == 0) { // 解密
for (int i = 15; i > -1; i--) {
L(p_IP, i, flag, k[i]);
}
}
int[] c=new int[64];
for(int i=0;i<IP_1.length;i++){
c[i]=p_IP[IP_1[i]-1];
}
byte[] c_byte=new byte[8];
for(int i=0;i<8;i++){
c_byte[i]=(byte) ((c[8*i]<<7)+(c[8*i+1]<<6)+(c[8*i+2]<<5)+(c[8*i+3]<<4)+(c[8*i+4]<<3)+(c[8*i+5]<<2)+(c[8*i+6]<<1)+(c[8*i+7]));
}
return c_byte;
}
public void L(int[] M, int times, int flag, int[] keyarray){
int[] L0=new int[32];
int[] R0=new int[32];
int[] L1=new int[32];
int[] R1=new int[32];
int[] f=new int[32];
System.arraycopy(M,0,L0,0,32);
System.arraycopy(M,32,R0,0,32);
L1=R0;
f=fFuction(R0,keyarray);
for(int j=0;j<32;j++){
R1[j]=L0[j]^f[j];
if (((flag == 0) && (times == 0)) || ((flag == 1) && (times == 15))) {
M[j] = R1[j];
M[j + 32] = L1[j];
}
else {
M[j] = L1[j];
M[j + 32] = R1[j];
}
}
}
public int[] fFuction(int [] r_content,int [] key){
int[] result=new int[32];
int[] e_k=new int[48];
for(int i=0;i<E.length;i++){
e_k[i]=r_content[E[i]-1]^key[i];
}
/********S盒替换:由48位变32位，现分割e_k，然后再进行替换*********/
int[][] s=new int[8][6];
int[]s_after=new int[32];
for(int i=0;i<8;i++){
System.arraycopy(e_k,i*6,s[i],0,6);
int r=(s[i][0]<<1)+ s[i][5];//横坐标
int c=(s[i][1]<<3)+(s[i][2]<<2)+(s[i][3]<<1)+s[i][4];//纵坐标
String str=Integer.toBinaryString(S_Box[i][r][c]);
while (str.length()<4){
str="0"+str;
}
for(int j=0;j<4;j++){
int p=Integer.valueOf(str.charAt(j));
if(p==48){
p=0;
}else if(p==49){
p=1;
}else{
System.out.println("To bit error!");
}
s_after[4*i+j]=p;
}
}
/******S盒替换结束*******/
/****P盒替代****/
for(int i=0;i<P.length;i++){
result[i]=s_after[P[i]-1];
}
return result;
}
/**生成子密钥**/
public void generateKeys(String key){
while (key.length()<8){
key=key+key;
}
key=key.substring(0,8);
byte[] keys=key.getBytes();
int[] k_bit=new int[64];
//取位值
for(int i=0;i<8;i++){
String k_str=Integer.toBinaryString(keys[i]&0xff);
if(k_str.length()<8){
for(int t=0;t<8-k_str.length();t++){
k_str="0"+k_str;
}
}
for(int j=0;j<8;j++){
int p=Integer.valueOf(k_str.charAt(j));
if(p==48){
p=0;
}else if(p==49){
p=1;
}else{
System.out.println("To bit error!");
}
k_bit[i*8+j]=p;
}
}
//k_bit是初始的64位长密钥，下一步开始进行替换
/***********PC-1压缩****************/
int [] k_new_bit=new int[56];
for(int i=0;i<PC1.length;i++){
k_new_bit[i]=k_bit[PC1[i]-1];/////这个减1注意点
}
/**************************/
int[] c0=new int[28];
int[] d0=new int[28];
System.arraycopy(k_new_bit,0,c0,0,28);
System.arraycopy(k_new_bit,28,d0,0,28);
for(int i=0;i<16;i++){
int[] c1=new int[28];
int[] d1=new int[28];
if(LFT[i]==1){
System.arraycopy(c0,1,c1,0,27);
c1[27]=c0[0];
System.arraycopy(d0,1,d1,0,27);
d1[27]=d0[0];
}else if(LFT[i]==2){
System.arraycopy(c0,2,c1,0,26);
c1[26]=c0[0];
c1[27]=c0[1];//这里手残之前写成c1
System.arraycopy(d0,2,d1,0,26);
d1[26]=d0[0];
d1[27]=d0[1];
}else{
System.out.println("LFT Error!");
}
int[] tmp=new int[56];
System.arraycopy(c1,0,tmp,0,28);
System.arraycopy(d1,0,tmp,28,28);
for (int j=0;j<PC2.length;j++){//PC2压缩置换
sub_key[i][j]= tmp[PC2[j]-1];
}
c0=c1;
d0=d1;
}
}
}
复制代码总结
关于DES算法原理要是想弄懂不是一篇文章就可以搞清楚的，首先你要去找一本书看下DES的介绍，然后弄懂每个步骤，然后写代码实现一个简单的DES算法。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html
作者：GeneralAndroid文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/4963.html