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CatInRl/FeistelTest.java

Created May 21, 2018 09:55
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FeistelTest.java
package com.example.demo;
/**
*
*@author generalandroid
*
*Feistel密码算法
* **/
public class FeistelTest {
/**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;
public static void main(String[] args){
FeistelTest feistelTest=new FeistelTest("TEST","ABCDE");
feistelTest.encrypt();
feistelTest.decrypt();
}
public FeistelTest(String content,String key){
generateKey(key);
divideGroups(content);
System.out.println("原始明文："+content+"\n原始密钥："+key);
}
public void encrypt(){
StringBuilder c=new StringBuilder();
for(int i=0;i<pContent.length;i++){
cContent[i]=loop(pContent[i],0);
c.append(cContent[i]);
}
System.out.println("密文:\n"+c.toString());
}
public void decrypt(){
StringBuilder p=new StringBuilder();
for(int i=0;i<cContent.length;i++){
pContent[i]=loop(cContent[i],1);
p.append(pContent[i]);
}
System.out.println("明文：\n"+p.toString().substring(0,origin_length));
}
/**生成子密钥，采用简单移位操作来实现**/
public void generateKey(String key){
while (key.length()<16){
key=key+key;
}
key=key.substring(0,16);
// System.out.println("after sub key:"+key);
for(int i=0;i<16;i++){
key=swapStr(key,i);
keys[i]=key;
}
// System.out.println(Arrays.toString(keys));
}
private String swapStr(String key,int i){
char last=key.charAt(key.length()-1);
key=last+key.substring(0,key.length()-1);
// System.out.println("i:"+i+"\t key:"+key);
return key;
}
/**对明文进行分组**/
public void divideGroups(String content){
int g_num;
int m_num;
int b_num;
origin_length=content.length();
g_num=origin_length/8;
m_num=origin_length%8;
b_num=8-m_num;
// System.out.println("g_num:"+g_num+"\t m_num:"+m_num+"\t b_num:"+b_num);
if(m_num!=0){
for (int i=0;i<=b_num;i++){
content=content+b_num;
}
}
g_num=content.length()/8;
pContent=new String[g_num];
cContent=new String[g_num];
for(int i=0;i<g_num;i++){
pContent[i]=content.substring(8*i,8*(i+1));
}
// System.out.println(Arrays.toString(pContent));
}
/**轮加密与解密**/
public String loop(String content,int flag){
if(flag==0){
for(int i=0;i<16;i++){
content=f(i,content,flag);
}
}else if(flag==1){
for(int i=15;i>-1;i--){
content=f(i,content,flag);
}
}
return content;
}
/**f函数**/
public String f(int time,String content,int flag){
if(content.length()>8){
System.out.println("ERROR!!!!!");
}
String LE=content.substring(0,4);
String RE=content.substring(4,8);
String LE1=null;
String RE1=null;
String key=keys[time];
// System.out.println("LE:"+LE+"\t RE:"+RE+"\t key:"+key);
char[] tmp=new char[4];
for(int j=0;j<4;j++){
tmp[j]=(char)(RE.charAt(j)^key.charAt(4*j)^LE.charAt(j));
}
// System.out.println("tmp re:"+Arrays.toString(tmp));
LE1=RE;
RE1=new String(tmp);
// System.out.println("time:"+time+"\t L:"+LE1+RE1+"\t key:"+key);
if (((flag == 0) && (time == 15)) || ((flag == 1) && (time == 0))) {
return RE1+LE1;
}
return LE1+RE1;
}
}
/****
* 运行结果：
*
*
原始明文：Android将军->GeneralAndroid
原始密钥：ABCDE
密文:
oAB尴ooc尀冿uehbtDXlGdthoFB@7101
明文：
Android将军->GeneralAndroid
*
* *****/
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