置换加密算法2

置换密码算法的原理是不改变明文字符，而是按照某一规则重新排列消息中的比特或字符顺序，才而实现明文信息的加密。置换密码有时又称为换位密码。

矩阵换位法是实现置换密码的一种常用方法。它将明文中的字母按照给定的顺序安排在一个矩阵中，然后用根据密钥提供的顺序重新组合矩阵中的字母，从而形成密文。例如，明文为attack begins at five，密钥为cipher，将明文按照每行6个字母的形式排在矩阵中，形成如下形式：

根据密钥cipher中各个字母在字母表中出现的先后顺序，给定一个置换：

由密钥cipher通过getTheMatrix方法得到f矩阵。

根据上面的置换，将原有居住中的字母按照第１列、第４裂、第５裂、第３裂、第２列、第６列的顺序排列，则有下面的形式：

这里经过了一点处理就是当输入的字母数不是密钥长度的整数倍时，在输入的备加密字符串加上几个“#”来完成补全，然后参加到加密的过程中去，从而得到如下的密文：

a siteaet

b vci #agt#knf#

其解密过程是根据密钥的字母数作为列数，将密文按照列、行的顺序写出，再根据由密钥给出的矩阵置换产生新的矩阵，从而恢复明文。

本实验中也使用了上述的测试用例，主要经过两次依据矩阵的变换，都是使用矩阵f中的下面一行中的数值所在列来替换上面一行数值表示的列的值，从而来改变起序列、完成加密。

解密中用到

groupedSource[i][j]=temp[i][secretMatrix[secretMatrix[j]]];

来完成将原来经过矩阵转变来的字符序列逆转，从而得到起加密前的矩阵。

【代码部分】

package Practice1;

import java.util.Arrays;

import java.util.Scanner;

public class ReplaceDemo {

private String sourceString = "attack begins at five";

private String keyString = "cipher";

private int[] secretMatrix;

private char groupedSource[][];

private void getSource(){//Get the source String

Scanner scan = new Scanner(System.in);

System.out.print("Please input the string what you want to encrypt:\t"); sourceString = scan.nextLine();

System.out.print("Please input the key string for you:\t");

keyString = scan.next();

}

public ReplaceDemo(){//constructor for this class

getSource();

}

private void groupSourceString(){//make groups for sourceString according by the keyString

int sourceLen = sourceString.length();

int keyLen = keyString.length();

groupedSource = new char[sourceLen/keyLen+1][keyLen];

if (sourceLen%keyLen!=0){

for (int i = 0;i < (keyLen - sourceLen%keyLen);i++){

sourceString += "#";

}

}

sourceLen = sourceString.length();

for(int i = 6,j=0;i <= sourceLen;i+=keyLen,j++){

groupedSource[j] = sourceString.substring(i-keyLen, i).toCharArray(); }

}

private void getTheMatrix(){//get the Matrix for the encrypt

char[] temp01 = keyString.toCharArray();

secretMatrix = new int[keyString.length()];

Arrays.sort(temp01);

for (int i = 0;i < keyString.length();i++){

for (int j = 0;j

if (keyString.toCharArray()[i]==temp01[j]){

secretMatrix[i] = j;

}

}

}

}

private void changeSourceMatix(){

groupSourceString();

char temp[][] = new char[groupedSource.length][keyString.length()]; for (int i = 0;i < groupedSource.length;i++){

for (int j = 0;j < keyString.length();j++){

temp[i][j] = groupedSource[i][j];

}

}//请教Java老师

for (int i = 0;i < groupedSource.length - 1;i++){

for (int j = 0;j < keyString.length();j++){

groupedSource[i][j] = temp[i][secretMatrix[j]];

}

}

}

private void getEncryptedString(){//get the matrix which will be printed. groupSourceString();

changeSourceMatix();

char temp[][] = new char[groupedSource.length][keyString.length()]; for (int i = 0;i < groupedSource.length;i++){

for (int j = 0;j < keyString.length();j++){

temp[i][j] = groupedSource[i][j];

}

}

for (int i = 0;i < groupedSource.length - 1;i++){

for (int j = 0;j < keyString.length();j++){

groupedSource[i][j] = temp[i][secretMatrix[j]];

}

}

}

public void print1(){//print the code have Encrypted

getEncryptedString();

for(int i = 0;i < keyString.length();i++){

for(int j = 0;j < groupedSource.length-1;j++){

System.out.print(groupedSource[j][i]);

}

}

System.out.println();

}

//decryption process

private void groupEncryptedString(){

int sourceLen = sourceString.length();

int keyLen = keyString.length();

char[][] temp = new char[keyLen][sourceLen/keyLen+1];

for (int i = 0;i < keyLen;i++){

temp[i] = sourceString.substring(i*sourceLen/keyLen,

(i+1)*sourceLen/keyLen).toCharArray();

}

groupedSource = new char[sourceLen/keyLen+1][keyLen];

for(int j = 0; j < sourceLen/keyLen;j++){

for (int i = 0;i < keyLen;i++){

groupedSource[j][i] = temp[i][j];

}

}

}

private void getDecryptString(){//get the matrix which will be printed. groupEncryptedString();

char temp[][] = new char[groupedSource.length][keyString.length()]; for (int i = 0;i < groupedSource.length;i++){

for (int j = 0;j < keyString.length();j++){

temp[i][j] = groupedSource[i][j];

}

}

for (int i = 0;i < groupedSource.length - 1;i++){

for (int j = 0;j < keyString.length();j++){

groupedSource[i][j] = temp[i][secretMatrix[secretMatrix[j]]];

}

}

}

public void print2(){//print the code have Encrypted

getDecryptString();

for(int j = 0;j < groupedSource.length-1;j++){

for(int i = 0;i < keyString.length();i++){

System.out.print(groupedSource[j][i]);

}

}

System.out.println();

}

public static void main(String args[]){

ReplaceDemo RD = null;

Scanner scanin = null;

System.out.println("please select the method that you want to operate:\t(select “0” for encrypte and select “1” for decrypt.)"); scanin = new Scanner(System.in);

int selected = scanin.nextInt();

while(selected==0 || selected==1){

RD = new ReplaceDemo();

RD.getTheMatrix();

if (selected == 0){

RD.print1();

}

else{

RD.print2();

}

System.out.println("please select the method that you want to operate:\t(select “0” for encrypte and select “1” for decrypt.)"); scanin = new Scanner(System.in);

selected = scanin.nextInt();

}

System.out.println("Your operate is over!Thank you!");

}

}

【测试用例】如下图：