playfair.java

Java实现传统算法加密解密

import java.util.*;
import java.io.*;

public class Playfair {
	/**
	 * input file containing plaintext
	 */
	private File inFile;
	
	/**
	 * planar int array of key matrix
	 */
	char m[][];
	
	/**
	 * ArrayList of plaintext and cipher
	 */
	ArrayList ap , ac;
	
	public Playfair(){
		ap = new ArrayList();
		ac = new ArrayList();
		m =new char[5][5];
	}
	
	public void createMatrix(String keyStr){
		System.out.println("Key is "+keyStr);
		ap.clear();
		ac.clear();
		LinkedHashSet keySet = new LinkedHashSet();
		char[] keyArray = keyStr.toUpperCase().toCharArray();
		for (int i=0;i<keyArray.length;i++){
			char temp = keyArray[i];
			if(temp=='I')
				temp = 'J';
			keySet.add(temp);
		}
		for (int n=65;n<91;n++){
			if(n!=73)
			keySet.add((char)n);
		}
		Object key[] = keySet.toArray();
		
		System.out.println("Playfair matri:");
		for (int i = 0; i <5; i++) {
			for (int j = 0; j < 5; j++) {
				m[i][j]=((Character)key[i*5+j]).charValue();
				System.out.print(m[i][j]);
			}
			System.out.println("");
		}
	}
	
	public void encrypt(File in,String keyText)throws IOException{
	
		createMatrix(keyText);
		
		inFile = in;
		FileReader fr = new FileReader(inFile);
		FileWriter fw = new FileWriter(inFile.getParent()
				+ "/Playfair_cipher.txt");
		StringBuffer sb = new StringBuffer();
		
		//read plaintext from input file and change to uppercase
		int temp;
		while ((temp = fr.read()) != -1) {
			if ((temp >= 65 && temp <= 90) || (temp >= 97 && temp <= 122))
				sb.append((char) temp);
		}
		fr.close();
		char[] plainChar = sb.toString().toUpperCase().toCharArray();

		for (int i = 0; i < plainChar.length; i++) {
			char ch= plainChar[i];
			if(ch == 'I') ch = 'J';
			ap.add(ch);
		}
		
		//insert "X" into 2 same character of plaintext 
		boolean addX = false;
		for (int i = 0; i < (ap.size())/2; i++) {
			if(addX){
				i=0;
				addX=false;
			}
			//TODO check
			if(ap.get(i*2).equals(ap.get(i*2+1))){
				addX = true;
				ap.add(i*2+1,'X');
			}	
		}
		//if the number of plaintext is odd,add "X" at the end
		if(ap.size()%2!=0) ap.add(ap.size(), 'X');
		
		
		
		int r1=5,l1=5;
		int r2 =5, l2 =5;
		
		for (int i = 0; i < ap.size()/2; i++) {
			for (int j = 0; j < 5; j++) {
				for (int j2 = 0; j2 < 5; j2++) {
					if(((Character)ap.get(i*2)).charValue()==m[j][j2]){
						r1=j;
						l1=j2;
						
					}
					if(((Character)ap.get(i*2+1)).charValue()==m[j][j2]){
						r2 = j;
						l2 = j2;
					}
				}
			}
			if(r1==r2){
				ac.add(i*2,m[r1][(l1+1)%5]);
				ac.add(i*2+1,m[r2][(l2+1)%5]);
			}else if(l1==l2){
				ac.add(i*2,m[(r1+1)%5][l1]);
				ac.add(i*2+1,m[(r2+1)%5][l2]);
			}else{
				ac.add(i*2,m[r1][l2]);
				ac.add(i*2+1,m[r2][l1]);
			}		
		}
		
		//writer cipher to output file
		for (int i = 0; i < ac.size(); i++) {
			fw.write(((Character) ac.get(i)).charValue());
		}
		fw.close();
		System.out.println("Playfair encryption ok");
	}
	
	public void decrypt()throws IOException{
		FileWriter fw = new FileWriter(inFile.getParent()
				+ "/Playfair_decrypt.txt");
		
		ap = new ArrayList(ac);
		ac.clear();
		
		//decrypt
		int r1=5,l1=5;
		int r2 =5, l2 =5;
		
		for (int i = 0; i < ap.size()/2; i++) {
			for (int j = 0; j < 5; j++) {
				for (int j2 = 0; j2 < 5; j2++) {
					if(((Character)ap.get(i*2)).charValue()==m[j][j2]){
						r1=j;
						l1=j2;
						
					}
					if(((Character)ap.get(i*2+1)).charValue()==m[j][j2]){
						r2 = j;
						l2 = j2;
					}
				}
			}
			if(r1==r2){
				ac.add(i*2,m[r1][(l1+4)%5]);
				ac.add(i*2+1,m[r2][(l2+4)%5]);
			}else if(l1==l2){
				ac.add(i*2,m[(r1+4)%5][l1]);
				ac.add(i*2+1,m[(r2+4)%5][l2]);
			}else{
				ac.add(i*2,m[r1][l2]);
				ac.add(i*2+1,m[r2][l1]);
			}		
		}
		
		//writer cipher to output file
		for (int i = 0; i < ac.size(); i++) {
			fw.write((((Character) ac.get(i)).toString().toLowerCase()).charAt(0));
		}
		fw.close();
		System.out.println("Playfair decryption ok");
		
	}
	
	

}