RSA加密算法

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Test{
	
	/**
	 * 需要加密的字符串
	 */
//	public final static String STRING = "Hello world!";
	public final static String STRING = "Hello world! It is a beautiful day.";
//	public final static String STRING = "Hello world! It is a beautiful day. Hello world! It is a beautiful day. Hello world! It is a beautiful day.";
	
	public static void main(String[] args){
		
		System.out.println("============1.寻找质数=========");
		int[] primeNum = getPQE();
		System.out.println("p="+primeNum[0]+", q="+primeNum[1]+", e="+primeNum[2]);
		
		
		System.out.println("============2.生成密钥=========");
		KeyPair key = getKeyPair(primeNum[0], primeNum[1], primeNum[2]);
		System.out.println(key);
		
		
		System.out.println("============3.加密============");
		ArrayList<Long> list = encryToList(STRING, key);
		String s = encryToString(STRING, key);
		System.out.println("加密后的文本是：");
		System.out.println(s);
		
		
		System.out.println("============4.解密============");
		System.out.println("解密之后的文本是：");
		System.out.println(decry(list, key));
		
	}
	
	
	/**
	 * 4.解密加密后的值的list
	 * @param list
	 * @param key
	 * @return
	 */
	static String decry(ArrayList<Long> list, KeyPair key){
		
		StringBuilder sb = new StringBuilder();
		List<Long> delist = new ArrayList<Long>();
		for (long ch : list) {
			BigInteger a = BigInteger.valueOf(ch).pow(key.getD());
			BigInteger b = a.mod(BigInteger.valueOf(key.getN()));
			delist.add(b.longValue());
			
			sb.append((char)b.longValue());
			
//			System.out.println((char)ch+" "+ch+"\t"+b+" "+(char)b.longValue());
		}
		
		return new String(sb);
	}
	
	
	
	/**
	 * 3.加密成String形式
	 * @param string
	 * @param key
	 * @return
	 */
	static String encryToString(String string, KeyPair key){
		
		StringBuilder sb = new StringBuilder();
		
		byte[] str = string.getBytes();
		
		for (long ch : str) {
			
			BigInteger a = BigInteger.valueOf(ch).pow(key.getE());
			BigInteger b = a.mod(BigInteger.valueOf(key.getN()));
			
			sb.append((char)b.longValue());
			
//			System.out.println((char)ch+" "+ch+"\t"+b+" "+(char)b.longValue());
		}
		
		return new String(sb);
	}
	/**
	 * 3.加密成list形式
	 * @param string
	 * @param key
	 * @return
	 */
	static ArrayList<Long> encryToList(String string, KeyPair key){
		
		byte[] str = string.getBytes();
		
		ArrayList<Long> list = new ArrayList<Long>();
		
		for (long ch : str) {
			
			BigInteger a = BigInteger.valueOf(ch).pow(key.getE());
			BigInteger b = a.mod(BigInteger.valueOf(key.getN()));
			list.add(b.longValue());
			
//			System.out.println((char)ch+" "+ch+"\t"+b+" "+(char)b.longValue());
		}
		
		return list;
		
	}
	
	
	
	/**
	 * 2.生成密钥
	 * @param p
	 * @param q
	 * @param e
	 * @return
	 */
	static KeyPair getKeyPair(long p, long q, long e){
		KeyPair key = new KeyPair();
		
		long n = p*q;
		long euler = (p-1)*(q-1); // e必须与euler互质，1<e<euler
		// 计算满足下式的数 d
		long d = 0L;
		for(long i=1; ; i++){
//			System.out.println("-- 正在寻找公钥 "+i+" --");
			if(e*i%euler == 1){
				d = i;
				break;
			}
		}
		
		key.setE((int)e);
		key.setD((int)d);
		key.setN((int)n);
		
		return key;
	}
	
	
	/**
	 * 1.寻找三个质数
	 * @return
	 */
	static int[] getPQE(){
		List<Integer> numList = new ArrayList<Integer>();
		for(int i=101; i<500; i++){
			if(isPrime((long)i)){
				numList.add(i);
//				System.out.println("----- "+i+" -----");
			}
		}
		Random random = new Random();
		int p = 0;
		int q = 0;
		int e = 0;
		
		p = numList.get(random.nextInt(numList.size()));
		do {
			q = numList.get(random.nextInt(numList.size()));
		} while (p==q);
		do {
			e = numList.get(random.nextInt(numList.size()));
		} while (e==p || e==q);
		
		return new int[]{p,q,e};
	}
	
	
	/**
	 * 0.判断一个数是否质数
	 * @param num
	 * @return
	 */
	static boolean isPrime(long num){
		if(num<=0) return false;
		for(int i=2; i<num; i++){
			if(num%i==0){
				return false;
			}
		}
		return true;
	}
	
	
		
}


// 密钥
class KeyPair {
	
	private int e;
	private int d;
	private int n;

	public void setE(int e) {
		this.e = e;
	}

	public int getE() {
		return e;
	}

	public void setD(int d) {
		this.d = d;
	}

	public int getD() {
		return d;
	}

	public void setN(int n) {
		this.n = n;
	}

	public int getN() {
		return n;
	}

	public int[] getPublicKey(){ 
		return new int[]{e,n};
	}
	public String getPublicKeyStr(){ 
		return "公钥：("+e+","+n+")";
	}
	
	public int[] getPrivateKey(){ 
		return new int[]{d,n};
	}
	public String getPrivateKeyStr(){ 
		return "私钥：("+d+","+n+")";
	}
	
	public String toString() {
		return ("KeyPair["+getPublicKeyStr()+","+getPrivateKeyStr()+"]");
	}
}