JAVA的非对称加密算法RSA——加密和解密

package com.joe.main;  
  
import java.io.*;  
import java.math.BigInteger;  
import java.util.ArrayList;  
  
/**
 * @Description Demo说明： 
 *              1、按照加密解密和签名验签的逻辑,编写简单的demo,不涉及java中继承的RSA相关类和Sigesture签名类 
 *              2、只能对数字和字母进行加密, 不涉及编码和解码问题 。 3、不做数字签名和验证了,涉及到提取信息摘要。 
 */  
public class EnAndDe {  
    private long p = 0;  
    private long q = 0;  
    private long n = 0;  
    private long t = 0; // 欧拉函数  
  
    private long e = 0; // 公匙  
    private long d = 0; // 密匙  
  
    private String mc; // 明文  
    private long c = 0; // 密文  
    private long word = 0; // 解密后明文  
  
    // 判断是一个数 x 否为素数素数就是判断在 (2,√x)范围内有没有除1外的因数,如果没有则x数素数  
    public boolean isPrime(long t) {  
        long k = 0;  
        k = (long) Math.sqrt((double) t);  
        for (int i = 2; i <= k; i++) {  
            if ((t % i) == 0) {  
                return false;  
            }  
        }  
        return true;  
    }  
  
    // 随机产生大素数(1e6数量级，注意，太大了要超出范围)  
    public void bigprimeRandom() {  
        do {  
            p = (long) (Math.random() * 1000000);  
        } while (!this.isPrime(p));  
        do {  
            q = (long) (Math.random() * 1000000);  
        } while (p == q || !this.isPrime(q));  
    }  
  
    // 输入PQ  
    public void inputPQ() throws Exception {  
  
        this.bigprimeRandom();  
        System.out.println("自动生成两个大素数p,q分别为:" + this.p + " " + this.q);  
  
        this.n = (long) p * q;  
        this.t = (long) (p - 1) * (q - 1);  
  
        System.out.println("这两个素数的乘积为p*q：" + this.n);  
        System.out.println("所得的t=(p-1)(q-1)：" + this.t);  
    }  
  
    // 求最大公约数  
    public long gcd(long a, long b) {  
        long gcd;  
        if (b == 0)  
            gcd = a;  
        else  
            gcd = gcd(b, a % b);  
        return gcd;  
  
    }  
  
    // 生成公匙  
    public void getPublic_key() throws Exception {  
        do {  
  
            this.e = (long) (Math.random() * 100000);  
            // e满足 e∈(1, ψ(n))且e与ψ(n)最大公约数为1,即 e与t互质  
        } while ((this.e >= this.t) || (this.gcd(this.t, this.e) != 1));  
        System.out.println("生成的公钥为：" + "(" + this.n + "," + this.e + ")");  
    }  
  
    // 生成私钥 e*d=1(modψ(n))==> d = (kψ(n)+1) / e  
    public void getPrivate_key() {  
        long value = 1; // value 是e和d的乘积  
        outer: for (long k = 1;; k++) {  
            value = k * this.t + 1;  
            if ((value % this.e == 0)) {  
                this.d = value / this.e;  
                break outer;  
            }  
        }  
        System.out.println("产生的一个私钥为：" + "(" + this.n + "," + this.d + ")");  
    }  
  
    // 输入明文  
    public void getText() throws Exception {  
        System.out.println("请输入明文：");  
        BufferedReader stdin = new BufferedReader(new InputStreamReader(  
                System.in));  
        mc = stdin.readLine();  
  
    }  
  
    // 解密密文  
    public void pascolum() throws Exception {  
        this.getText();  
        System.out.println("输入明文为: " + this.mc);  
        // 加密  
        ArrayList cestr = new ArrayList();  
        for (int i = 0; i < mc.length(); i++) {  
            this.c = this.colum((long) mc.charAt(i), this.n, this.e);  
            cestr.add(c);  
        }  
        System.out.println("加密后所得的密文为：" + cestr);  
        // 解密  
        StringBuffer destr = new StringBuffer();  
        for (int j = 0; j < cestr.size(); j++) {  
            this.word = this.colum(Long.parseLong(cestr.get(j).toString()),  
                    this.n, this.d);  
            destr.append((char) word);  
        }  
        System.out.println("解密后所得的明文为：" + destr);  
  
    }  
  
    // 加密、解密计算  
    public long colum(long mc, long n, long key) {  
        BigInteger bigy = new BigInteger(String.valueOf(mc));  
        BigInteger bign = new BigInteger(String.valueOf(n));  
        BigInteger bigkey = new BigInteger(String.valueOf(key));  
        return Long.parseLong(bigy.modPow(bigkey, bign).toString());// 备注1  
    }  
  
    public static void main(String[] args) {  
        try {  
            EnAndDe t = new EnAndDe();  
            t.inputPQ();  
            t.getPublic_key();  
            t.getPrivate_key();  
            t.pascolum();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
  
}