rsa.java

介绍了用java编辑RSA算法实现

/**
 * <p>Title:RSA算法 </p>
 *
 * <p>Description:简单实现RSA算法、以及利用RSA算法实现加密、解密、签名、验证 </p>
 *
 * <p>Copyright: Copyright (c) 2008/5/27</p>
 *
 * <p>Company: 建工学院</p>
 *
 * @author 04信息（1）程晟
 * @version 1.0
 */



import java.io.*;
import java.math.BigInteger;
import java.util.ArrayList;
public class RSA {
    private long p = 0;
    private long q = 0;
    private long n = 0;
    private long m = 0;

    private long public_key = 0; //公匙
    private long private_key = 0; //密匙

    private String text ; //明文
    private long secretword = 0; //密文
    private long word = 0; //解密后明文


    //判断是否为素数
    public boolean primenumber(long t) {
        long k = 0;
        k = (long) Math.sqrt((double) t);
        boolean flag = true;
        outer:for (int i = 2; i <= k; i++) {
            if ((t % i) == 0) {
                flag = false;
                break outer;
            }
        }
        return flag;
    }
    //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.primenumber(p));
        do{
            q=(long)(Math.random()*1000000);
        }while(p==q||!this.primenumber(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.m = (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m=(p-1)(q-1)：" + this.m);
    }

    //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);
        //System.out.println("gcd:" + gcd);
        return gcd;

    }

    //生成公匙
    public void getPublic_key() throws Exception {
        do {
                   
            this.public_key=(long)(Math.random()*100000);
        } while ((this.public_key >= this.m) ||
                 (this.gcd(this.m, this.public_key) != 1));
        System.out.println("生成的公钥为：" + this.public_key);
    }

    //计算得到密匙
    public void getPrivate_key() {
        long value = 1;
        outer:for (long i = 1; ; i++) {
            value = i * this.m + 1;
            //System.out.println("value:    " + value);
            if ((value % this.public_key == 0) &&
                (value / this.public_key < this.m)) {
                this.private_key = value / this.public_key;
                break outer;
            }
        }
        System.out.println("产生的一个私钥为：" + this.private_key);
    }

    //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));
         text = stdin.readLine();


    }

    //加密、解密计算
    public long colum(long y, long n, long key) {
        BigInteger bigy=new BigInteger(String.valueOf(y));
        //System.out.println(bigy);
        BigInteger bign=new BigInteger(String.valueOf(n));
        BigInteger bigkey=new BigInteger(String.valueOf(key));
        //System.out.println(Long.parseLong(bigy.modPow(bigkey,bign).toString()));
        return Long.parseLong(bigy.modPow(bigkey,bign).toString());
    }

    //加密后解密
    public void pascolum() throws Exception {
        this.getText();
        System.out.println("输入明文为: " + this.text);
        //加密
        ArrayList cestr=new ArrayList();
        for (int i = 0; i < text.length(); i++) {
            this.secretword = this.colum( (long)text.charAt(i), this.n,
                                         this.public_key);
            cestr.add(secretword);
        }
        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.private_key);
          destr.append((char)word);
        }
        System.out.println("解密后所得的明文为：" +destr);

    }

    //签名后验证
    public void signautre() throws Exception {
        System.out.println("输入明文为: " + this.text);
        //签名
        ArrayList cestr=new ArrayList();
        for (int i = 0; i < text.length(); i++) {
            this.secretword = this.colum( (long)text.charAt(i), this.n,
                                         this.private_key);
            cestr.add(secretword);
        }
        System.out.println("签名后所得的密文为：" +cestr);
        //验证
        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.public_key);
          destr.append((char)word);
        }
        System.out.println("解密后所得的明文为：" +destr);
        if(destr.toString().equals(text)) {
            System.out.println("签名有效");
        }else {
            System.out.println("签名无效");
        }

    }

    public static void main(String[] args)  {
        try {
            RSA t = new RSA();
            t.inputPQ();
            t.getPublic_key();
            t.getPrivate_key();
            t.pascolum();
            t.signautre();
        }catch(Exception ex) {
            System.out.println(ex.getMessage());
        }
    }

}