rsa.java

java程序实现的RSA算法

import java.math.BigInteger;

public class RSA {
	

	public static void main(String args[])
	{
		int n = 65531;//
		int e = 17;//(e,n)公钥
		int d = 1;//(d,n)私钥
		int p = 1;//素数1
		int q = 1;//素数2

		long begin = System.currentTimeMillis();
		RSA rsa = new RSA();
		if(args.length>2)
		{
			try
			{
				//通过控制台赋值
				n = Integer.parseInt(args[0]);
				e = Integer.parseInt(args[1]);
			}
			catch(Exception ex)
			{
				System.out.println("输入的必须是数字！");
			}
			
		}
		for(int i=1;;i++)
		{
			
			 if(rsa.isss(i))
			 {
				 for(int j=1;;j++)
				 {
					 if(rsa.isss(j))
					 {
						 if(i*j == n)
						 {
							 p = i;
							 q = j;
							 break;
						 }else if(i*j >n)
								break;
					 }
				 }
				 if((p!=1)&&(q!=1))
						break;
				 if(i>n/2)
				 {
					 System.out.println("没有得到答案！");
					 return;
				 }
			 }			
		}
		
		System.out.println("n = " + n);
		System.out.println("p = " + p);
		System.out.println("q = " + q);
		System.out.println("p*q = " + p*q);
		
		int eulerValue = (p-1)*(q-1);//欧拉值
		for(int i=1;i<n/2;i++)
		{
			if(e*i%eulerValue == 1)
			{
				d = i;
				break;
			}
		}
		System.out.println("e = " + e);
		System.out.println("d = " + d);
		System.out.println("公钥(e,n): ("+e+","+n+")");
		System.out.println("私钥(d,n): ("+d+","+n+")");
		
		BigInteger nB = new BigInteger(String.valueOf(n).getBytes());
	    BigInteger eB = new BigInteger(String.valueOf(e).getBytes());
	    BigInteger dB = new BigInteger(String.valueOf(d).getBytes());	    
	    System.out.println("nB= "+nB);
	    System.out.println("eB= "+eB);
	    System.out.println("dB= "+dB);
	    
	    /*
	     * 加密与解密
	     * 参照Skey_RSA.java,Enc_RSA.java,Dec_RSA.java 
	     * 调试时按这个顺序执行
	     */
	    BigInteger m = null;
	    String s = "Hello world";
	    byte ptext[]=s.getBytes();
	    m=new BigInteger(ptext);
	    System.out.println("m= "+m);
	    BigInteger c=m.modPow(eB,nB); //加密
	    
	    //String str = "71761D5F9D9C32B936AE92DBD0F39D9C8549AA5CAA22DE8FAA5CAC403F021543B8993AA178C93C5C";
	    //BigInteger c = new BigInteger(str.getBytes());
	    
	    m=c.modPow(dB,nB);//解密
	    System.out.println("m= "+m);
	    String s1 = new String(m.toByteArray());
	    System.out.println("解密后明文为：" + s1);
	    
		long end = System.currentTimeMillis();
		System.out.println("消耗的时间为：" + (end-begin)/1000 + "s");

	}

	public boolean isss(int i)
	{//求素数
		int j;
		for(j=2;j<=i/2;j++)
		{
			if (i%j==0)
			{
				return false;
			}
		}
		return true;
	}
}