RSA算法

先说下这个算法，RSA公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。

这个算法的名字也是他们三个人名字首字母，RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。

package rsa; 

import java.math.BigInteger; 



public class RSA { 

 private long p,q,e,d,n; 

 public RSA(){ 

  int pIndex = (int)(Math.random()*10); 

  int qIndex; 

  int eIndex; 

  do{ 

   qIndex = (int)(Math.random()*10); 

  } 

  while(qIndex==pIndex); 

  do{ 

   eIndex = (int)(Math.random()*10); 

  } 

  while(eIndex==pIndex||eIndex==pIndex); 

  p = 1033; 

  q = 2017; 

  e = 29437; 

  n = p*q; 

  d = calculateD(); 

 } 

 private long calculateD(){ 

  long t0 = 0,t1 = 1,t2 = -1; 

  long r0 = (p-1)*(q-1), m = r0,r1 = e ,r2 = -1; 

  do{ 

   long q = r0/r1; 

   r2 = r0-r1*q; 

   if(r2==0)break; 

   t2 = t0 - t1*q; 

   while(t2<0){ 

    t2+=m; 

   } 

   if(t2>=m){ 

    t2 %= m; 

   }     

   r0 = r1; 

   r1 = r2; 

   t0 = t1; 

   t1 = t2; 

  }while(r2!=0); 

  if(r1!=1){ 

   return 0; 

  } 

  else{ 

   return t2; 

  } 

 } 

  

 public long getE() { 

  return e; 

 } 

 public long getN() { 

  return n; 

 } 

 public long getD() { 

  return d; 

 } 

 public BigInteger encode(BigInteger data){ 

  return pow(data,d).mod(new BigInteger(n+"")); 

 } 

 public BigInteger decode(BigInteger code){ 

  return pow(code,e).mod(new BigInteger(n+"")); 

 } 

 public BigInteger pow(BigInteger data,long p){ 

  data = data.pow((int)p); 

  return data; 

 } 

 public static void main(String args[]){ 

  RSA rsa = new RSA(); 

   

  BigInteger data = new BigInteger("222222"); 

  long oldtime = System.currentTimeMillis(); 

  BigInteger code = rsa.encode(data); 

  long newtime = System.currentTimeMillis(); 

  double codetime = ((double)(newtime-oldtime))/1000; 

  oldtime = System.currentTimeMillis(); 

  BigInteger decode = rsa.decode(code); 

  newtime = System.currentTimeMillis(); 

  double decodetime = ((double)(newtime-oldtime))/1000; 

  System.out.println("privateKey:"+rsa.d); 

  System.out.println("publickKey:"+rsa.e); 

  System.out.println("N:"+rsa.n); 

  System.out.println("data:"+data); 

  System.out.println("code:"+code+" time:"+codetime); 

  System.out.println("decode:"+decode+" time:"+decodetime); 



 } 



}