RSA 公钥加密算法

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); 

 } 

}