RSA算法的实现方法——Java版放送

RSA算法的实现方法——Java版放送

阅读次数: 59次 发布时间: 2010-03-03 11:22:40发布人: 大Q

来源: 中文JAVA技术网

一开始不知道有BigInteger这个大数类，居然自己去实现了一个，写了大数加法后，才发现有现成的T_T

以下是引用片段：
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);

}

}