RSA算法的Java实现

import java.math.BigInteger;
import java.security.SecureRandom;
public class CRSA{
private final static SecureRandom random = new SecureRandom();
private BigInteger SK;
private BigInteger PK;
private BigInteger npq;
CRSA(int N){
SecureRandom rnd = new SecureRandom();
BigInteger p = new BigInteger(N/2,200,rnd);
BigInteger q = new BigInteger(N/2,200,rnd);
BigInteger f =(p.subtract(new BigInteger("1")).multiply(q.subtract(new BigInteger("1"))));
npq =p.multiply(q);
PK =new BigInteger("65537");
SK =PK.modInverse(f);
}
BigInteger encrypt(BigInteger message){
return message.modPow(PK, npq);
}
BigInteger decrypt(BigInteger encrypted){
return encrypted.modPow(SK, npq);
}
public String output(){
String str = "";
str = str + "\n 公钥 :"+ PK +"\n";
str = str + "\n 私钥 :"+ SK +"\n";
return str;
}
public static void main(String[] a){
int N;
byte length[]=new byte[10];
System.out.print("input N：");
try{
System.in.read(length);
}
catch(Exception e){}
String str = new String(length);
N = Integer.parseInt(str.trim());
CRSA key =new CRSA(N);
BigInteger message =new BigInteger(N-1,random);
BigInteger encrypt =key.encrypt(message);
BigInteger decyrpt =key.decrypt(encrypt);
System.out.println(key.output());
System.out.println("the source info: " + message + "\n");
System.out.println("the encrypted info: " + encrypt + "\n");
System.out.println("the decyrpted info: " + decyrpt + "\n");
}
}