public static void main(String args[]) 
{
  try {
    RSADemo rsa=new RSADemo();
    rsa.generateKey();
    byte[] data=rsa.encrypt("luanpeng".getBytes());
    byte[] data1=rsa.decrypt(data);
    String str=new String(data1);
    System.out.println(str);
  } catch (Exception e) {
    System.out.println(e.toString());
  }
}

package com.lp.app.safe;

import java.security.*;
import java.security.interfaces.*;
import java.math.*;

public class RSADemo {
  public RSADemo() {
  }
  PublicKey pbkey;
  PrivateKey prkey;
  public void generateKey() {
    try {
      KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
      kpg.initialize(1024);
      KeyPair kp = kpg.genKeyPair();
      pbkey = kp.getPublic();
      prkey = kp.getPrivate();
    } catch (Exception e) {
    }
  }

  //加密，需要公鑰
  public byte[] encrypt(byte[] ptext) throws Exception {
    // 獲取公鑰及參數(shù)e,n
    RSAPublicKey pbk = (RSAPublicKey)pbkey;
    BigInteger e = pbk.getPublicExponent();
    BigInteger n = pbk.getModulus();
    // 獲取明文m
    BigInteger m = new BigInteger(ptext);
    // 計(jì)算密文c
    BigInteger c = m.modPow(e, n);
    return c.toByteArray();
  }

  //使用私鑰進(jìn)行解密
  public byte[] decrypt(byte[] ctext) throws Exception {
    // 讀取密文
    BigInteger c = new BigInteger(ctext);
    // 讀取私鑰
    RSAPrivateKey prk = (RSAPrivateKey)prkey;
    BigInteger d = prk.getPrivateExponent();

    // 獲取私鑰參數(shù)及解密
    BigInteger n = prk.getModulus();
    BigInteger m = c.modPow(d, n);

    // 顯示解密結(jié)果
    byte[] mt = m.toByteArray();
    return mt;
  }
}