import java.security.Key;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.security.spec.PKCS8EncodedKeySpec;

import java.security.spec.X509EncodedKeySpec;   

import javax.crypto.Cipher;   

import sun.misc.BASE64Decoder;

import sun.misc.BASE64Encoder;   

public class RSAHelper {   

      public static PublicKey getPublicKey(String key) throws Exception {

            byte[] keyBytes;

            keyBytes = (new BASE64Decoder()).decodeBuffer(key);   

            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

            KeyFactory keyFactory = KeyFactory.getInstance("RSA");

            PublicKey publicKey = keyFactory.generatePublic(keySpec);

            return publicKey;

      }   

      public static PrivateKey getPrivateKey(String key) throws Exception {

            byte[] keyBytes;

            keyBytes = (new BASE64Decoder()).decodeBuffer(key);   

            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

            KeyFactory keyFactory = KeyFactory.getInstance("RSA");

            PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

            return privateKey;

      }   

      public static String getKeyString(Key key) throws Exception {

            byte[] keyBytes = key.getEncoded();

            String s = (new BASE64Encoder()).encode(keyBytes);

            return s;

      }   

      public static void main(String[] args) throws Exception {   

            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");

            //密钥位数

            keyPairGen.initialize(1024);

            //密钥对

            KeyPair keyPair = keyPairGen.generateKeyPair();   

            // 公钥

            PublicKey publicKey = (RSAPublicKey) keyPair.getPublic();   

            // 私钥

            PrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   

            String publicKeyString = getKeyString(publicKey);

            System.out.println("public:\n" + publicKeyString);   

            String privateKeyString = getKeyString(privateKey);

            System.out.println("private:\n" + privateKeyString);   

            //加解密类

            Cipher cipher = Cipher.getInstance("RSA");//Cipher.getInstance("RSA/ECB/PKCS1Padding");   

            //明文

            byte[] plainText = "我们都很好！邮件：@sina.com".getBytes();   

            //加密

            cipher.init(Cipher.ENCRYPT_MODE, publicKey);

            byte[] enBytes = cipher.doFinal(plainText);   

           //通过密钥字符串得到密钥

            publicKey = getPublicKey(publicKeyString);

            privateKey = getPrivateKey(privateKeyString);   

            //解密

            cipher.init(Cipher.DECRYPT_MODE, privateKey);

            byte[]deBytes = cipher.doFinal(enBytes);   

            publicKeyString = getKeyString(publicKey);

            System.out.println("public:\n" +publicKeyString);   

            privateKeyString = getKeyString(privateKey);

            System.out.println("private:\n" + privateKeyString);   

            String s = new String(deBytes);

            System.out.println(s);   

      }   

}