java 加密 rsa例子

import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
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.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
public class EncrypRSA {
public static final String KEY_ALGORITHM = "RSA";
/**
* BASE64解密
*
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptBASE64(String key) throws Exception {
return (new BASE64Decoder()).decodeBuffer(key);
}
/**
* BASE64加密
*
* @param key
* @return
* @throws Exception
*/
public static String encryptBASE64(byte[] key) throws Exception {
return (new BASE64Encoder()).encodeBuffer(key);
}

/**
* 加密
* @param publicKey
* @param srcBytes
* @return
* @throws NoSuchAlgorithmException
* @throws NoSuchPaddingException
* @throws InvalidKeyException
* @throws IllegalBlockSizeException
* @throws BadPaddingException
*/
protected byte[] encrypt(RSAPublicKey publicKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
if(publicKey!=null){
//Cipher负责完成加密或解密工作，基于RSA
Cipher cipher = Cipher.getInstance("RSA");
//根据公钥，对Cipher对象进行初始化
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte[] resultBytes = cipher.doFinal(srcBytes);
return resultBytes;
}
return null;
}

/**
* 解密
* @param privateKey
* @param srcBytes
* @return
* @throws NoSuchAlgorithmException
* @throws NoSuchPaddingException
* @throws InvalidKeyException
* @throws IllegalBlockSizeException
* @throws BadPaddingException
*/
protected byte[] decrypt(RSAPrivateKey privateKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
if(privateKey!=null){
//Cipher负责完成加密或解密工作，基于RSA
Cipher cipher = Cipher.getInstance("RSA");
//根据公钥，对Cipher对象进行初始化
cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] resultBytes = cipher.doFinal(srcBytes);
return resultBytes;
}
return null;
}
/**
* @param args
* @throws NoSuchAlgorithmException
* @throws BadPaddingException
* @throws IllegalBlockSizeException
* @throws NoSuchPaddingException
* @throws InvalidKeyException
*/
public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException ,Exception{
EncrypRSA rsa = new EncrypRSA();
String msg = "公钥和私钥";
//KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
//初始化密钥对生成器，密钥大小为1024位
keyPairGen.initialize(1024);
//生成一个密钥对，保存在keyPair中
KeyPair keyPair = keyPairGen.generateKeyPair();
//得到私钥
RSAPrivateKey oraprivateKey = (RSAPrivateKey)keyPair.getPrivate();
//得到公钥
RSAPublicKey orapublicKey = (RSAPublicKey)keyPair.getPublic();

byte[] publicKeybyte =orapublicKey.getEncoded();
String publicKeyString = encryptBASE64(publicKeybyte);
System.out.println(publicKeyString);

byte[] privateKeybyte =oraprivateKey.getEncoded();
String privateKeyString = encryptBASE64(privateKeybyte);
System.out.println(privateKeyString);

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
PKCS8EncodedKeySpec privatekcs8KeySpec = new PKCS8EncodedKeySpec(decryptBASE64(privateKeyString));
PrivateKey privateKey= keyFactory.generatePrivate(privatekcs8KeySpec);

X509EncodedKeySpec publicpkcs8KeySpec = new X509EncodedKeySpec(decryptBASE64(publicKeyString));
PublicKey publicKey = keyFactory.generatePublic(publicpkcs8KeySpec);

//用公钥加密
byte[] srcBytes = msg.getBytes();
byte[] resultBytes = rsa.encrypt((RSAPublicKey)publicKey, srcBytes);

String base64Msg= encryptBASE64(resultBytes);

byte[] base64MsgD = decryptBASE64(base64Msg);

//用私钥解密
byte[] decBytes = rsa.decrypt((RSAPrivateKey) privateKey, base64MsgD);

System.out.println("明文是:" + msg);
System.out.println("双重加密后是:" +base64Msg);
System.out.println("解密后是:" + new String(decBytes));
}
}