非对称加密RSA算法实现

package com.test.rsa;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;

import javax.crypto.Cipher;

public class RSAUtil {

/**
* 加密
*/
public static byte[] encrypt(PublicKey pk, byte[] data) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
cipher.init(Cipher.ENCRYPT_MODE, pk);
int blockSize = cipher.getBlockSize();// 获得加密块大小，如：加密前数据为128个byte，而key_size=1024
// 加密块大小为127
// byte,加密后为128个byte;因此共有2个加密块，第一个127
// byte第二个为1个byte
int outputSize = cipher.getOutputSize(data.length);// 获得加密块加密后块大小
int leavedSize = data.length % blockSize;
int blocksSize = leavedSize != 0 ? data.length / blockSize + 1 : data.length / blockSize;
byte[] raw = new byte[outputSize * blocksSize];
int i = 0;
while (data.length - i * blockSize > 0) {
if (data.length - i * blockSize > blockSize)
cipher.doFinal(data, i * blockSize, blockSize, raw, i * outputSize);
else
cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i * outputSize);
// 这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到
// ByteArrayOutputStream中，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了
// OutputSize所以只好用dofinal方法。

i++;
}
return raw;
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}

/**
* 解密
*/
public static byte[] decrypt(PrivateKey pk, byte[] raw) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
cipher.init(cipher.DECRYPT_MODE, pk);
int blockSize = cipher.getBlockSize();
ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
int j = 0;

while (raw.length - j * blockSize > 0) {
bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
j++;
}
return bout.toByteArray();
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}

/**
*
* 根据本地的RSAKey文件获取KeyPair
*
* @throws Exception
*/
public static KeyPair getKeyPair(String rsaKeyStore) throws Exception {
FileInputStream fis = new FileInputStream(rsaKeyStore);
ObjectInputStream oos = new ObjectInputStream(fis);
KeyPair kp = (KeyPair) oos.readObject();
oos.close();
fis.close();
return kp;
}

/**
*
* 存储KeyPair到本地
*
* @throws Exception
*/
public static void saveKeyPair(KeyPair kp, String path) throws Exception {
FileOutputStream fos = new FileOutputStream(path);
ObjectOutputStream oos = new ObjectOutputStream(fos);
// 生成密钥
oos.writeObject(kp);
oos.close();
fos.close();
}

/**
*
* 用于生成公匙或私匙
*
* @throws NoSuchAlgorithmException
*
*/
public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {

SecureRandom sr = new SecureRandom();
KeyPairGenerator kg = KeyPairGenerator.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
// 注意密钥大小最好为1024,否则解密会有乱码情况.
kg.initialize(1024, sr);
KeyPair genKeyPair = kg.genKeyPair();
return genKeyPair;

}

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

// 获取公匙及私匙
KeyPair generateKeyPair = getKeyPair("E:\\code\\key");
//生成公钥及私钥
//KeyPair generateKeyPair = generateKeyPair();

// 公匙 用于前台加密
PublicKey publicKey = generateKeyPair.getPublic();
System.out.println(publicKey);

// 私匙 存储在后台用于解密
PrivateKey privateKey = generateKeyPair.getPrivate();
System.out.println(privateKey);

// 存储KeyPair到本地用于后期解密 注意修改前台RSAKeyPair
//saveKeyPair(generateKeyPair,"E:\\code\\key");

// 测试加密解密
String test = "saaaa";
// test = "阿斯顿发送对发生地发送盗伐水电费圣达菲sadfsadf爱上对方爱上对方";

byte[] en_test = encrypt(publicKey, test.getBytes());
System.out.println("加密后字符:" + new String(en_test));

byte[] de_test = decrypt(privateKey, en_test);
System.out.println("解密后字符:" + new String(de_test));

}

}