Java非对称加密算法RSA

流程分析： 

1. 甲方构建密钥对儿，将公钥公布给乙方，将私钥保留。
2. 甲方使用私钥加密数据，然后用私钥对加密后的数据签名，发送给乙方签名以及加密后的数据；乙方使用公钥、签名来验证待解密数据是否有效，如果有效使用公钥对数据解密。
3. 乙方使用公钥加密数据，向甲方发送经过加密后的数据；甲方获得加密数据，通过私钥解密。

package cn.tzz.java.crypto;

import java.io.IOException;
import java.security.Key;
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.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
public class RSACryptUtil {

	public static final String KEY_ALGORITHM = "RSA";
	public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
	
	private static final String PUBLIC_KEY = "RSAPublicKey";
	private static final String PRIVATE_KEY = "RSAPrivateKey";
	
	
	public static String encryptBASE64(byte[] key) {  
		return (new BASE64Encoder()).encodeBuffer(key);  
	}
	
	public static byte[] decryptBASE64(String key) throws IOException {  
		return new BASE64Decoder().decodeBuffer(key);
	}
	
	/**初始化密钥*/
	public static Map<String, Object> initKey() {
		KeyPairGenerator keyPairGen;
		Map<String, Object> keyMap = new HashMap<String, Object>(2);
		try {
			keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
			keyPairGen.initialize(1024);
			KeyPair keyPair = keyPairGen.generateKeyPair();
			RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();// 公钥
			RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();// 私钥
			keyMap.put(PUBLIC_KEY, publicKey);
			keyMap.put(PRIVATE_KEY, privateKey);
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return keyMap;
	}
	
	/**获取私钥*/
	public static String getPrivateKey(Map<String, Object> keyMap){
		Key key = (Key) keyMap.get(PRIVATE_KEY);
		return encryptBASE64(key.getEncoded());
	}
	
	/**获取公钥*/
	public static String getPublicKey(Map<String, Object> keyMap){
		Key key = (Key) keyMap.get(PUBLIC_KEY);
		return encryptBASE64(key.getEncoded());
	}
	
	/**用公钥解密*/
	public static byte[] decryptByPublicKey(byte[] data, String key) throws Exception {
		byte[] keyBytes = decryptBASE64(key);// 对密钥解密
		// 取得公钥
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicKey = keyFactory.generatePublic(x509KeySpec);
		// 对数据解密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, publicKey);
		return cipher.doFinal(data);
	}
	
	/**用私钥解密*/
	public static byte[] decryptByPrivateKey(byte[] data, String key) throws Exception {
		byte[] keyBytes = decryptBASE64(key);// 对密钥解密
		// 取得私钥
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
		// 对数据解密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		return cipher.doFinal(data);
	}
	
	/**用公钥加密*/
	public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception {
		byte[] keyBytes = decryptBASE64(key);// 对公钥解密
		// 取得公钥
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicKey = keyFactory.generatePublic(x509KeySpec);
		// 对数据加密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		return cipher.doFinal(data);
	}
	
	/**用私钥加密*/
	public static byte[] encryptByPrivateKey(byte[] data, String key) throws Exception {
		byte[] keyBytes = decryptBASE64(key);// 对密钥解密
		// 取得私钥
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
		// 对数据加密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		return cipher.doFinal(data);
	}
	
	/**
	 * 用私钥对信息生成数字签名
	 * @param data 加密数据
	 * @param privateKey 私钥
	 */
	public static String sign(byte[] data, String privateKey) throws Exception {
		byte[] keyBytes = decryptBASE64(privateKey);// 解密由base64编码的私钥
		// 构造PKCS8EncodedKeySpec对象
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		// KEY_ALGORITHM 指定的加密算法
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		// 取私钥匙对象
		PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
		// 用私钥对信息生成数字签名
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initSign(priKey);
		signature.update(data);
		return encryptBASE64(signature.sign());
	}
	
	/**
	 * 校验数字签名
	 * @param data 加密数据
	 * @param publicKey 公钥
	 * @param sign 数字签名
	 * 
	 * @return 校验成功返回true 失败返回false
	 * 
	 */
	public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
		byte[] keyBytes = decryptBASE64(publicKey);// 解密由base64编码的公钥
		
		// 构造X509EncodedKeySpec对象
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
		// KEY_ALGORITHM 指定的加密算法
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		// 取公钥匙对象
		PublicKey pubKey = keyFactory.generatePublic(keySpec);
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initVerify(pubKey);
		signature.update(data);
		// 验证签名是否正常
		return signature.verify(decryptBASE64(sign));
	}
	
}

 
测试类：

package cn.tzz.java.crypto;

import java.util.Map;

import org.junit.Test;

public class RSACryptUtilTest {

	private static String publicKey;
	private static String privateKey;
	
	static {
		Map<String, Object> keyMap = RSACryptUtil.initKey();
		publicKey = RSACryptUtil.getPublicKey(keyMap);
		privateKey = RSACryptUtil.getPrivateKey(keyMap);
		System.out.println("公钥: \n\r" + publicKey);
		System.out.println("私钥： \n\r" + privateKey);
	}
	
	@Test
	public void test(){
		try {
			System.out.println("公钥加密---私钥解密");
			String date = "123456";
			byte[] encodedData = RSACryptUtil.encryptByPublicKey(date.getBytes(), publicKey);
			String encodedStr = RSACryptUtil.encryptBASE64(encodedData);
			byte[] decodedData = RSACryptUtil.decryptByPrivateKey(RSACryptUtil.decryptBASE64(encodedStr), privateKey);
			String outputStr = new String(decodedData);
			System.out.println("加密前: " + date + "\n\r" + "加密后: " + encodedStr + "\n\r" + "解密后: " + outputStr);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	
	@Test
	public void testSign() throws Exception {
		try {
			System.out.println("私钥加密---公钥解密");
			String inputStr = "123456";
			byte[] data = inputStr.getBytes();
			
			byte[] encodedData = RSACryptUtil.encryptByPrivateKey(data, privateKey);
			
			byte[] decodedData = RSACryptUtil.decryptByPublicKey(encodedData, publicKey);
			
			String outputStr = new String(decodedData);
			System.out.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
			
			System.out.println("私钥签名——公钥验证签名");
			// 产生签名
			String sign = RSACryptUtil.sign(encodedData, privateKey);
			System.out.println("签名:\r" + sign);
			// 验证签名
			boolean status = RSACryptUtil.verify(encodedData, publicKey, sign);
			System.out.println("状态:\r" + status);
		
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}