非堆成加密算法DH

DH算法为网络交换数据提供了安全保障。

DH算法，密钥一致协议。

它是这样的，由甲方产出一对密钥（公私钥），乙方按照甲方公钥产生乙方密钥对（公私钥）。

双方使用同一种对车改加密算法构建本地密钥对数据加密。这样，在互通了本地密钥算法后，甲乙双方公开自己的公钥，使用对方的公钥和自己的私钥加密数据，同时可以使用对方的公钥和自己的私钥进行解密数据。

当然，这不单单在两方之间进行，还可以为多方共享数据通讯。

该算法来源于中国的同余定理----中国馀数定理。

流程：

1.甲方构建密钥，产生公私钥，将公钥发送给乙方，双方约定数据加密算法，乙方通过甲方公钥构建公私钥，乙方将公钥给甲方。也就是现在甲方手中有，甲方公私钥和乙方公钥，乙方有乙方公私钥和甲方公钥。

2.甲方使用甲方私钥+乙方公钥+约定数据加密算法构建本地密钥，然后通过本地密钥加密数据，将加密后数据发送给乙方。乙方使用乙方私钥+甲方公钥+约定数据加密算法=本地密钥，然后用此密钥解密数据。

3.乙方使用乙方私钥+甲方公钥+约定数据加密算法构建本地密钥，然后通过本地密钥加密数据，将加密后的数据发送给甲方。甲方使用甲方私钥+乙方公钥+约定数据加密算法=本地密钥，使用本地密钥解密数据。

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;

/**
 * DH安全编码组件
 */
public abstract class DHCoder extends Coder {
	public static final String ALGORITHM = "DH";

	/**
	 * 默认密钥字节数
	 * 
	 * <pre>
	 * DH
	 * Default Keysize 1024  
	 * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
	 * </pre>
	 */
	private static final int KEY_SIZE = 1024;

	/**
	 * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。
	 */
	public static final String SECRET_ALGORITHM = "DES";
	private static final String PUBLIC_KEY = "DHPublicKey";
	private static final String PRIVATE_KEY = "DHPrivateKey";

	/**
	 * 初始化甲方密钥
	 * 
	 * @return
	 * @throws Exception
	 */
	public static Map<String, Object> initKey() throws Exception {
		KeyPairGenerator keyPairGenerator = KeyPairGenerator
				.getInstance(ALGORITHM);
		keyPairGenerator.initialize(KEY_SIZE);

		KeyPair keyPair = keyPairGenerator.generateKeyPair();

		// 甲方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 甲方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);
		return keyMap;
	}

	/**
	 * 初始化乙方密钥
	 * 
	 * @param key
	 *            甲方公钥
	 * @return
	 * @throws Exception
	 */
	public static Map<String, Object> initKey(String key) throws Exception {
		// 解析甲方公钥
		byte[] keyBytes = decryptBASE64(key);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

		// 由甲方公钥构建乙方密钥
		DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();

		KeyPairGenerator keyPairGenerator = KeyPairGenerator
				.getInstance(keyFactory.getAlgorithm());
		keyPairGenerator.initialize(dhParamSpec);

		KeyPair keyPair = keyPairGenerator.generateKeyPair();

		// 乙方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 乙方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);

		return keyMap;
	}

	/**
	 * 加密<br>
	 * 
	 * @param data
	 *            待加密数据
	 * @param publicKey
	 *            甲方公钥
	 * @param privateKey
	 *            乙方私钥
	 * @return
	 * @throws Exception
	 */
	public static byte[] encrypt(byte[] data, String publicKey,
			String privateKey) throws Exception {

		// 生成本地密钥
		SecretKey secretKey = getSecretKey(publicKey, privateKey);

		// 数据加密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 解密<br>
	 * 
	 * @param data
	 *            待解密数据
	 * @param publicKey
	 *            乙方公钥
	 * @param privateKey
	 *            乙方私钥
	 * @return
	 * @throws Exception
	 */
	public static byte[] decrypt(byte[] data, String publicKey,
			String privateKey) throws Exception {

		// 生成本地密钥
		SecretKey secretKey = getSecretKey(publicKey, privateKey);
		// 数据解密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 构建密钥
	 * 
	 * @param publicKey
	 *            公钥
	 * @param privateKey
	 *            私钥
	 * @return
	 * @throws Exception
	 */
	private static SecretKey getSecretKey(String publicKey, String privateKey)
			throws Exception {
		// 初始化公钥
		byte[] pubKeyBytes = decryptBASE64(publicKey);

		KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

		// 初始化私钥
		byte[] priKeyBytes = decryptBASE64(privateKey);

		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);
		Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);

		KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
				.getAlgorithm());
		keyAgree.init(priKey);
		keyAgree.doPhase(pubKey, true);

		// 生成本地密钥
		SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);

		return secretKey;
	}

	/**
	 * 取得私钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static String getPrivateKey(Map<String, Object> keyMap)
			throws Exception {
		Key key = (Key) keyMap.get(PRIVATE_KEY);

		return encryptBASE64(key.getEncoded());
	}

	/**
	 * 取得公钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static String getPublicKey(Map<String, Object> keyMap)
			throws Exception {
		Key key = (Key) keyMap.get(PUBLIC_KEY);

		return encryptBASE64(key.getEncoded());
	}
}

import static org.junit.Assert.*;

import java.util.Map;

import org.junit.Test;

public class DHCoderTest {

	@Test
	public void test() throws Exception {
		// 生成甲方密钥对儿
		Map<String, Object> aKeyMap = DHCoder.initKey();
		String aPublicKey = DHCoder.getPublicKey(aKeyMap);
		String aPrivateKey = DHCoder.getPrivateKey(aKeyMap);

		System.err.println("甲方公钥:\r" + aPublicKey);
		System.err.println("甲方私钥:\r" + aPrivateKey);
		
		// 由甲方公钥产生本地密钥对儿
		Map<String, Object> bKeyMap = DHCoder.initKey(aPublicKey);
		String bPublicKey = DHCoder.getPublicKey(bKeyMap);
		String bPrivateKey = DHCoder.getPrivateKey(bKeyMap);
		
		System.err.println("乙方公钥:\r" + bPublicKey);
		System.err.println("乙方私钥:\r" + bPrivateKey);
		
		String aInput = "abc ";
		System.err.println("原文: " + aInput);

		// 由甲方公钥，乙方私钥构建密文
		byte[] aCode = DHCoder.encrypt(aInput.getBytes(), aPublicKey,
				bPrivateKey);

		// 由乙方公钥，甲方私钥解密
		byte[] aDecode = DHCoder.decrypt(aCode, bPublicKey, aPrivateKey);
		String aOutput = (new String(aDecode));

		System.err.println("解密: " + aOutput);

		assertEquals(aInput, aOutput);

		System.err.println(" ===============反过来加密解密================== ");
		String bInput = "def ";
		System.err.println("原文: " + bInput);

		// 由乙方公钥，甲方私钥构建密文
		byte[] bCode = DHCoder.encrypt(bInput.getBytes(), bPublicKey,
				aPrivateKey);

		// 由甲方公钥，乙方私钥解密
		byte[] bDecode = DHCoder.decrypt(bCode, aPublicKey, bPrivateKey);
		String bOutput = (new String(bDecode));

		System.err.println("解密: " + bOutput);

		assertEquals(bInput, bOutput);
	}

}