Java加密技术之DH

我们分析DH加密算法，一种适基于密钥一致协议的加密算法。 DH Diffie-Hellman算法(D-H算法)，密钥一致协议。是由公开密钥密码体制的奠基人Diffie和Hellman所提出的一种思想。简单的说就是允许两名用户在公开媒体上交换信息以生成一致的、可以共享的密
接下来我们分析DH加密算法，一种适基于密钥一致协议的加密算法。
DH
Diffie-Hellman算法(D-H算法)，密钥一致协议。是由公开密钥密码体制的奠基人Diffie和Hellman所提出的一种思想。简单的说就是允许两名用户在公开媒体上交换信息以生成"一致"的、可以共享的密钥。换句话说，就是由甲方产出一对密钥（公钥、私钥），乙方依照甲方公钥产生乙方密钥对（公钥、私钥）。以此为基线，作为数据传输保密基础，同时双方使用同一种对称加密算法构建本地密钥（SecretKey）对数据加密。这样，在互通了本地密钥（SecretKey）算法后，甲乙双方公开自己的公钥，使用对方的公钥和刚才产生的私钥加密数据，同时可以使用对方的公钥和自己的私钥对数据解密。不单单是甲乙双方两方，可以扩展为多方共享数据通讯，这样就完成了网络交互数据的安全通讯！该算法源于中国的同余定理——中国馀数定理。

 

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；双方约定数据加密算法；乙方通过甲方公钥构建密钥对儿，将公钥公布给甲方，将私钥保留。
2.甲方使用私钥、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，发送给乙方加密后的数据；乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥对数据解密。
3.乙方使用私钥、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，发送给甲方加密后的数据；甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥对数据解密。



通过java代码实现如下：

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    
*     
* @author 梁栋  http://www.bt285.cn http://www.5a520.cn  
* @version 1.0    
* @since 1.0    
*/     
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());      
    }      
}    

再给出一个测试类：

import static org.junit.Assert.*;      
     
import java.util.Map;      
     
import org.junit.Test;      
     
/** *//**    
*     
* @author 梁栋  http://www.bt285.cn http://www.feng123.com  
* @version 1.0    
* @since 1.0    
*/     
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);      
    }      
     
}    

控制台输出：

甲方公钥:   
MIHfMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYXrgHz   
W5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpDTWSG   
kx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgANDAAJAdAWBVmIzqcko   
Ej6qFjLDL2+Y3FPq1iRbnOyOpDj71yKaK1K+FhTv04B0zy4DKcvAASV7/Gv0W+bgqdmffRkqrQ==   
  
甲方私钥:   
MIHRAgEAMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYX   
rgHzW5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpD   
TWSGkx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgAQyAjACJRfy1LyR   
eHyD+4Hfb+xR0uoIGR1oL9i9Nk6g2AAuaDPgEVWHn+QXID13yL/uDos=   
  
乙方公钥:   
MIHfMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYXrgHz   
W5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpDTWSG   
kx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgANDAAJAVEYSfBA+I9nr   
dWw3OBv475C+eBrWBBYqt0m6/eu4ptuDQHwV4MmUtKAC2wc2nNrdb1wmBhY1X8RnWkJ1XmdDbQ==   
  
乙方私钥:   
MIHSAgEAMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYX   
rgHzW5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpD   
TWSGkx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgAQzAjEAqaZiCdXp   
2iNpdBlHRaO9ir70wo2n32xNlIzIX19VLSPCDdeUWkgRv4CEj/8k+/yd   
  
原文: abc    
解密: abc    
===============反过来加密解密==================    
原文: def    
解密: def