Java加密技术(五)——非对称加密算法的由来DH

Java非对称加密算法dh
    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:Coder类见 Java加密技术(一)
Java代码  收藏代码
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
* @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:
Java代码  收藏代码
import static org.junit.Assert.*; 
 
import java.util.Map; 
 
import org.junit.Test; 
 
/**

* @author 梁栋
* @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:
Console代码  收藏代码
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  


如我所言,甲乙双方在获得对方公钥后可以对发送给对方的数据加密,同时也能对接收到的数据解密,达到了数据安全通信的目的!
posted @ 2013-11-07 10:39  crazy_itman  阅读(352)  评论(0编辑  收藏  举报