23、Java加密技术（五）——非对称加密算法的由来DH

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<转>http://snowolf.iteye.com/blog/382422
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。

java代码实现如下：

package org.nick.encrypt;
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 
 * @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());  
    }  
}

import java.math.BigInteger;
import java.util.Map;

import org.nick.encrypt.Coder;
import org.nick.encrypt.DESCoder;
import org.nick.encrypt.DHCoder;
import org.nick.encrypt.PBECoder;
import org.nick.encrypt.RSACoder;
public class Test
{
   
    public static void main(String[] str) throws Exception {  
    	// 甲方生成密钥对儿  
        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);  
          
        // 乙方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);  
  
  
        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);  
    }
}

甲方公钥:
MIIBpjCCARsGCSqGSIb3DQEDATCCAQwCgYEA/X9TgR11EilS30qcLuzk5/YRt1I870QAwx4/gLZR
JmlFXUAiUftZPY1Y+r/F9bow9subVWzXgTuAHTRv8mZgt2uZUKWkn5/oBHsQIsJPu6nX/rfGG/g7
V+fGqKYVDwT7g/bTxR7DAjVUE1oWkTL2dfOuK2HXKu/yIgMZndFIAccCgYEA9+GghdabPd7LvKtc
NrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwWeotU
fI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFMO/7P
SSoCAgIAA4GEAAKBgD40KS0d3OKp/rksZ6JU8toQjJL6zIH03Xg3e8R0sHZm223T29nrvrrZ9/uo
1/x3xtcwioHnJ/oIlfg5iSiXKHXDx3M1t9xUN+lxQcxkuMFGYuNzjN9n97n18BXl7fwCSSRMwM39
zh1oRtkZTkfOkCUR/MST7KRnTXu35MSWK89q

甲方私钥:
MIIBZgIBADCCARsGCSqGSIb3DQEDATCCAQwCgYEA/X9TgR11EilS30qcLuzk5/YRt1I870QAwx4/
gLZRJmlFXUAiUftZPY1Y+r/F9bow9subVWzXgTuAHTRv8mZgt2uZUKWkn5/oBHsQIsJPu6nX/rfG
G/g7V+fGqKYVDwT7g/bTxR7DAjVUE1oWkTL2dfOuK2HXKu/yIgMZndFIAccCgYEA9+GghdabPd7L
vKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwW
eotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFM
O/7PSSoCAgIABEICQEp8f42nnx7lygf/ChtUNOWP1vinFaP1n2t2kbLbaB4nfWKvA14VjYLAbbE0
F16Yrl4Vd8sGxyl1KLWpyqVUgY0=

乙方公钥:
MIIBpzCCARsGCSqGSIb3DQEDATCCAQwCgYEA/X9TgR11EilS30qcLuzk5/YRt1I870QAwx4/gLZR
JmlFXUAiUftZPY1Y+r/F9bow9subVWzXgTuAHTRv8mZgt2uZUKWkn5/oBHsQIsJPu6nX/rfGG/g7
V+fGqKYVDwT7g/bTxR7DAjVUE1oWkTL2dfOuK2HXKu/yIgMZndFIAccCgYEA9+GghdabPd7LvKtc
NrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwWeotU
fI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFMO/7P
SSoCAgIAA4GFAAKBgQCngK9V04ojxOtZE2XiMu9/P1Q1gihqv/o/6K6hFaXpf4U4VUEsJAbx87pK
rJolqy6b3RKjuWaAvR4u2U82eDphKSwD9lM4wli/XZsS1/N3sJotbcECaI/WBgj/dcqw/QMHyXPT
ju1FusRr11ZgIfsEV/hQSKEe43FW3X+8oxkGhQ==

乙方私钥:
MIIBZgIBADCCARsGCSqGSIb3DQEDATCCAQwCgYEA/X9TgR11EilS30qcLuzk5/YRt1I870QAwx4/
gLZRJmlFXUAiUftZPY1Y+r/F9bow9subVWzXgTuAHTRv8mZgt2uZUKWkn5/oBHsQIsJPu6nX/rfG
G/g7V+fGqKYVDwT7g/bTxR7DAjVUE1oWkTL2dfOuK2HXKu/yIgMZndFIAccCgYEA9+GghdabPd7L
vKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwW
eotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFM
O/7PSSoCAgIABEICQDDyNwjFNX6EIMkXMoT/pD/wkeAzRZOAnwOD854SmDOtDBlSgZqtuMxru5iq
J5FcoAXVNOhx0tL7OzmCKxLJiEE=

原文: abc
解密: abc
===============反过来加密解密==================
原文: def
解密: def
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！