package Asymmetric.encryption;

import org.apache.commons.codec.binary.Hex;
import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.util.Objects;

/**
 * {@link http://www.cnblogs.com/allanzhang/}
 * @author 小卖铺的老爷爷
 * DH 相当于外面的一层封装。进行密钥交换用的。并不是一种明确的加解密算法
 */
public class DHTest {
    public static final String src = "laoyeye dh";

    public static void main(String[] args) throws Exception {
        jdkDH();
    }

    public static void jdkDH() throws Exception {
        //发送方初始化自己的密钥对，并且把公钥发送给接收方
        KeyPairGenerator senderKeyPairGenerator = KeyPairGenerator.getInstance("DH");
        senderKeyPairGenerator.initialize(512);
        KeyPair senderKeyPair = senderKeyPairGenerator.generateKeyPair();
        PublicKey senderPublicKey = senderKeyPair.getPublic();//公钥是要发送给接收方的，此处同一类内省略该操作

        //接收方用发送方的公钥初始化自己的密钥对
        DHParameterSpec dhParameterSpec = ((DHPublicKey) senderPublicKey).getParams();//用发送方的公钥产生算法参数
        KeyPairGenerator receiverKeyPairGenerator = KeyPairGenerator.getInstance("DH");
        receiverKeyPairGenerator.initialize(dhParameterSpec);//初始化接收方的KeyPairGenerator
        KeyPair receiverKeyPair = receiverKeyPairGenerator.generateKeyPair();//生产接收方的密钥对

        //DES密钥构建
        KeyAgreement keyAgreement = KeyAgreement.getInstance("DH");
        //接收方根据自己的私钥和发送方的公钥创建DES密钥
        keyAgreement.init(receiverKeyPair.getPrivate());//接收方的私钥
        keyAgreement.doPhase(senderKeyPair.getPublic(), true);//发送方的公钥
        SecretKey receiverDesKey = keyAgreement.generateSecret("DES");

        //发送方根据自己的私钥和接收方的公钥创建DES密钥
        keyAgreement.init(senderKeyPair.getPrivate());
        keyAgreement.doPhase(receiverKeyPair.getPublic(), true);
        SecretKey senderDesKey = keyAgreement.generateSecret("DES");

        //判断两方得到的DES密钥是不是相等的
        if (Objects.equals(senderDesKey, receiverDesKey)) {
            System.out.println("双方密钥相同");
        }

        //加密
        Cipher cipher = Cipher.getInstance("DES");
        cipher.init(Cipher.ENCRYPT_MODE, senderDesKey);
        byte[] result = cipher.doFinal(src.getBytes());
        System.out.println("JDK DH ENCRYPT:" + Hex.encodeHexString(result));

        //解密
        cipher.init(Cipher.DECRYPT_MODE, receiverDesKey);
        result = cipher.doFinal(result);
        System.out.println("JDK DH DECRYPT:" + new String(result));

    }

}

package Asymmetric.encryption;

import java.security.AlgorithmParameterGenerator;
import java.security.AlgorithmParameters;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Security;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;
import javax.crypto.spec.DHParameterSpec;

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
/**
 * {@link http://www.cnblogs.com/allanzhang/}
 * @author 小卖铺的老爷爷
 *
 */
public class ElGamalTest {

    public static final String src = "laoyeye Elgamal test";
    public static void main(String[] args) 
    {
        jdkElgamal();

    }
    // jdk实现：“公钥加密，私钥解密” ， 因为Elgamal不支持“私钥加密、公钥解密”。
    public static void jdkElgamal()
    {        
        try 
        {
            // 加入对BouncyCastle支持  
            Security.addProvider(new BouncyCastleProvider());
            
            // 初始化密钥
            AlgorithmParameterGenerator algorithmParameterGenerator = AlgorithmParameterGenerator.getInstance("Elgamal");
            // 初始化参数生成器
            algorithmParameterGenerator.init(256);
            // 生成算法参数
            AlgorithmParameters algorithmParameters = algorithmParameterGenerator.generateParameters();
            // 构建参数材料
            //JDK没有提供对ei的支持，但是jce框架提供了构建秘钥对的方式DHParameterSpec
            DHParameterSpec dhParameterSpec = (DHParameterSpec)algorithmParameters.getParameterSpec(DHParameterSpec.class);
            // 实例化密钥对生成器
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("Elgamal");    
            // 初始化密钥对生成器  
            keyPairGenerator.initialize(dhParameterSpec, new SecureRandom());
            KeyPair keyPair = keyPairGenerator.generateKeyPair();
            // 公钥
            PublicKey elGamalPublicKey = keyPair.getPublic();
            // 私钥 
            PrivateKey elGamalPrivateKey = keyPair.getPrivate();
            System.out.println("Public Key:" + Base64.encodeBase64String(elGamalPublicKey.getEncoded()));
            System.out.println("Private Key:" + Base64.encodeBase64String(elGamalPrivateKey.getEncoded()));
            // 初始化公钥  
            // 密钥材料转换
            X509EncodedKeySpec x509EncodedKeySpec2 = new X509EncodedKeySpec(elGamalPublicKey.getEncoded());
            // 实例化密钥工厂
            KeyFactory keyFactory = KeyFactory.getInstance("Elgamal");
            // 产生公钥
            PublicKey publicKey2 = keyFactory.generatePublic(x509EncodedKeySpec2);
            // 数据加密 
            // Cipher cipher = Cipher.getInstance("Elgamal");
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm()); 
            cipher.init(Cipher.ENCRYPT_MODE, publicKey2);
            byte[] result2 = cipher.doFinal(src.getBytes());
            System.out.println("Elgamal ---- 加密:" + Base64.encodeBase64String(result2));
            // 数据解密
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec5 = new PKCS8EncodedKeySpec(elGamalPrivateKey.getEncoded());
            keyFactory = KeyFactory.getInstance("Elgamal");
            PrivateKey privateKey5 = keyFactory.generatePrivate(pkcs8EncodedKeySpec5);
//            Cipher cipher5 = Cipher.getInstance("Elgamal");
            Cipher cipher5 = Cipher.getInstance(keyFactory.getAlgorithm()); 
            cipher5.init(Cipher.DECRYPT_MODE, privateKey5);
            byte[] result5 = cipher5.doFinal(result2);
            System.out.println("Elgamal ---- 解密:" + new String(result5));
        } catch (Exception e) {
            e.printStackTrace();
        }
        
    }
        
}