import java.security.AlgorithmParameterGenerator;
import java.security.AlgorithmParameters;
import java.security.Key;
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.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
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.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
//import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
/**
* 非对称加密算法ElGamal算法组件
* 非对称算法一般是用来传送对称加密算法的密钥来使用的。相对于RSA算法，这个算法只支持私钥加密公钥解密
* @author kongqz
* */
public class ElGamalCoder {
//非对称密钥算法
public static final String KEY_ALGORITHM="ElGamal";
/**
* 密钥长度，DH算法的默认密钥长度是1024
* 密钥长度必须是8的倍数，在160到16384位之间
* */
private static final int KEY_SIZE=256;
//公钥
private static final String PUBLIC_KEY="ElGamalPublicKey";
//私钥
private static final String PRIVATE_KEY="ElGamalPrivateKey";
/**
* 初始化密钥对
* @return Map 甲方密钥的Map
* */
public static Map<String,Object> initKey() throws Exception{
//加入对BouncyCastle支持
Security.addProvider(new BouncyCastleProvider());
AlgorithmParameterGenerator apg=AlgorithmParameterGenerator.getInstance(KEY_ALGORITHM);
//初始化参数生成器
apg.init(KEY_SIZE);
//生成算法参数
AlgorithmParameters params=apg.generateParameters();
//构建参数材料
DHParameterSpec elParams=(DHParameterSpec)params.getParameterSpec(DHParameterSpec.class);
//实例化密钥生成器
KeyPairGenerator kpg=KeyPairGenerator.getInstance(KEY_ALGORITHM) ;
//初始化密钥对生成器
kpg.initialize(elParams,new SecureRandom());
KeyPair keyPair=kpg.generateKeyPair();
//甲方公钥
PublicKey publicKey= keyPair.getPublic();
//甲方私钥
PrivateKey privateKey= keyPair.getPrivate();
//将密钥存储在map中
Map<String,Object> keyMap=new HashMap<String,Object>();
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
/**
* 公钥加密
* @param data待加密数据
* @param key 密钥
* @return byte[] 加密数据
* */
public static byte[] encryptByPublicKey(byte[] data,byte[] key) throws Exception{
//实例化密钥工厂
KeyFactory keyFactory=KeyFactory.getInstance(KEY_ALGORITHM);
//初始化公钥
//密钥材料转换
X509EncodedKeySpec x509KeySpec=new X509EncodedKeySpec(key);
//产生公钥
PublicKey pubKey=keyFactory.generatePublic(x509KeySpec);
//数据加密
Cipher cipher=Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
return cipher.doFinal(data);
}
/**
* 私钥解密
* @param data 待解密数据
* @param key 密钥
* @return byte[] 解密数据
* */
public static byte[] decryptByPrivateKey(byte[] data,byte[] key) throws Exception{
//取得私钥
PKCS8EncodedKeySpec pkcs8KeySpec=new PKCS8EncodedKeySpec(key);
KeyFactory keyFactory=KeyFactory.getInstance(KEY_ALGORITHM);
//生成私钥
PrivateKey privateKey=keyFactory.generatePrivate(pkcs8KeySpec);
//数据解密
Cipher cipher=Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* 取得私钥
* @param keyMap 密钥map
* @return byte[] 私钥
* */
public static byte[] getPrivateKey(Map<String,Object> keyMap){
Key key=(Key)keyMap.get(PRIVATE_KEY);
return key.getEncoded();
}
/**
* 取得公钥
* @param keyMap 密钥map
* @return byte[] 公钥
* */
public static byte[] getPublicKey(Map<String,Object> keyMap) throws Exception{
Key key=(Key) keyMap.get(PUBLIC_KEY);
return key.getEncoded();
}
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
//初始化密钥
//生成密钥对
Map<String,Object> keyMap=ElGamalCoder.initKey();
//公钥
byte[] publicKey=ElGamalCoder.getPublicKey(keyMap);
//私钥
byte[] privateKey=ElGamalCoder.getPrivateKey(keyMap);
//System.out.println("公钥：/n"+Base64.encodeBase64String(publicKey));
//System.out.println("私钥：/n"+Base64.encodeBase64String(privateKey));
System.out.println("================密钥对构造完毕,甲方将公钥公布给乙方，开始进行加密数据的传输=============");
String str="ElGamal密码交换算法";
System.out.println("/n===========甲方向乙方发送加密数据==============");
System.out.println("原文:"+str);
//乙方使用公钥对数据进行加密
byte[] code2=ElGamalCoder.encryptByPublicKey(str.getBytes(), publicKey);
//System.out.println("===========乙方使用公钥对数据进行加密==============");
//System.out.println("加密后的数据："+Base64.encodeBase64String(code2));
//甲方使用私钥对数据进行解密
byte[] decode2=ElGamalCoder.decryptByPrivateKey(code2, privateKey);
System.out.println("甲方解密后的数据："+new String(decode2));
}
}
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