Java加密技术（七）

ECC

ECC-Elliptic Curves Cryptography，椭圆曲线密码编码学，是目前已知的公钥体制中，对每比特所提供加密强度最高的一种体制。在软件注册保护方面起到很大的作用，一般的序列号通常由该算法产生。

当我开始整理《Java加密技术（二）》的时候，我就已经在开始研究ECC了，但是关于Java实现ECC算法的资料实在是太少了，无论是国内还是国外的资料，无论是官方还是非官方的解释，最终只有一种答案——ECC算法在jdk1.5后加入支持，目前仅仅只能完成密钥的生成与解析。

如果想要获得ECC算法实现，需要调用硬件完成加密/解密（ECC算法相当耗费资源，如果单纯使用CPU进行加密/解密，效率低下），涉及到Java
Card领域，PKCS#11。

其实，PKCS#11配置很简单，但缺乏硬件设备，无法尝试！



尽管如此，我照旧提供相应的Java实现代码，以供大家参考。



通过java代码实现如下：Coder类见 Java加密技术（一）

Java代码



import java.math.BigInteger;

import java.security.Key;

import java.security.KeyFactory;

import java.security.interfaces.ECPrivateKey;

import java.security.interfaces.ECPublicKey;

import java.security.spec.ECFieldF2m;

import java.security.spec.ECParameterSpec;

import java.security.spec.ECPoint;

import java.security.spec.ECPrivateKeySpec;

import java.security.spec.ECPublicKeySpec;

import java.security.spec.EllipticCurve;

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.NullCipher;



import sun.security.ec.ECKeyFactory;

import sun.security.ec.ECPrivateKeyImpl;

import sun.security.ec.ECPublicKeyImpl;



/**

* ECC安全编码组件

*

* @author 梁栋

* @version 1.0

* @since 1.0

*/

public abstract class ECCCoder extends Coder {



public static final String ALGORITHM = "EC";

private static final String PUBLIC_KEY = "ECCPublicKey";

private static final String PRIVATE_KEY = "ECCPrivateKey";



/**

* 解密<br>

* 用私钥解密

*

* @param data

* @param key

* @return

* @throws Exception

*/

public static byte[] decrypt(byte[] data, String key) throws Exception {

// 对密钥解密

byte[] keyBytes = decryptBASE64(key);



// 取得私钥

PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

KeyFactory keyFactory = ECKeyFactory.INSTANCE;



ECPrivateKey priKey = (ECPrivateKey) keyFactory

.generatePrivate(pkcs8KeySpec);



ECPrivateKeySpec ecPrivateKeySpec = new ECPrivateKeySpec(priKey.getS(),

priKey.getParams());



// 对数据解密

// TODO Chipher不支持EC算法 未能实现

Cipher cipher = new NullCipher();

// Cipher.getInstance(ALGORITHM, keyFactory.getProvider());

cipher.init(Cipher.DECRYPT_MODE, priKey, ecPrivateKeySpec.getParams());



return cipher.doFinal(data);

}



/**

* 加密<br>

* 用公钥加密

*

* @param data

* @param privateKey

* @return

* @throws Exception

*/

public static byte[] encrypt(byte[] data, String privateKey)

throws Exception {

// 对公钥解密

byte[] keyBytes = decryptBASE64(privateKey);



// 取得公钥

X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);

KeyFactory keyFactory = ECKeyFactory.INSTANCE;



ECPublicKey pubKey = (ECPublicKey) keyFactory

.generatePublic(x509KeySpec);



ECPublicKeySpec ecPublicKeySpec = new ECPublicKeySpec(pubKey.getW(),

pubKey.getParams());



// 对数据加密

// TODO Chipher不支持EC算法 未能实现

Cipher cipher = new NullCipher();

// Cipher.getInstance(ALGORITHM, keyFactory.getProvider());

cipher.init(Cipher.ENCRYPT_MODE, pubKey, ecPublicKeySpec.getParams());



return cipher.doFinal(data);

}



/**

* 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());

}



/**

* 初始化密钥

*

* @return

* @throws Exception

*/

public static Map<String, Object> initKey() throws Exception {

BigInteger x1 = new BigInteger(

"2fe13c0537bbc11acaa07d793de4e6d5e5c94eee8", 16);

BigInteger x2 = new BigInteger(

"289070fb05d38ff58321f2e800536d538ccdaa3d9", 16);



ECPoint g = new ECPoint(x1, x2);



// the order of generator

BigInteger n = new BigInteger(

"5846006549323611672814741753598448348329118574063", 10);

// the cofactor

int h = 2;

int m = 163;

int[] ks = { 7, 6, 3 };

ECFieldF2m ecField = new ECFieldF2m(m, ks);

// y^2+xy=x^3+x^2+1

BigInteger a = new BigInteger("1", 2);

BigInteger b = new BigInteger("1", 2);



EllipticCurve ellipticCurve = new EllipticCurve(ecField, a, b);



ECParameterSpec ecParameterSpec = new ECParameterSpec(ellipticCurve, g,

n, h);

// 公钥

ECPublicKey publicKey = new ECPublicKeyImpl(g, ecParameterSpec);



BigInteger s = new BigInteger(

"1234006549323611672814741753598448348329118574063", 10);

// 私钥

ECPrivateKey privateKey = new ECPrivateKeyImpl(s, ecParameterSpec);



Map<String, Object> keyMap = new HashMap<String, Object>(2);



keyMap.put(PUBLIC_KEY, publicKey);

keyMap.put(PRIVATE_KEY, privateKey);



return keyMap;

}



}

请注意上述代码中的TODO内容，再次提醒注意，Chipher不支持EC算法 ，以上代码仅供参考。Chipher、Signature、KeyPairGenerator、KeyAgreement、SecretKey均不支持EC算法。为了确保程序能够正常执行，我们使用了NullCipher类，验证程序。

照旧提供一个测试类：

Java代码



import static org.junit.Assert.*;



import java.math.BigInteger;

import java.security.spec.ECFieldF2m;

import java.security.spec.ECParameterSpec;

import java.security.spec.ECPoint;

import java.security.spec.ECPrivateKeySpec;

import java.security.spec.ECPublicKeySpec;

import java.security.spec.EllipticCurve;

import java.util.Map;



import org.junit.Test;



/**

*

* @author 梁栋

* @version 1.0

* @since 1.0

*/

public class ECCCoderTest {



@Test

public void test() throws Exception {

String inputStr = "abc";

byte[] data = inputStr.getBytes();



Map<String, Object> keyMap = ECCCoder.initKey();



String publicKey = ECCCoder.getPublicKey(keyMap);

String privateKey = ECCCoder.getPrivateKey(keyMap);

System.err.println("公钥: \n" + publicKey);

System.err.println("私钥： \n" + privateKey);



byte[] encodedData = ECCCoder.encrypt(data, publicKey);



byte[] decodedData = ECCCoder.decrypt(encodedData, privateKey);



String outputStr = new String(decodedData);

System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);

assertEquals(inputStr, outputStr);

}

}

控制台输出：

Console代码



公钥:

MEAwEAYHKoZIzj0CAQYFK4EEAAEDLAAEAv4TwFN7vBGsqgfXk95ObV5clO7oAokHD7BdOP9YMh8u

gAU21TjM2qPZ



私钥：

MDICAQAwEAYHKoZIzj0CAQYFK4EEAAEEGzAZAgEBBBTYJsR3BN7TFw7JHcAHFkwNmfil7w==



加密前: abc



解密后: abc