Java加密算法（七）——非对称加密算法最高级ECC

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加密算法（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加密算法（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
 * 
 */
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。

再提供一个测试类：

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;

/**
 * 
 * ECC测试
 */
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

　　来源于：http://snowolf.iteye.com/blog