Java加密技术（七）——非对称加密算法最高级ECC

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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） 

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
     * 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
     * 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 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 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 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 keyMap = new HashMap(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： 

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 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： 

公钥:
MEAwEAYHKoZIzj0CAQYFK4EEAAEDLAAEAv4TwFN7vBGsqgfXk95ObV5clO7oAokHD7BdOP9YMh8u
gAU21TjM2qPZ

私钥：
MDICAQAwEAYHKoZIzj0CAQYFK4EEAAEEGzAZAgEBBBTYJsR3BN7TFw7JHcAHFkwNmfil7w==

加密前: abc

解密后: abc