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） 

 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