手写区块链（二）：区块链开发中的密码学知识

手写区块链中会采用各种密码学知识

对称加密-加密秘钥和解密秘钥是同一个，缺点是秘钥无法被安全传递，常用的对称加密算法有

DES,3DES（TripleDES），AES

非对称加密-公钥加密，私钥解密

公钥由私钥生成，私钥可以推导出公钥，公钥无法推导出私钥。优点：解决秘钥传输中的安全行问题。

常用算法RSA,ECC

如何验证发送方是正确的

哈希：将一段数据经过计算转换成一段定长数据

不可逆性：几乎无法通过哈希推导出原文

无碰撞性：两个不同的原文hash后值一定不一样

常用算法MD5,SHA256

数字签名

公私钥对，私钥签名，公钥解签名

下面是这几个签名算法的具体java实现

package com.fj.blockchainmy.security;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.MessageDigest;

/**
 * @author: yangchun
 * @description:
 * @date: Created in 2019-11-12 15:38
 */
public class Coder {
    public static final String KEY_SHA = "SHA";
    public static final String KEY_MD5 = "MD5";

    /**
     * MAC算法可选以下多种算法
     *
     * <pre>
     * HmacMD5
     * HmacSHA1
     * HmacSHA256
     * HmacSHA384
     * HmacSHA512
     * </pre>
     */
    public static final String KEY_MAC = "HmacMD5";

    /**
     * BASE64解密
     *
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptBASE64(String key) throws Exception {
        return (new BASE64Decoder()).decodeBuffer(key);
    }

    /**
     * BASE64加密
     *
     * @param key
     * @return
     * @throws Exception
     */
    public static String encryptBASE64(byte[] key) throws Exception {
        return (new BASE64Encoder()).encodeBuffer(key);
    }

    /**
     * MD5加密
     *
     * @param data
     * @return
     * @throws Exception
     */
    public static byte[] encryptMD5(byte[] data) throws Exception {

        MessageDigest md5 = MessageDigest.getInstance(KEY_MD5);
        md5.update(data);

        return md5.digest();

    }

    /**
     * SHA加密
     *
     * @param data
     * @return
     * @throws Exception
     */
    public static byte[] encryptSHA(byte[] data) throws Exception {

        MessageDigest sha = MessageDigest.getInstance(KEY_SHA);
        sha.update(data);

        return sha.digest();

    }

    /**
     * 初始化HMAC密钥
     *
     * @return
     * @throws Exception
     */
    public static String initMacKey() throws Exception {
        KeyGenerator keyGenerator = KeyGenerator.getInstance(KEY_MAC);

        SecretKey secretKey = keyGenerator.generateKey();
        return encryptBASE64(secretKey.getEncoded());
    }

    /**
     * HMAC加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptHMAC(byte[] data, String key) throws Exception {

        SecretKey secretKey = new SecretKeySpec(decryptBASE64(key), KEY_MAC);
        Mac mac = Mac.getInstance(secretKey.getAlgorithm());
        mac.init(secretKey);

        return mac.doFinal(data);

    }
}

package com.fj.blockchainmy.security;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.crypto.Cipher;
import java.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;

/**
 * @author: yangchun
 * @description:
 * @date: Created in 2019-11-12 15:24
 */
public class RSACoder extends Coder{
    public static final String KEY_ALGORITHM = "RSA";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    private static final String PUBLIC_KEY = "RSAPublicKey";
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    /**
     * 用私钥对信息生成数字签名
     *
     * @param data
     *            加密数据
     * @param privateKey
     *            私钥
     *
     * @return
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        // 解密由base64编码的私钥
        byte[] keyBytes = decryptBASE64(privateKey);

        // 构造PKCS8EncodedKeySpec对象
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取私钥匙对象
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 用私钥对信息生成数字签名
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(priKey);
        signature.update(data);

        return encryptBASE64(signature.sign());
    }

    /**
     * 校验数字签名
     *
     * @param data
     *            加密数据
     * @param publicKey
     *            公钥
     * @param sign
     *            数字签名
     *
     * @return 校验成功返回true 失败返回false
     * @throws Exception
     *
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {

        // 解密由base64编码的公钥
        byte[] keyBytes = decryptBASE64(publicKey);

        // 构造X509EncodedKeySpec对象
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取公钥匙对象
        PublicKey pubKey = keyFactory.generatePublic(keySpec);

        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(pubKey);
        signature.update(data);

        // 验证签名是否正常
        return signature.verify(decryptBASE64(sign));
    }

    /**
     * 解密<br>
     * 用私钥解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(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 = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        return cipher.doFinal(data);
    }

    /**
     * 解密<br>
     * 用公钥解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] data, String key) throws Exception {
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br>
     * 用公钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception {
        // 对公钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br>
     * 用私钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(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 = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);

        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 {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);

        KeyPair keyPair = keyPairGen.generateKeyPair();

        // 公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

        // 私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

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

        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }
}

package com.blockchain.security;

import java.security.MessageDigest;
import java.util.UUID;

import org.eclipse.jetty.util.security.Credential.MD5;

/**
 * 加密工具类
 * 
 * @author aaron.rao
 *
 */
public class CryptoUtil {
   private CryptoUtil() {
   }

   public static String SHA256(String str) {
      MessageDigest messageDigest;
      String encodeStr = "";
      try {
         messageDigest = MessageDigest.getInstance("SHA-256");
         messageDigest.update(str.getBytes("UTF-8"));
         encodeStr = byte2Hex(messageDigest.digest());
      } catch (Exception e) {
         System.out.println("getSHA256 is error" + e.getMessage());
      }
      return encodeStr;
   }

   public static String MD5(String str) {
      String resultStr = MD5.digest(str);
      return resultStr.substring(4, resultStr.length());
   }

   public static String UUID() {
      return UUID.randomUUID().toString().replaceAll("\\-", "");
   }

   private static String byte2Hex(byte[] bytes) {
      StringBuilder builder = new StringBuilder();
      String temp;
      for (int i = 0; i < bytes.length; i++) {
         temp = Integer.toHexString(bytes[i] & 0xFF);
         if (temp.length() == 1) {
            builder.append("0");
         }
         builder.append(temp);
      }
      return builder.toString();
   }

}