Java简单实现proofOfWork基本原理（使用SHA256加密）

引言

这两天开始学习区块链相关知识，在B站学习到有人用Js实现了proofOfWork基本原理，就自己用Java写了一下

proofOfWork

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;

public class proofOfWork extends SHA256{
     
    /**
     * 随机字符串
     * @param length
     * @return
     */
    public static String getRandomString(int length){
     
        String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random random=new Random();
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<length;i++){
     
            int number=random.nextInt(62);
            sb.append(str.charAt(number));
        }
        return sb.toString();
    }

    public static void main(String[] args){
     
        long starttime = System.currentTimeMillis();
        SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日-hh时mm分ss秒");
        Date startdate = new Date(starttime);
        String str = "Default";
        int count = 1;//计数
        while(true){
     
            if(!getSHA256(str).substring(0,5).equals("00000")) {
     
                str = getRandomString(10);
                count++;
            } else {
     
                long finishtime = System.currentTimeMillis();
                Date finishdate = new Date(finishtime);
                System.out.println("Start: " + starttime);
                System.out.println(format.format(startdate));
                System.out.println("Finish: " + finishtime);
                System.out.println(format.format(finishdate));
                System.out.println("String: " + str + " Count: " + count);
                System.out.println(getSHA256(str));
                break;
            }
        }
    }
}

其中用到的随机字符串参考: https://www.cnblogs.com/jpfss/p/9772019.html

SHA256

参考自: https://blog.csdn.net/weixin_34411563/article/details/91991570

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA256 {
     

    /**
     * 利用java原生的类实现SHA256加密
     *
     * @param str 加密后的报文
     * @return
     */
    public static String getSHA256(String str) {
     
        MessageDigest messageDigest;
        String encodestr = "";
        try {
     
            messageDigest = MessageDigest.getInstance("SHA-256");
            messageDigest.update(str.getBytes("UTF-8"));
            encodestr = byte2Hex(messageDigest.digest());
        } catch (NoSuchAlgorithmException e) {
     
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
     
            e.printStackTrace();
        }
        return encodestr;
    }

    /**
     * 将byte转为16进制
     *
     * @param bytes
     * @return
     */
    private static String byte2Hex(byte[] bytes) {
     
        StringBuffer stringBuffer = new StringBuffer();
        String temp = null;
        for (int i = 0; i < bytes.length; i++) {
     
            temp = Integer.toHexString(bytes[i] & 0xFF);
            if (temp.length() == 1) {
     
                // 1得到一位的进行补0操作
                stringBuffer.append("0");
            }
            stringBuffer.append(temp);
        }
        return stringBuffer.toString();
    }

    /**
     * 调用并测试SHA256
     * @param args
     */
    public static void main(String[] args){
     
        System.out.println("The hash you need is: " + getSHA256("%^&*%^&"));
    }
}