cyberpirate92

public void mine(int difficulty) throws NoSuchAlgorithmException { 
  String pre = ""; 
  for (; pre.length() < difficulty; pre += "0"); 
  while(!getHash().startsWith(pre)) 
    nonce++;
}

cyberpirate92

5FECEB66FFC86F38D952786C6D696C79C2DBC239DD4E91B46729D73A27FB57E9	1527703318986	0	Hello 
E5A6134694C22742C88639C8E3442BDF19FB7843F829B2351B24CB0CCC9AA917	1527703318986	0	World 
759F215F98C2374696552663280BBC90378741DBD36B067A6DF0FAA50DD38769	1527703318986	0	Whatever 
Is valid chain : true 
Is valid chain : false

cyberpirate92

public static void main(String[] args) { 
  try { 
    var blockChain = new BlockChain(); 
    
    Block block1 = new Block("Hello"); 
    Block block2 = new Block("World"); 
    Block block3 = new Block("Whatever"); 
    
    blockChain.addBlock(block1); 
    blockChain.addBlock(block2); 

cyberpirate92

5FECEB66FFC86F38D952786C6D696C79C2DBC239DD4E91B46729D73A27FB57E9	1527703318986	0	Hello 
E5A6134694C22742C88639C8E3442BDF19FB7843F829B2351B24CB0CCC9AA917	1527703318986	0	World 
759F215F98C2374696552663280BBC90378741DBD36B067A6DF0FAA50DD38769	1527703318986	0	Whatever 
Is valid chain : true

cyberpirate92

public class Main { 
  public static void main(String[] args) { 
    try { 
      var blockChain = new BlockChain(); 
      
      Block block1 = new Block("Hello"); 
      Block block2 = new Block("World"); 
      Block block3 = new Block("Whatever"); 
      
      blockChain.addBlock(block1); 

cyberpirate92

import java.security.NoSuchAlgorithmException; 
import java.util.ArrayList; 
import java.util.List; 

public class BlockChain { 
  public List<Block> chain; 
  
  public BlockChain() { 
    chain = new ArrayList<>(); 
  } 

cyberpirate92

public class Block {
  public long nonce; 
  private long timestamp; 
  public String transactionData; 
  public String previousBlockHash; 
  
  public Block(String transactionData) { 
    nonce = 0; 
    timestamp = System.currentTimeMillis(); 
    this.transactionData = transactionData; 

cyberpirate92

import java.security.MessageDigest; 
import java.security.NoSuchAlgorithmException; 
import java.nio.charset.StandardCharsets; 
public class CryptoHelper { 
  public static String sha256(String text) throws NoSuchAlgorithmException { 
    MessageDigest digest = MessageDigest.getInstance("SHA-256"); 
    digest.update(text.getBytes(StandardCharsets.UTF_8)); 
    byte[] hash = digest.digest(); 
    StringBuffer sb = new StringBuffer(); 
    for (int i = 0; i < hash.length; i++) 

cyberpirate92

BD5370EB390348AA71C25C65E700E36E81BA370C665C6398BAEF7C8843C0A1C2

cyberpirate92

$ java HashBreaker 

Nonce Finder 
Message : Block 4152799093110700000277418AFAF4F19430EDE51B573FAE4C3DCB13B20352A43778802DF0E12F 
Difficulty : 5 

Calculating... 

Valid Nonce : 691412 
Hash : 00000FDAD0C18DB1C15980029F94D6C37DE8B316FF531B9E7ACA233EC95545CE