Know Initial Guide for Implementing Blockchain in Java Technology

Know Initial Guide for Implementing Blockchain in Java Technology

Blockchain is the backbone technology behind digital cryptocurrencies such as Bitcoin. In this tutorial, we’ll explore the basic concepts of blockchain technology while implementing a small app in Java that will focus on these ideas.

Lastly, we’ll discuss some advanced topics and real-world use cases for blockchain outside its traditional realm of digital currencies.

What Is Blockchain?

So, let’s first define what exactly blockchain is…

Well, it traces its origin back to the whitepaper published by Satoshi Nakamoto on Bitcoin, back in 2008. Blockchain is a decentralized ledger of information. It consists of blocks of data connected through the use of cryptography.

A network node connects over the public network and contains this blockchains database at all times. When you put all these pieces together, you can see how valuable blockchain technology could become for many different applications outside of just cryptocurrency-based transactions.

There are a few key points worth mentioning about blockchain technology. Let’s discuss them:

Tamper-proof – Blockchain blocks are cryptographically secure, which means that tampering with any one block will result in all subsequent blocks being changed accordingly.

Decentralized – Blockchain networks don’t rely on central servers or master nodes, rather every single node participates to keep the network running smoothly and securely.

Transparent – All nodes participating in the system validate each other’s transactions, making it difficult for anyone within the system to tamper with anything without detection.

How does Blockchain work?

Well, now it’s time to learn about how blockchain works. Let’s start with the basics: at its core, a single block can contain multiple transactions or other types of valuable data – for example, an input and output transaction

Mining a Block

We represent a block by its hash value. Producing the hash value of a block is called mining the block, which can often take up significant computing power because it serves as the proof of work. The hash of a typical block includes this information.

Primarily, the hash of a block consists of its transactions- timestamps and all.

The hash also consists of a nonce (a random number) used in cryptography.

Finally, the hash of the current block also includes the hash of its predecessor(s). Nodes across the network will sometimes compete to mine blocks at once; mining involves solving a computationally difficult problem. When this happens, there is an agreement among nodes that whoever solves it first will win!

In this way, a newly-mined block becomes part of the blockchain when it is verified by the nodes. There are different types of consensus protocols that we can use for verification purposes.

Nodes in the network adopt one type of protocol to detect or reject an impostor branch (malicious). So even if you introduce an impostor branch to the system, it will soon be detected and rejected by most nodes in the system.

Basic Blockchain in Java:

Now that we have an understanding of what blockchain is and how it operates, let’s start building a basic application in java. Our simple example here will illustrate the basic concepts we have just seen.

Building a production-grade app entails many considerations which are beyond the scope of this tutorial. Nonetheless, we’ll touch upon some advanced topics later on.

Implementing a Block:

Firstly, we need to define a Java object that will hold the data for our block. Let’s take a look at what it contains:

Hash of the previous block—essential for building out the chain.

The actual data—any information having value, like a contract.

The timestamp of when this block was created.

A nonce—an arbitrary number used in cryptography.

// Java implementation for creating// a block in a Blockchain import java.util.Date; public class Block { // Every block contains// a hash, previous hash and// data of the transaction madepublic String hash;public String previousHash;private String data;private long timeStamp; // Constructor for the blockpublic Block(String data,String previousHash){this.data = data;this.previousHash= previousHash;this.timeStamp= new Date().getTime();this.hash= calculateHash();} // Function to calculate the hashpublic String calculateHash(){// Calling the “crypt” class// to calculate the hash// by using the previous hash,// timestamp and the dataString calculatedhash= crypt.sha256(previousHash+ Long.toString(timeStamp)+ data); return calculatedhash;}}

Finally, the hash of this object; is calculated based on other data.

Calculating the Hash

Now, how do we calculate the hash of a block? We’ve used methods that tell us about hashing blocks before but have not seen one implemented yet. This method implements calculating hashes for blocks.

Calculating hashes is nothing more than mapping input data (which could be anything) to output data (also random). Hashes are very sensitive and unforgiving when it comes to changing even the smallest bit of input information.

The only way someone can know what was originally hashed would be if they know both the original pieces being hashed as well as all previous hashes – which would take years’ worth of computing power.

It’s difficult enough to create new hashes without altering anything at all; these properties make hashing perfect for encryption purposes! Let’s see how we calculate a hash in Java.

First, we concatenate different parts of the block to generate a hash.

Then, we get an instance of the SHA-256 hash function from MessageDigest.

Then, we generate the hash value of our input data (a byte array)

Finally, we transform the byte array into a hex string.

// Java program for Generating Hashes import java.security.MessageDigest; public class crypt { // Function that takes the string input// and returns the hashed string.public static String sha256(String input){try {MessageDigest sha= MessageDigest.getInstance(“SHA-256”);int i = 0; byte[] hash= sha.digest(input.getBytes(“UTF-8”)); // hexHash will contain// the Hexadecimal hashStringBuffer hexHash= new StringBuffer(); while (i < hash.length) {String hex= Integer.toHexString(0xff & hash[i]);if (hex.length() == 1)hexHash.append(‘0’);hexHash.append(hex);i++;} return hexHash.toString();}catch (Exception e) {throw new RuntimeException(e);}}}

Storing the Blocks: Now, let us store these blocks in an ArrayList of Block type, along with their hash values by calling the constructor for each block.

// Java implementation to store// blocks in an ArrayList import java.util.ArrayList; public class GFG { // ArrayList to store the blockspublic static ArrayList<Block> blockchain= new ArrayList<Block>(); // Driver codepublic static void main(String[] args){// Adding the data to the ArrayListblockchain.add(new Block(“First block”, “0”));blockchain.add(new Block(“Second block”,blockchain.get(blockchain.size() – 1).hash)); blockchain.add(new Block(“Third block”,blockchain.get(blockchain.size() – 1).hash)); blockchain.add(new Block(“Fourth block”,blockchain.get(blockchain.size() – 1).hash)); blockchain.add(new Block(“Fifth block”,blockchain.get(blockchain.size() – 1).hash));}}

Blockchain Validity: Ultimately, it is necessary to check the validity of a blockchain. To do this, one must create a boolean method which verifies if the hashed value (hash) matches its own calculated hash. If every block has an identical hashed value than it is assumed to be valid. Below is an implementation for this validation process

// Java implementation to check// validity of the blockchain // Function to check// validity of the blockchainpublic static Boolean isChainValid(){Block currentBlock;Block previousBlock; // Iterating through// all the blocksfor (int i = 1;i < blockchain.size();i++) { // Storing the current block// and the previous blockcurrentBlock = blockchain.get(i);previousBlock = blockchain.get(i – 1); // Checking if the current hash// is equal to the// calculated hash or notif (!currentBlock.hash.equals(currentBlock.calculateHash())) {System.out.println(“Hashes are not equal”);return false;} // Checking of the previous hash// is equal to the calculated// previous hash or notif (!previousBlock.hash.equals(currentBlock.previousHash)) {System.out.println(“Previous Hashes are not equal”);return false;}} // If all the hashes are equal// to the calculated hashes,// then the blockchain is validreturn true;}

Wrapping Up

Blockchain is a decentralized network system where data breaches are very hard to happen. This is because every block has its own unique and different hash code so it would be hard for someone to tamper with the data without changing all blocks at once.

Or! having access to other users’ private keys would make hacking even harder. Hacking through blockchain can also be done but it would leave some fingerprints behind that could easily identify what happened and who did it. Facing Issues in blockchain implementation? Hire java Developers for proper guidance.