PrivateChain

Created own Private Blockchain with Node.js and architect a blockchain data model. Focused on the development of a private chain of blocks which is cryptographically secure and immutable. Created a backend API web service with Express.js Framework that is consumable for client applications.

Prerequisites

You need to download & install the stable version of Node.js. from their website. Download the Postman for the testing PrivateChain API Endpoints.

Libraries Used

levelDb - Fast & simple storage - a Node.js-style LevelDB wrapper.
Crypto-Js - JavaScript library of crypto standards.
Express.js - Fast, unopinionated, minimalist web framework for Node.js.
Express JSON Bodyparser - Node.js body parsing middleware.

Configuring your project

The package.json file has been included in the project. Use NPM to initialize your project and download project dependencies.

npm install

Testing Blockchain

To run Node server on http://localhost:8000

node index.js

Running the server will instantiate 10 blocks if the blockchain height is 0.

this.getBlockHeight().then(height => {
            //Check if block height is 0
            console.log('Height of Blockchain: ' + height);
            if (height === -1) {
                //Create the Genesis Block - The first block in the blockchain
                this.addBlock(
                    new Block('First block in the chain - Genesis block')
                ).then(() => console.log('Genesis Block created!'))
                    .then(() => this.addBlock(new Block('Second Block')))
                    .then(() => this.addBlock(new Block('Third Block')))
                    .then(() => this.addBlock(new Block('Fourth Block')))
                    .then(() => this.addBlock(new Block('Fifth Block')))
                    .then(() => this.addBlock(new Block('Sixth Block')))
                    .then(() => this.addBlock(new Block('Seventh Block')))
                    .then(() => this.addBlock(new Block('Eight Block')))
                    .then(() => this.addBlock(new Block('Ninth Block')))
                    .then(() => this.addBlock(new Block('Tenth Block')))
            }
        });

Download and use Postman to send the requests to Node server.

To retrieve block use GET with Postman

http://localhost:8000/block/$height - Use block height number in place of $height

You will retrieve block JSON data at block height 0 : http://localhost:8000/block/0

{
    "hash": "54e3a3bf870a189b954563b615077de329696c0c454d02007f67903b8268a4a0",
    "height": 0,
    "body": "First block in the chain - Genesis block",
    "time": "1541672582",
    "previousBlockHash": ""
}

To add new Block to PrivateChain use POST with Postman

http://localhost:8000/block

Add JSON block data with non-empty string to "body"

{
    "hash": "",
    "height": 0,
    "body": "Add your String data here",
    "time": "0",
    "previousBlockHash": ""
}