Building Your Own Private Blockchain

About

Building your Private Blockchain utilizing Node.js with LevelDB.

Download the project.
Run npm install to install the project dependencies
The project uses the following dependencies npm install level - Fast and Simple storage wrapper npm install crypto-js - JavaScript library of crypto standards

Block.js - Creates a new block
Blockchain.js - Creates a new blockchain class which has the following methods

generateGenesisBlock - Creates Genesis block when the BlockChain is created
getBlockHeight - Method that returns the height of the BlockChain
getBlock - Method to get the block data
addBlock - Method to add block to the BlockChain
validateBlock - Method that validates the blocks
validateBlockLink - Method that validates the link(hash) between the blocks
validateBlockChain - Method that validates the blockchain
_modifyBlock - Utility method to modify block(for testing)
clearDBData - Utility method to clear test data
LevelSandbox.js - Implements the data interaction for your Private Blockchain. It is the Data Access Layer for the application

addLevelDBData - Method that adds data to LevelDB.
getLevelDBData - Method to fetch data from LevelDB.
getBlocksCount - Method to get the count(key) from Level DB.
delLevelDBData - Utility method to delete the test data.
getAllBlocks - Utility method to fetch entire data.
simpleChain.js - File which has all the methods to test the various functionalities to validate the BlockChain.

In order to validate a BlockChain, the block is validated first and later the link(hash) between the blocks is validated. This ensures that the blocks are not tampered and broken. Once a block becomes Invalid, the entire blockchain becomes Invalid notifying all the blocks following the tampered block.

Open command prompt and type node simpleChain.js (make sure the functionality to be tested is uncommented)