Blockchain Simulation API powered by NodeJS & Express

A proof of concept simulation of a blockchain hosted on a decentralized network.

To run the app locally:

Clone the repository and run npm install to install all the necessary node_modules for running the application.
Simulate the project being run on multiple devices by running npm run node_1, npm run node_2, npm run node_3, npm run node_4, and npm run node_5 in separate terminal tabs.
More addresses can be added by adding the following line(s) to the package.json file under scripts:

"node_6": "nodemon --watch dev -e js dev/networkNode.js [number] http://localhost:[number]"

API Root URLS:

Available API Endpoints:

Endpoints	Request Type	Description
`/blockchain`	GET	Returns the complete blockchain at the root node
`/transaction`	POST	Adds the specified transaction to pending transactions
`/transaction/broadcast`	POST	Creates a new transaction and broadcasts the transaction to all the other nodes in the network, adding the transaction to each of the node's pending transactions
`/mine`	GET	Mines a new block by producing a proof of work (Uses SHA256 encryption). Returns whether block was mined successfully. Issues a reward transaction of 12.5 to the miner and broadcasts the mining to all the other network nodes.
`/receive-new-block`	POST	Adds the received block to the current node's blockchain
`/register-and-broadcast-node`	POST	Adds the specified node address to the network nodes of the current blockchain and broadcasts the node address to all the other existing network nodes to simulate a decentralized blockchain network.
`/register-node`	POST	Adds the specified node address to the network nodes of the current blockchain
`/register-nodes-bulk`	POST	Adds the specified network nodes to the current blockchain's network nodes
`/consensus`	GET	Uses the Longest Chain Rule to find a consensus among all the network nodes to decide whether to update the chain at the current node. Compares length of current node's chain to the other nodes' chains and sets the current node's chain to the longest chain in the network.
`/block/:hash`	GET	Returns the block with the specified hash
`/transaction/:id`	GET	Returns the transaction and block with the specified transaction id
`/address/:address`	GET	Returns the balance and transactions of the specified user address

Blockchain Class (blockchain.js)

The Blockchain class is a prototype data abstraction for a blockchain.

Default Constructor

constructor() {
        this.chain = [] //A list of all the blocks in the blockchain
        this.pendingTransactions = [] //All the pending transactions before the block has been mined
        this.nodeURL = nodeURL; //The current address of the node
        this.networkNodes = []; //A list of all the other nodes in the decentralized network
        //Genesis Block
        this.createBlock(0, '0', '0');
}

Available Functions

createBlock(nonce, prevHash, hash)

Creates a new block with the specified nonce, prevHash, and hash

nonce (Number used once) - unique number to be found when mining for the block
prevHash - the hash of the previous block in the chain
hash - the hash of the current block

getPrevBlock()

Returns the previous block in the chain

createTransaction(amount, sender, recipient)

Creates a new transaction with the specified sender, recipient, and amount

amount - the amount of value to be sent to the recipient
sender - the address of the sender
recipient - the address of the recipient

addTransactionToPendingTransactions(transaction)

Adds the specified transaction to the pending transactions of the blockchain

transaction - a transaction object

{
    amount,
    sender,
    recipient,
    id
}

hash(prevHash, curBlockData, nonce)

Creates a SHA256 encryption hash for the specified prevHash, curBlockData, and nonce

prevHash - the hash of the previous block in the chain
curBlockData -

{
   transactions: [], //The current transactons in the block
   index: 0 //index of the block in the chain
}

nonce (Number used once) - unique number to be found when mining for the block

proofOfWork(prevHash, curBlockData)

Finds the nonce associated with the specified prevHash and curBlockData that begins with "0000"

prevHash - the hash of the previous block in the chain
curBlockData -

{
   transactions: [], //The current transactons in the block
   index: 0 //index of the block in the chain
}

chainIsValid(blockchain)

Returns true or false based on whether the specified blockchain has matching hashes and previous hashes as well as a hash that starts with "0000"

blockchain - a list of all blocks in the blockchain

getBlock(hash)

Returns the block with the specified hash

hash - the hash of the current block

getTransaction(id)

Returns the transaction and block with the specified transaction id

id - The unique id of the transaction

getAddressData(address)

Returns the balance and transactions of the specified user address

address - A unique address of the user

sguduguntla/Blockchain-API-Simulation