Learn what a Bitcoin miner really do by just looking at this JS source code

bitcoin-miner

Super-slow yet very educative Bitcoin miner (BTC/BCH) in Javascript

Install

$ npm install bitcoin-miner

Usage

const BTCMiner = require('bitcoin-miner');
// View this block in Block Explorer:  https://insight.bitpay.com/block/00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9
// Get it in JSON format: https://insight.bitpay.com/api/block/00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9
const block = {
	version: 536870912,
	previousblockhash: '00000000000000000061abcd4f51d81ddba5498cff67fed44b287de0990b7266',
	merkleroot: '871148c57dad60c0cde483233b099daa3e6492a91c13b337a5413a4c4f842978',
	time: 1515252561,
	bits: '180091c1'
};
let nonce = 45291990 // initial nonce

const miner = new BTCMiner(block);

// Calculate the target based on current dificulty for this block (block.bits)
const target = miner.getTarget();
console.log('The target for this block is:');
console.log(target.toString('hex'));

let hash;
let found = false;

console.log('\n[Start Mining with initial nonce:', nonce, ']');
while (nonce < (45291990+10000) && !found) { // check the next 1000 nonces starting from 45291990
	hash = miner.getHash(nonce);
	found = miner.checkHash(hash);
	console.log(hash.toString('hex'), nonce, found ? '<- nonce FOUND!!' : '');
	if (found) {
		miner.verifyNonce(block, nonce);
	}
	nonce++;
}

Example Output

API

getTarget()

Returns the target Buffer for that block based on it's bits (difficulty).

getHash(nonce)

Returns the sha256sha256 hash Buffer for that block's nonce .

checkHash(hash)

Returns a Boolean with true if the hash is lower than the target and viceversa.

checkHash(block, hash)

Print colored verification of the hash against the target on the console (the code shows another way to build the block header in javascript).

Related

• Bitcoin mining the hard way: the algorithms, protocols, and bytes - Inspiration for this module.
• What is (bitcoin) "difficulty" - Bitcoin Difficulty calculations and algorithms.

License

MIT © Carlos Guerrero