wallet.js

let EC = require("elliptic").ec,
    fs = require("fs");

const ec = new EC('secp256k1'),
    privateKeyLocation = __dirname + '/wallet/private_key';

exports.initWallet = () => {
    let privateKey;
    if (fs.existsSync(privateKeyLocation)) {
        const buffer = fs.readFileSync(privateKeyLocation, 'utf8');
        privateKey = buffer.toString();
    } else {
        privateKey = generatePrivateKey();
        fs.writeFileSync(privateKeyLocation, privateKey);
    }

    const key = ec.keyFromPrivate(privateKey, 'hex');
    const publicKey = key.getPublic().encode('hex');
    return ({ 'privateKeyLocation': privateKeyLocation, 'publicKey': publicKey });
};

const generatePrivateKey = () => {
    const keyPair = ec.genKeyPair();
    const privateKey = keyPair.getPrivate();
    return privateKey.toString(16);
};