key.js

/* eslint-disable no-console */

/** @module Key */
'use strict';

const crypto = require('crypto');

const errors = require('./errors');

const encoding = 'hex';

const emptyBuffer = Buffer.alloc(256);

const KEY_SIZE = 32;

class Key {
  constructor(keyBuffer) {
    // check thay the key size is KEY_SIZE
    if (keyBuffer.length !== 16 && keyBuffer.length !== KEY_SIZE) {
      throw errors.wrongKeyLength;
    }

    // Make sure the key is not empty
    if (emptyBuffer.equals(keyBuffer)) {
      throw errors.emptyKey;
    }

    this.buffer = keyBuffer;
  }

  /**
   * Generates a new cryptographically secure random key
   * @return {Promise<Key>} Returns a Key in case of success, an Error otherwise.
   */
  static generate(keySize) {

    return new Promise((resolve, reject) => {

      // read keySize bits of random data
      crypto.randomBytes(keySize, (err, buf) => {

        // reject the promise in case of error
        if (err) {
          reject(err);
          return;
        }

        // Debugging in case is needed
        // console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);
        // console.log('=========');

        // resolve successfully the promise in case of a valid key
        resolve(new Key(buf));
      });
    });
  }

  /**
   * Returns the key HEX encoded
   * @return {string} HEX encoded string
   */
  toString() {
    return this.buffer.toString(encoding);
  }
}

module.exports = Key;