generateBase32Key.js

// Adapted from Python's implementation of randrange.
// https://github.com/python/cpython/blob/master/Lib/random.py

const crypto = require('crypto');
const bases = require('bases');

const START = 33554432; // '100000'
const END = 1073741824; // 'ZZZZZZ'

function getrandbits(k) {
  const numbytes = Math.floor((k + 7) / 8);
  const x = crypto.randomBytes(numbytes).readUIntBE(0, numbytes);

  return x >>> (numbytes * 8 - k);
}

function randbelow(n) {
  const k = n.toString(2).length;
  let r = getrandbits(k);
  while (r >= n) {
    r = getrandbits(k);
  }

  return r;
}

function randrange(start, stop) {
  const width = stop - start;

  return start + randbelow(width);
}

function getRandomKey() {
  return bases.toBase32(randrange(START, END));
}

module.exports = getRandomKey;