Sending single sign in tokens using Keybaord HID for TOTP sign in

Finally got it working using built in SHA1 of the crypto module and a custom implementation of HMAC. Performance: ~16ms per token

var crypto = require('crypto');

var TOTP = function(secret)
{
  var base32decode = function(encoded)
  {
    encoded = encoded.toUpperCase();
    var result = [],
        buffer = 0,
        next = 0,
        bitsLeft = 0,
        charValue = 0,
        i = 0;
    for ( ; i < encoded.length; i++ ) {
      charValue = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'.indexOf(encoded.charAt(i));
      buffer <<= 5;
      buffer |= charValue & 31;
      bitsLeft += 5;
      if (bitsLeft >= 8) {
        result[next++] = (buffer >> (bitsLeft - 8)) & 0xFF;
        bitsLeft -= 8;
      }
    }
    return result;
  };

  var intToByteArray = (x) => [0, 0, 0, 0, x >> 24 & 0xFF, x >> 16 & 0xFF, x >> 8 & 0xFF, x & 0xFF];

  var keyBytes = base32decode(secret);

  if ( keyBytes.length > 64 ) {
    keyBytes = [].slice.call(crypto.SHA1(keyBytes));
  }

  while ( keyBytes.length < 64 ) {
    keyBytes.push(0x00);
  }

  var o_key_pad = keyBytes.map((byte) => byte ^ 0x5c);
  var i_key_pad = keyBytes.map((byte) => byte ^ 0x36);

  var digest = function(messageBytes) {
    return crypto.SHA1(o_key_pad.concat(crypto.SHA1(i_key_pad.concat(messageBytes))));
  };

  this.generate = function(tokenPeriod, digits) {
    tokenPeriod = (tokenPeriod == undefined ? 30 : tokenPeriod) * 1000;
    digits = digits == undefined ? 6 : digits;
    var epoch = Math.floor(new Date().getTime() / tokenPeriod);
    var hmacBytes = digest(intToByteArray(epoch));
    var offset = hmacBytes[hmacBytes.length - 1] & 0x0F;
    var dt = ((hmacBytes[offset] & 0x7f) << 24) | (hmacBytes[offset + 1] << 16) | (hmacBytes[offset + 2] << 8) | hmacBytes[offset + 3];
    return dt % Math.pow(10, digits);
  };
};

var totp = new TOTP("NBQW44ZAO52XE43UEBUXG5BANZSSAZTVMNVWS3THEBTWM3RAMRZWY23HNIQGY23TMRVGO3DLNIQHGZDMNNTWUZDTNJTWY2ZAONSGWZDL");

setWatch(function() {
  var start = new Date().getTime();
  var otp = totp.generate();
  var end = new Date().getTime();
  console.log(otp);
  console.log('Took: ' + (end - start) + 'ms');
}, BTN, {debounce:100,repeat:true, edge:"rising"});