MoneyPot new crashpoint generation

gistfile1.js

var crypto =  require('crypto');

function divisible(hash, mod) {
  /* Reduce the hash digit by digit to stay in the signed 32-bit integer range. */
  var val = hash.split('').reduce(function(r,d) {
    return ((r << 4) + parseInt(d,16)) % mod ; }, 0);
  return val == 0;
}

function genCrashpoint(serverSeed, clientSeed) {

  /* Calculate the hash using HMAC-SHA256 */
  var hash = crypto.createHmac('sha256', serverSeed);
  hash = hash.update(clientSeed).digest('hex');

  /* In 1 of 101 games the game crashes instantly. */
  if (divisible(hash, 101))
    return 0;

  /* Use the most significant 52-bit from the hash
     to calculate the crash point */
  var h = parseInt(hash.slice(0,52/4),16);
  var e = Math.pow(2,52);

  /* Assuming the 52-bit prefix is uniformly distributed
     then r is uniformly distributed over [0,1). */
  var r = h / e;

  /* Perfect is the perfectly continuous distributed
     multiplier for a zero sum game. */
  var perfect    = 1 / (1 - r);

  /* Apply a house edge to the perfect distribution. */
  var houseEdge  = (perfect-1) * 0.01;
  var multiplier = perfect - houseEdge;

  // return Math.floor(multiplier * 100);

  /* Inlining and simplifying the above yields the following version
     which is slightly more numerically stable. The multiplication
     100 * e still leaves the exactly representable integers.
  */
  return Math.floor((100 * e - h) / (e - h));
}