Basics of Online Shuffling

Category: Are the Cards Dealt Fairly?

This is part of an ongoing series about whether the Cards you'’re dealt in Online Poker are fair.

In this post, I'm going to try to give a very simplified explanation of how cards are shuffled in online poker rooms. This is a topic that can get very complex.

The goal of a shuffle is card randomization. The player needs to know that any unused card has an equal probability of being dealt next as any other unused card. But in the case of playing cards, random does not mean there are infinite possibilities.

Since a deck of cards has 52 cards, there are a limited number of orderings possible. The number is extremely large, but it is not infinite. If you ever took a higher-level math or statistics class, you'll know about factorials. The number of possible deck orderings is 52-factorial -- noted as 52! This number is around 130,000,000,000,000,000,000,000,000,000,000,000,000,000,000 -- a very large number indeed.

At the beginning of a hand, a software algorithm picks one of those decks and deals out the hand. So far, that part seems pretty simple. If a software program can get a random number and pick a deck from that number of possibilities and do this honestly and accurately, we must admit that this meets our criteria for a fair game.

For a little more detail, I'll quickly summarize how Paradise Poker accomplishes this.

The first step is getting a truly random number. This can actually be a bit more difficult than it seems. Here is how Paradise Poker handles this:

We have two main sources of these random bits. First, the rng on the server samples the low order bits of the CPU's time stamp counter (667MHz) at irregular parts of the program and when data is received from client connections, and uses it to add to the entropy in our large seed.

Secondly (and mainly) the client programs send their own 32-bits of entropy with every action they make and with several of the other packets they send to the server. The client's entropy is gathered from both mouse and keyboard movements, as well as the lower 32-bits of their CPU time stamp counters.

From all this random gobbledygrokdata, they get a 2016 bit seed and use their 31-bit random function shuffling algorithm to generate a shuffled deck.

If all of this is implemented correctly, you truly do have a completely unpredictable deck that meets our critera for a fair deal.

To learn more about how Paradise Poker shuffles their cards, click HERE.

Where this series is going:
  • Did you know a poker site once had a flaw in their shuffling algorithm and RNG? Does your favorite site suffer from the same problems?
  • What about results -- has anyone looked at dealt cards to see if the game is fair?
  • Are any sites reviewed by auditing firms?
All those entries are coming up soon. Keep visiting.

You can find prior entries on this topic here:
Live Cardroom Deck Shuffles

Online Shuffling - Setting Expectations