What Type of Random Number Generator is Used in the Casino Gaming Industry? [closed]

Answer 1

For a casino gaming applications, I think the seeding of the algorithm is the most important part to make sure all games "booted" up don't run through the same sequence or some small set of predictable sequences. That is, the source of entropy leading to the seed for the starting position is the critical thing. Beyond that, any good quality random number generator where each bit position as has a ~50/50 probability of being 1/0 and the period is relatively long would be sufficient. For example, something like the Mersenne twister PRNG has such properties.

Using cryptographically secure random generators only becomes important when the actual output of the random generator can be viewed directly. For example, if you were monitoring each number actually generated by the number generator - after viewing many numbers in the sequence - with a non-cryptographic generator information about that sequence can lead to establishing information about all the internal state of the generator. At this point, if you know what the algorithm looks like, you would be able to predict future numbers and that would be bad. The cryptographic generator prevents that reverse engineering back to the internal state so that predicting future numbers becomes "impossible".

However, in the case of a casino game, you would (or should) have no visibility to the actual numbers being generated under the hood. Each time a random number is generated - say a 32-bit number - that number will be used then, for example, mod 52 for a deck shuffling algorithm....no where in that process do you have any idea what numbers were being generated by the algorithm to shuffle that deck. That is, most of the bits of "randomness" is just being thrown out and even the ones being used you have no visibility to. Therefore, no way to reverse engineer the state.

Getting back to a true source of entropy to seed the whole process, that is the hard part. See the Wikipedia entry on entropy for some starting points on techniques.

As an aside, if you did want cryptographically sequence random numbers from a "regular" algorithm, a simple approach is to take a few random numbers in sequence, concatenate them together and then run something like MD5 or SHA-1 on them and the result is just as random and also cryptographically secure. That is, you just made your own "secure" random number generator.

Answer 2

We've been using the Protego R210-USB TRNG (and the non-usb version before that) as random seed generators in casino applications, with java.security.SecureRandom on top. We had The Swedish National Laboratory of Forensic Science perform a separate audit of the R210, and it passed without a flaw.

Answer 3

Casino slot machines generate random numbers continuously at very high speed and use the most recent result(s) when the user pulls the lever (or hits the button) to spin the reels.

Even a simplistic generator can be used. Even if you knew the algorithm used, you cannot observe where in the sequence it is because nearly all the results are discarded. If somehow you did know where it was in the sequence, you'd have to have millisecond or better timing to take advantage of it.

Modern "mechanical reel" machines use PRNGs and drive the reels with stepper motors to simulate the old style spin-and-brake.

• http://en.wikipedia.org/wiki/Slot_machine#Random_number_generators
• http://entertainment.howstuffworks.com/slot-machine3.htm

Answer 4

I suppose anything goes for apps and offshore gambling nowadays, but all these other answers are incomplete, at least for Nevada Gaming Control Board licensed machines, which I believe the question is originally about.

The technical specifications for RNGs licensed in Nevada for gaming purposes are laid out in Regulation 14.040(2).

As of May 24, 2012, here is a summary of the rules a RNG must follow:

1. Static seeds cannot be used. You have to seed the RNG using a millisecond time source or other true entropy source which has no external readout anywhere on the machine. (This helps to reduce the incidence of "magic number" attacks)
2. The RNG must continue generating numbers in its sequence at least 100 times per second when the game is not being played. (This helps to avoid timing attacks)
3. RNG outputs cannot be reused; they must be used exactly once if at all and then thrown away.
4. Multi-system cabinets must use a separate RNG and separate seed for each game.
5. Games that use RNGs for helping to choose numbers on behalf of the player (such as Lotto Quick Pick) must use a separate RNG for that process.
6. Games must not roll RNGs until they are actually needed in a game. (i.e. you need to wait until the player chooses to deal or spin before generating RNGs)
7. The RNG must pass a 95% confidence chi-squared test based on 10,000 trials as apart of a system test. It must display a warning if this test fails, and it must disable play if it fails twice in a row.
8. It must remember, and be able to report on, the last 10 test results as described in 7.
9. Every possible game outcome must be generatable by the RNG. As a pessimal example, linear congruential generators don't actually generate every possible output in their range, so they're not very useful for gaming.

Additionally, your machine design has to be submitted to the gaming commission and it has to be approved, which is expensive and takes lots of time. There are a few third-party companies that specialize in auditing your new RNG to make sure it's random. Gaming Laboratories publishes an even stricter set of standards than Nevada does. They go into much greater detail about the limitations of hardware RNGs, and Nevada in particular likes to see core RNGs that it's previously approved. This can all get very expensive, which is why many developers prefer to license an existing previously-approved RNG for new game projects.

Here is a fun list of random number generator attacks to keep you up late at night.

For super-nerds only: the source for most USB hardware RNGs is typically an avalanche diode. However, the thermal noise produced by this type of diode is not quantum-random, and it is possible to influence the randomness of an avalanche diode by significantly lowering the temperature.

As a final note, someone above recommended just using a Mersenne Twister for random number generation. This is a Bad Idea unless you are taking additional entropy from some other source. The plain vanilla Mersenne Twister is highly inappropriate for gaming and cryptographic applications, as described by its creator.