How can I generate truly (not pseudo) random numbers with C#?

Question

I know that the Random class can generate pseudo-random numbers but is there a way to generate truly random numbers?

Answer 1

The answer here has two main sides to it. There are some quite important subtleties to which you should pay due attention...

The Easy Way (for simplicity & practicality)

The RNGCryptoServiceProvider, which is part of the Crypto API in the BCL, should do the job for you. It's still technically a pseudo-random number generated, but the quality of "randomness" is much higher - suitable for cryptographic purposes, as the name might suggest.

There are other crypographic APIs with high quality pseudo random generaters available too. Algorithms such as the Mersenne twister are quite popular.

Comparing this to the Random class in the BCL, it is significantly better. If you plot the numbers generated by Random on a graph, for example, you should be able to recognise patterns, which is a strong sign of weakness. This is largely due to the fact that the algorithm simply uses a seeded lookup table of fixed size.

The Hard Way (for high quality theoretical randomness)

To generate truly random numbers, you need to make use of some natural phenomenon, such as nuclear decay, microscopic temperature fluctuations (CPU temperature is a comparatively conveient source), to name a few. This however is much more difficult and requires additional hardware, of course. I suspect the practical solution (RNGCryptoServiceProvider or such) should do the job perfectly well for you.

Now, note that if you really do require truly random numbers, you could use a service such as Random.org, which generates numbers with very high randomness/entropy (based on atmospheric noise). Data is freely available for download. This may nonetheless be unnecessarily complicated for your situation, although it certainly gives you data suitable for scientific study and whatnot.

The choice is yours in the end, but at least you should now be able to make an informative decision, being aware of the various types and levels of RNGs.

Answer 2

short answer: It is not possible to generate TRULY RANDOM NUMBERS using only C# and a computer..

long(er) answer: Only by means of employing an external device capable of generating "randomness" such as a white noise generator or similar - and capturing the output of that device as a seed for your random numbers (which could be accomplished using C# and some P/Invoke)

Answer 3

True random numbers can only be generated if there is a truly random physical input device that provides the seed for the random function.

Whether anything physical and truly random exists is still debated (and likely will be for a long time) by the science community.

Psuedo-random number generators are the next best thing and the best are very difficult to predict.

Answer 4

Years ago i heard of a fairly simple method that increases the randomness of standard algorithms (provided by built-in libraries and not taking external input.)

This is the process:

• Create a long array (1000 or more items?) of numbers
• Populate the array with random numbers the standard way
• When a random number is required, generate a random index into the array and return the number contained at that position
• Create a new random number at the array index to replace the number used

This ought to dramatically improve the randomness of your results without the need for external input.

EDIT: Here's a sample library that implements the above-described algorithm in C++: http://www.boost.org/doc/libs/1_39_0/libs/random/random-generators.html

-paul

Answer 5

I was debating building a random number generator based off twitter or one of the other social networking sites. Basically use the api to pull recent posts and then use that to seed a high quality pseudo random number generator. It probably isn't any more effective than randomizing off the timer but seemed like fun. Besides it seems like the best use for most of the stuff people post to twitter.

Answer 6

As John von Neumann joked, "Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin."

Regards

MArk

Answer 7

I always liked this idea, for the retro 60s look:

Lavarand

Answer 8

Take a look at using an algorithm like Yarrow or Fortuna with entropy accumulation. The point with these algorithms is that they keep track of entropy as a measure of theoretical information content available for predicting future numbers by knowing the past numbers and the algorithms used to produce them; and they use cryptographic techniques to fold new entropy sources into the number generator.

You'll still need an external source of random data (e.g. hardware source of random numbers), whether that's time of keystrokes, or mouse movement, or hard disk access times, or CPU temperature, or webcam data, or stock prices, or whatever -- but in any case, you keep mixing this information into the entropy pools, so that even if the truly random data is slow or low quality, it's enough to keep things going in an unpredictable fashion.

Answer 9

There is no "true" random in computers, everything is based on something else. For some (feasible) ways to generate pseudorandom data, try something such as a pool of the HD temp, CPU temp, network usage (packets/second) and possibly hits/second to the webserver.