Two Plus Two Older Archives - RNG and radioactive decay

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I hear people talking about sites using Thermal noise and radioactive decay and all sorts of other stuff to randomly generate cards..Can someone explain this to me better? How's it work?

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Random number generators use a physical source of random information. It usually consists of an extremely sensitive sensor, or a sensor on a really weak signal that is amplified whole lot. The real trick is that your measuring something that that it's constantly changing, effectively at random.

Thermal noise methods, for example, actually measure electric current caused by the random motion of electrons. A big current is causes when there are huge numbers of electrons moving in one direction, but there are also some electrons moving at random at all times, even when there's no current in a wire. The thermal noise systems measure that teeny, tiny amount of electrical noise, which is constantly moving back and forth.

You can think of it like there being zero current in a wire; in actuality, there is sometimes 0.000000001 amps, and sometimes -0.000000001 amps. On average, it's zero. A sensitive enough meter can read the current going back and forth. It can read it is as positive or negative at any point in time. If you keep reading whether the level is positive or negative, you get a stream of plusses and minuses, which you can report as 0's and 1's, and the sequence of them will be random.

You can do a similar trick with senitive meters and a radioactive substance (just a tiny, tiny bit of it will do -- perfectly safe.) A radioactive substance emits particles which can be measured. The exact timing and/or quantity of the emissions is essentially random. Think of the staticky noise of a Geiger counter; the static is essentially the noise of radioactive decay amplified through a speaker. Instead of running it to a speaker, you can measure it as negative and positive and spawn a random series of zeroes and ones.

You then use these zeroes and ones as the bits in a binary number, and bang, you have random numbers!

There is a lot more to it, of course, such as ensuring that there is no bias, and that you ensuing random stream not only generates random changes, but also generates a proper distribution of random numbers, including proper numbers of runs. (A random number generator that never repeats a number three times isn't really random, right?) There's a whole field of study for this stuff. . . I have a friend who works explicitly in that field, ensuring that the random generators work properly. He works as a mathematician for a major slot machine vendor!

You can get one of these random noise generators as a plug-in device for a server, or some are actually on add-in cards. These days, there are very, very good pRNG's for computers available which, combined with a little bit of random noise (like mouse movements and time stamps) really don't require the physical noise generators, but the poker sites like to make things as bullet-proof as possible for the paranoid -- and to ensure that the random schemes can't be cracked. Physical noise generators just can't be predicted, even by the smarters algorithm snooper.