Talk:Hardware random number generator

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[edit] half truths

This article needs lots of work: it's full of half-truths.

[edit] XOR and bias

I quote the article in its current state: "Let the probability of a bit stream producing a 1 be 1/2 + e, where -1/2 < e < 1/2. Then e is the bias of the bitstream. If two bit uncorrelated bit streams with bias e are exclusive-or-ed together, then the bias of the result will be 2e^2."

In fact, the actual answer is -2e^2. For example, suppose you XOR two bitstreams together which have a bias of e=1/2. By the definition above, this means that both bitstreams produce ones every time. Since 1 XOR 1 = 0, the resulting bitstream would have a bias of -1/2, which is equal to -2e^2. You can prove the general case youself easily.

A while ago, I fixed the answer in this article to be -2e^2 but Matt Crypto reverted my change. He incorrectly cited the Piling-up Lemma. But the piling up lemma defines the bias differently: in the Piling-up lemma, the bias is e if the probability of the bitstream producing a 0 is 1/2+e, whereas this article defines the bias as e if the probabilitiy of produccing a 1 is 1/2+e.

I have corrected the article again. Hopefully Matt Crypto will read more carefully before reverting good changes in the future.

--DavidGrayson 17:58, 19 February 2006 (UTC)

[edit] trancendental numbers

article contains the phrase:

"or even trancendental number such as pi, or e, or phi."

I am not sure what number the author refers to by phi. Phi is somtimes used the represent the number called the 'devine ration' or 'golden section'. That number is not a trancendental number but a simple algebraic number.

I haven't edited, because I don't know if phi also refers to some well known trancendental number.

You are right, and I have edited it to a more correct state. Dysprosia 12:08, 22 Aug 2003 (UTC)

Hello. This is an interesting article. I have reworked the introduction. The main change has been to emphasize hardware rng in the intro; the previous rev had a lot of stuff about pseudo-rng's, which is interesting but a digression in the intro. Yes, it is necessary at some point to contrast the two, but putting that before a description of hardware rng's seems to be putting the cart before the horse. -- There is also a depreciative tone in the comparison with pseudo-rng's, to the effect that pseudo-rng's are bad because they're not really random. Well, that's a feature, not a bug; whether it's a problem depends on the purpose for which numbers are needed, and this article needn't, and shouldn't, take a stance one way or another. Happy editing, Wile E. Heresiarch 14:58, 31 Mar 2004 (UTC)

[edit] Revision

I made a pass at editing it. I moved the section about attacks on RNGs to the random number generator attack article. I also deleted the paragraph on using lossless compressing to improve entropy. I am not aware of anyone who does that and I'm not sure it would work on a stream that was close to random.

It could still be tighter. --agr 21:41, 9 Dec 2004 (UTC)

Why isn't this located at True random-number generator? --Smack 23:26, 22 Dec 2004 (UTC)

There are some who question the existance ot "true random numbers." I'm not one of them, but it's perhaps best to use a more neutral title. You're free to add a redirect if you wish. --agr 04:50, 23 Dec 2004 (UTC)
There's a lot to be said for not making bold claims in titles, but this article's present title strikes me as short-sighted and misleading. I've noticed a tendency among Wikipedists (and others) to, when describing a phenomenon, note its superficial aspects rather than its essential aspects. In this case, the essence of an RNG of this type is that its randomness is based on some acceptably random physical phenomenon (ex. radioactive decay), rather than just an algorithm. The fact that it is implemented in "hardware" is entirely secondary, but also inaccurate, as any RNG must include both "hard" and "soft" components. --Smack 19:09, 3 Jan 2005 (UTC)
The use of the word "hardware" to distinguish RNG's based on random physical processes from PRNGs is common in the field and antidates Wikipedia. The best terminology might be to reserve "Random Number Generator" for those based on random processes and use Pseudo-Random Number Generator for algorithm only methods. Unfortunately, that would mislead too many people because so many computer programming languages have a "Random Number Generator" that is in fact pseudorandom. I believe the word hardware has stuck because it makes the point that users need something beyond what is in the normal computer CPU to be assured of unpredictability. Anyway, its an established term of art and Wikipedia should respect that. It may make sense to work this discussion into the article, however. I may give that a try. --agr 22:17, 3 Jan 2005 (UTC)
If I may be so pedantic, the word you're looking for is 'antedate'. --Smack (talk) 18:01, 11 Jan 2005 (UTC)

[edit] Naming

I've moved this back from "Hardware random-number generator"; usage seems to favour leaving out the hyphen. See this Google test. — Matt Crypto 19:04, 23 Dec 2004 (UTC)

[edit] Question on existance of randomness

I removed the annon. question "This also raises the question whether true randomness exists?" from the "Contrast with pseudo-random number generators" section. A theoretical basis for the existance of true randomness lies in the laws of Physics. See the articles and discussions on Quantum Mechanics and in particular the Bell test experiments. --agr 11:34, 16 May 2005 (UTC)

[edit] Unilateral edits

I hate to be a drive-by editor, but reading this page gives me enough of a headache to want to fix it. Most Wikipedia articles grow without bounds and this one is no exception.

I can't even tell if it's trying to be about hardware RNGs attached to a computer (that seems to be the intent and would be how I'd classify a hardware RNG) yet it has significant discussion of traditional random sources such as cards and dice. I hate to do a hack-n-slash job on the article, but that's what I'm sorely tempted to do.

The text about early uses of random number tables belongs somewhere but it has little to do with hardware RNGs. Ditto with the comment about Galton, applications of random numbers, etc. Is there a need for an article on the history and uses of random numbers? I could start one; it would be an interesting topic to research. There are several articles where snippets of random number history are randomly duplicated, and such an article would also give the "state of sin" people a place to get the von Neumann quote off their chest once and for all. (That joke's a funny-once... at best.)

The information about bias, software whitening, etc. seems a bit too detailed for this article. It's interesting (and perhaps useful) without a doubt, I just feel it's overkill for an overview-level article about hardware RNGs. Again, worthy of a place, just probably not here and certainly not at the level it's currently at. 12.103.251.203 01:15, 2 April 2006 (UTC)

12,103...,
I think your expectations for such an article are misplaced. Random is a very subtle and difficult concept. All of the considerations here are apposite for randomness, and the various methods attempting to make real hardware generators are relevant. Your objection seems to be that this is not the overview article you wanted to see. Perhaps there should be a Randomness -- an overview article. I agree that it might be interesting to research, and I think i'd probably want to contribute to such a thing. As for the snippets observation, well you're right. However, there is no requirement for minimum word expenditure in any particular content area. Randomness being so tricky and so routinely fumbled by those accostomed to it, WP is fully justified inattempting to include some perspective in places readers might need it. And note avoiding duplication, however annoying to the well-informed.
In short, while I sympathize with your plaint, I can't agree that it's quite right for this article. ww 03:09, 4 April 2006 (UTC)

[edit] Physical basis

The section on the physical basis for randomness had some negative information content, confusing quantum and thermal noise. I revised it, but it could use some more work; e.g., I didn't find a precise citation in the statistical mechanics articles for the statement I wanted, namely that every degree of freedom of a physical system at thermal equilibrium has a particular amount of randomness. All this information comes from an undergraduate physics education, but surely one can find articles that give a more complete discussion. --Dylan Thurston 06:18, 10 April 2006 (UTC)

I did an edit pass and took out statements about thermal noise being predictable in principle (it isn't) and some other unsupported stuff. I think the article you are looking for is the Equipartition theorem.--agr 13:49, 10 April 2006 (UTC)
Thanks for the corrections. "In ways not easily characterized by the laws of physics" is just right. But I think there is a point to be made about thermal noise vs quantum noise. If you know the complete initial state of a quantum system (like the beam splitter), you cannot predict its future behaviour (modulo potential disagreement about the laws of physics, which should perhaps be acknowledged). OTOH, if you knew the complete initial state of (say) a noisy resistor, you could predict its future behaviour for a while, at least until the underlying quantum uncertainty gets magnified until it has macroscopic effects. Surely this is worth mentioning? I haven't done the calculations; perhaps the magnification in question is very quick and the distinction is not worth mentioning in realistic situations? --Dylan Thurston 23:21, 10 April 2006 (UTC)
Even if the electrons in a resistor were acting as a perfect classical gas, knowing on the order of Avagadro's number of initial states is totally unrealistic. It certainly has no effect on the construction of hardware random number generators. But the electrons are not a classical gas. If they were, they would instantly radiate all their heat energy due to the ultraviolet catastrophe. Thermal noise from a resistor is essentially the same as black body radiation. The electrons are constrained to a finite, though large, number of energy states and which state they end up in after a collision is determined by quantum probabilities. If I remember correctly the collision rate is on the order of 9 billion times per second per electron at room temp. And there are lots of other effects: inelastic scattering, interaction with photons and phonons, the resistor is in thermal contact with the air, etc. --agr 20:46, 11 April 2006 (UTC)


[edit] truly randomizing in BASIC external link??

This was added 20 June 06. Seems rather questionable to me. any comments? ww 16:55, 20 June 2006 (UTC)

[edit] Truly Random perl module

I've reworded the mention of this module in the article. It originally said that the module created real random numbers. Someone changed it to say it created pseudorandom numbers. I settled on saying that the writers claim it does real random. Can anyone say for sure? -- BillWeiss | Talk 06:36, 5 October 2006 (UTC)