True random number generator [closed]

Question

Sorry for this not being a "real" question, but Sometime back i remember seeing a post here about randomizing a randomizer randomly to generate truly random numbers, not just pseudo random. I dont see it if i search for it.

Does anybody know about that article?

Answer 1

John von Neumann once said something to the effect of "anyone attempting to generate random numbers via algorithmic means is, of course, living in sin."

Not even /dev/random is random, in a mathematician's or a physicist's sense of the word. Not even radioisotope decay measurement is random. (The decay rate is. The measurement isn't. Geiger counters have a small reset time after each detected event, during which time they are unable to detect new events. This leads to subtle biases. There are ways to substantially mitigate this, but not completely eliminate it.)

Stop looking for true randomness. A good pseudorandom number generator is really what you're looking for.

Answer 2

An algorithm for truly random numbers cannot exist as the definition of random numbers is:

Having unpredictable outcomes and, in the ideal case, all outcomes equally probable; resulting from such selection; lacking statistical correlation.

There are better or worse pseudorandom number generators (PRNGs), i.e. completely predictable sequences of numbers that are difficult to predict without knowing a piece of information, called the seed.

Now, PRNGs for which it is extremely hard to infer the seed are cryptographically secure. You might want to look them up in Google if that is what you seek.

Another way (whether this is truly random or not is a philosophical question) is to use random sources of data. For example, unpredictable physical quantities, such as noise, or measuring radioactive decay.

These are still subject to attacks because they can be independently measured, have biases, and so on. So it's really tricky. This is done with custom hardware, which is usually quite expensive. I have no idea how good /dev/random is, but I would bet it is not good enough for cryptography (most cryptography programs come with their own RNG and Linux also looks for a hardware RNG at start-up).

Answer 3

To summarize some of what has been said, our working definition of what a secure source of randomness is is similar to our definition of cryptographically secure: it appears random if smart folks have looked at it and weren't able to show that it isn't completely unpredictable.

There is no system for generating random numbers which couldn't conceivably be predicted, just as there is no cryptographic cipher that couldn't conceivably be cracked. The trusted solutions used for important work are merely those which have proven to be difficult to defeat so far. If anyone tells you otherwise, they're selling you something.

Cleverness is rarely rewarded in cryptography. Go with tried and true solutions.

Answer 4

It's not possible to obtain 'true' random numbers, a computer is a logical construct that can't possibly create 'truly' random anything, only pseudo-random. There are better and worse pseudo-random algorithms out there, however.

In order to obtain a 'truly' random number you need a physical random source, some gambling machines actually have these built in - often it's a radioactive source, the radioactive decay (which as far as I know is truly random) is used to generate the numbers.

Answer 5

I believe that was on thedailywtf.com - ie. not something that you want to do.

It is not possible to get a truly random number from pseudorandom numbers, no matter how many times you call randomize().

You can get "true" random numbers from special hardware. You could also collect entropy from mouse movements and things like that.