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I'm making a little web application which needs to randomize stuff. Just a little example of what's it gonna have: returns a random number between and 10 to the user.

I'm planning to do it using Javascript and jQuery (the calculator itself).

My question is: How can I make its functions truly random and not pseudo-random? Is the PHP function perhaps more random than the Javascript ones?

For the sake of the question, let's say what I want is a true random number between X and Y.

Grijesh Chauhan
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frrlod
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  • [Some source to generate true random numbers](http://stackoverflow.com/questions/15038174/generate-random-numbers-without-using-any-external-functions/15040471#15040471) – Grijesh Chauhan Jun 16 '13 at 12:58
  • It is not possible to *create* truly random numbers. In order for computers to create randomness they have to start with some initial value or state (often called the *seed*). That is why it is called *pseudo-random*; it is not *really* random, but for most things it is random enough. – Sverri M. Olsen Jun 16 '13 at 13:13

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No function that you call will be "truly random". They are all PRNGs; most PRNGs are, in fact, quite good and I'd be surprised if they were inadequate for your application. Also, while a few PRNGs are notorious for their small period (Java's Random comes to mind), every modern language that I know of—including JavaScript, PHP, and (with its crypto packages) Java—have very good PRNGs.

The best way to collect "more random" data is to obtain it from an external random source. One possibility is to ask the user to move the mouse around in a window for a certain period of time, collecting the mouse coordinates at regular intervals. Some military, banking, and other high-security systems use hardware like thermal noise sensors to obtain data that is as close to random as one can hope; however, such hardware support is not going to be available to a web app.

Note that hacks like using the system clock are no better than PRNGs; most PRNGs initialize their seed with a combination of such data.

Ted Hopp
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  • For the sake of completeness, it should be pointed out that while this has been true in computing for decades, many microprocessors being built now (such as Intel's "Ivy Bridge" chips) have a TRNG on-chip that changes the game. One can indeed get true random numbers now from code (albeit code that accesses special hardware). – Lee Daniel Crocker Jun 17 '13 at 11:27
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You have not understood the Matrix movies. ;) One function is not "more random" than one in another language. All functions are equally pseudo random. "Pseudo" means that the computer cannot, by definition, pull a random number out of thin air. It just can't. A computer computes, strictly, based on rules, accurately. There's no randomness anywhere in the system. For all its supposed power, randomness is the one thing a computer simply cannot do (that, and making coffee).

For true randomness, you need an outside, natural source. Like measuring atomic decay, or some such thing which is not predictable and truly random. Anything else is just pseudo-randomness, which may be of varying quality.

Good PRNGs try to collect "outside interference" in an entropy pool; e.g. Linux' /dev/random takes into account system driver "noise" which may be based on "random" packets hitting the ethernet port, or the user's mouse movements. How truly random that is is debatable, but it's very very hard to predict at least and suitably random for most purposes.

deceze
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I don't think there's any way to remove the deterministic aspect of randomness from a program completely. You can do all you want to minimize, mitigate, and obfuscate whatever process you're using to "pull numbers from a hat", but you can never truly make it perfectly random.

You can fashion out a process with sufficient detail to make it practically random, but true random may be impossible.

Richard Neil Ilagan
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While you can't achive true random with your code in php you can use random.org API. You could connect through curl in php or through ajax in javascript. They are using atmospheric noise as a random seed as far as i know.

Patryk Ziemkowski
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It is not possible to generate truly random variables on a computer. However, you may improve standard generators. Suppose, you have two basic generators. You create a table and fill it with values from the first generator. Then, if you want to get a number, the second one generates an index and returns correspondent value from the table. This value is then replaced with the new one... I forgot how this generator is called... Hope, it helps. P.S. Sorry for my English.

Nik Ved
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My suggestion is that you generate a binary random string by encrypting the local time and date by an encryption algorithm. In this case try to gather all possible sources of "random" data, and load these both as input message and input key.

As you have seen from previous answers, above, your use and your requirements of your random data are important. A number is "random" if it is difficult or impossible for your application to guess its value in advance. Note that the same number source may be considered random for some applications while they are not random in others. Evidently you will have serious problems in case you need high quality random numbers for a demanding application.

TRNG98 True Random Numbers

TRNG98.se
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