Are there any Javascript CSPRNGs?

Question

I'm writing some software that requires the use of a CSPRNG with javascript for use in the browser and I'm wondering what libraries are available. Crypto-js doesn't seem to have a CSPRNG I can directly call (unless I missed it?). I've looked through the Stanford crypto js library, but I'm uncertain how much analysis this code has gotten. http://bitwiseshiftleft.github.io/sjcl/doc/symbols/sjcl.random.html

They appear to be implementing Schneier's Fortuna: http://sourceforge.net/projects/fortunaprng/

I've also seen https://www.clipperz.com/open_source/javascript_crypto_library/.

My question is there a well vetted crypto js library that has a well designed CSPRNG that generates values independently of some browser support? Or with a standard all modern browsers implement? And where is the entropy source? I'm used to crypto with languages like java and C++, not this fragmented world.

Answer 1

I would try to avoid doing any cryptography using javascript… but that's just my personal opinion.

Anyway, if you really want to walk the Javascript path, you could skip the libraries and take a look at the window.crypto.getRandomValues() function, as long as you can live with the fact that it's an experimental API and not yet supported in all browsers… it should work on current versions of Firefox and Chrome though.

And for Opera, there's Math.Random() which has been implemented as a CSRNG. But you should be aware that Math.Random will only be a CSRNG in Opera (only in Opera, not any other browser!!!), and that the function will only return 53 bits of entropy on each call.

Besides that, I don't know of any further CSRNGs being available in Javascript, or in Javascript libraries.

EDIT

Some stuff that might help you find solutions to your quest:

• "Symmetric Cryptography in Javascript - Stanford Crypto Group" mentions (among other things) entropy-collection for crypto-purposes,
• and some sites out there (like https://www.grc.com/r&d/js.htm ) practically show entropy-collection for crypto-purposes using somewhat similar solutions as mentioned in the above paper.