Math.random on V8 not random enough

[pmontrasio]

I just read TIFU by using Math.random() (discussion on HN at https://news.ycombinator.com/item?id=10598065). TL;DR this is what Math.random yields on Firefox

and this is what it yields on V8

The author suggests using crypto.getRandomValues in the browser. That populates a typed array with random values. Example:

> var random_int32 = new Uint32Array(5);
> crypto.getRandomValues(random_int32)
[3893288831, 502897280, 4154045839, 415033321, 3522955257]

https://developer.mozilla.org/en-US/docs/Web/API/RandomSource/getRandomValues

[jalada]

As far as I know, JSEncrypt already uses crypto.getRandomValues when it can.

JSEncrypt uses JSBN behind the scenes, and that has a PRNG that first tries getRandomValues. If that's not available, it uses mouse entropy. If it runs out of mouse entropy then yes, it falls back to Math.random.

https://github.com/travist/jsencrypt/blob/master/lib/jsbn/rng.js

[zoloft]

@jalada exactly, thank you :) (closing now)

[pmontrasio]

I'm afraid I didn't check the code well enough. Sorry for wasting your time.

[jalada]

Not a problem @pmontrasio, I actually came here to double check JSEncrypt because of the same blog post.

[zoloft]

@pmontrasio & @jalada P.S. kudos to @ctso for his work in #6