[amper5and]

JavaScript security is really the best way to go for this type of service. At some point there needs to be a trade-off between the application goals and maximum theoretical security.

Chrome has native crypto.getRandomValues() and Safari's Math.random() was changed to use Arc4 PRNG back in 2008. I'm not sure if it has been updated to account for the flaws in the first bytes of Arc4, but if it has then this is cryptographically strong.

I don't know where Firefox and the other browsers stand on CSPRNGs, but as more and more implement crypto.getRandomValues(), this will improve services relying on client-side crypto.

[rarrrrrr]

For Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=322529