Re: New function: secure-random-bytes

[Julian Scheid <julians37@gmail.com>]

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On Tue, Mar 19, 2013 at 5:49 AM Paul Eggert <eggert@cs.ucla.edu> wrote:

> On 03/18/13 03:26, Leo Liu wrote:
>
> > From that discussion (almost two years ago) there was clearly interest
> > in having a strongly random source. The solution you proposed looks
> > excellent. Are there any progress on this matter?
>
> There's been no progress, alas.
> Yours is the first sign of interest that I've seen since then.
> I may be able to find a student or two
> who might volunteer to work on this; we'll see.
>
> There's one extra wrinkle I'd like to add while we're at it:
> if available we should use the random-number instructions
> in recent implementations of x86 and x86-64 architectures
> as this should yield even better performance.
>
> http://en.wikipedia.org/wiki/RdRand


I'm working on an implementation of SASL authentication and for that I
need to generate a reasonably secure nonce.

Performance is not an issue in my application because it only needs to
perform authentication every now and then, and each time only a single
nonce is needed.

I'm now using `(random t)' but that's brittle: I don't see a way to
guarantee that the random data it produces is of sufficient quality.

(There's a chance both /dev/urandom is unavailable (perhaps because
Emacs is running in a chroot or a container) and GnuTLS initialization
throws an error, in which case `random' would silently fall back to a
non-secure source.  I suppose it's good enough for my use case but it
does highlight the absence of `secure-random-bytes'.)

I wonder, is there anything speaking against adding a simple
implementation now and worrying about maximal performance later?

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