On Jan 22, 2014, at 8:13 AM, Dan Harkins <[email protected]> wrote:

>  "Ask your OS" is putting faith in the guy that wrote the relevant code
> in your OS.

Yes, exactly.

> It might be a reasonable leap but it's a leap nevertheless.

We put faith in the (~85%) guy for all the other crypto code as well, so I 
don't see the leap.

> Recent events should tell us that we should not trust a single source for
> these things (even if we are told that this single source is actually the
> output of a bunch of uncorrelated sources of entropy being mixed up).

That's one interpretation. Another is that attackers will look for bad 
implementations and use those as best they can.

>  I see value in draft-eastlake-randomness3 and I also see value in an
> Informational RFC on a good DRBG for those who feel the need to have
> a belt as well as suspenders.

We disagree here; the chance that the person writing the belt will get it wrong 
and make their crypto trivial to break for an attacker who knows the weakness 
seems much higher to me than the change that the OS got it wrong. Yes, we could 
put some warning at the front of the new document about this, but that warning 
will be ignored by programmers who are sure they know this stuff.

I could see writing something that forces them to mix in randomness from the OS 
to their possibly-borked DRBG in the hopes that at least that step will fix 
their problems. However, if we do that, nearly all the interesting technical 
stuff in the current document is just confusing fluff. The new document reduces 
to "use an HMAC with the randomness from your OS as the key and whatever stuff 
you think is random as the data; done".

--Paul Hoffman
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