Re: [TLS] A closer look at ROBOT, BB Attacks, timing attacks in general, and what we can do in TLS

Nikos Mavrogiannopoulos <nmav@redhat.com> Fri, 15 December 2017 14:20 UTC

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From: Nikos Mavrogiannopoulos <nmav@redhat.com>
Date: Fri, 15 Dec 2017 15:19:56 +0100
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Subject: Re: [TLS] A closer look at ROBOT, BB Attacks, timing attacks in general, and what we can do in TLS
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On Fri, Dec 15, 2017 at 2:01 AM, Hanno Böck <hanno@hboeck.de>; wrote:

> On Thu, 14 Dec 2017 16:45:57 -0800
> Colm MacCárthaigh <colm@allcosts.net>; wrote:
>
> > But what would that look like? What would we do now, in advance, to
> > make it easy to turn off AES? For example.
>
> I think this is the wrong way to look at it.
>
> From what I'm aware nobody is really concerned about the security of
> AES. I don't think that there's any need to prepare for turning off AES.
>
> The problem with PKCS #1 v1.5 is that it survived so long *after* its
> was known that it was bad. I really recommend everyone who wants to
> know how protocols go bad to read up on the Bleichenbacher
> countermeasures in TLS 1.0, 1.1 and 1.2 - and particularly the last
> one. The chapter in 1.2 is a nightmare and I seriously fail to
> understand how anyone could have seen that and think it's a good idea
> to do that in order to stay compatible with a standard that was already
> deprecated at that point.
>
> We know that when this group decided to deprecate both PKCS #1 1.5 and
> RSA encryption that there were people trying to lobby against that. I'm
> glad that this wasn't successful.
>

RSA PKCS #1 1.5 decryption and signatures are far from deprecated. In fact
the security of TLS 1.3 is heavily tied to these primitives if servers
support TLS 1.2 and RSA (see [0]) alongside TLS 1.3. It would be very nice
if we can only deprecate RSA PKCS#1 1.5 at some point.

regards,
Nikos

[0]. https://github.com/tlswg/tls13-spec/pull/1123