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

Hanno Böck <> Fri, 15 December 2017 01:01 UTC

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Date: Fri, 15 Dec 2017 02:01:16 +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 Thu, 14 Dec 2017 16:45:57 -0800
Colm MacCárthaigh <> 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.

I think the takeaway is just as simple as this: If you know an algorithm
is bad get rid of it and don't try to "rescue" it over into the next

Hanno Böck

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