Re: [TLS] [Cfrg] 3DES diediedie

"Steven M. Bellovin" <smb@cs.columbia.edu> Thu, 01 September 2016 02:54 UTC

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From: "Steven M. Bellovin" <smb@cs.columbia.edu>
To: "Derek Atkins" <derek@ihtfp.com>
Date: Wed, 31 Aug 2016 22:54:13 -0400
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Cc: David McGrew <mcgrew@cisco.com>, "cfrg@irtf.org" <cfrg@irtf.org>, Jon Callas <jon@callas.org>, tls@ietf.org
Subject: Re: [TLS] [Cfrg] 3DES diediedie
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On 31 Aug 2016, at 10:17, Derek Atkins wrote:

> "Steven M. Bellovin" <smb@cs.columbia.edu> writes:
>
>> Yes.  To a large extent, the "IoT devices are too puny for real
>> crypto" is a hangover from several years ago. It was once true; for
>> the most part, it isn't today, but people haven't flushed their cache
>> from the old received wisdom.
>
> This is certainly true for AES, mostly because many small chips are
> including AES accelerators in hardware.  It's not quite true for public
> key solutions; there are still very small devices where even ECC takes
> too long (and yes, there are cases where 200-400ms is still too long).
>
Certainly plausible.  What I'm saying is (a) don't assert, measure; and
(b) measure again next year because tech keeps improving.

As for your specific points: if AES is indeed feasible, we don't need
new ciphers.  If elliptic curve is too slow, the only answer is architectures
that don't use public key at all; we're not going to find new, cheaper
public key algorithms without a *lot* of effort and the people who can
do that sort of thing are too busy working on post-quantum crypto.

The remaining approach is a cheaper protocol than TLS.  That shouldn't
be hard at all, especially if we're going back to KDCs.


        --Steve Bellovin, https://www.cs.columbia.edu/~smb