Re: [TLS] A la carte handshake negotiation

Kyle Rose <krose@krose.org> Wed, 22 July 2015 11:09 UTC

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Date: Wed, 22 Jul 2015 07:09:24 -0400
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From: Kyle Rose <krose@krose.org>
To: Peter Gutmann <pgut001@cs.auckland.ac.nz>
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Subject: Re: [TLS] A la carte handshake negotiation
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>>Furthermore, comparing the strengths of kex, auth, ciphering and PRF seems
>>like comparing apples, orangles, pears and kumquants.
>>
>>Even if the nominal strengths are the same, the scaling of strengths is going
>>to be different (e.g. the quadric vs. linear sub-treshold scaling for ECDH vs.
>>symmetric).
>
> +1.  It's just more numerology:

In that case, we should dispense with any larger key sizes and
recommend exactly one per algorithm, and vary only on algorithm.
Adopting this would simplify things even further by reducing the
cipher set list by an order of magnitude.

Sadly, I'm guessing there are numerological requirements in various
standards and regulations that make it necessary to keep both AES-128
and AES-256 around, for example. There are also a ton of existing
2048-bit RSA keys that aren't going anywhere for a while.

I'm also skeptical of statements like "Using any known technology it's
unlikely that humans can ever get beyond about 2^^100 operations",
because that's true exactly up until it isn't. An open question is
whether the innovation that undoes this will also subsume much larger
keys.

Kyle