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Re: [Pqc] Hybridizing with preshared keys

Douglas Stebila <dstebila@gmail.com> Wed, 06 September 2023 21:22 UTC

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From: Douglas Stebila <dstebila@gmail.com>
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Date: Wed, 06 Sep 2023 17:22:25 -0400
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To: Paul Hoffman <paul.hoffman@icann.org>
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Subject: Re: [Pqc] Hybridizing with preshared keys
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For TLS, there is the hybrid KEM/DH mechanism in [1].  But as that is already taking place in the context of the TLS handshake, it seems to me that it is not the right place to mix in a pre-shared key: just use TLS's existing PSK mechanism.

Douglas

[1] https://datatracker.ietf.org/doc/draft-ietf-tls-hybrid-design/


> On Sep 6, 2023, at 11:25 AM, Paul Hoffman <paul.hoffman@icann.org> wrote:
> 
> Arrrgh. I was being too subtle/cute. Let me try again.
> 
> Greetings again. Some people are actively suggesting that one way to make a quantum-safe KEM is to mix a preshared key with a classical KEM or a PQC KEM. There are different ways that those preshared keys are distributed to the two parties.
> 
> My question is: of the hybrid KEM approaches that are being standardized in the IETF, which are and are not useful for mixing in preshared keys?
> 
> --Paul Hoffman
> 
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