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Re: [CFRG] NSA vs. hybrid

Martin Thomson <mt@lowentropy.net> Tue, 07 December 2021 00:41 UTC

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Date: Tue, 07 Dec 2021 11:41:15 +1100
From: Martin Thomson <mt@lowentropy.net>
To: cfrg@irtf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/4T7Apoo8SUGLen5LrHXYcJyxSC0>
Subject: Re: [CFRG] NSA vs. hybrid
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On Tue, Dec 7, 2021, at 11:27, Blumenthal, Uri - 0553 - MITLL wrote:
> For sensitive data, problem (1) is relevant now - because, as you said, 
> ciphertexts could be recorded now and broken/decrypted decade(s) later, 
> when CRQC is available. Hybrid won't help here (and those who don't 
> expect CRQC to arrive, can stay with ECC).

I'm sorry, is that right?  Are you asserting that a hybrid key exchange can be broken later?  I was under the impression that if I paired ECC with a PQ algorithm (and didn't mess it up) I could get the best of the two, assuming that the KDF and AEAD and whatnot are also OK.

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