Combining Post-Quantum and Classical KEM

Marc

12/30/22, 6:39 AM

I came across this paper "Hybrid Key Encapsulation Mechanisms", were three methods are defined that allow a secure combination of a classical key encapsulation with a post-quantum key encapsulation.

In terms of security and performance all three of them seem to be equally good.

For the second method, called "DualPRF Combiner", it is written:

OurdualPRFcombiner is inspired by the key derivation in TLS 1.3 [Res18] and models Whyte et al.’sproposal for supporting hybrid key exchange in TLS 1.3 [WFZGM17]. In TLS 1.3, HKDF’s extract functionis applied to the raw ECDH shared secret; the result is then fed through HKDF’s expand function with the(hashed) transcript as (part of) the label.

So I am asking myself, whether usage of a secure HKDF, such as HKDF with SHA2-512 woulf be sufficient as HKDF-extract and HKDF-expand would serve as dPRF and PRF from the combiner.

0 + 1

post-quantum-cryptography

key-derivation

key-exchange

hkdf

kem

Maarten Bodewes

12/30/22, 1:10 PM

HKDF-Extract and HKDF-Expand together make up HKDF. You seem to be asking if you could use HKDF as function for HKDF-Expand, which would mean turning the algorithm inside out (and besides, HKDF-Expand has a clear definition and is build around HMAC).

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Combining Post-Quantum and Classical KEM

TH: ผสมผสาน Post-Quantum และ Classical KEM

RO: Combinând KEM post-cuantic și clasic

RU: Сочетание постквантовой и классической КЭМ

VI: Kết hợp KEM hậu lượng tử và cổ điển

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