Versatile Quantum-Safe Hybrid Key Exchange and Its Application to MACsec

Advancements in quantum computing pose a significant threat to most of the cryptography currently deployed in our communications networks. Fortunately, cryptographic building blocks to mitigate this threat are already available; mostly based on Post-Quantum Cryptography (PQC) and Quantum Key
Distribution (QKD), but also on symmetric cryptography techniques. Notably, those building blocks must be deployed as soon as possible to communication networks due to the “harvest-now decrypt-later” attack scenario, which is already challenging our sensitive and encrypted data today.

Following an agile and defense-in-depth approach, Hybrid Authenticated Key-Exchange (HAKE) protocols have recently been gaining significant attention. Such protocols have the benefit of modularly combining classical (symmetric) cryptography, PQC, and QKD to achieve strong confidentiality, authenticity, and
integrity guarantees for network channels. Unfortunately, only a few protocols have been proposed yet (mainly, Muckle and Muckle+) with different flexibility guarantees. Looking at available standards in the network domain – especially at the Media Access Control Security (MACsec) standard –, we believe that HAKE protocols could already bring strong security benefits to MACsec today. MACsec is a standard designed to secure communication at the data link layer in Ethernet networks by providing confidentiality, authenticity, and integrity for all traffic between trusted nodes. Moreover, it establishes secure channels within a Local Area Network (LAN), ensuring that data remains protected from eavesdropping, tampering, and unauthorized access, while operating transparently to higher-layer protocols. Currently, MACsec does not offer enough protection against the aforementioned threats.

In this work, we tackle the challenge and propose a new versatile HAKE protocol, dubbed VMuckle, which is sufficiently flexible for use in MACsec. The use of VMuckle in MACsec provides LAN participants with hybrid quantum-safe key material to ensure secure communication even in the event of cryptographically
relevant quantum computers.