Enhancing Quantum Key Distribution via McEliece-based hybrid PQC-QKD architecture

Abstract Quantum Key Distribution (QKD) offers information-theoretic security; however, its practicality is limited by an inherently low secret key rate. In this work, we propose a cryptographic enhancement of QKD by incorporating post-quantum public key encryption, namely Classic McEliece. We propose a novel hybrid PQC-QKD protocol named BBM that employs QC-LDPC based McEliece cryptosystem to encrypt the basis string in QKD, thereby skipping the sifting step and consequently improving the secret key rate. We only need to assume the short-term security of the McEliece cryptosystem during the protocol run to achieve the everlasting security of the distilled keys. Our analysis demonstrates that this integration not only enhances the achievable secret key rate by $\sim 2\times $ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> </mml:math> in the BB84 protocol but also provides resistance against photon number splitting attack, and inherits a fallback mechanism in its design. This marks a significant improvement in terms of efficiency, security, and reliability over conventional BB84-like QKD protocols.