Towards Efficient and Secure Communication in Near-Term Quantum-Classical Networks via Linear-Code Secret Sharing

In the absence of scalable, long-distance quantum communication, secure communication in the near-term will rely on clever uses of quantum-classical networks. Complementary strategies in this vein are offered by Quantum Key Distribution (QKD), in which keys are distributed through shared quantum states, and Post-Quantum Cryptography (PQC), which approach security through certain classical problems. Despite active investigations in both efforts, these strategies face their respective limitations. QKD is limited by transmission loss over long distances and loopholes in physical implementation; meanwhile, the security of any PQC relies on the unproven hardness of the underlying problem. In this work, we develop a framework that combines keys produced from QKD and PQC through linear-code secret sharing. Specifically, we consider a secure key distribution scheme based on Reed-Solomon codes, and analyze its security and efficiency. In comparison to the naive XOR combination at a similar performance, our scheme has a security advantage which grows linearly with the number of key distribution links available. Furthermore, the flexibility of the scheme allows a tradeoff between security and efficiency which is optimal for such schemes based on linear codes. Our scheme presents a practical approach towards secure communication that can be tailored to the needs of the network.