Relaxing the Single Point of Failure in Quantum Key Distribution Networks: An Overview of Multi-path Approaches

Quantum Key Distribution (QKD) networks are receiving growing attention by researchers and funding agencies, with the largest projects spanning hundreds of kilometers and large, multi-national initiatives well under way. The growing scale of QKD networks poses some extra challenges, in particular due to the current impossibility of establishing end-to-end security between nodes: for large distances, reliance on intermediate trusted nodes is required, an aspect which increases the attack surface of QKD networks. A possible mitigation strategy for this problem lies in leveraging the complexity of the network: by making use of multiple paths and applying techniques issued from cryptography and/or error-correcting theory, it is possible to mitigate some attacks and force an adversary to compromise more nodes in the network.

This paper discusses relevant approaches to leverage multi-path aspects of QKD networks for increased security, analyzing the different security assumptions, guarantees, and performance of different techniques, and presenting their applicability to the different networks.