Foiling covert channels and malicious classical post-processing units in quantum key distribution

Abstract

© 2019, The Author(s). The existing paradigm for the security of quantum key distribution (QKD) suffers from two fundamental weaknesses. First, covert channels have emerged as an important threat and have attracted a lot of attention in security research in conventional information and communication systems. Covert channels (e.g. memory attacks) can fatally break the security of even device-independent quantum key distribution (DI-QKD), whenever QKD devices are re-used. Second, it is often implicitly assumed that the classical post-processing units of a QKD system are trusted. This is a rather strong assumption and is very hard to justify in practice. Here, we propose a new paradigm for the security of QKD that addresses these two fundamental problems. Specifically, we show that by using verifiable secret sharing and multiple optical devices and classical post-processing units, one could re-establish the security of QKD. Our techniques are rather general and they apply to both DI-QKD and non-DI-QKD.