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abstract: 'Existing security proofs of quantum key distribution (QKD) suffer from two fundamental weaknesses. First, memory attacks have emerged as an important threat to the security of even device-independent quantum key distribution (DI-QKD), whenever QKD devices are re-used. This type of attacks constitutes an example of covert channels, which have attracted a lot of attention in security research in conventional cryptographic and communication systems. 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 simple solution to 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.'
author:
- Marcos Curty$^1$
- 'Hoi-Kwong Lo$^{2}$'
title: 'Foiling covert channels and malicious classical post-processing units in quantum key distribution'
---

Introduction
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There has been much interest in the subject of quantum key distribution (QKD) in recent years because it holds the promise of providing information-theoretically secure communications based on the laws of quantum physics 