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arXiv:1711.08724 · npj Quantum Information

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

Marcos Curty, Hoi‐Kwong Lo

Published Feb 6, 2019• 35 citations
arXivHTMLPDF

Abstract

Abstract 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.

DOI
10.1038/s41534-019-0131-5

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Abstract 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.
The current paradigm for the security of quantum key distribution (QKD) relies on the legitimate users of the system trusting their devices, which include both the quantum communication components and the classical post-processing units. However, in view of the memory attacks recently proposed against device-independent QKD, as well as the many hardware and software Trojan Horse attacks that threaten the security of conventional cryptography today, such trust is a very strong and unjustified assumption. Here we review a recent proposal to solve this problem based on the use of verifiable secret sharing and redundancies. We show that this approach can deliver secret key rates which are comparable to those obtained in an ideal scenario with honest devices.
Abstract The malicious manipulation of quantum key distribution (QKD) hardware is a serious threat to its security, as, typically, neither end users nor QKD manufacturers can validate the integrity of every component of their QKD system in practice. One possible approach to re-establish the security of QKD is to use a redundant number of devices. Following this idea, we address various corruption models of the possibly malicious devices and show that, compared to the most conservative model of active and collaborative corrupted devices, natural assumptions allow to significantly enhance the secret key rate or considerably reduce the necessary resources. Furthermore, we show that, for most practical situations, the resulting finite-size secret key rate is similar to that of the standard scenario assuming trusted devices.
Device-independent quantum key distribution (DI-QKD) is often seen as the ultimate key exchange protocol in terms of security, as it can be performed securely with uncharacterised black-box devices. The advent of DI-QKD closes several loopholes and side-channels that plague current QKD systems. While implementing DI-QKD protocols is technically challenging, there have been recent proof-of-principle demonstrations, resulting from the progress made in both theory and experiments. In this review, we will provide an introduction to DI-QKD, an overview of the related experiments performed, and the theory and techniques required to analyse its security. We conclude with an outlook on future DI-QKD research.
The fabrication of quantum key distribution (QKD) systems typically involves several parties, thus providing Eve with multiple opportunities to meddle with the devices. As a consequence, conventional hardware and/or software hacking attacks pose natural threats to the security of practical QKD. Fortunately, if the number of corrupted devices is limited, the security can be restored by using redundant apparatuses. Here, we report on the demonstration of a secure QKD setup with optical devices and classical postprocessing units possibly controlled by an eavesdropper. We implement a 1.25 GHz chip-based measurement-device-independent QKD system secure against malicious devices on both the measurement and the users' sides. The secret key rate reaches 137 bps over a 24 dB channel loss. Our setup, benefiting from a high clock rate, miniaturized transmitters, and a cost-effective structure, provides a promising solution for widespread applications requiring uncompromising communication security.
Abstract Quantum key distribution (QKD) protocols are unconditionally secure, providing that quantum devices are truthful. Device-independent quantum key distribution (DI-QKD) protocols offer the prospect of distributing secret keys with minimal assumptions. The DI-QKD protocols are hard to implement using the current technologies as they require all the quantum devices to be uncharacterized. Measurement device independent quantum key distribution (MDI-QKD) protocols assume that the measurement devices are not truthful; the adversary might make them. MDI-QKD is secure but more challenging to implement. Receiver-device-independent quantum key distribution (RDI-QKD) protocols assume that the receiver's measurement devices can be viewed as a black box while the sender's device can be trusted. RDI-QKD relies on reasonable assumptions that make it easy to implement using the current state-of-the-art technology. We propose an RDI-QKD protocol, called DGL22. DGL22 is secure against all known attacks that are allowed by quantum mechanics. DGL22 provides several benefits over previous protocols, including the capability to attain high communication and sifting efficiency.