Quantum key distribution with post-processing driven by physical unclonable functions

TL;DR

The conditions under which physical unclonable functions can be integrated in currently available quantum key distribution systems are discussed in order to facilitate the generation and the distribution of the necessary pre-shared key with the smallest possible cost in the security of the systems.

Abstract

Quantum key-distribution protocols allow two honest distant parties to establish a common truly random secret key in the presence of powerful adversaries, provided that the two users share beforehand a short secret key. This pre-shared secret key is used mainly for authentication purposes in the post-processing of classical data that have been obtained during the quantum communication stage, and it prevents a man-in-the-middle attack. The necessity of a pre-shared key is usually considered as the main drawback of quantum key-distribution protocols, which becomes even stronger for large networks involving more that two users. Here we discuss the conditions under which physical unclonable function can be integrated in currently available quantum key-distribution systems, in order to facilitate the generation and the distribution of the necessary pre-shared key, with the smallest possible cost in the security of the systems. Moreover, the integration of physical unclonable functions in quantum key-distribution networks allows for real-time authentication of the devices that are connected to the network.

Figures (8)

• Figure 1: Schematic presentation of the main steps and the flow of data in a QKD protocol.
• Figure 2: Schematic representations of a point-to-point QKD link (a) and of the man-in-the-middle attack (b).
• Figure 3: Schematic representation of a physical unclonable function (PUF). The token (sometimes also referred to as PUF tag), is a device with internal physical disorder. The internal disorder of the token is imprinted into its response to a physical challenge. The raw response is processed classically in order to yield a nearly perfect and robust random key.
• Figure 4: Integration of PUFs in a point-to-point QKD link. (a) Each pair of QKD boxes is associated with two PUFs namely, PUF$_{\rm A}$ and PUF$_{\rm B}$. A PUF generates a random key as a response to a challenge. The manufacturer creates a database of challenge-response pairs (CRPs), where only the joint keys are stored. (b) With the purchase of the QKD boxes, the users also have access to the corresponding PUFs. Moreover, one of them (say Alice), receives a copy of the database. For the generation of a common random key, which will seed the first QKD session, Alice and Bob interrogate their PUFs independently with the same randomly chosen challenge. The corresponding entry is permanently removed from the database, while Bob also keeps track of the used challenges. This procedure can be performed again, e.g., if the first QKD session aborts, and a new QKD session is necessary.
• Figure 5: Full-mesh QKD network involving $n$ users. (a) In the absence of a key distribution center (KDC), the total number of pre-shared keys is $n(n-1)/2$, while each new user has to share $n$ keys with each one of the other existing users. (b) In the presence of a KDC, each user shares a key with the KDC only.