We present a distance bounding (DB) protocol that employs quantum-bits (qubits) in the implementation of the rapid-bit exchange (a.k.a., challenge-response) phase, instead of classical bits. This is not the first attempt at using qubits in a DB protocol, as Abidin et al. proposed a way to implement DB protocols using qubits in RFIDSec 2016 [1]. We improve upon Abidin et al.'s protocol and make it resistant to photon number splitting attacks. In addition, our new protocol eliminates the need for communication from the prover to the verifier in the last authentication phase, which is necessary in the protocol by Abidin et al.
We present a distance bounding (DB) protocol that employs quantum-bits (qubits) in the implementation of the rapid-bit exchange (a.k.a., challenge-response) phase, instead of classical bits. This is not the first attempt at using qubits in a DB protocol, as Abidin et al. proposed a way to implement DB protocols using qubits in RFIDSec 2016 [1]. We improve upon Abidin et al.'s protocol and make it resistant to photon number splitting attacks. In addition, our new protocol eliminates the need for communication from the prover to the verifier in the last authentication phase, which is necessary in the protocol by Abidin et al.
Distance-bounding (DB) protocols let a verifier upper-bound a prover's physical distance by timing rapid challenge-response exchanges. Quantum communication promises simpler DB protocols with stronger security guarantees, yet existing quantum distance-bounding (QDB) proposals are analysed in ad-hoc models and, to the best of our knowledge, lack a common game-based treatment of standard fraud attacks. We contribute (i) a reusable security framework for QDB that fixes system and timing assumptions, specifies a quantum-capable adversary model, formalises distance-, mafia-, and terrorist-fraud experiments, and includes a simple i.i.d. depolarizing noise model; and (ii) an application of this framework to a published QDB protocol. For this protocol we characterise the honest per-round acceptance probability under noise and lift it to the multi-round setting, yielding explicit completeness guarantees as a function of the number of fast rounds, the acceptance threshold, and the noise parameter. For active adversaries we bound the per-round success probability of distance-fraud attacks and analyse the best known mafia-fraud strategy, deriving corresponding multi-round soundness bounds. We also show that the protocol is inherently insecure against terrorist-fraud in our model. The framework cleanly separates protocol-independent definitions from protocol-specific analysis and can be used to evaluate existing and future QDB protocols on a common basis.
Quantum distance-bounding (QDB) protocols let a verifier check that a prover is both genuine and physically nearby. During a timed fast phase of quantum communication, the verifier measures round-trip times to obtain an upper bound on the prover's distance. For a uniform comparison, we isolate the fast phase and study one-round distance-fraud (DF) and mafia-fraud (MF) games. For discrete-variable QDB, we show that these games reduce to convex optimization problems and can therefore be solved exactly with semidefinite programming; each MF value comes with an explicit attack achieving it and a matching certificate that no attack does better. This contrasts with quantum position verification, where an attack is split between two separated parties, so its optimization is nonconvex and analyses rely on relaxations. In our MF game, the cooperating pair collapses to a single sequential strategy, which keeps the game convex and its exact value computable. Across the discrete-variable protocols we examine, the best one-round DF attack succeeds with the same probability (1/2) for every protocol, whereas MF clearly separates the protocols. For continuous-variable QDB, we report estimated attack success probabilities from a calibrated Gaussian attack model. The benchmark covers protocols whose fast phase itself authenticates the prover; designs that follow Brands and Chaum and instead bind the fast phase with a final authenticated message, like the earliest QDB proposal, fall outside it and are treated separately. Of the four protocols studied, two had no previously known one-round attack values, and we report the first ones; for the other two, we find MF attacks with higher success probability than previously reported. Overall, one-round MF resistance depends on whether an attacker can use information revealed early by the prover to answer a fresh challenge from the verifier.
Time-of-flight distance-bounding protocols are potentially useful in RFID and NFC environments and are designed to discourage a number of attacks that take advantage of the inherent assumption that a token and reader that manages to communicate are located in close physical proximity to each other. These protocols are dependent on time measurements made at the physical layer of the communication channel, and thus require special high bandwidth channels with low latency. Executing a distance-bound protocol on a suitable channel in a constrained environment would potentially allow for bit errors during communication. Currently, terrorist fraud is discouraged in distance-bounding protocols by ensuring that a prover collaborating with an the attacker in this fraud has to make his secret key known to the attacker. We discuss the effect of making a protocol resistant to bit errors and show that the approach to design protocols against terrorist fraud is significantly weakened by error resistance, as a prover is potentially able to keep his key secret or hinder an attacker from learning his key.
A new interactive quantum zero-knowledge protocol for identity authentication implementable in currently available quantum cryptographic devices is proposed and demonstrated. The protocol design involves a verifier and a prover knowing a pre-shared secret, and the acceptance or rejection of the proof is determined by the quantum bit error rate. It has been implemented in modified Quantum Key Distribution devices executing two fundamental cases. In the first case, all players are honest, while in the second case, one of the users is a malicious player. We demonstrate an increase of the quantum bit error rate around 25% in the latter case compared to the case of honesty. The protocol has also been validated for distances from a back-to-back setup to more than 60 km between verifier and prover. The security and robustness of the protocol has been analysed, demonstrating its completeness, soundness and zero-knowledge properties.
Quantum communication, leveraging the principles of quantum mechanics, offers unparalleled security and efficiency for data transmission. This study integrates quantum algorithms with photonic quantum key distribution (QKD) protocols, focusing on the Z-gate optical qubit algorithm and the SARG04 protocol. The Z-gate, a phase-flip operator, plays a pivotal role in maintaining coherence in photonic qubits, while the SARG04 protocol enhances security against photon-number-splitting (PNS) attacks. Simulations demonstrate that the Z-gate algorithm optimizes coherence times up to 0.995 ms, enabling longer quantum communication distances of approximately 150 km under ideal conditions. Concurrently, the SARG04 protocol generates secure keys of varying lengths (5 bits to 52 bits) depending on transmitted qubits and matching bases. By integrating these methodologies, this research aims to enhance the robustness and scalability of photonic QKD systems, bridging theoretical insights with practical implementations in quantum security.
Location (or distance) information of a device plays a significant role in current location-based systems. How to determine the location of a device or verify the location claims made by a device is challenging, as devices are untrusted and may have an incentive to claim a false location. In secure localization and positioning system, the trusted verifier(s) interact with the untrusted prover to determine its location or validate its location claim. In this thesis, we mainly focus on one of the prominent areas of such systems: distance bounding. Distance (upper) bounding (DUB) allows a verifier to verify whether a proving party is located within a certain distance bound. DUB protocols have many applications in secure authentication and location-based services. This thesis has two main contributions. The first is that we consider the dual problem of distance lower bounding (DLB), where the prover proves it is outside a distance bound from the verifier. We motivate this problem through a number of application scenarios and model security against distance fraud (DF), Man-in-the-Middle (MiM), and collusion fraud (CF) attacks. We prove impossibility of security against these attacks without making physical assumptions. We propose approaches to the construction of secure protocols under reasonable physical assumptions and give detailed design of a DLB protocol with security analysis using our proposed model. This is the first treatment of the DLB problem in the untrusted prover setting with a number of applications, raising new research directions and opportunities in location based services. We discuss our results and propose directions for future research. One of the main assumptions which DUB protocols rely on is that the time that the prover spends in receiving the challenge, processing, and sending the response is negligible compared to the propagation time of the signal between the prover and verifier. This strict requirement poses difficulties on the implementation of DUB protocols and limits the possible development of applications for distance bounding as well. The second contribution in this thesis is that we design a novel one-round DUB protocol that uses one-way transmission time to estimate the distance instead of round-trip time, so that the assumption of negligible processing time is not required any longer. In order to prove the security, we formalize the notion of time in a distributed environment with adversarial users. In this model, time is implemented by a trusted party broadcasting unpredictable timestamps at a high frequency. We show that the timestamp is proved to be fresh and unpredictable. We then extend the time model to formalize DUB protocols and define corresponding attacks. Finally, we prove the security of our proposed distance bounding protocol and discuss potential issues when implementing such protocol. Besides these two main contributions, we also have the following two contributions: (1) we identify and analyze a new attack: false rejection attack, which poses serious threat to proximity-based authentications that uses distance bounding protocol for proximity evaluation; (2) We investigate the feasibility of replay attack in context-based proximity authentication using real-world data.