Tunable Asymmetric Delay Attack in Quantum Clock Synchronization

TL;DR

This paper addresses the vulnerability of quantum clock synchronization (QCS) to asymmetric delays in nonreciprocal channels and proposes tunable asymmetric delay attack (T-ADA) to dynamically control attack parameters. The authors formalize a parametric attack model with amplitude, timing, and trajectory functions, and demonstrate three attack patterns—jump, spike, and gradual—that degrade short- or long-term synchronization differently. Experimental results on a 10 km round-trip QCS show that jumps cause permanent offsets, spikes induce short-term disruptions with partial recovery, and gradual attacks silently accumulate errors, revealing distinct vulnerability profiles. The work highlights the need for secure QCS architectures with dynamic threat modeling, threshold-aware monitoring, and multi-path redundancy to counteract adaptable, covert timing attacks.

Abstract

Quantum clock synchronization underpins modern secure communications and critical infrastructure, yet its fundamental dependence on channel reciprocity introduces an exploitable vulnerability to asymmetric delay attacks. Current attack strategies rely on static delays, limiting their ability to target application-specific stability requirements. Here, we propose a tunable asymmetric delay attack (T-ADA) that dynamically controls delay parameters to induce manipulate synchronization accuracy. Through experimental implementation, we demonstrate how tailored attack trajectories can selectively compromise system stability across different scenarios. This work uncovers key vulnerabilities in synchronization protocols under customizable attacks and provide a foundation for developing secure and resilient quantum clock synchronization systems.

Figures (7)

• Figure 1: The diagram of the round-trip QCS scheme. FPC: fiber polarization controller, DWDM: dense wavelength division multiplexer, BS: beam splitter, OC: optical circulator, $\mathrm{D_1, D_2, D_3, D_4}$: superconducting nanowire single-photon detector, $\mathrm{TDC}$: time-to-digital converter, $\mathrm{QAC}$: rubidium atomic clock, $\mathrm{MDL}$: motorized optical delay line. $\mathrm{PC}_A$, $\mathrm{PC}_B$ and $\mathrm{PC}_E$ represent Alice's, Bob's, and Eve's personal computers, respectively. $\mathrm{PC}_A$ and $\mathrm{PC}_B$ are statistical photon intensity correlation functions, while $\mathrm{PC}_E$ is configured with a software attack module for the T-ADA scheme.
• Figure 2: Time deviation under three attack patterns in experimental conditions
• Figure 3: The clock difference of the round-trip QCS system was evaluated across six distinct experimental groups with varying jump attack configurations: $0$ ps, $-10$ ps, $-50$ ps, $-100$ ps, $-200$ ps, $-500$ ps, each measured over a $500$-second time interval. The clock difference was adjusted by adding $-9900$ ps, with this value serving as the reference point ($0$ ps).
• Figure 4: Effects of spike attacks. The clock difference of the round-trip QCS system, with $9900$ ps set as the reference point $0$. The pink region represents the spike attack. The five distinct attacks occurred at different times: $330$ s, $662$ s, $1022$ s, $1376$ s, and $1709$ s, with their corresponding magnitudes increasing from $-500$ ps to $-100$ ps.
• Figure 5: The impact of gradual attacks in experiments, with $9900$ ps set as the reference point $0$. The first attack involves injecting $-2$ ps per $35$ seconds on a unidirectional path, with a total duration of $2100$ seconds and remaining unchanged thereafter. The second attack increases the injection rate to $-4$ ps per $35$ seconds on the unidirectional path, while simultaneously maintaining an opposite injection rate on the round-trip path. After this, the injection rate is adjusted to $4$ ps every $35$ seconds again, extending the attack duration to $3500$ seconds.

Theorems & Definitions (3)

• Definition 1
• Definition 2
• Definition 3