In Moscow, Russia

In Vigo, Spain

Characterisation of electroluminescence in avalanche single-photon detectors

The project will focus on experimental characterisation of backflash light from single-photon detectors based on avalanche photodiodes, using a photon-number-resolving superconducting photon detector as a sensor. The results could provide deeper insight into the backflash source statistics (which is known to be super-Poissonian, but there’s room for a more precise characterisation), as well as into spectral properties of the backflash light. The student will assemble and operate an experimental setup and analyse the results.

Unambiguous state discrimination using linear optics and displacement operation

The project is the first step in experimentally implementing a man-in-the-middle attack on coherent-one-way quantum key distribution protocol, as proposed in [J. Rey-Dominguez et al., Quantum Sci. Technol. 9, 035044 (2024)]. We want to demonstrate this attack on a commercial quantum key distribution system from ID Quantique. The student will implement and test a setup for the main element of this attack: unambiguous state discrimination using linear optics, displacement operation, and single-photon detectors.

Laser damage of fiber-optic components

The project investigates the resilience of quantum key distribution (QKD) systems against the laser-damage attack by a 1550-nm pulsed laser. The key project output and its novelty consist in updating the security threat models posed by high-intensity pulsed laser tampering. In addition, this study will provide valuable results in the field of laser damage itself, providing systematic experimental results on damage threshold depending on laser parameters. The student will test fiber-optic components (such as isolators, circulators, attenuators, wavelength multiplexers, photodiodes) under exposure to laser pulses, explain damage mechanisms for different exposure regimes, and analyse risks for QKD security. The fiber-optic components will be characterised across the entire parameter range of the laser available, including different pulse durations (50 ps through 1 ns) and repetition rate (5 MHz through 2 GHz).

Laser-seeding attack on light sources in quantum key distribution

The project investigates the efficiency of the laser-seeding attack on weak coherent light sources used in quantum key distribution (QKD). To date, QKD security analysis primarily accounts for threats posed by a continuous-wave attacking laser. This project aims to update system security boundaries using new experimental data with a pulsed seeding laser. The latter has a higher peak power and may thus be able to control semiconductor laser sources insensitive to the continuous-wave seeding. The student will build an experimental setup to simulate the attack, test laser sources of two different types (single-laser and injection-locking tandem; the latter is more resistant against this attack), and analyse the results.

Demonstration of a supply-chain attack on quantum key distribution system

The security of cryptographic equipment relies not only on the cryptographic protocol and the quality of its implementation, but also on the system hardware components acquired from third parties being free of intentionally introduced backdoors and malicious modifications. In quantum key distribution (QKD), this class of attacks and their mitigation have not been explored. Almost all the optical and electronic components in industrial QKD systems come from external suppliers and may be subject to tampering either at their origin or in transit. A demonstration of this attack on a QKD system will stimulate the discussion and awareness of this problem in the QKD community. The student will disassemble the optical part of a commercial QKD product (under guidance), identify components and their function, and select one of the components for malicious modification. He will then modify the component taking care that the modification does not impair its external appearance and its performance in the QKD system (which will be verified experimentally), yet creates an effective backdoor. He will model how the backdoor allows to compromise the key.

Security testing of multi-element superconducting single-photon detectors

Multi-pixel superconducting nanowire single-photon detectors (mp-SNSPDs) have been proposed as a countermeasure against bright-light attacks on quantum key distribution [F. Grünenfelder et al., Nat. Photonics 17, 422 (2023)]. The underlying assumption is that single-photon pulses will trigger only one pixel, while classical (multi-photon) pulses, used in the known attacks, will trigger multiple pixels simultaneously, enabling attack detection. However, this assumption has not yet been experimentally verified. A practical test of this concept is necessary to assess whether an adversary could, under specific conditions, selectively activate individual pixels and bypass the security mechanism. The student will conduct three experimental tests that study spatial, temporal, and spectral response of the detector to bright-light illumination. The experiment uses mp-SNSPD, light sources, and characterisation instruments in our lab. The results will be analysed by the student in relation to the security of quantum key distribution.

Energy-time and memory effects in single-photon detectors

While several types of security vulnerabilities in single-photon detectors are known, new ones are discovered from time to time. The student will work on experimental testing of single-photon detectors for two unpublished vulnerabilities named in the title that may further challenge the implementation security of quantum key distribution. Contact for details.

“Lockpicking” security bags and design of tampering tools

Seals and tamper-evident enclosures are known for at least five millennia. The modern versions of the latter include a plastic security bag, which is a mass-produced item that has many applications in commerce, banking, law enforcement, healthcare, and other areas. The security bag has several features that make an attempt of its unauthorised opening leave visible traces [V. Makarov, Elect. Polit. 13, issue 1, 5 (2025)]. Nevertheless, the real security level of these products has not been explored. The student will design, make, and test a precision mechanical tool for cutting open heat-sealed seams on the bag, and also rig tools for tracelessly re-welding them. The tools will be used for compromising different bag samples. In case a promising tampering method is found, a blind trial on users and forensic laboratories will be staged. The findings will be reported in open literature.