Actual quantum key distribution network nodes may be vulnerable to side-channel attacks such as electromagnetic leakage. In this study, we measured electromagnetic emissions from a prototype quantum key distribution device implementing a time-bin decoy-state BB84 protocol with Y and Z bases. We measured the electromagnetic spectra and waveforms at distances of 0 m and 3 m from the transmitter and receiver inside an anechoic chamber. The results showed that the transmitter was the primary source of electromagnetic leakage, and distinct differences were observed between the quantum states generated at the third harmonic of the 1241.6 MHz clock.
Actual quantum key distribution network nodes may be vulnerable to side-channel attacks such as electromagnetic leakage. In this study, we measured electromagnetic emissions from a prototype quantum key distribution device implementing a time-bin decoy-state BB84 protocol with Y and Z bases. We measured the electromagnetic spectra and waveforms at distances of 0 m and 3 m from the transmitter and receiver inside an anechoic chamber. The results showed that the transmitter was the primary source of electromagnetic leakage, and distinct differences were observed between the quantum states generated at the third harmonic of the 1241.6 MHz clock.
The security provided by Quantum Key Distribution (QKD) can be strongly compromised by interception of the raw and sifted key through side channels, such as the practical characteristics of electronic components used in the transmitter and receiver modules. Some out-of-band electromagnetic attacks have already been identified and tested in components used in QKD, such as quantum random number generators. In this presentation, we explore out-of-band electromagnetic attacks of other components used in a quantum receiver, such as Single Photon Avalanche Diodes (SPADs), and the time-correlated single-photon counting module. We measured the electromagnetic (EM) radiated emissions of the components to quantify the emanation levels and evaluate the vulnerability that this QKD side channel may present. The test was conducted in an anechoic chamber up to 1 GHz, at 3 m distance, and rotating the SPAD to provide radiation from four azimuth angles. Results show that measurable radiated pulses are generated by the SPAD in this frequency range due to dark count pulses and due to incoming Single-Photon level pulses. Dark counts of few kHz and Single-Photon level counts of hundreds of kHz were considered in the tests. EM radiation frequency bands with main emissions and electric field strengths are identified for both operation conditions.
As quantum key distribution progresses into commercial products and services, there is growing interest in technological solutions that improve performance and/or reduce costs. We present an experimental demonstration of the polarization-based three-level decoy-state BB84 quantum key distribution (QKD) protocol, at a clock frequency of 50 MHz, that relies on fewer resources at the receiver and increases robustness to side-channel attacks for both the transmitter and receiver. A single-laser source and cascade of electro-optic modulators provide the four polarization states, while a photonic recombiner with time-multiplexed inputs enables detection with a single detector.
The security of current key exchange protocols such as Diffie-Hellman key exchange is based on the hardness of number theoretic problems. However, these key exchange protocols are threatened by weak random number generators, advances to CPU power, a new attack from the eavesdropper, and the emergence of a quantum computer. Quantum Key Distribution (QKD) addresses these challenges by using quantum properties to exchange a secret key without the risk of being intercepted. Recent developments on the QKD system resulted in a stable key generation with fewer errors so that the QKD system is rapidly becoming a solid commercial proposition. However, although the security of the QKD system is guaranteed by quantum physics, its careless implementation could make the system vulnerable. In this paper, we proposed the first side-channel attack on plug-and-play QKD system. Through a single electromagnetic trace obtained from the phase modulator on Alice's side, we were able to classify the electromagnetic trace into four classes, which corresponds to the number of bit and basis combination in the BB84 protocol. We concluded that the plug-and-play QKD system is vulnerable to side-channel attack so that the countermeasure must be considered.
Over recent decades, quantum key distribution (QKD) has arisen as a promising solution for secure communications; however, like all cryptographic protocols, implementations of QKD can open security vulnerabilities. Until now, the study of physical vulnerabilities in QKD setups has focused primarily on the optical channel. In classical cryptoanalysis, power and electromagnetic side-channel analysis are powerful techniques that can be used to access secret information about the encryption key in symmetric-key algorithms. Such attacks have rarely been used in QKD, since they require an eavesdropper to have access to Alice’s or Bob’s setup; however, security proofs of QKD protocols generally assume that these setups are secure, making it crucial to understand the security measures required to ensure this protection. In this work, we propose and implement a power side-channel analysis of a QKD system by exploiting the power consumption of the electronic driver controlling the electro-optical components of the QKD transmitter. QKD modules typically require very precise electronic drivers, such as field-programmable gate arrays (FPGAs). Here, we show that the FPGA’s power consumption can leak information about the QKD operation and consequently the transmitted key. Our results are consistent and show critical information leakage, having reached a maximum accuracy of 73.35% in predicting transmitted qubits at a 100-MHz repetition frequency. We also discuss possible countermeasures to prevent such an attack.
Quantum Key Distribution (QKD) promises information-theoretic security based on the fundamental laws of quantum mechanics. However, practical implementations deviate from idealized models and are therefore susceptible to side-channel attacks that exploit physical imperfections rather than theoretical vulnerabilities. Over the past two decades, a wide range of attacks have been demonstrated against QKD systems, including those targeting detectors, sources, timing information, power consumption, and electromagnetic emissions. This paper addresses a selection of a few side-channel attacks reported in the literature, classifying them according to their underlying physical mechanisms and attack strategies. We analyze their impact on the security of different QKD protocols and platforms, and highlight how experimental demonstrations have shaped the community's understanding of implementation security. In addition, we present and evaluate mitigation techniques proposed to date, such as device-independent and measurement-device-independent QKD, hardware countermeasures, monitoring strategies, and so on. We also identify open challenges and promising directions for enhancing the robustness of future quantum communication systems.
While ideal quantum key distribution (QKD) systems are well-understood, practical implementations face various vulnerabilities, such as side-channel attacks resulting from device imperfections. Current security proofs for decoy-state BB84 protocols either assume uniform phase randomization of Alice’s signals, which is compromised by practical limitations and attacks like injection locking, or rely on a (partially) characterized phase distribution. This work presents an experimental method to characterize the phase de-randomization from injection locking using a heterodyne detection setup, providing a lower bound on the degree of isolation required to protect QKD transmitters against injection-locking attacks. The methods presented are source-agnostic and can be used to evaluate general QKD systems against injection-locking attacks.