Doctoral thesis
Open access

Practical Security of Quantum Technologies

DirectorsZbinden, Hugoorcid
Defense date2021-02-25

Quantum technologies are driving more and more interest both in academia and industry thanks to their promising performances in terms of security. In reality, practical systems suffer from imperfections compared to theoretical models which could be exploited by an eavesdropper if no protection is implemented. Bridging the gap between theory and practice is therefore one of the main challenges of this field today. During this thesis, I worked on different aspects of the practical security of quantum technologies. This ranges from the modeling of the entropy source of a quantum random number generator (QNRG) to the study of the vulnerabilities of quantum key distribution (QKD) implementations against hacking. In the first part, I focus on the modeling of a commercial QRNG chip from ID Quantique. More specifically, I present the model we developed for the quantum entropy source of the device. We estimate that this fully integrated device can provide a quantum min-entropy of 0.98 per bit. Importantly, this near-unity quantum entropy is achievable without post-processing reducing the power consumption of the chip, making it suitable for mobile devices. Moreover, we show that this high-quality entropy is robust against imperfections. On the side of QKD security, I begin by studying the behavior of negative-feedback avalanche diode (NFAD) detectors under a blinding attack. After showing their vulnerability to this attack and testing the resilience of a countermeasure based on the monitoring of the mean photocurrent, I present an improved countermeasure. This allows Bob to detect more advanced blinding strategies where Eve modulates her blinding power to reduce her impact on the mean photocurrent. In the last part of this thesis, I present a novel method to prevent the blinding attack based on statistical measurements with a multi-pixel detector. Through this approach, we can estimate an upper bound on Eve's information on the key exchanged. An analysis of the finite-key effects estimates that this countermeasure can be effective for distances up to 250km. The applicability of this countermeasure with current technology is shown with a 2-pixel superconducting detector.

  • Quantum key distribution
  • Single-photon detector
  • Quantum random number generator
  • Quantum hacking
Research group
  • European Commission - Quantum Communications for ALL [675662]
Citation (ISO format)
GRAS, Gaétan Daniel Michel. Practical Security of Quantum Technologies. 2021. doi: 10.13097/archive-ouverte/unige:155689
Main files (1)

Technical informations

Creation10/25/2021 11:32:00 AM
First validation10/25/2021 11:32:00 AM
Update time05/26/2023 12:47:00 PM
Status update05/26/2023 12:47:00 PM
Last indexation09/18/2023 9:33:20 PM
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