title: Real-time monitoring of single-photon detectors against eavesdropping in quantum key distribution systems.
abstract: By employing real-time monitoring of single-photon avalanche photodiodes we demonstrate how two types of practical eavesdropping strategies, the after-gate and time-shift attacks, may be detected. Both attacks are identified with the detectors operating without any special modifications, making this proposal well suited for real-world applications. The monitoring system is based on accumulating statistics of the times between consecutive detection events, and extracting the afterpulse and overall efficiency of the detectors in real-time using mathematical models fit to the measured data. We are able to directly observe changes in the afterpulse probabilities generated from the after-gate and faint after-gate attacks, as well as different timing signatures in the time-shift attack. We also discuss the applicability of our scheme to other general blinding attacks.
authors.affiliation: Centre for Telecommunication Studies, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, Brazil. thiago@opto.cetuc.puc-rio.br
authors.forename: Thiago Ferreira
authors.initials: TF
authors.lastname: da Silva
authors.forename: Guilherme B
authors.initials: GB
authors.lastname: Xavier
authors.forename: Guilherme P
authors.initials: GP
authors.lastname: Temporão
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: von der Weid
mesh_terms: D016494:Computer Security / Q000295:instrumentation*; D003199:Computer Systems; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010783:Photometry / Q000295:instrumentation* / Q000379:methods*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*