title: Thermal blinding of gated detectors in quantum cryptography.
abstract: It has previously been shown that the gated detectors of two commercially available quantum key distribution (QKD) systems are blindable and controllable by an eavesdropper using continuous-wave illumination and short bright trigger pulses, manipulating voltages in the circuit [Nat. Photonics 4, 686 (2010)]. This allows for an attack eavesdropping the full raw and secret key without increasing the quantum bit error rate (QBER). Here we show how thermal effects in detectors under bright illumination can lead to the same outcome. We demonstrate that the detectors in a commercial QKD system Clavis2 can be blinded by heating the avalanche photo diodes (APDs) using bright illumination, so-called thermal blinding. Further, the detectors can be triggered using short bright pulses once they are blind. For systems with pauses between packet transmission such as the plug-and-play systems, thermal inertia enables Eve to apply the bright blinding illumination before eavesdropping, making her more difficult to catch.
authors.affiliation: Department of Electronics and Telecommunications, Norwegian University of Science and Technology, Trondheim, Norway. lars.lydersen@iet.ntnu.no
authors.forename: Lars
authors.initials: L
authors.lastname: Lydersen
authors.forename: Carlos
authors.initials: C
authors.lastname: Wiechers
authors.forename: Christoffer
authors.initials: C
authors.lastname: Wittmann
authors.forename: Dominique
authors.initials: D
authors.lastname: Elser
authors.forename: Johannes
authors.initials: J
authors.lastname: Skaar
authors.forename: Vadim
authors.initials: V
authors.lastname: Makarov
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008029:Lighting / Q000295:instrumentation* / Q000379:methods*; D011789:Quantum Theory; D013696:Temperature; D014159:Transducers