Superlinear threshold detectors in quantum cryptography

Abstract

We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systems using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear toward the end of the gate. For systems expecting substantial loss, or for systems not monitoring loss, this would allow eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance

Comment on “Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography” [Appl. Phys. Lett. 98, 231104 (2011)]

“…19,20 In this particular case, we have already shown that an eavesdropper using temporally tailored light of short pulses containing less than 120 photons can threaten the security of QKD. 4 This faint after-gate attack would not be detectable with the countermeasure proposed by Yuan et al, since the pulses would not cause an "anomalously high" current, but rather a current similar to the current caused by a single photon. Therefore, this serves as an example of the risk associated with closing loopholes in an intuitive way.…”

“…For instance, one such discrepancy allows the tailored bright illumination attacks, [1][2][3] recently shown also to be applicable against superconducting nanowire single-photon detectors. 4,5 In this case, the loophole is caused by the response of qubit measurement devices (detectors) to swarms of qubits (bright illumination). The question is how to counter such loopholes.…”

A XTC based Authentication Scheme for MANET

“…Lars Lydersen et al [28] provide a theory named superlinear threshold detector.In this theory a detector has a superior probability to identify photons if it receives them simultaneously rather than at after some time.In quantum key distribution systems superlinear threshold detectors permits eaves-dropping full secret key distribution. Lars Lydersen et al [28] introduces detector control attack and analyze how it executes for key distribution.They compute the superlinearity in superconducting single-photon detectors based on previous published data, and gated avalanche photodiode detectors based on own dimensions.…”

Risk Analysis of Trojan-Horse Attacks on Practical Quantum Key Distribution Systems

“…kHz for this specific experiment [12]) of the SPADs in Bob. One may thus assume that the SPAD sees the light from the OPO as quasi-CW essentially.…”

“…Such theory-practice deviations usually arise due to technical deficiencies and operational imperfections in the system hardware or firmware. The field of quantum hacking investigates such deviations [4][5][6] and many proof-of-principle quantum hacking attacks have been devised and performed on practical QKD systems in the last decade [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”