Improved finite-key security analysis of quantum key distribution against Trojan-horse attacks

Abstract

Most security proofs of quantum key distribution (QKD) disregard the effect of information leakage from the users' devices, and, thus, do not protect against Trojan-horse attacks (THAs). In a THA, the eavesdropper injects strong light into the QKD apparatuses, and then analyzes the back-reflected light to learn information about their internal setting choices. Only a few recent works consider this security threat, but predict a rather poor performance of QKD unless the devices are strongly isolated from the channel. Here, we derive finite-key security bounds for decoy-state-based QKD schemes in the presence of THAs, which significantly outperform previous analyses. Our results constitute an important step forward to closing the existing gap between theory and practice in QKD.

A fully passive transmitter for decoy-state quantum key distribution

“…THAs). Notwithstanding, current security proofs against THAs in the active setting typically require the intensity of the back-reflected light to be minuscule for the information leakage to be irrelevant (as an example, the analyses in [10][11][12] demand such intensity to lie below 10 −7 or 10 −8 photons/pulse). In contrast to this, much less isolation is expected to be required to deal with laser-seeding attacks in the PT.…”

“…This premise opens the door for the so-called Trojan horse attacks (THAs) [4][5][6][7][8], where an adversary injects bright light pulses into a QKD transmitter/receiver and then measures the back-reflected light, aiming to extract information about the setting choices. Notably, a possible solution to deal with information leakage in the QKD transmitter consists of trying to upper bound Eve's accessible information gain and account for it in the estimation of the secret key length [9][10][11][12]. Note, however, that this approach relies on modelling the information leakage to a certain extent, and it requires to add significant optical isolation to prevent a severe drop of the secret key rate and the achievable distance.…”

Experimental study of secure quantum key distribution with source and detection imperfections

“…introducing two-decoy method, which has been proved to provide a tighter bound than one-decoy method, would an efficient way; Ref. [40,63] provides a loss tolerant protocol which has a better performance than the traditional GLLP analysis with leaky source. It is possible to use the loss tolerant protocol to make the key rate performance better.…”

Improvement and security analysis of multi-ring discrete modulation continuous variable quantum secret sharing scheme

“…Second, from a theoretical analysis perspective, we can relax the strict assumptions of most current security proofs to incorporate these potential impacts into security analysis. [35] In the security analysis of CVQSS, when Eve employs a THA, it always has a certain impact on the excess noise of the CVQSS system. This impact is easily noticed by Alice and Bob, hence the failure of the attack.…”