Extended analysis of the Trojan-horse attack in quantum key distribution

Abstract

The discrete-variable QKD protocols based on BB84 are known to be secure against an eavesdropper, Eve, intercepting the flying qubits and performing any quantum operation on them. However, these protocols may still be vulnerable to side-channel attacks. We investigate the Trojan-Horse sidechannel attack where Eve sends her own state into Alice's apparatus and measures the reflected state to estimate the key. We prove that the separable coherent state is optimal for Eve amongst the class of multi-mode Gaussian attack states, even in the presence of thermal noise. We then provide a bound on the secret key rate in the case where Eve may use any separable state.

Hacking Alice's box in continuous-variable quantum key distribution

“…As we show in the appendix, the original and effective parameters are related by the same Eqs. (21) and (22), but where k becomes the following function of bothn and m [32] k(n, m) = m 2 (2n + 1) + 1.…”

“…Here we consider a Trojan horse attack, where Eve sends extra photons into Alice's device, in order to gain information about the states being sent through the main quantum channel without disturbing the signal state. Such an attack may be used in DV protocols [21], in order to distinguish decoy states from signal states or to gain information about Alice's basis choice. Here we assume a CV protocol based on the modulation of coherent states [22], so that the attack is against the modulator.…”

Verifiable quantum protocol for dynamic secure multiparty summation based on homomorphic encryption *

“…According to [28,29], if the used message particles are photons, there exist two types of Trojan horse attacks that may pose security threats to the proposed protocol: (1) The first one is the delayed photon attack. For this attack, we can assist the players in determining whether the received photons are single-photon or multi-photon by introducing PNS (photon number splitters).…”

Statistical analysis of quantum-entangled-network generation

“…Considerable progress has been made in understanding and building upon the Innsbruck protocol, since it is one of the most promising routes to constructing longdistance quantum communication. Much of this work has focused on aspects such as the relation between the key rate and experimental imperfections [34], the specifics of how to implement the system with atomic ensembles [35], understanding and improving the robustness against channel noise [15,36] or side-channel attacks [37][38][39][40]. However, one important aspect is often overlooked, namely the statistical factor of waiting times arising from probabilistic completion times of different elements.…”