Quantum-Space Attacks

TL;DR

This paper introduces a general framework for analyzing quantum key distribution protocols that operate in larger, more realistic quantum spaces, and classifies various known attacks within this new quantum-space attack paradigm.

Contribution

It presents a novel method called quantum-space attack, which assesses the actual enlarged quantum space used in practical QKD protocols, filling a gap in security analysis.

Findings

Classified recent attacks using the quantum-space attack framework

Analyzed a new attack on interferometry-based QKD

Provided a general approach for realistic QKD security assessment

Abstract

Theoretical quantum key distribution (QKD) protocols commonly rely on the use of qubits (quantum bits). In reality, however, due to practical limitations, the legitimate users are forced to employ a larger quantum (Hilbert) space, say a quhexit (quantum six-dimensional) space, or even a much larger quantum Hilbert space. Various specific attacks exploit of these limitations. Although security can still be proved in some very special cases, a general framework that considers such realistic QKD protocols, as well as} attacks on such protocols, is still missing. We describe a general method of attacking realistic QKD protocols, which we call the `quantum-space attack'. The description is based on assessing the enlarged quantum space actually used by a protocol, the `quantum space of the protocol'. We demonstrate these new methods by classifying various (known) recent attacks against several QKD schemes, and by analyzing a novel attack on interferometry-based QKD.