Fundamental feasibility of preventing information leakage in QKD devices

Determine whether it is fundamentally possible to guarantee, in practical implementations of Quantum Key Distribution (QKD), that devices such as single-photon detectors, quantum random number generators (QRNGs), and classical computing hardware leak only the information specified by the protocol—for example, preventing any external leakage of raw key material—and, if so, identify the design and shielding conditions required to achieve this non-leakage.

Background

Within the assumptions underlying QKD, the paper highlights a critical implementation-level requirement: devices must not leak relevant or secret information beyond what the protocol specifies. This includes components such as single-photon detectors, QRNGs, and classical computers that process raw key material. The authors note that typical mitigation involves hardware shielding, but question whether such non-leakage can be guaranteed in principle.

This issue directly impacts QKD’s claimed security, since physical side-channel leakage could undermine confidentiality and authenticity even when protocol-level proofs hold. The authors explicitly state that the fundamental possibility of achieving non-leakage is unresolved, positioning it as a key open question that bridges practical engineering constraints and the theoretical security guarantees of QKD.