Project
Ghillie
A decoy-state BB84 telemetry simulator and quantum-kernel detector for attacks hidden in the noise of a quantum key distribution link.
Problem
Quantum key distribution proves its protocol secure but says nothing about the hardware underneath, so operators monitor the channel for implementation attacks. An adversary with a kleptographic foothold in the generator of a public per-block value can hide attacked blocks inside honest noise, gating them on a predicate of a discrete logarithm. Detecting them then becomes a discrete-logarithm problem: hard for every efficient classical monitor, but not for a quantum kernel that can recover the hidden value with Shor’s algorithm.
Approach
Ghillie is a decoy-state BB84 telemetry simulator, with a positive key rate to 142 km, together with classical and quantum-kernel detectors. It is the experimental basis of the accompanying paper, which formalises these cryptographically camouflaged attacks, reduces their hardness to an established learning separation, and proves that a single-frequency fidelity kernel cannot represent an interval predicate.
Results
From 10- to 14-bit groups over two seeds, a classical monitor read 0.458 to 0.516 on camouflaged attacks while the quantum kernel read 1.000; both caught overt attacks above 0.99.
Finite-precision recovery under depolarising noise and a hardened predicate lowered the quantum result to 0.916–0.983, with the classical monitor at chance. A feasibility probe on IBM Heron processors tracked the exact kernel within 0.034.
These are the author's reported results (see the paper).
Limitations
The advantage is asymptotic and awaits fault-tolerant quantum hardware.
It holds only when the feature map matches the adversary's predicate: a low-frequency map read 0.545 on a residue pattern and 0.982 once aligned.
Results come from simulation plus a small hardware feasibility probe.