An Efficient Secret Communication Scheme for the Bosonic Wiretap Channel
Esther Hänggi, Iyán Méndez Veiga, Ligong Wang
TL;DR
The paper addresses secret communication over a practical bosonic wiretap channel by introducing an explicit scheme that relies on coherent-state transmission, pulse-position modulation, randomness extractors, and Reed-Solomon codes. It achieves information-theoretic secrecy against quantum adversaries using the Quantum Leftover Hash Lemma, while maintaining polynomial-timeEncoding/decoding. The authors derive both asymptotic results, showing the scheme reaches the dominant term of the secrecy capacity in the low-photon regime, and finite-block-length bounds that quantify error and security trade-offs. The work offers a tangible path toward implementing secret optical communication with off-the-shelf hardware, though it notes coupling between parameters and points to future improvements for finite-power scenarios and hardware imperfections.
Abstract
We propose a new secret communication scheme over the bosonic wiretap channel. It uses readily available hardware such as lasers and direct photodetectors. The scheme is based on randomness extractors, pulse-position modulation, and Reed-Solomon codes and is therefore computationally efficient. It is secure against an eavesdropper performing coherent joint measurements on the quantum states it observes. In the low-photon-flow limit, the scheme is asymptotically optimal and achieves the same dominant term as the secrecy capacity of the same channel.