Code-based physical layer secret key generation in passive optical networks

To guarantee secure transmissions is an important target of passive optical networks (PONs). Modern standards for PONs, however, impose the adoption of symmetric encryption algorithms in downstream but do not do the same in upstream, where the secret keys may be transmitted in clear. Because of non- ideal optical network components, this exposes the PON to the risk of eavesdropping. In this paper, a novel technique for securely generating and sharing secret keys in passive optical networks is proposed. It exploits randomness at the physical layer and key distillation based on coding techniques. The main attack strategies are considered and the design parameters of the proposed protocol are discussed, both in analytical terms and through numerical examples. The cost in terms of complexity with respect to standard approaches affected by possible vulnerabilities is also assessed.