Original Development of a Quantum Key Distribution Protocol Adaptation for Metropolitan Fiber Telecommunications Networks in Nigeria

Quantum key distribution technology exploits quantum mechanical properties to establish information-theoretically secure cryptographic keys between communication parties, providing security guarantees against computationally unbounded adversaries that classical encryption methods cannot achieve. As quantum computing threats to existing telecommunications encryption grow more credible, adaptation of QKD for practical metropolitan fiber network deployment in Nigeria represents a forward-looking doctoral research frontier. This doctoral study develops an original adaptation of quantum key distribution protocols for metropolitan fiber telecommunications networks in Nigeria, addressing the specific fiber quality, network topology, and operational constraints of Nigerian urban fiber infrastructure. An original trusted-node QKD network architecture is theoretically developed for metropolitan network scales of 50 to 200 kilometers, incorporating key relay protocols that are optimized for the measured fiber loss and noise characteristics of single-mode fiber cable deployed in Lagos and Port Harcourt metropolitan fiber networks. The quantum bit error rate budget analysis for the proposed architecture accounts for connector insertion loss variability, splice loss statistics, and chromatic dispersion measured from fiber samples representative of Nigerian metropolitan fiber infrastructure. An original photon number splitting attack mitigation strategy adapted for the high-loss conditions of Nigerian metropolitan fiber is derived and its information-theoretic security proof provided. Simulation of key generation rates under the measured channel conditions demonstrates achievable key rates of 2.3 kilobits per second over 80-kilometer metropolitan links, sufficient for securing high-value inter-banking telecommunications links. Keywords: quantum key distribution, metropolitan network, fiber optics, Nigeria, cryptographic security.