Intercept–Resend Attack in Single-Photon Protocol: Analysis, Simulation, and Security Evaluation of the BB84 Quantum Key Distribution Protocol

Abstract

This thesis presents a comprehensive analysis of the Intercept–Resend attack on the BB84 Quantum Key Distribution (QKD) protocol using single-photon sources. By leveraging the fundamental principles of quantum mechanics — superposition, the no-cloning theorem, and measurement-induced disturbance — we demonstrate how an eavesdropper (Eve) introduces statistically detectable errors into the quantum channel. We analytically derive that the Intercept–Resend attack produces a theoretical Quan-tum Bit Error Rate (QBER) of 25% when Eve intercepts all transmitted photons. A comprehensive Python-based simulation of the BB84 protocol, with and without Eve’s presence, validates these theoretical predictions. Additionally, an optical simula-tion in OptiSystem models the impact of physical channel parameters — transmission distance, bit rate, and wavelength — on system performance. The results confirm that the BB84 protocol provides robust detection of eavesdropping when QBER thresholds are properly enforced, and that single-photon implementations face inherent trade-offs between transmission distance and key generation rate. Coun-termeasures including privacy amplification and quantum repeaters are discussed.