A Simulated QKD Protocol Using KCBS Contextuality: Comparison with BB84

This paper presents a detailed theoretical and simulation-based comparison between the BB84 quantum key distribution (QKD) protocol and a proof-of-concept contextuality-based QKD protocol (CTX-QKD) under depolarizing noise. We begin by contrasting classical cryptography’s computational security with quantum cryptography’s information-theoretic guarantees. The physics of quantum cryptography, including superposition, entanglement, and the no-cloning theorem, is explored, followed by a mathematical analysis of BB84 and a proposed CTX-QKD framework. Performance metrics include the quantum bit error rate (QBER) for BB84 and contextuality violation measures for CTX-QKD, with confidence intervals derived from proper statistical bounds. A comprehensive simulation methodology using QuTiP, NumPy, and SciPy is described. Simulation results demonstrate that while BB84 shows expected noise tolerance up to 11% QBER, the CTX-QKD protocol maintains strong contextuality violations of the fundamental security condition under high noise conditions where BB84 fails. This study highlights the potential of contextuality as a resource for quantum cryptography and demonstrates a proof-of-concept for physics-based cryptographic security beyond traditional approaches.