Quantum Key Distribution Protocols: Security Analysis and Real-World Implementations

Quantum Key Distribution (QKD) has emerged as a critical component of secure communication in the post-quantum era. This study provides a comparative security and performance analysis of leading QKD protocols—BB84, E91, and Continuous Variable QKD—using experimental and simulated data from terrestrial and satellite-based implementations. Key metrics such as secret key rate, bit error rate, and resistance to quantum attacks are analyzed. Regression and predictive modeling are used to quantify performance decay over distance and noise. The results indicate BB84's robustness and broad applicability, while CV-QKD offers throughput advantages in short-range networks. Keywords: Quantum Key Distribution, QKD, BB84, E91, Continuous Variable QKD, Cryptographic Security, Quantum Communication, Post-Quantum Security