Satellite Quantum Key Distribution: Analysis, Modeling, Performance Evaluation, and Validation

Digital security is a critical concern in modern society, and quantum cryptography offers a promising defense against the threat posed by quantum computers to existing encryption systems. Quantum key distribution (QKD) provides an unconditionally secure method for symmetric key exchange, but its range is limited over optical fiber. Satellite-based QKD can overcome these distance constraints, making it a key component of future global secure communication networks. This paper presents the modeling and performance evaluation of a satellite QKD system implementing the BB84 protocol with two decoy states, considering both active and passive receiver configurations. We introduce a dedicated evaluation methodology and tool to estimate key generation rates, incorporating finite key effects (FKE), a critical factor given the short and dynamic visibility intervals of satellite-to-ground links. Our results are validated against publicly available experimental data from the Micius satellite QKD experiments, showing strong agreement and confirming the reliability of our approach. Then, we apply the tool to conduct a comparative analysis of LEO and GEO satellite QKD, demonstrating its versatility across scenarios. This work enables more accurate and realistic performance assessments, which are essential for the development of reliable and secure satellite-based quantum communication systems.