HT-ADA: Scalable Hierarchical-Tree Quantum Key Distribution with Adaptive Optimization and Entropy-Enhanced Security

Traditional QKD protocols limit scalability in multi-user networks due topoint-to-point designs and static decoy states. We propose HT-ADA, a novel hierarchical tree quantum key distribution protocol integrating per-link adaptive decoy allocation (ADA), Hoeffding-bound eavesdropper detection, and entropy-based key analysis within a composable security framework. HT-ADA distributes secure keys across multi-node tree networks, dynamically adjusting decoy probabilities to optimize detection sensitivity while minimizing communication overhead. Numerical simulations under realistic fiber-based noise (2%) and attack conditions (Eve strength 0.1-0.3) demonstrate 99% detection rates, near-ideal entropy (0.999 bits), and 2.7× higher key rates compared to static-decoy schemes across 8-32 node networks. HT-ADA provides a scalable, composable framework for future quantumnetworks with experimentally realistic parameters.