Q-CSKDF: A Continuous and Security Key Derivation Function for Quantum Key Distribution

Quantum Key Distribution (QKD) offers a novel approach to address the challenges posed by quantum computations in classical ciphers. Due to hardware limitations and the stochastic nature of QKD protocols, the secure key generation rate is currently constrained and subject to fluctuations. However, users expect a consistent supply of keys at a stable rate while maintaining a secure threshold. To address this issue, we present a Quantum Continuous and Secure Key Derivation Function named Q-CSKDF that utilizes QKD keys to produce stable, high-rate, but secure derivated keys. Our approach satisfies both security and rate requirements in a full-period and continuous perspective, with a dynamic derivation expansion ratio determined by users' requirement of security level and key quantity and the amount of generated QKD keys. Extensive semi-physical experiments demonstrate Q-CSKDF's capability to consistently generate high-rate derived keys while ensuring the desired level of security.