An Enhanced Hybrid Post-Quantum Digital Signature Scheme and Its Application

In order to meet the challenges brought by quantum computing, research on post-quantum cryptography has been carried out comprehensively. Among them, the most influential one is the post-quantum cryptography algorithm standardization project initiated by NIST. In July 2022, NIST announced that the Dilithium, Falcon, and SPHINCS+ algorithms were selected as candidate schemes for the standardization of post-quantum cryptographic digital signatures. The OQS project team is committed to promoting the transition of existing security protocols to standardized post-quantum algorithms and is currently the mainstream open-source post-quantum project. This paper improves the post-quantum hybrid digital signature scheme used by the OQS project team. Firstly, the hybrid digital signature scheme used in this project is studied, and it is found that there are security risks. Subsequently, an enhanced scheme is constructed and implemented using the hybrid algorithm combiner proposed by Nina Bindel et al., solving the security issues. The unforgeability and 2 -non-separability of the enhanced scheme are verified through formal analysis, and forward compatibility is achieved. The enhanced scheme shows obvious advantages in key generation efficiency and signature verification efficiency. Under some algorithms, the speed of signature verification of the improved scheme is 60 % of the original scheme. Meanwhile, the enhanced scheme also demonstrates stability in terms of time and storage overhead. Finally, the TLS1.3 protocol PSK mechanism is implemented using the enhanced scheme. This is the first implementation of post-quantum algorithm security protection in the PSK mechanism of the TLS protocol. This scheme can resist man-in-the-middle attacks while meeting the requirements of forward compatibility.