Paper 2020/763

Practical Quantum-Safe Stateful Hybrid Key Exchange Protocol

Abstract

Shor's quantum algorithm, running in quantum computers, can efficiently solve integer factorization problem and discrete logarithm problem in polynomial time. This poses an urgent and serious threat to long-term security with recent accelerated evolution of quantum computing. However, National Institute of Standards and Technology (NIST) plans to release its standard of post-quantum cryptography between 2022 and 2024. It is crucially important to propose an early solution, which is likely secure against quantum attacks and classical attacks, and likely to comply with the future NIST standard. A robust combiner combines a set of 2 or more cryptography primitives into a new primitive of the same type, and guarantees that if anyone of the ingredient primitive is secure, then the resulting primitive is secure. This work proposes the first construction of robust combiner for Key Encapsulation Mechanism (KEM), with optimal amortized performance. From our robust combiner of KEMs, we construct efficient stateful hybrid Key Exchange Protocol (KEP), which is more suitable for two parties who will communicate with each other frequently.