Hybrid Keys in Practice: Combining Classical, Quantum and Post-Quantum Cryptography

Abstract

Currently, with the threat of quantum computer attacks, the idea of combining several same-type primitives has reemerged. This is also the case for cryptographic keys where a hybrid quantum key exchange combination allows for preserving the security guarantees of pre-quantum schemes and achieving quantum resistance of post-quantum schemes. In this article, we present a concrete 3-key combiner system implemented on a Field Programmable Gate Arrays (FPGA) platform. Our system involves a pre-quantum Key EXchange scheme (KEX), a post-quantum key encapsulation mechanism, and a Quantum Key Distribution (QKD) algorithm. The proposed 3-key combiner is proven to be secure in the quantum standard model and it is INDistinguishable under a Chosen-Ciphertext Attack (IND-CCA). Our combiner can run in small FPGA platforms due to its relatively low resources usage. In particular, the key combiner without QKD is able to output up to 1 624 keys per second and the key combiner with QKD is able to output up to 9.2 keys per second.

Currently, with the threat of quantum computer attacks, the idea of combining several same-type primitives has reemerged. This is also the case for cryptographic keys where a hybrid quantum key exchange combination allows for preserving the security guarantees of pre-quantum schemes and achieving quantum resistance of post-quantum schemes. In this article, we present a concrete 3-key combiner system implemented on a Field Programmable Gate Arrays (FPGA) platform. Our system involves a pre-quantum Key EXchange scheme (KEX), a post-quantum key encapsulation mechanism, and a Quantum Key Distribution (QKD) algorithm. The proposed 3-key combiner is proven to be secure in the quantum standard model and it is INDistinguishable under a Chosen-Ciphertext Attack (IND-CCA). Our combiner can run in small FPGA platforms due to its relatively low resources usage. In particular, the key combiner without QKD is able to output up to 1 624 keys per second and the key combiner with QKD is able to output up to 9.2 keys per second.