Paper 2025/2143

New Post-Quantum IBE leveraging maturity, efficiency and security of standard schemes

Abstract

Many Identity-Based Encryption (IBE) schemes rely on the hardness of the Discrete Logarithm Problem, making them vulnerable to quantum attacks. In recent years, lattice-based cryptography has emerged as a source of Post-Quantum cryptosystems, for example with Kyber, Dilithium and Falcon chosen by NIST to be standardized as ML-KEM, ML-DSA and FN-DSA. Some IBEs have also been proposed over lattices, but they can still be considered as interesting theoretical constructions, the community's attention having been more on the NIST competition than on optimizing IBEs, assessing their security, and protecting them against physical attacks. So, in this paper, we build a new IBE scheme from the basic blocks of the highly studied ML-KEM, ML-DSA and ModFalcon, to put both their maturity and efficiency at the benefits of IBE. More precisely, we leverage the Module-NTRU trapdoor from ModFalcon to enable extraction of secret keys, we use the encryption and decryption algorithms from ML-KEM, and the modular arithmetic and Number-Theoretic Transform from ML-DSA. Therefore, being able to reuse code from widely deployed schemes, our IBE is much easier to implement and maintain in practice, and can benefit from existing (and future) optimizations, hardware accelerators, and side-channel protections, with very little to no additional work. We also prove the IND-sID-CPA-security of our scheme under standard assumptions, and precisely describe the algorithms and the choice of concrete parameters.