Unif-NTT: A Unified Hardware Design of Forward and Inverse NTT for PQC Algorithms

Polynomial multiplications based on the number theoretic transform (NTT) are critical in lattice-based post-quantum cryptography algorithms. Therefore, this paper presents a platform-agnostic unified hardware accelerator design (Unif-NTT) to compute the forward and inverse operations of the NTT for the CRYSTALS-Kyber algorithm. Moreover, a unified design (Unif-BU) of the Cooley-Tukey and Gentleman-Sande butterflies is presented using two adders, multipliers, subtractors, routing multiplexers and barret-based modular reduction units. Finally, a dedicated controller is implemented for efficient control functionalities. The implementation results are realized on field-programmable gate array (FPGA) and application-specific integrated circuit (ASIC) platforms. The Unif-NTT requires 1664 and 1792 clock cycles for one forward and inverse NTT computations, respectively. It can operate up to a maximum frequency of $212MHz$ and $2.5GHz$ over Virtex-7 FPGA and 28nm ASIC platforms, respectively. The Unif-NTT is 26% more efficient in Area-Time-Product compared to the most area-optimized NTT accelerator from the state-of-the-art. The Unif-NTT design is suited for applications that demand reasonable hardware resources with processing speed.