GRASP: Accelerating Hash-Based PQC Performance on GPU Parallel Architecture

SPHINCS+, one of the Post-Quantum Cryptography Digital Signature Algorithms (PQC-DSA) selected by NIST in the third round, features very short public and private key lengths but faces significant performance challenges compared to other post-quantum cryptographic schemes, limiting its suitability for real-world applications. In scenarios involving a large number of concurrent signing or verification tasks, these performance bottlenecks become particularly critical. To address these challenges, we propose the GPU-based paRallel Accelerated SPHINCS+(GRASP), which leverages GPU technology to enhance the efficiency of SPHINCS+signing and verification processes. We propose an adaptable parallelization strategy for SPHINCS+, analyzing its signing and verification processes to identify critical sections for efficient parallel execution. Utilizing CUDA, we perform bottom-up optimizations, focusing on memory access patterns and hypertree computation, to enhance GPU resource utilization. These efforts, combined with kernel fusion technology, result in significant improvements in throughput and overall performance. Compared to previous works, our approach achieves the highest occupancy. Extensive experimentation demonstrates that our optimized CUDA implementation of SPHINCS+achieves superior performance. Specifically, our GRASP scheme delivers throughput improvements ranging from 1.09× to 3.45× compared to state-of-the-art GPU-based solutions and surpasses the NIST reference implementation by over three orders of magnitude, highlighting a significant performance advantage.