Improving Stateless Hash-Based Signatures [chapter]

Jean-Philippe Aumasson, Guillaume Endignoux
2018 Lecture Notes in Computer Science  
We present several optimizations to SPHINCS, a stateless hash-based signature scheme proposed by Bernstein et al. in 2015: PORS, a more secure variant of the HORS few-time signature scheme used in SPHINCS; secret key caching, to speed-up signing and reduce signature size; batch signing, to amortize signature time and reduce signature size when signing multiple messages at once; mask-less constructions to reduce the key size and simplify the scheme; and Octopus, a technique to eliminate
more » ... ies from authentication paths in Merkle trees. Based on a refined analysis of the subset resilience problem, we show that SPHINCS' parameters can be modified to reduce the signature size while retaining a similar security level and computation time. We then propose Gravity-SPHINCS, our variant of SPHINCS embodying the aforementioned tricks. Gravity-SPHINCS has shorter keys (32 and 64 bytes instead of ≈ 1 KB), shorter signatures (≈ 30 KB instead of 41 KB), and faster signing and verification for the same security level as SPHINCS.
doi:10.1007/978-3-319-76953-0_12 fatcat:g2u7geczxzap7omn57u6anfmgm