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 redundancies 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.
CITATION STYLE
Aumasson, J. P., & Endignoux, G. (2018). Improving stateless hash-based signatures. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 10808 LNCS, pp. 219–242). Springer Verlag. https://doi.org/10.1007/978-3-319-76953-0_12
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