Paper 2025/2069
Shorter Hash-Based Signatures Using Forced Pruning
, University of Isfahan, Google (United States)Abstract
The stateless hash-based digital signature algorithm (SLH-DSA) is a post-quantum signature scheme based on the SPHINCS$^+$ framework that was recently standardized by NIST. Although it offers many benefits, a drawback of SLH-DSA is that it has relatively large signatures. Several techniques have been proposed to reduce the signature size of SPHINCS-like schemes, and NIST is actively evaluating variants with shorter signatures for possible future standardization. We explore using forced pruning in the few-time signature scheme used by SPHINCS$^+$ to reduce the overall signature size. Prior work suggested similar ideas, but claimed that the improvement from forced pruning was small. We re-visit this conclusion by performing a detailed theoretical analysis of forced pruning along with a more thorough exploration of its benefits. We show that forced pruning can improve upon SPHINCS+C (Oakland 2023) in all respects, and can reduce the overall signature size for the "smaller SPHINCS$^+$" variants proposed by Fluhrer and Dang by up to 20% with minimal effect on signing time. Our results thus show that forced pruning can be a beneficial optimization for hash-based signatures.
Metadata
- Available format(s)
-
PDF
- Category
- Public-key cryptography
- Publication info
- Published by the IACR in CRYPTO 2026
- Keywords
- Hash-based signaturespost-quantum cryptography
- Contact author(s)
-
m8abri @ gmail com
jkatz2 @ gmail com - History
- 2026-06-17: revised
- 2025-11-10: received
- See all versions
- Short URL
- https://ia.cr/2025/2069
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2025/2069,
author = {Mehdi Abri and Jonathan Katz},
title = {Shorter Hash-Based Signatures Using Forced Pruning},
howpublished = {Cryptology {ePrint} Archive, Paper 2025/2069},
year = {2025},
url = {https://eprint.iacr.org/2025/2069}
}
