1. The SPHINCS+ Signature Framework 2019 CCS PQC Signatures
    Daniel J. Bernstein, Andreas Hülsing, Stefan Kölbl, Ruben Niederhagen, Joost Rijneveld and Peter Schwabe
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    [Show BibTex Citation]

    @misc{cryptoeprint:2019:1086,
    author = {Daniel J. Bernstein and Andreas Hülsing and Stefan Kölbl and Ruben Niederhagen and Joost Rijneveld and Peter Schwabe},
    title = {The SPHINCS+ Signature Framework},
    howpublished = {Cryptology ePrint Archive, Report 2019/1086},
    year = {2019},
    note = {\url{https://eprint.iacr.org/2019/1086}},
    }

We introduce SPHINCS+, a stateless hash-based signature framework. SPHINCS+ has significant advantages over the state of the art in terms of speed, signature size, and security, and is among the nine remaining signature schemes in the second round of the NIST PQC standardization project. One of our main contributions in this context is a new few-time signature scheme that we call FORS. Our second main contribution is the introduction of tweakable hash functions and a demonstration how they allow for a unified security analysis of hash-based signature schemes. We give a security reduction for SPHINCS+ using this abstraction and derive secure parameters in accordance with the resulting bound. Finally, we present speed results for our optimized implementation of SPHINCS+ and compare to SPHINCS-256, Gravity-SPHINCS, and Picnic.

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