# SPHINCS+ - **Algorithm type**: Digital signature scheme. - **Main cryptographic assumption**: hash-based signatures. - **Principal submitters**: Andreas Hülsing. - **Auxiliary submitters**: Jean-Philippe Aumasson, Daniel J. Bernstein,, Christoph Dobraunig, Maria Eichlseder, Scott Fluhrer, Stefan-Lukas Gazdag, Panos Kampanakis, Stefan Kölbl, Tanja Lange, Martin M. Lauridsen, Florian Mendel, Ruben Niederhagen, Christian Rechberger, Joost Rijneveld, Peter Schwabe. - **Authors' website**: https://sphincs.org/ - **Specification version**: NIST Round 3 submission. - **Implementation source**: https://github.com/PQClean/PQClean/commit/7eb978b4a733696bd7197278aa84216095674524 with copy_from_upstream patches, which takes it from: - https://github.com/sphincs/sphincsplus - **Implementation license (SPDX-Identifier)**: CC0-1.0. ## Parameter set summary | Parameter set | Security model | Claimed NIST Level | Public key size (bytes) | Secret key size (bytes) | Signature size (bytes) | |:-----------------------------:|:-----------------|---------------------:|--------------------------:|--------------------------:|-------------------------:| | SPHINCS+-Haraka-128f-robust | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-Haraka-128f-simple | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-Haraka-128s-robust | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-Haraka-128s-simple | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-Haraka-192f-robust | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-Haraka-192f-simple | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-Haraka-192s-robust | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-Haraka-192s-simple | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-Haraka-256f-robust | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-Haraka-256f-simple | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-Haraka-256s-robust | EUF-CMA | 5 | 64 | 128 | 29792 | | SPHINCS+-Haraka-256s-simple | EUF-CMA | 5 | 64 | 128 | 29792 | | SPHINCS+-SHA256-128f-robust | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-SHA256-128f-simple | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-SHA256-128s-robust | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-SHA256-128s-simple | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-SHA256-192f-robust | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-SHA256-192f-simple | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-SHA256-192s-robust | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-SHA256-192s-simple | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-SHA256-256f-robust | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-SHA256-256f-simple | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-SHA256-256s-robust | EUF-CMA | 5 | 64 | 128 | 29792 | | SPHINCS+-SHA256-256s-simple | EUF-CMA | 5 | 64 | 128 | 29792 | | SPHINCS+-SHAKE256-128f-robust | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-SHAKE256-128f-simple | EUF-CMA | 1 | 32 | 64 | 17088 | | SPHINCS+-SHAKE256-128s-robust | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-SHAKE256-128s-simple | EUF-CMA | 1 | 32 | 64 | 7856 | | SPHINCS+-SHAKE256-192f-robust | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-SHAKE256-192f-simple | EUF-CMA | 3 | 48 | 96 | 35664 | | SPHINCS+-SHAKE256-192s-robust | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-SHAKE256-192s-simple | EUF-CMA | 3 | 48 | 96 | 16224 | | SPHINCS+-SHAKE256-256f-robust | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-SHAKE256-256f-simple | EUF-CMA | 5 | 64 | 128 | 49856 | | SPHINCS+-SHAKE256-256s-robust | EUF-CMA | 5 | 64 | 128 | 29792 | | SPHINCS+-SHAKE256-256s-simple | EUF-CMA | 5 | 64 | 128 | 29792 | ## SPHINCS+-Haraka-128f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage?‡ | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:----------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ‡For an explanation of what this denotes, consult the [Explanation of Terms](#explanation-of-terms) section at the end of this file. ## SPHINCS+-Haraka-128f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-128s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-128s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-192f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-192f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-192s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-192s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-256f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-256f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-256s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-Haraka-256s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | aesni | x86\_64 | All | AES | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-128f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-128f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-128s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-128s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-192f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-192f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-192s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-192s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-256f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-256f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-256s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHA256-256s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-128f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-128f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-128s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-128s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-192f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-192f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-192s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-192s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-256f-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-256f-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-256s-robust implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## SPHINCS+-SHAKE256-256s-simple implementation characteristics | Identifier in upstream | Supported architecture(s) | Supported operating system(s) | CPU extension(s) used | No branching-on-secrets claimed? | No branching-on-secrets checked by valgrind? | Large stack usage? | |:------------------------:|:----------------------------|:--------------------------------|:------------------------|:-----------------------------------|:-----------------------------------------------|:---------------------| | clean | All | All | None | True | True | False | | avx2 | x86\_64 | All | AVX2 | True | True | False | Are implementations chosen based on runtime CPU feature detection? **Yes**. ## Explanation of Terms - **Large Stack Usage**: Implementations identified as having such may cause failures when running in threads or in constrained environments.