Algorithm

SPHINCS+

Family: hash-based.

SPHINCS+ is a signature scheme that uses only hash functions, submitted to the NIST post-quantum competition. A hypertree of many small signature trees lets it sign without keeping any state. Because the signer need not track used keys, it is easier to deploy safely than XMSS or LMS. Signatures are large, and NIST later standardized a close variant as SLH-DSA.

Safety: High

Why this rating

Security rests only on the properties of the hash function. The scheme is stateless, so there is no one-time-key reuse risk. Signatures are large and signing is slow. The submitted version differs slightly from the final SLH-DSA standard, so deployments should check which one they use.

Standard

https://sphincs.org/

Research

• The SPHINCS+ Signature Framework (2019)
• SPHINCS+ Submission Specification, Round 3.1

Implemented by

• PQClean