SLH-DSA (SPHINCS+)

Stateless hash-based signature scheme standardized as the conservative fallback — its security rests on nothing but hash functions.

Core Principles & Analysis

• If every lattice assumption fell tomorrow, SLH-DSA would still stand — hash functions are cryptography's weakest assumption.
• The price of paranoia: signatures up to 49 kilobytes, versus about 2.4 KB for ML-DSA.
• Being stateless, it avoids the key-reuse catastrophes that haunt stateful hash-based schemes.

Specifications & Metrics

• FAMILY: Hash-based
• STATUS: Standardized
• STANDARD: FIPS 205
• YEAR: 2024
• SIGNATURE SIZE: 7.8–49 KB