Algorithms
What is SLH-DSA?
Also known as SPHINCS+.
Stateless Hash-Based Digital Signature Algorithm. NIST's hash-based signature standard, finalised as FIPS 205 in August 2024. Twelve parameter sets across SHA2 / SHAKE hash families. Conservative security based solely on hash-function strength - used by QNSI on Government tier when lattice assumptions are not acceptable.
Decision context
Why SLH-DSA matters
SLH-DSA offers a standardized hash-based alternative to lattice signatures. Its different security assumptions make it useful for diversity and long-lived authenticity, while its larger signatures and performance profile require deliberate protocol, storage, bandwidth, and verification-capacity planning.
How to evaluate SLH-DSA
Confirm the precise SHA2 or SHAKE parameter set and whether the application can carry its signature size and latency. Exercise signing and verification with authoritative vectors, malformed inputs and rotation. Document where hash-based diversity is required instead of presenting every workload as needing the same primitive.
Algorithms
Algorithms evidence boundary
Algorithm names alone do not establish security or deployment readiness. Parameter set, implementation, key and signature sizes, execution boundary, validation status, and failure behaviour all matter. Buyers should distinguish a standardized primitive from a product path that has independently demonstrated that primitive in production.
Deep dive
SLH-DSA on QNSI
NIST's hash-based digital signature standard, finalised August 2024 as FIPS 205. SLH-DSA's security rests only on the hardness of finding hash function preimages - the most conservative assumption available - making it the natural choice for long-archival signatures and government-tier policy.
For parameter sets, key and signature sizes, NIST ACVP conformance status, and when to use it, see the full SLH-DSA algorithm reference.
FAQ
Common questions
What is SLH-DSA?
Stateless Hash-Based Digital Signature Algorithm. NIST's hash-based signature standard, finalised as FIPS 205 in August 2024. Twelve parameter sets across SHA2 / SHAKE hash families. Conservative security based solely on hash-function strength - used by QNSI on Government tier when lattice assumptions are not acceptable.
Why does SLH-DSA matter?
SLH-DSA offers a standardized hash-based alternative to lattice signatures. Its different security assumptions make it useful for diversity and long-lived authenticity, while its larger signatures and performance profile require deliberate protocol, storage, bandwidth, and verification-capacity planning.
How should SLH-DSA be evaluated?
Confirm the precise SHA2 or SHAKE parameter set and whether the application can carry its signature size and latency. Exercise signing and verification with authoritative vectors, malformed inputs and rotation. Document where hash-based diversity is required instead of presenting every workload as needing the same primitive.
What is SLH-DSA also known as?
SLH-DSA is also known as SPHINCS+. Stateless Hash-Based Digital Signature Algorithm. NIST's hash-based signature standard, finalised as FIPS 205 in August 2024. Twelve parameter sets across SHA2 / SHAKE hash families. Conservative security based solely on hash-function strength - used by QNSI on Government tier when lattice assumptions are not acceptable.
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