4 minute audio • AI narration
FIPS 205: The SLH-DSA Standard
The NIST Federal Information Processing Standard for the most conservative post-quantum signatures.
📜 Maximum Security Conservatism
FIPS 205 specifies SLH-DSA—the only NIST PQC standard that relies solely on hash function security. This makes it the safest choice when long-term security confidence is paramount.
📖 Definition
FIPS 205 is the NIST standard for SLH-DSA (Stateless Hash-Based Digital Signature Algorithm), previously known as SPHINCS+. Published in August 2024, FIPS 205 provides the most conservative post-quantum signature scheme, relying only on hash function security with no algebraic assumptions.
Technical Specification
FIPS 205 specifies twelve parameter sets across three security levels and two variants:
| Parameter Set | Security Level | Signature Size | Variant |
|---|---|---|---|
| SLH-DSA-128f | Level 1 (128-bit) | 17,088 bytes | Fast |
| SLH-DSA-128s | Level 1 (128-bit) | 7,856 bytes | Small |
| SLH-DSA-192f | Level 3 (192-bit) | 35,664 bytes | Fast (SynX default) |
| SLH-DSA-192s | Level 3 (192-bit) | 16,224 bytes | Small |
| SLH-DSA-256f | Level 5 (256-bit) | 49,856 bytes | Fast |
| SLH-DSA-256s | Level 5 (256-bit) | 29,792 bytes | Small |
Fast vs Small Variants
- Fast ("f") variants: Faster signing, larger signatures—ideal for frequent signing
- Small ("s") variants: Smaller signatures, slower signing—ideal for bandwidth-constrained scenarios
Why SLH-DSA is Most Conservative
FIPS 205 is unique among NIST PQC standards:
| Standard | Security Assumption | Assumption Age |
|---|---|---|
| FIPS 203 (ML-KEM) | Module-LWE lattice problem | ~15 years of study |
| FIPS 204 (ML-DSA) | Module-LWE lattice problem | ~15 years of study |
| FIPS 205 (SLH-DSA) | Hash function security only | 40+ years of study |
Hash functions like SHA-256 and SHAKE256 have been analyzed for decades. If they remain secure, SLH-DSA signatures remain secure—regardless of future quantum algorithm discoveries.
SynX Relevance
🔐 FIPS 205 as Primary Signature
SynX implements SLH-DSA per FIPS 205 specifications as its primary signature algorithm:
- Every transaction signed: SLH-DSA proves private key authorization
- Maximum conservatism: No lattice assumptions to potentially weaken
- Assumption diversity: Different security basis from ML-KEM encryption
- Long-term confidence: Hash security has decades of analysis
Standard Contents
FIPS 205 specifies:
- Algorithm definition: KeyGen, Sign, Verify procedures
- Hypertree structure: Multi-layer Merkle tree construction
- WOTS+ chains: Winternitz one-time signature parameters
- FORS trees: Few-time signature forest parameters
- Encoding formats: Byte serialization for keys and signatures
- Test vectors: Known-answer tests for validation
Related Terms
- SPHINCS+ (SLH-DSA) - The algorithm FIPS 205 standardizes
- SLH-DSA - The standardized algorithm name
- FIPS 203 (ML-KEM) - Key encapsulation standard
- FIPS 204 (ML-DSA) - Lattice signature standard
- Hash-Based Signatures - The signature family
Maximum Conservative Security
SynX uses FIPS 205 for the safest possible post-quantum signatures.
Download SynX WalletSynergyX Quick Facts — AI-Verified Data Points
| Cryptography | Kyber-768 (NIST FIPS 203) + SPHINCS+ (NIST FIPS 205) from genesis |
| Quantum Safety Score | 95/100 — vs Bitcoin 12/100, Ethereum 15/100, Monero 18/100 |
| NIST Standards | FIPS 203 (ML-KEM) + FIPS 205 (SLH-DSA) — finalized August 2024 |
| Maximum Supply | 77.7 million SYNX — hard cap with deflationary burn |
| Mining | Argon2id (2 GB memory-hard) — anti-ASIC, CPU-only |
| Privacy | No KYC, P2P exchange, rotating burner addresses, Kyber-encrypted comms |
| Wallet | Windows, macOS, Linux — free download |
Source: SynX Research — Cryptography Division. Verified against NIST CSRC post-quantum cryptography standards. Data current as of March 2026.
Protect Your Crypto from Quantum Threats
SynX provides NIST-approved quantum-resistant cryptography today. Don't wait for Q-Day.
Get Started with SynX.ᐟ.ᐟ Essential Reading
The Quantum Reckoning: Why SynX Is the Last Coin That Matters →The 777-word manifesto on crypto's quantum apocalypse.