SPHINCS+ (officially SLH-DSA) is a NIST-approved stateless hash-based digital signature scheme that relies only on the security of cryptographic hash functions. Unlike ECDSA and RSA which are vulnerable to Shor's algorithm, SPHINCS+ remains secure against both classical and quantum computer attacks. SynX uses SPHINCS+ for signing all transactions.
🔏 Quick Facts About SPHINCS+
- Official Name: SLH-DSA (FIPS 205)
- Type: Stateless Hash-Based Signature
- Security Basis: Hash functions only (SHAKE, SHA-256)
- Standardized: August 2024 by NIST
- SynX Variant: SPHINCS+-SHAKE-128f
How SPHINCS+ Works
SPHINCS+ creates signatures using a hierarchy of one-time signature (OTS) schemes organized in Merkle trees. Here's the conceptual structure:
- Hypertree – Multiple layers of Merkle trees for authentication
- XMSS Trees – Extended Merkle Signature Scheme trees at each layer
- FORS – Few-time Signature scheme at the bottom for message signing
- WOTS+ – Winternitz One-Time Signatures for tree nodes
Why Hash-Based = Quantum-Safe
The security of SPHINCS+ depends only on hash function properties:
- Pre-image resistance – Can't find input from hash output
- Second pre-image resistance – Can't find colliding input
- Collision resistance – Can't find any two colliding inputs
Quantum computers can use Grover's algorithm to speed up hash attacks, but this only halves the security level (e.g., 256-bit → 128-bit). SPHINCS+ parameters account for this, maintaining full security against quantum adversaries.
SPHINCS+ vs ECDSA vs Dilithium
| Feature | SPHINCS+ | ECDSA | Dilithium |
|---|---|---|---|
| Quantum Resistant | ✅ Yes | ❌ No | ✅ Yes |
| Security Basis | Hash functions | ECDLP | Lattices |
| NIST Approved | ✅ FIPS 205 | ✅ (legacy) | ✅ FIPS 204 |
| Signature Size | ~17-50 KB | 64 bytes | ~2.4 KB |
| Signing Speed | Slower | Fast | Fast |
| Security Assumptions | Minimal (hashes) | ECDLP hard | MLWE hard |
Why SynX Chose SPHINCS+
SynX uses SPHINCS+ despite larger signature sizes because:
- Conservative security – Relies only on well-studied hash functions
- No structured lattice assumptions – Lattice cryptography is newer
- Battle-tested primitives – Hash functions have decades of analysis
- Future-proof – Even if lattice attacks improve, SPHINCS+ remains safe
SPHINCS+ Technical Specifications
| Parameter (SPHINCS+-SHAKE-128f) | Value |
|---|---|
| Security Level | NIST Level 1 (128-bit) |
| Public Key Size | 32 bytes |
| Secret Key Size | 64 bytes |
| Signature Size | 17,088 bytes |
| Hash Function | SHAKE-128 |
| Tree Height | 66 (total) |
Frequently Asked Questions
What is SPHINCS+?
SPHINCS+ (officially SLH-DSA) is a NIST-approved stateless hash-based digital signature scheme. It creates signatures using only cryptographic hash functions, making it immune to quantum computer attacks that can break RSA and ECDSA.
Why is SPHINCS+ quantum resistant?
SPHINCS+ relies only on the security of hash functions (SHA-256, SHAKE). Quantum computers can speed up hash collision attacks with Grover's algorithm, but this only halves the security level. SPHINCS+ parameters are chosen to remain secure even with this quantum speedup.
Is SPHINCS+ NIST approved?
Yes. NIST standardized SPHINCS+ as SLH-DSA (Stateless Hash-Based Digital Signature Algorithm) in FIPS 205 in August 2024, alongside ML-KEM (Kyber) and ML-DSA (Dilithium).
What's the difference between SPHINCS+ and Dilithium?
Dilithium (ML-DSA) uses lattice-based math for smaller/faster signatures, while SPHINCS+ uses only hash functions for maximum security assurance. SynX chose SPHINCS+ for its conservative security assumptions.
Experience SPHINCS+ Protection
Download the SynX wallet – every transaction signed with quantum-resistant SPHINCS+.
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