SPHINCS+ Signatures Explained: Hash-Based Security

SPHINCS+ (now SLH-DSA under FIPS 205) provides digital signatures for the SynX quantum-resistant wallet. This stateless hash-based scheme offers the strongest quantum resistance confidence.

Why Hash-Based Signatures?

Hash-based signatures have unique advantages:

• Security relies ONLY on hash function properties
• No mathematical structure for quantum algorithms to exploit
• Most conservative post-quantum approach
• Minimal cryptographic assumptions

SPHINCS+ Architecture

SPHINCS+ combines multiple hash-based constructions:

• WOTS+: One-time signature scheme
• XMSS: Merkle tree authentication
• FORS: Few-time signature for index selection
• Hypertree: Hierarchy of Merkle trees for efficiency

Parameter Options

How Signing Works

In the SynX quantum-resistant wallet:

1. Transaction data is hashed
2. FORS generates initial signature fragment
3. WOTS+ signs the FORS public key
4. Merkle authentication path proves validity
5. Complete signature authorizes transaction

Stateless Operation

SPHINCS+ is stateless, meaning:

• No counter or state to maintain
• Same key can sign unlimited messages
• No risk of state desynchronization
• Simpler wallet implementation

Signature Size Trade-off

SPHINCS+ signatures are larger than ECDSA:

• ECDSA: 64 bytes
• SPHINCS+: 7-29 KB depending on parameters
• Trade-off: Larger size for quantum security
• Acceptable for blockchain transactions

Why SynX Chose SPHINCS+

The SynX quantum-resistant wallet selected SPHINCS+ because:

• Maximum confidence in quantum resistance
• Conservative security assumptions
• NIST standardization (FIPS 205)
• Stateless simplifies wallet design

Frequently Asked Questions

Do larger signatures slow transactions?

Signature verification is fast. Network handles larger data without significant delay.

Could SPHINCS+ be broken?

Would require breaking hash functions (SHA-256, etc.)—foundational to all cryptography.