Winternitz Signature
The Winternitz signature improves on Lamport's by signing each digit (rather than each bit) with a hash chain, reducing signature and key sizes.
Purpose
To optimize Lamport signature efficiency; a building block of the SPHINCS+ signature.
Mechanism
For each base-w digit d_i, the private key is x_i and the public key is y_i=H^w(x_i). The signature is σ_i=H^{d_i}(x_i). Verification checks H^{w-d_i}(σ_i)=y_i. Larger w shrinks signatures but increases computation.
Use cases
- Post-quantum signatures
- SPHINCS+
- Hash chains