Quantum-access security of the Winternitz one-time signature scheme
This work provides foundational security guarantees for post-quantum cryptography, addressing a critical problem for secure digital signatures in quantum computing environments.
The paper addresses the quantum-access security of the Winternitz one-time signature scheme by filling a gap in prior analysis for Lamport OTS and extending it to Winternitz OTS, developing a new tool for analyzing hash chains in the quantum random oracle model.
Quantum-access security, where an attacker is granted superposition access to secret-keyed functionalities, is a fundamental security model and its study has inspired results in post-quantum security. We revisit, and fill a gap in, the quantum-access security analysis of the Lamport one-time signature scheme (OTS) in the quantum random oracle model (QROM) by Alagic et al.~(Eurocrypt 2020). We then go on to generalize the technique to the Winternitz OTS. Along the way, we develop a tool for the analysis of hash chains in the QROM based on the superposition oracle technique by Zhandry (Crypto 2019) which might be of independent interest.