Paper 2026/948

Anamorphic Construction For The Winternitz OTS Scheme Family

João Gabriel Feres, Universidade Federal de Santa Catarina

Bruno Bianchi Pagani, Universidade Federal de Santa Catarina

Ricardo Custódio, Universidade Federal de Santa Catarina

Abstract

The Winternitz One-Time Signature~(WOTS) scheme is a fundamental primitive in post-quantum cryptography that relies solely on the security of its hash function, has been standardized, and serves as a critical building block for standardized hash-based signatures such as XMSS, LMS, and SPHINCS. However, schemes are traditionally analyzed under the assumption that their private keys are correctly utilized and kept secure. This assumption is broken when facing an adversary with high surveillance capabilities that can order the disclosure of users' private keys. Anamorphic cryptography is a branch of covert communication research that investigates how cryptography operates in such adversarial settings. In this article, we propose the first anamorphic constructions for the WOTS family of signature schemes and show that these constructions are indistinguishable from their traditional counterparts. We formalize these constructions within a game-based framework and prove their security under standard anamorphic assumptions, showing that the resulting schemes satisfy anamorphic indistinguishability. Lastly, we briefly discuss and compare the anamorphic length capabilities and the characteristics of each construction method. Our results show that WOTS and its variants can support an anamorphic covert channel that is resilient in highly adversarial environments.

@misc{cryptoeprint:2026/948,
      author = {Lucas Mayr and João Gabriel Feres and Bruno Bianchi Pagani and Ricardo Custódio},
      title = {Anamorphic Construction For The Winternitz {OTS} Scheme Family},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/948},
      year = {2026},
      url = {https://eprint.iacr.org/2026/948}
}