Practical anamorphic group signature scheme based on MAYO

Abstract With the advancement of quantum computing and increasing demands for privacy protection in decentralized applications such as blockchain, digital signature schemes face significant challenges in simultaneously achieving anonymity, traceability, and resistance to dictatorship surveillance. Recently, anamorphic signatures were introduced to address extreme censorship scenarios, enabling parties to embed hidden messages within authenticated signatures even when communication channels and keys are entirely controlled by an adversarial dictator. Motivated by this scenario, we propose the first anamorphic group signature scheme based on the MAYO multivariate post-quantum signature algorithm. Our scheme achieves indistinguishable embedding of anamorphic messages into signatures, enabling confidential communication that remains undetectable even under strict monitoring. We further introduce an efficient confirmation and disavowal protocol combining 3-pass and 5-pass MQ identification protocols, facilitating secure member identification without compromising anonymity. Finally, a lightweight signature-opening mechanism based on salted hash bindings ensures that only the group manager can disclose signer identities during disputes. Our construction provides a practical, quantum-resistant, and dictator-resistant cryptographic toolset, making it particularly suitable for consortium blockchains, private chains, and regulated governmental networks.