Deanonymizable Scoped Linkable Ring Signatures
This work provides a new cryptographic primitive for applications requiring both privacy and accountability, such as consent management in healthcare, by combining scoped linkability with decentralized deanonymization without relying on a centralized opener.
The paper introduces Deanonymizable Scoped Linkable Ring Signatures (DSLRS), a novel signature scheme that integrates scoped linkability and decentralized accountability (on-demand deanonymization) in a single scheme, addressing trust requirements for use-cases like healthcare consent management. The scheme is defined and proven secure under ECDLP and DDH assumptions in the Random Oracle Model.
Although ring signatures offer highly desirable privacy requirements like anonymity and ad-hoc group formation with signer autonomy, they partially lack trust requirements like linkability and accountability that are required for strict use-cases, such as consent management in healthcare. Existing signature schemes fail to natively integrate scoped linkability with decentralized accountability (on-demand deanonymization) in a single scheme without relying on separate commitments or a centralized opener. We therefore introduce Deanonymizable Scoped Linkable Ring Signatures (DSLRS). The originality of the DSLRS is manifold. DSLRS uses scopes (context identifiers) and dynamic key images to provide scoped linkability and unlinkability across different scopes. Decentralized accountability is provided thanks to two ELGamal components deeply embedded in the signature, and a decentralized deanonymization network of k-of-N nodes that can collaboratively extract the signer's public key. DSLRS scheme is defined and proved under the ECDLP and DDH hardness assumptions in the Random Oracle Model (ROM). Formal security definitions and formal reduction proofs are provided before introducing a blockchain-based instantiation for a consent management application using DSLRS.