Anonymous Signature Linkability via Signer-Specific Secrets
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Solution Overview
Problem
Current anonymous signature schemes, such as ring and group signatures, do not allow signers to prove that they have produced a set of signatures without revealing their identity.
Innovation Solution
A method is introduced that generates a signer-specific secret and augments messages with a message-unique value related to this secret, enabling the signer to produce a proof that an arbitrary set of signed messages embed the same secret, which can be anonymously verified by a third party, thus allowing user-controlled linkability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anonymous signature schemes (ring signatures or group signatures) are used to protect signer anonymity, then signer identity is hidden, but the signer cannot prove that they have produced a set of signatures
Solution Approach 1:
The secret key is segmented into two parts: a signer-specific secret (x) that remains private and a public key that is shared. The signer-specific secret is used to create proofs of authorship, while the public key enables anonymous signing. This segmentation allows the system to provide both anonymity and provable authorship simultaneously.
Solution Approach 2:
A message-unique value (β) is introduced as an intermediary element that connects the signer's identity to the signature without revealing the signer's identity. This value is derived from the signer-specific secret and the message, and it enables the verification of authorship while preserving anonymity. The intermediary allows the system to bridge the gap between anonymity and provable authorship.
2Reliability
If traditional anonymous signature schemes are used, then signer identity is protected, but linkability of signatures to the same signer is lost
Solution Approach 1:
The system performs preliminary actions by embedding the signer-specific secret into the signature structure through the message-unique value (β) during the signing process. This preliminary embedding enables future linkability verification without requiring additional interactions or revealing the signer's identity at the time of signing.
Solution Approach 2:
The signature structure is enhanced with additional parameters including the message-unique value (β) and a proof component. These parameter changes transform the traditional anonymous signature into one that supports both anonymity and user-controlled linkability, allowing the same signer to be identified across multiple signatures without compromising their anonymity.
3Adaptability or versatility
If proofs of authorship are added to anonymous signatures, then linkability is enabled, but system complexity increases
Solution Approach 1:
The proof of authorship functionality is extracted as a separate, optional component that can be added to traditional anonymous signature schemes. Rather than redesigning the entire signature system, the invention extracts and adds only the necessary elements (message-unique value and proof generation/verification mechanisms) to enable linkability while keeping the core anonymous signature functionality intact.
Data Source
AI summary
A method to enhance an anonymous signature scheme with user-controlled linkability includes generating, by a signer of a ring signature scheme or a group signature scheme, a signer-specific secret (x) and generating a secret key based on the generated secret (x). The signer augments a message to be signed with a message-unique value that is related to the signer-specific secret (x) thereby generating an augmented message. The signer signs the augmented message with the secret key of the signer and produces a proof that an arbitrary set of signed messages embed the signer-specific secret (x). The signer anonymously publishes the produced proof for verification by a third-party verifier.