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Reflow is a novel signature scheme supporting unlinkable signatures by multiple parties authenticated by means of zero-knowledge credentials. Reflow integrates with blockchains and graph databases to ensure confidentiality and authenticity of signatures made by disposable identities that can be verified even when credential issuing authorities are offline. We implement and evaluate Reflow smart contracts for Zenroom and present an application to produce authenticated material passports for resource-event-agent accounting systems based on graph data structures. Reflow uses short and computationally efficient authentication credentials and can easily scale signatures to include thousands of participants.

Ensuring privacy and protection from issuer corruption in digital identity systems is crucial. We propose a method for selective disclosure and privacy-preserving revocation of digital credentials using second-order Elliptic Curves and Boneh-Lynn-Shacham (BLS) signatures. We make holders able to present proofs of possession of selected credentials without disclosing them, and we protect their presentations from replay attacks. Revocations may be distributed among multiple revocation issuers using publicly verifiable secret sharing (PVSS) and activated only by configurable consensus, ensuring robust protection against issuer corruption. Our system's unique design enables extremely fast revocation checks, even with large revocation lists, leveraging optimized hash map lookups.