Forward-looking consistency in Attribute-Based Credentials

Forward-looking consistency in Attribute-Based Credentials: A privacy-preserving way to determine the revocation status of credentials after presentation

van Bruggen, Christian (TU Delft Electrical Engineering, Mathematics and Computer Science)

Erkin, Z. (mentor)
Wang, H. (graduation committee)
van Deventer, O. (graduation committee)

Delft University of Technology

2020-11-24

Authentication mechanisms play an important role in everyday digital interactions and allow users to prove their identity to others. Privacy-preserving Attribute-Based Credential Systems (PABCSs) allow users to authenticate by presenting their credential attributes, while multiple presentations remain unlinkable and untraceable. A revocation mechanism allows the credential issuer to revoke a credential, for example when the attributes of a user change. Verifiers can in turn determine the revocation status of the presented credential. This thesis considers situations in which a verifier needs to determine the revocation status of a credential after the presentation. This stronger revocation level, also described as forward-looking consistency, has not been researched before in PABCSs. To address this gap, we present the PABC-FLC design, a PABCS with forward-looking consistency. Our design allows users to remain offline after presentation, without compromising on the privacy properties. To avoid an impossibility result, we introduce a new participant called the Non-Revocation Prover (NRP). The NRP facilitates a verifier in determining the revocation status of a credential, even though neither the verifier nor the issuer have to trust the NRP. We show that our PABC-FLC design has a comparable experimental runtime to a credential system without revocation mechanism. This experiment shows our design has a runtime overhead of +20 ms (+32%) during presentation and +20 ms (+34%) during verification. Concluding that our PABC-FLC design is a feasible PABCS with forward-looking consistency, while remaining unlinkable and untraceable.

attribute-based credentials
revocation
forward-looking consistency

http://resolver.tudelft.nl/uuid:871e17aa-a023-461f-88b1-80d83c21de92

Student theses

master thesis

© 2020 Christian van Bruggen