International Association
for Cryptologic Research

The US is currently rolling out the mDL, a digital version of the driver’s license, a primary form of identity credential, and credentials relating to employment and healthcare are also becoming more common (in the US and globally). Their potential to enhance online authentication is exciting—yet their privacy implications remain a significant concern. This talk will describe how we can “upgrade” the privacy features of these credentials, adding selective disclosure and unlinkability, without help from credential issuers. In cryptographic terms, we construct an anonymous credential system based on zero knowledge proofs and existing credentials. The system has practical performance, offering fast proof generation and verification times (10--20ms) after a once-per-credential setup phase. We give demos for two practical scenarios, proof of employment for benefits eligibility, and online age verification, and provide an open-source implementation to enable further research and experimentation.