CACS: A Cloud Privacy-Preserving Attribute Management System

We present Centralized Attribute Collection Service (CACS), a system for storing credentials in the cloud, with satisfying privacy properties for users, and additional assurances for relying parties. The system deploys privacy-enhancing technologies to protect users’ identities and credentials presented to relying parties. At the same time, the system can vouch for the trustfulness of issuers to relying parties. The system also allows users to obtain the access logs for their credentials, enabling them to compare them against their usage. The presentation of credentials to relying parties follows the standard protocols of Mobile Driving Licence (mDL, ISO 18013-5).