The need for privacy-respecting use of unique identifiers in emerging European eID cards has been underlined by many. The emerging privacy-ABCs (Attribute-based Credentials) technologies have significant potential in this area. One of the goals of the European Project ABC4Trust is to provide a common unified architecture for privacy-ABCs that is independent of the specific technologies existing today (e.g. Idemix, U-Prove) and support the federation and interoperability between them. In this talk I will highlight the most relevant issues of the ABC4Trust architecture and how the project implements it and deploys it in actual production pilots.