The proposed European system for electronic identities, authentication, and trust services (eIDAS) enables remote authentication of an identity card (and selected data of the card) to an eID service. The core system has already been running on the German identity card since 2010. We analyze an extension proposed by Bundesdruckerei that enables the protocol to authenticate further transaction data such as phone numbers or PGP keys. In particular we prove cryptographically that the extension provides strong authenticity guarantees. We also discuss privacy aspects of the solution, preventing the card and the service provider of the eIDAS system to learn the actual transaction data.