The principle of carpooling is on a path of increasing popularity. In combination with self-driving cars, we are going to encounter new ways to travel collectively. This, however, brings us to new problems. Self Driving cars would depend on a supervised and coordinated system, which would allow it to track all journeys of the passenger and therefore create an extended knowledge graph about a real person. The solution to this is a user management system, which would mask the actual identity of a user and make them untrackable. The goal of this work is to give an overview of the latest technology, which can be used to identify and authenticate the user without revealing their identity neither to the owners of the self-driving cars nor to the carpooling platform itself. Moreover, it provides a sample implementation, running on mobile and Blockchain technology, and identifies potential weak points regarding the currently available technologies. In addition to the identification and authentication mechanism, we provide a reputation system, which enables all parties to rate each other, without revealing their identity of themself or knowing the identity of the party, that is rated. Likewise, we also indicate possible ways, in which the authentication system could be extended to run in a real-world environment.