  In the future world of safe traffic, intelligent transportation systems play
a vital role. The connections between traffic participants and systems on the
one and infrastructure and service providers on the other side are a necessary
prerequisite for informed and safe driving. The key for the connection between
all stakeholders is a reliable and secure connection. Reliability can be
achieved in different ways. For the information exchange, we utilize hybrid
communication technologies in different scenarios. This includes long-range
technologies like DAB+ and cellular networks and short- and medium-range
technologies like ETSI ITS G5 or RFID. Those technologies can only be used if
messages transmitted via the wireless communication links are protected.
Protection not only means encryption but most importantly means to verify if
the data was sent by a legit sender. This is a necessary requirement for a
recipient to trust the data received. In ITS, transmitted data could be used
for user tracing and collection of user data. Therefore, a communication system
should be designed in such a way that personal user data is protected. The user
must be untraceable, but nevertheless able to use all services without
limitations. In this paper, we describe the approach and ideas we took to
design a secure hybrid communication architecture that is at the same time data
protection friendly.
