Looking at the automobiles and their equipment today it can be seen that the majority of cars have already a navigation system on board. However, these devices may not only be used for navigation purposes, but also perhaps as a system for displaying traffic signals inside the car. In order to realise that, many technical and non-technical issues and aspects have to be discussed and thought about, thus ensuring a safe and secure system. Telematic Services are very useful services and their value is increasing with the idea of displaying traffic signals only inside the car and not on the road anymore. Here it is essentially for the safety that the signals which have to be displayed are transferred correctly and in time to the on-board unit in the car. To realise that, a secure system architecture has to be developed. This ensures that the transmitted data reaches the receiver correctly and that it is not changed or injected by unauthorised parties. This paper will investigate a security concept for installing the Virtual Traffic Signal-system inside of vehicles, which will replace common traffic signals on the road in the next few years.