I. Introduction
Network functions [1] require access to various control data signaled in different ways to utilize their functionalities. Moreover, the diversity and amount of the processed control data increases accordingly. Hence, the communication endpoints have to allow more and more access to information about themselves. Thus, the network functions are able to observe and possibly exploit information. Furthermore, even third parties can observe and possibly exploit information while it is transferred in cleartext. The de facto method applied so far to provide information confidentiality for two communicating endpoints is end-to-end encryption. However, the network functions then have no longer access to the encrypted control data and they cannot accomplish their tasks anymore. Therefore, it becomes impossible to utilize the benefits of the network functions if end-to-end encryption is applied. These issues indicate that it is so far only possible to realize one of the two goals – information confidentiality and smart network functions – at once.