I. Introduction
While the digitalization finds its way in every aspect of our lives, security properties of information and operation technology systems start to receive more attention. This is also true for critical infrastructures like railway services, which can become the target of attackers. Rail Safe Transport Application (RaSTA) is a safety-critical network protocol designed for the fast and reliable transport of control messages between railway interlocking systems, as well as signalling and switching equipment. The protocol is an important piece in the transformation of interlocking systems from proprietary, monolithic blocks towards modularized and standardized systems to optimize cost and enable interchangeability. In turn, the security of the modularized system must be investigated to avoid compromising safety [1]. Since a communication protocol, as well as the underlying network connection, present a prominent attack surface, it is important to be aware of their security properties and possible vulnerabilities.