Security Analysis of the RaSTA Safety Protocol

RaSTA is a transport protocol that has been designed to be deployed in the safety-critical domain of railway signalling. The protocol provides safety properties such as message authenticity, integrity, timeliness, and sequence. However, critical railway infrastructures face cyber attacks and therefore require security measures. We investigate the security properties of RaSTA by analysing weaknesses of the utilized MD4 algorithm in the context where RaSTA is utilized. To overcome the weaknesses, we propose relevant enhancements to the protocol that maintain the safety properties and additionally provide secure message authentication. We evaluate our work using the computation time for message authentication which is crucial for the utilization of RaSTA in a safety-critical network.