With a rise in the deployment of electronics in today’s systems especially in automobiles, the task of securing them against various attacks has become a major challenge. In particular, the most vulnerable points are: (i) communication paths between the Electronic Control Units (ECUs) and between sensors & actuators and the ECU, (ii) remote software updates from the manufacturer and the in-field system. However, when including additional mechanisms to secure such systems, especially real-time systems, there will be a major impact on the real-time properties and on the overall performance of the system. Therefore, the goal of this work is to deploy a minimal security module in a target real-time system and to analyze its impact on the aforementioned properties of the system, while achieving the goals of secure communication and authentic system update. From this analysis, it has been observed that, with the integration of such a security module into the ECU, the response time of the system is strictly dependent on the utilized communication interface between the ECU processor and the security module. The analysis is performed utilizing the security module operating at different frequencies and communicating over two different interfaces i.e., Low-Pin-Count (LPC) bus and Memory-Mapped I/O (MMIO) method.