Timed Automaton-Based Quantitative Feasibility Analysis of Symmetric Cipher in Embedded RTOS: A Case Study of AES

The real-time operating system (RTOS) has a wide range of application domains and provides devices with the ability to schedule resources. Because of the restricted resources of embedded devices and the real-time constraints of RTOS, the application of cryptographic algorithms in these devices will affect the running systems. The existing approaches for RTOS ciphers’ evaluation are mainly provided by experimental data performance analysis, which, however, lack a clear judgment on the affected RTOS performance indicators, such as task schedulability, bandwidth, as well as a quantitative prediction of the remaining resources of RTOS. By focusing on task schedulability in RTOS, this paper provides a timed automaton-based quantitative approach to judge the feasibility of ciphers in embedded RTOS. First, a cryptographic algorithm execution overhead estimation model is established. Then, by combining the overhead model with a sensitivity analysis method, we can analyze the feasibility of the cryptographic algorithm. Finally, a task-oriented and timed automaton-based model is built to verify the analysis results. We take AES as a case study and carry out experiments on embedded devices. The experimental results show the effectiveness of our approach, which will provide specific feasibility indicators for the application of cryptographic algorithms in RTOS.