A Distributed WCET Computation Scheme for Smart Card Operating Systems

Smart card operating systems have to face very hard constraints in terms of available memory space and computing power. Nonetheless, the specifications of most smart card platforms impose strict deadlines for communications between the card and the terminal to which it is connected. This advocates the real time paradigm to guarantee response times and thus introduces the need for computation of WCET on these very constrained devices. Besides, smart card operating systems have very strict security requirements which must be taken into account by all parts of the operating system, including the WCET computation algorithm. Unfortunately, most of the classical algorithms for computing WCET do not address resourcelimitation or security issues. We propose in this paper a novel scheme for safely computing WCET on a very constrained device such as a smart card. We first present the Camille operating system for smart cards, and then describe the main issues when computing WCET on very constrained devices. We then detail the architecture we propose to compute WCET in the Camille operating system and illustrate it on an example of a simple embedded algorithm. We conclude by presenting the future work we plan to conduct.