Transforming out Timing Leaks in Practice An Experiment in Implementing Programming Language-Based Methods for Con dentiality

When it comes to granting mobile code access to conndential information , great care has to be taken if the code originates from an untrused source and the information is to remain conndential. If the program has access to the Internet during its execution, it has the possibility to leak information in many subtle ways, including through its temporal behaviour. This paper reports on practical experience from implementing a system that removes timing leaks from Java byte-code programs by transformation. We describe the problems we have encountered and the solutions we have made when we have adapted our previously developed transformation designed for a while-language (see Aga00]), to Java byte-code.