In this work we consider a security model for resource constrained embedded systems, where memory is sometimes measured in a handful of kilobytes. Such systems normally do not include any security or safety mechanisms. The minority that do provide such functionalities often do so in an inflexible and ad hoc manner. The simple separation kernel demonstrated in this work enables a dynamic security model with minimal overhead and footprint. Furthermore, the provided functionality is simple enough to be used as a basis for provable security in embedded systems.