Service-orientation is a highly useful means of developing flexible, agile, and dependable software systems, and is a paradigm that has been increasingly adopted into Grid Computing middleware. However, service-orientation brings with it new challenges in the fields of dependability and security that need to be addressed by the High Assurance Systems community in order to provide sufficient support to enable servicebased Grid applications to offer non-trivial Quality of Service guarantees. This paper discusses some of the new dependability and security challenges introduced by service-orientation, and for the first time introduces CROWN-C - a Grid middleware system that features specific enhancements designed to support the development and assessment of highly secure, dependable, service-oriented Grid systems and applications. The architecture of the new middleware is discussed, and the architecture and functionality of each dependability and security enhancement is described, alongside the results of experimental evaluations of each enhancement. Future work is then discussed.