Embodiments of the present invention provide a service access control system having a service object for providing services, a messaging service facility and one or more spoke entities for accessing services provided by the service object, wherein the messaging service facility comprises one or more cells each having an input address and an output address, wherein at least one of the input address and the output address is linked to the other via a cryptographic key, the cell providing a message communication link between the spoke entity and a set of functions on the service object associated with the cell.