Protecting personal privacy is already seen as a crucial requirement in the implementation of service provisioning in the ubiquitous environment. From the view point of preserving personal privacy, the simplest approach would be for users not to reveal any kind of private information at any time while keeping the number of available services unrestricted. Meanwhile, from the service provider's point of view, though this has been not clearly stated so far, their service logics should also be hidden from others because those logics may leak their know-how. This paper presents a novel ubiquitous service provisioning mechanism mat gives more opportunities for users to get available services while preserving the secrecy of users' and providers' sensitive information. The basic idea of this mechanism is to share service execution procedures between the service provider and the user by exchanging converted, service logic described in the form of Bayesian decision networks. This paper describes the proposed mechanism and the conversion algorithm for the Bayesian networks, and details the system architecture and implementation.