In this manuscript, we are interested in the specification and decentralized execution of administrative workflows. We present a grammatical model to specify such processes by indicating, in addition to their fundamental elements, the permissions (reading, writing and execution) of each actor in relation to each of the tasks that compose them. We then present a decentralized and artifact-centric execution model of these processes, on a Peer to Peer (P2P) Workflow Management System (WfMS). Our execution model allows the confidential execution of certain tasks by ensuring that, each actor potentially has only a partial perception of the overall process execution status. In our approach, we propose various stable projection algorithms, making it possible to obtain, to verify the coherence and to guarantee the convergence of the various potentially partial perceptions. Our algorithms are then coded and tested using a graphical tool to simulate the decentralized execution of administrative processes.