The challenge of pervasive computing consists in offering access to computing services anywhere and anytime with any devices. However, before it becomes a reality, the problems of access control and authentication have to be solved, among others. Existing solutions are inadequate without adaptation to this specific environment. Among the promising approaches, the trust paradigm seems to be more flexible than others. We base this proposal on this paradigm to implement a distrust model, so-called APC (Access Pass Certificate). The main objective of this model is to enable authorized user to roam and to access trusted sites though they are not known locally. A user can claim two kinds of APCs provided by two kinds of sites: the home site (where the user has an account) and the trusted site (that trusts the user). Using these certificates, the user can progressively extend her access scope. This model implements a decentralized mapping policy, where the correspondence between the user’s home profile and her rights in the trusted sites is determined by the trusted site. This distrust model and its implementation are presented in this article where we exhibit its importance for large but controlled access in pervasive environments