In distributed systems especially in pervasive environments, the users usually face difficulties to obtain permissions to use the surrounding resources. Either they have an account locally, or they can show a certificate obtained beforehand given them the access. Problems arise when they arrive in an unknown environment occurring in a pervasive environment. In this paper, we propose the Chameleon architecture which offers users an access if they arrive with trusted certificates. These certificates may be gathered during her trip. Then, according to a trust relationships, a direct or a transitive site access is provided. We describe a new kind of certificate to set up a contextual broader access. Indeed, the X316 enables users to blind some attributes of their personal information embedded in the certificate and to disclose only what is mandatory for a given access.