Pervasive systems enable us to have an overview of what digital environments will look like in the future. Opportunities given by pervasive systems, both in terms of applications and services to the user are manifold and very promising. From the user point of view, privacy and security of her personal data is a real issue, which must be addressed to make pervasive systems accepted. A wide adoption of pervasive systems can not be possible without an integrated approach to security. We propose a model of security and privacy for pervasive environments, integrated with an architecture, namely PerSE, in which privacy is a main concern and is at the core of the conception.