Date Added: Nov 2007
Data outsourcing is becoming today a successful solution that allows users and organizations to exploit external servers for the distribution of resources. Some of the most challenging issues in such a scenario are the enforcement of authorization policies and the support of policy updates. Since a common approach for protecting the outsourced data consists in encrypting the data themselves, a promising approach for solving these issues is based on the combination of access control with cryptography. This paper is in itself not new, but the problem of applying it in an outsourced architecture introduces several challenges.