The scope and character of today’s computing environments are progressively shifting from traditional, one-on-one client-server interaction to the new cooperative paradigm. It then becomes of primary importance to provide means of protecting the secrecy of the information, while guaranteeing its availability to legitimate clients. Operating online querying services securely on open networks is very difficult; therefore many enterprises outsource their data center operations to external application service providers. A promising direction toward prevention of unauthorized access to outsourced data is represented by encryption. However, data encryption is often supported for the sole purpose of protecting the data in storage while allowing access to plaintext values by the server, which decrypts data for query execution. In this paper, we present a simple yet robust single-server solution for remote querying of encrypted databases on external servers. Our approach is based on the use of indexing information attached to the encrypted database, which can be used by the server to select the data to be This paper extends the previous work by the authors appeared under the title “Balancing

Database outsourcing is becoming increasingly popular introducing a new paradigm, called database-as-a-service (DAS), where an organization’s database is stored at an external service provider. In such a scenario, access control is a very important issue, especially if the data owner wishes to publish her data for external use. In this paper, we first present our approach for the implementation of access control through selective encryption. The focus of the paper is then the presentation of the experimental results, which demonstrate the applicability of our proposal.