Schema‐level access control policies for XML documents

The purpose of this paper is to consider the secure publishing of XML documents, where a single copy of an XML document is disseminated and a stated role‐based access control policy (RBACP) is enforced via selective encryption. It describes a more efficient solution over previously proposed approaches, in which both policy specification and key generation are performed once, at the schema‐level. In lieu of the commonly used super‐encryption technique, in which nodes residing in the intersection of multiple roles are encrypted with multiple keys, it describes a new approach called multi‐encryption that guarantees each node is encrypted at most once.

This paper describes two alternative algorithms for key generation and single‐pass algorithms for multi‐encrypting and decrypting a document. The solution typically results in a smaller number of keys being distributed to each user.

The paper proves the correctness of the presented algorithms, and provides experimental results indicating the superiority of multi‐encryption over super‐encryption, in terms of encryption and decryption time requirements. It also demonstrates the scalability of the approach as the size of the input document and complexity of the schema‐level RBACP are increased.

An extension of this work involves designing and implementing re‐usability of keyrings when a schema or ACP is modified. In addition, more flexible solutions for handling cycles in schema graphs are possible. The current solution encounters difficulty when schema graphs are particularly deep and broad.

The experimental results indicate that the proposed approach is scalable, and is applicable to scenarios in which XML documents conforming to a common schema are to be securely published.

This paper contributes to the efficient implementation of secure XML publication systems.