Secure Publishing using Schema-level Role-based Access Control Policies for Fragments of XML Documents

Abstract

Popularity of social networks is growing rapidly and secure publishing is an important implementation tool for these networks. At the same time, recent implementations of access control policies (ACPs) for sharing fragments of XML documents have moved from distributing to users numerous sanitized sub-documents to disseminating a single document multi-encrypted with multiple cryptographic keys, in such a way that the stated ACPs are enforced. Any application that uses this implementation of ACPs will incur a high cost of generating keys separately for each document. However, most such applications, such as secure publishing, use similar documents, i.e. documents based on a selected schema. This paper describes RBAC defined at the schema level, (SRBAC), and generation of the minimum number of keys at the schema level. The main advantage of our approach is that for any application that uses a fixed number of schemas, keys can be generated (or even pre-generated) only once, and then reused in all documents valid for the given schema. While in general, key generation at the schema level has to be pessimistic, our approach tries to minimize the number of generated keys. Incoming XML documents are efficiently encrypted using single-pass SAX parsing in such a way that the original structure of these documents is completely hidden. We also describe distributing to each user only keys needed for decrypting accessible nodes, and for applying the minimal number of encryption operations to an XML document required to satisfy the protection requirements of the policy.

Schema‐level access control policies for XML documents

“…(Müldner et al , 2006) described key generation at the document level, and (Bertino et al , 2002; Zhang et al , 2003) describe how to generate keys for documents and for DTDs/schema; however, since at the schema level some conditions cannot be evaluated, keys must be generated at both the schema and document levels. A more recent paper (Müldner et al , 2008) described schema‐level key generation, but it only described the implementation using symbolic grammar paths. In addition, testing was limited to a single schema, and two documents valid in this schema, for which the average multi‐encryption and decryption time was provided.…”