Design and Implementation of the Security Model for XML Documents

[[abstract]]Abstract In this dissertation we aim at the deisgn and implementation of the security model for XML documents. First, we propose an operational model which defines the process of encrypting data and embedding digital signatures which sign the data in an original XML docuemnt. It provides element-wise encryption that is more general than previous forms of XML security, by including element, content of element, and two types of attribute encryption. Moreover, the model of temporal-based element-wise digital signature is novel. Based on the generalized operational model, we define a new language – called document security language (DSL) – to support it. Two different implementations further demonstrate its practicability. In addition, we have developed a DSL editor and the DSL API to support the proposed operational model. The research following the XML security, we explore a little further into the XML query related issues. Although the W3C proposed the XQuery language, which is designed to be broadly applicable across all types of XML data sources, this language does not provide a security mechanism in its query expressions. We have designed a new XML query language, called the secure XML Query (sXQuery) language that is derived from XQuery and reinforced with a security mechanism; sXQuery combines the specification ability of both the XQuery language and the document security language which is designed to specify the scope and encryption details of XML. Furthermore, we address how to optimally query encrypted XML documents using XQuery, with the key point being how to eliminate redundant decryption so as to accelerate the querying. We have proposed a processing model that can automatically and appropriately translate the XQuery statements for encrypted XML documents.