Towards attribute encryption and a generalized encryption model for XML

In this paper, we first investigate the necessity of attribute encryption which was not adopted in the current XML encryption syntax of W3C (released in December 2002). Some positive and negative aspects of attribute encryption as highlighted by the W3C's XML encryption working group and motivating examples are quoted and discussed. We then propose a generalized encryption model for XML whose encryption scopes include an element, the content of an element, and two different kinds of attribute encryption. We show that it is feasible to specify attribute encryption and its combination with other encryption scopes from the proposed encryption model. The syntax of the encrypted document and the corresponding transformation language are presented. Two different implementations further demonstrate its practicability.