Affiliations: [a] CERIAS and CS Department, Purdue University, Recitation Building, 656 Oval Drive, West Lafayette, IN 47907-2086, USA. E-mail: bertino@cerias.purdue.edu | [b] Dipartimento di Scienze Chimiche, Fisiche e Matematiche, Universita' dell'Insubria, Via Valleggio, 11, 22100 Como, Italy. E-mail: elena.ferrari@uninsubria.it | [c] Dipartimento di Informatica e Comunicazione, Universita' degli Studi di Milano, Via Comelico, 39/41, 20135 Milano, Italy. Tel. +39 0250316346; Fax +39 0250316276; E-mail: mella@dico.unimi.it
Note: [*] A preliminary version of this paper appeared in: Proc. of the 16th Annual IFIP WG 11.3, Working Conference on Data and Application Security, Cambridge, UK, July 2002, pp. 211–227, with the title “A Framework for Distributed and Cooperative Updates of XML Documents”.
Abstract: Protection and secure exchange of Web documents is becoming a crucial need for many Internet-based applications. Securing Web documents entail addressing two main issues: confidentiality and integrity. Ensuring document confidentiality means that document contents can only be disclosed to subjects authorized according to specified security policies, whereas by document integrity we mean that the document contents are correct with respect to a given application domain and that the document contents are modified only by authorized subjects. While the problem of document confidentiality has been widely investigated in the literature, the problem of how to ensure that a document, when moving among different parties, is modified only according to the stated policies still lacks comprehensive solutions. In this paper we present a solution to this problem by proposing a model for specifying update policies, and an infrastructure supporting the specification and enforcement of these policies in a distributed and cooperative environment, in which subjects in different organizational roles can modify possibly different portions of the same document. The key aspect of our proposal is that, by using a combination of hash functions and digital signature techniques, we create a distributed environment that enables subjects, in most cases, to verify, upon receiving a document, whether the update operations performed on the document up to that point are correct with respect to the update policies, without interacting with the document server. Our approach is particularly suited for environments, such as mobile systems, pervasive systems, decentralized workflows, and peer-to-peer systems.
