School of Computing

Obligations of trust for privacy and confidentiality in distributed transactions

U.M.Mbanaso, G.S. Cooper, D.W. Chadwick, and Anne Anderson

Internet Research, 19(2):182-196, January 2009.


Abstract Purpose This paper describes a bilateral symmetric approach to authorization, privacy protection and obligation enforcement in distributed transactions. We introduce the concept of the Obligation of Trust (OoT) protocol as a privacy assurance and authorization mechanism that is built upon the XACML standard. The OoT allows two communicating parties to dynamically exchange their privacy and authorization requirements and capabilities, which we term a Notification of Obligation (NoB), as well as their commitments to fulfilling each others requirements, which we term Signed Acceptance of Obligations (SAO). We describe some applicability of these concepts and show how they can be integrated into distributed authorization systems for stricter privacy and confidentiality control. Design/Methodology/Approach Existing access control and privacy protection systems are typically unilateral and provider-centric, in that the enterprise service provider assigns the access rights, makes the access control decisions, and determines the privacy policy. There is no negotiation between the client and the service provider about which access control or privacy policy to use. We adopt a symmetric, more user-centric approach to privacy protection and authorization, which treats the client and service provider as peers, in which both can stipulate their requirements and capabilities, and hence negotiate terms which are equally acceptable to both parties. Findings We demonstrate how the Obligation of Trust protocol can be used in a number of different scenarios to improve upon the mechanisms that are currently available today. Practical Implications This approach will serve to increase trust in distributed transactions since each communicating party receives a difficult to repudiate digitally signed Acceptance of Obligations, in a standard language (XACML), which can be automatically enforced by their respective computing machinery. Originality/Value This paper adds to current research in trust negotiation, privacy protection and authorization by combining all three together into one set of standardized protocols. Furthermore, by providing hard to repudiate Signed Acceptance of Obligations messages, this strengthens the legal case of the injured party should a dispute arise.

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Bibtex Record

author = {U.M.Mbanaso and G.S. Cooper and D.W. Chadwick  and Anne Anderson},
title = {Obligations of Trust for Privacy and Confidentiality in Distributed Transactions},
month = {January},
year = {2009},
pages = {182-196},
keywords = {determinacy analysis, Craig interpolants},
note = {},
doi = {},
url = {},
    publication_type = {article},
    submission_id = {24334_1280421961},
    journal = {Internet Research},
    volume = {19},
    number = {2},

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