Supporting structured credentials and sensitive policies through interoperable strategies f.pdf

Supporting Structured Credentials and SensitivePolicies through Interoperable Strategies forAutomated Trust NegotiationTING YU and MARIANNE WINSLETTUniversity of Illinois at Urbana-ChampaignandKENT E. SEAMONSBrigham Young UniversityBusiness and military partners, companies and their customers, and other closely cooperatingparties may have a compelling need to conduct sensitive interactions on line, such as accessingeach others local services and other local resources. Automated trust negotiation is an approachto establishing trust between parties so that such interactions can take place, through the useof access control policies that specify what combinations of digital credentials a stranger mustdisclose to gain access to a local resource. A party can use many dierent strategies to negotiatetrust, oering tradeos between the length of the negotiation, the amount of extraneous infor-mation disclosed, and the computational eort expended. To preserve parties autonomy, eachparty should ideally be able to choose its negotiation strategy independently, while still beingguaranteed that negotiations will succeed whenever possible, i.e., that the two parties strategieswill interoperate. In this paper we provide the formal underpinnings for that goal, by formalizingthe concepts of negotiation protocols, strategies, and interoperation. We show how to model theinformation ow of a negotiation, for use in analyzing strategy interoperation. We also presenttwo large sets of strategies whose members all interoperate with one another, and show that thesesets contain many practical strategies. We develop the theory both for black-box propositionalcredentials and credentials with internal structure, and for access control policies whose contentsare (resp. are not) sensitive. We also discuss how these results t into TrustBuilder, our prototypesystem for trust negotiation.Categories and Subject Descriptors: K.6.5 [Management of Computing and InformationSystems]: Security and Protec