PROPERTIES OF SECURE TRANSACTION PROTOCOLS

Communication protocols are the computational basis for distributed el ectronic commerce systems, and thus the properties of these protocols define the forms of commerce possible in electronic systems. Existing protocols used for electronic commerce focus primarily on security pro perties, including message integrity, privacy and non-repudiation, and on basic transaction properties, usually just atomicity; their struct ural properties are limited to supporting two-party transactions with fixed semantics. We believe that the properties provided by these prot ocols limit their use to simple forms of commerce. In this paper we de fine the properties we believe are necessary for electronic commerce p rotocols. These include the security properties of existing protocols, and extend the transactional properties to include isolation and caus ality. Causality is a new property for transactions. It allows the ord er of the messages in a completed transaction to be independently veri fied, and thus inferences can be made about causal relationships betwe en messages. We also extend the structural properties to support scala bility, layering and separation of roles. Scalable protocols allow sev eral parties to join each transaction. Protocol layering enables arbit rary transaction semantics and greater system modularity. Separation o f roles provides independent adjudication of disputes between transact ion participants and allows the use of varied exchange media. We term a protocol with the above properties a secure transaction protocol. La stly, we present a protocol that provides these properties. We believe that this protocol can be used to support more complex and extended f orms of electronic commerce than existing protocols. (C) 1997 Elsevier Science B.V.