Protocol Messages. The following is a list of the protocol messages derived from Section 3. Note that each message, in addition to the domain-specific information being exchanged, has three identifiers: one, the agreement identifier that provides a context for messages to be correlated under; two, a message identifier that is unique in the context of each agreement; and, three, a correlation identifier which should be set to the message identifier of the message (if any) this message has been sent in reply to (thus a correlation identifier may be null if it does not relate to any other messages in the re-negotiation). – RenegotiationQuoteRequest. This message is only sent from the customer to the resource provider to indicate that they are interested in re-negotiating the current contract and to ask for a quote for the re-negotiated contract. – RenegotiationQuote is a message only sent from the resource provider to the customer and is a non-binding estimate of a new agreement. It may be sent in response to a RenegotiationQuoteRequest received from the customer, in which case the quote will be based on the new requirements of the customer, or it may be sent by the service provider unilaterally to indicate the provider wishes to re-negotiate the agreement. In the latter case the quote will be based on the provider’s requirements.
Protocol Messages. A A A A A → B, C : U = aP;V = a−1(H (U )S ) B → A, C : U = bP;V = b−1(H (U )S ) B B B B C → A, B :U = cP;V = c−1(H (U )S ) C C C C Verification and key computation: A verifies A B C eˆ(U B ,VB ).e(ˆUC ,VC ) = e(PˆKGC , H (UB )QB + H (UC )QC ) and computes B verifies k = eˆ(U ,U )a = e(ˆP, P)abc eˆ(U A ,VA ).e(ˆUC ,VC ) = e(PˆKGC , H (UA )QA + H (UC )QC ) and computes C verifies k = eˆ(U ,U )b = e(ˆP, P)abc eˆ(U B ,VB ).e(ˆU A ,VA ) = e(PˆKGC , H (UB )QB + H (UA )QA )
