Communication Model Sample Clauses

Communication Model. We assume a synchronous network, where all parties begin the protocol at the same time, the clocks of the parties progress at the same rate, and all messages are delivered within some known finite time ∆ > 0 (called the network delay) after being sent. In particular, messages of honest parties cannot be dropped from the network and are always delivered. Thus, we can consider protocols that execute in rounds of length ∆ where parties start executing round r at time (r 1)∆. We further assume that ∆ is public information and is known to all parties and the adversary, and any action carried out by any party can depend on ∆. With that in mind, and to avoid notation encumbrance, we omit ∆ from the list of inputs to algorithms and protocols in our definitions. Adversarial Model. The adversary model we consider in the paper is an amalgamation of two common adversaries in the literature. Formally, given two parameters ti ≤ ts < n/2 such that 2ti + ts < n, the adversary A can be described as a tuple A = (A0, A1, A2) such that – 0(Π, r, Trr) = r where r denotes the set of corrupt parties at round r. I.e. 0 is an algorithm that chooses for every round the set of corrupt parties, based on the description of the protocol Π, the round r, and the transcript Trr of the protocol up to round t. We distinguish between two types of adversaries in this context. A static adversary satisfies that A0(Π, r, Trr) = A0(Π, 0, Tr0) for all rounds

Communication Model. The communication model of our proposed scheme is shown in Figure 1. It includes three kinds of entities: the gateway node GWN, the user U and the sensor node S. A secure communication channel can be established between U and S. Once the user U intends to request a certain service or access the data via GWN, the authentication session is initiated. U first sends an authentication request the message M1 to GWN which requests GWN for authentication; after checking the validity of messages from U, GWN sends the message M2 to S. When receives the message M2 from GWN, S replies the confirmation message about session key establishment with message M3 to GWN. Then GWN verifies M3, generates and sends the message M4 including the message M3 to U. At last, after U authenticating GWN and S, U securely establishes a session key with S successfully. (1) M1 (2) M2

Communication Model. The proposed negotiation approach involves the use of multiple attributes of SWSs for negotiation. The proposal between SP and SR contains the values for multiple attributes and the decision of agreement is taken based upon their combined value. A utility value is used which is dependent on the values of all the attributes and represents the preference of corresponding SWS. Utility theory is the appealing form of representing inputs to decision-making under uncertainty for automated systems because it can readily be mapped onto numerical optimization-based approaches [19]. The initial values of various attributes and conditions for termination of negotiation between SWSs can be fetched from their corresponding service profiles. The communication model for the proposed utility model is shown in Figure 1. Figure shows the communication between SR and SP during the negotiation using Communicative Acts of FIPA [20]. As shown in Figure 1, the negotiation process starts with the request from SR to SP for providing the services. If the request is refused by the SP, the process is terminated. But, if the SP agreed to provide services, the SR sends a call to SP to send an initial proposal for starting the negotiation. At this step also, if the call for initial proposal is refused by the SP, then negotiation process got terminated, otherwise SP responses with an initial proposal to the SR. Now, if this proposal is acceptable to the SR, then it is informed to the SP. SP informs the SR about various parameters of agreement and the negotiation is terminated. In the case of rejection by SR, the SR sends a new proposal to SP. Now, SP checks the proposal and if acceptable, informs the SR with acceptance. The values of various agreement-parameters are informed by the SR to SP and the process is terminated. But in the case of rejection by SP, a new proposal is sent by the SP to SR. This process continues until either the proposal acceptable to both SP and SR occurs or the number of negotiation-steps exceeds the threshold limit. In the presented negotiation approach, the utility values for SR and SP can be calculated using the utility calculation models presented in [17] and [18]. SR SP request refuse [refused] agree [agreed] [refused] inform-done: inform [agreed] call for proposal refuse propose accept-proposal inform-done: inform inform-result: inform reject-proposal propose accept-proposal inform-done: inform inform-result: inform reject-proposal propose . . . Figure 1: C...