Broadcast Communication and Player Failure. This assume that all communication within the protocol takes place over reliable (and authenticated) broadcast channel, where all the non-faulty players have the same view of the broadcasted message (which can be null if the sender is faulty). This assume weak synchrony, i.e., the players have synchronized clocks and execute the protocol in synchronized rounds, and the messages from the non-faulty players must arrive within some time window, which assume is large enough to accommodate clock skews and reasonable communication delays. The assumption of reliable broadcast communication might be realistic for certain communication scenarios, e.g. Ethernet or wireless communication between close-by players. Otherwise, reliable broadcast must be implemented via a consensus protocol. Assume an honest but curious adversary which can additionally impose arbitrary stop faults on the (otherwise honest) players participating in the protocol. Additionally, the adversary can make each player stop at an arbitrary moment in the protocol execution, but any such node failure cannot violate the contract imposed by the reliable broadcast assumption. Throughout the paper assume that these stop faults are scheduled in arbitrary way by the adversary, except in the last section when Definition 1. (GKA Security) Consider an adversary algorithm A which observes an execution of the GKA protocol between n honest players, and, depending on bit b, is given the session key computed by this protocol (if b = 1) or a value chosen at random from the same domain as the sessions keys (if b = 0). The adversary A outputs a single bit b′. This define adversary’s advantage in attacking the GKA protocol as: GKAA Adv = | Pr [b′ = b] − 1/2 |
Broadcast Communication and Player Failure. This assume that all communication within the protocol takes place over reliable (and authenticated) broadcast channel, where all the non-faulty players have the same view of the broadcasted message (which can be null if the sender is faulty). This assume weak synchrony, i.e., the players have synchronized clocks and execute the protocol in synchronized rounds, and the messages from the non-faulty players must arrive within some time window, which assume is large enough to accommodate clock skews and reasonable communication delays. The assumption of reliable broadcast communication might be realistic for certain communication scenarios, e.g. Ethernet or wireless communication between close-by players. Otherwise, reliable broadcast must be implemented via a consensus protocol. Assume an honest but curious adversary which can additionally impose arbitrary stop faults on the (otherwise honest) players participating in the protocol. Additionally, the adversary can make each player stop at an arbitrary moment in the protocol execution, but any such node failure cannot violate the contract imposed by the reliable broadcast assumption. Throughout the paper assume that these stop faults are scheduled in arbitrary way by the adversary, except in the last section when This consider a weaker model of random faults which occur independently at every node with some fixed probability.
