Description of Model Sample Clauses

Description of Model. Our adversary is afforded enormous power. She controls all communication between entities, and can at any time ask an entity to reveal its long-term secret key. Furthermore she may at any time initiate sessions between any two entities, engage in multiple sessions with the same entity at the same time, and in some cases ask an entity to enter a session with itself. With such a powerful model it is not clear what it means for a protocol to be secure. Informally, we say that an AK protocol is secure if no adversary can learn anything about a session key held by an uncorrupted entity i (an entity whose long-term keying material she has not revealed), provided that i has computed that session key in the belief that it is shared with another entity j (who is also uncorrupted). Again informally, we will say that an AKC protocol is secure if the protocol distributes a key just like an AK protocol, and has the additional property that an accepting entity i is assured that it has been involved in a real-time communication with j. Therefore to make an entity accept in an AKC protocol, the adversary effectively has to act just like a wire. We now formalize the above discussion. An adversary, E, is a probabilistic polytime Turing Machine taking as input the security parameter 1k and the directory public-info. E has access to a collection of oracles: {Π s i,j : i ∈ I, j ∈ I, s ∈ {1, . . . , N2}} .

Description of Model. CPA provides a traditional, college-preparatory academic program with an intentional emphasis on character education and moral development. Critical Programmatic Elements. CPA views the following elements as key to programming: