Research On Several Problems In Universally Composable Security Framework

Modular design is a common approach for dealing with complex tasks in modern cryptology; in which the main problem is that the secure sub-protocols no longer remain their security in the hybrid protocol. Canetti presents universally composable (UC) security framework for designing secure hybrid protocol. In this paper, we state the basic model of UC framework, UC definition of security and UC conposable theorem .However, there is no mature way of designing and realizing ideal functionality, which is one of the centrel problems in the UC framework. After reasarching and summarizing current work, some useful notions and methods about above problem were proposed in this paperThe primative of key exhange is an elementary task in the cryptology. Although the ideal functiomality for the basic key exchange was proposed, there are some specific requirements of key exhange tasks have no supports of ideal functionalities, such as three-party key distribution and password-based three-party key exchange.We formulate and realize the definition of security for three-party key distribution within the UC framework. That is, an appropriate ideal functionality that captures the basic security requirements of three-party key distribution is formulated. We show that UC definition of security for three-party key distribution protocol is strictly more stringent than a previous definition of security which is termed AKE-security. Finally, we present a real-life protocol that securely realizes the formulated ideal functionality with respect to non-adaptive adversaries.Next, we study password-based key exchange in the three-party setting within the UC framework and design a hybrid protocol that UC-securely realizes such task. That is, we firstly define an appropriate ideal functionality for password-based three-party key exchange and brief analyse the relationship between UC definition of security and two conventional security definitions which are termed AKE-security and KP-security. Then, we partition the task into two sub-tasks, three-party key distribution and password-based two-party key exchange,. Finally, we present: a hybrid protocol for password-based three-party key exchange that is proved to be UC-secure with respect to non-adaptive party corruption. This disgin of hybrid protocol is a useful attempt of modular design within in the UC framework.