고려대학교

초록/요약

Group key management is essential to secure group communication: group key management can be classified into group key distribution and group key exchange. This dissertation introduces research results for group key distribution and group key exchange. Group Key Distribution. During the last decade, security models have been defined for two- and three-party key exchange protocols. Currently there is a growing research interest in security models for group key management schemes. While various security models and provably secure protocols have been proposed for group key exchange schemes, no results are known for group key distribution schemes in spite of their theoretical and practical importance. This dissertation defines a formal security model and proposes a conversion module for provably secure tree-based group key distribution. A formal security model and a conversion module for provably secure tree-based traitor-tracing are also proposed. The conversion module is extended to provide traceability. Group Key Exchange. Another result of this dissertation is an efficient group key exchange scheme with constant-round. In most group key exchange schemes proposed so far in the literature, the number of rounds is linear with respect to the number of group members. Such schemes are neither scalable nor practical since the number of group members may be quite large and the efficiency of the schemes is severely degraded with only one member's delay. The proposed scheme in this dissertation is efficient, where each member executes three modular exponentiations and at most O(n) XOR operations.