MULTIPLE ADDRESS CIPHERING COMMUNICATION METHOD AND ITS SYSTEM

PURPOSE:To execute multiple address ciphering communication safely even when members change dynamically. CONSTITUTION:A process A obtains a conversation key (a) ciphered by a secret key A from an authentication server 3 and verification information ciphered by a secret key alpha of a group management server 5. The authentication information includes the conversation key (a). Then the process A decodes the information by using its own ciphering key A, obtains a key a and applies subscription to a group G1 to a group management server 5 by using the conversation key (a). The authentication information is added to the application. The group management server 5 decodes the authentication information by using its own ciphering key alpha to check the authentication and to obtain the conversation key (a) and then distributes a common ciphered key g1 ciphered by the conversation key (a) to the process A. The process A decodes the common ciphering key g1 by using the conversation key (a) and executes multiple address ciphering communication by using the common ciphering key g1. As a result, the multiple address ciphering communication between processes whose group members change dynamically is executed properly.