Session Key Generation for a Group Call and Device for Security Control

Abstract-The presence of wireless links makes mobile ad hoc networks more vulnerable than wire-line networks to various forms of attack. Multimedia group communication applications over such Ad hoc networks need a group key to encrypt group call traffic. This security requirement for group communications can be fulfilled by applying dynamic group key management architecture. In this paper, we propose the key agreement architecture that can be realized by encrypting RTP (Real-time Protocol) packets with call-based dynamic group key. We also propose the key control device (KCD) that legally listen to any group call. We solve these contradictory sounding goals: encrypting call traffic and monitoring call traffic. The key agreement part forces every group member to calculate the key tree by means of an iterative Diffie-Hellman group key exchange. In the proposed key management, the transaction manager (TM) is designed to report call information so KCD may compute the same group key for security control. In contrast to the called members, the calling user (that is, TM) generates a random number that is temporarily used as its one time session key doing duty for its original private key. This one time session key will stop the group key being re-used and prevent exploitation of group key weaknesses. Finally, we analyze the computational load (C_load) and message transmission load (MT_load) required for group key computation.