In this paper, we present two new centralized group key management protocols based on the Chinese Remainder Theorem (CRT). By shifting more computing load onto the key server we optimize the number of re-key broadcast messages, user-side key computation, and number of key storages. The first protocol is the base Chinese Remaindering Group Key (CRGK) protocol, which with a group of n users requires the key server to do O(n) XORs, additions, multiplications, and Extended Euclidean Algorithm computations and broadcast 1 re-key message; each individual user is required to do only 1 modulo arithmetic and 1 XOR operation for each group key update. The second protocol is the Fast Chinese Remaindering Group Key (FCRGK) protocol, which only requires the key server to do O(n) XORs, additions, and multiplications most of the times with no change to the number of re-key messages and user computation per group key update. For both protocols each user only needs to store 2 keys all the time. One special attraction for our FCRGK protocol is that it allows most of the re-keying computation to be done preemptively, which means when a user-join or user-leave event happens the response time for the key server to send out the new group key can be very short.
Without physical boundaries, a wireless network faces many more security threats than a wired network does. Therefore, in the IEEE 802.16 standard a security sublayer is specified in the MAC layer to address the privacy issues across the fixed Broadband Wireless Access (BWA). Several articles have been published to address the flaws in IEEE 802.16 security after the IEEE standard 802.16-2001 was released. However, the IEEE standard 802.16-2004 revision does not settle all the discovered problems and additional flaws remain. This paper gives an overview of the IEEE 802.16 standard, focusing on the MAC layer and especially the security sublayer. We analyze the security flaws in the standard as well as in related works, and illustrate possible attacks to the authentication and key management protocols. Possible solutions are also proposed to prevent these attacks. Finally, we propose a security handover protocol that should be supported in the future 802.16e for mobility.
Without physical boundaries, a wireless network faces many more vulnerabilities than a wired network does. IEEE802.16 provides a security sublayer in the MAC layer to address the privacy issues across the fixed BWA (Broadband Wireless Access). Several articles have been published to address the flaws in IEEE802.16 security after IEEE802.16-2001 was released. However, even the enhanced version IEEE802.16-2004 does not settle all the problems and additional flaws emerge. In addition, we found that PKM (Privacy and Key Management) protocols version 2 (PKMv2), proposed by recently released IEEE802.16e, is also vulnerable to new attacks. In this paper, we first overview the IEEE802.16 standard, especially the security sublayer, and then investigate possible attacks on the basic PKM protocol in IEEE802.16 as well as in its other versions from related works and the newest PKMv2. We also give possible solutions to counter those attacks and verify our analysis using formal (BAN) logic.
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