802.11WEP.ppt

802.11 WEP 802.11 WEP 802.11 WEP Tzachy Reinman System and Network Security Course Computer Science and Engineering School Hebrew University, Jerusalem June 1, 2003 Outline Mobile Communication Overview 802.11 History, Variations, Topologies, Authentication Methods and more … WEP Encryption/Decryption, Frame Structure, Key Management, Building Blocks – CRC32 RC4 Next Lectures: WEP Weaknesses WEP Current Solutions and Future Mobile Communication What is Mobile Device? E.g. Laptop with wireless ethernet card Mobile Communication Characteristics Range limitations Lower bandwidth RF interferences - Higher error rate and packet loss (Up to 20%) ? Can be handled by TCP Dynamic topologies Data is transmitted over the Air Simpler, quicker, easy to install and less costly (up to 15%) than running cables ? Enjoying explosive growth Appropriate for temporary offices (army, Hollywood, etc.) Higher mobility Mobile Security Requirements Access Control - Authentication and Authorization Mutual Authentication Confidentiality, Integrity and Replay protection Over the Air What is 802.11? Wireless Local Area Network (WLAN) Protocol AKA Wi-Fi (Wireless Fidelity) Defined at 1997 by IEEE September 1999: 802.11b End of 2001: 802.11a 2002: 802.11g Target: Define Ethernet-like communication channel using radios instead of wires 802.11 advantages - longer ranges, higher speeds – make it the protocol of choice for Wireless LANs. 802.11 and the ISO stack 802.11 and the ISO stack 802.11 Variations Different variations of 802.11 correspond to different PHY sub-layers 802.11b - 2.4 GHz spectrum, max BW 11 Mbps 802.11a – 5.2 GHz spectrum, max BW 54 Mbps 802.11g – 2.4 GHz spectrum, max BW 54 Mbps All the variations of 802.11 use the same MAC sub-layer Security resides entirely in the MAC sub-layer Another Variation - 802.11e Adds quality-of-service features to MAC layer of 802.11b compatible networks error correction better bandwidth management significantly improves multimedia performance