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IWD2243 Wireless & Mobile Security

IWD2243 Wireless & Mobile Security. Chapter 1 : Wireless Fundamentals. 1.1 Wireless Medium. Radio Propagation Effects Harsh medium for signal propagation Distance between transmitter & receiver Physical environment Relative movement between transmitter & receiver

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IWD2243 Wireless & Mobile Security

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  1. IWD2243Wireless & Mobile Security Chapter 1 : Wireless Fundamentals Prepared by : Zuraidy Adnan, FITM UNISEL

  2. 1.1 Wireless Medium • Radio Propagation Effects • Harsh medium for signal propagation • Distance between transmitter & receiver • Physical environment • Relative movement between transmitter & receiver • Attenuation : drop in signal strength as the signal propagates in any medium. • Near (1/r2) & Far (1/r4) Prepared by : Zuraidy Adnan, FITM UNISEL

  3. 1.1 Wireless Medium (cont.) • Shadow fading (slow fading) : Changes in the signal strength occurring due to the changes in operating environment. • Raleigh fading (fast fading) : Changes in signal strength due to the relative motion of the order of a few centimeters. • Inter-symbol interference – effect of multipath Prepared by : Zuraidy Adnan, FITM UNISEL

  4. 1.1 Wireless Medium (cont.) • Hidden terminal problem • See figure 1.1b page 6 • Collisions of node A and C while reaching B • Exposed terminal problem • See figure 1.1c page 7 • Node C senses the medium and find it busy since node B has start transmitting Prepared by : Zuraidy Adnan, FITM UNISEL

  5. 1.1 Wireless Medium (cont.) • Bandwidth • Bandwidth is always expensive (in wireless) • Almost all countries the wireless spectrum is controlled by government • Only certain band are allowed for commercial use • All protocol designed revolve around this constraint • Other constraint • Trend – wireless need to be mobile • Small devices – limited processing power, limited battery life Prepared by : Zuraidy Adnan, FITM UNISEL

  6. 1.2 Wireless Networking Basics • Wireless Local Area Network (WLAN) • 1997 – IEEE – 802.11 WLAN standard – 2Mbps • 1999 – IEEE – 802.11b – 11Mbps – 2.4Ghz band • Small area coverage – office building • Security features – encryption, frequency hopping, firewalls • Drawback – high initial cost, limited range, possibility of mutual interference, the need to security-enabled client • LANs and WLAN – OSI model • See figure 1.2 page 10 Prepared by : Zuraidy Adnan, FITM UNISEL

  7. 1.2 Wireless Networking Basics (cont.) • WLAN – advantages & disadvantages • See page 12 & 13 chapter 1 • Current WLAN standard • 802.11a – 5GHz, compatible with 802.11b • Signal interference by 802.11b user • 802.11b (Wi-Fi) – 2.4Ghz band – 11Mbps – 4 to 7Mbps • Some manufacturers – 802.11b – 22Mbps • Future WLAN standard • IEEE – 802.11g – 2.4Ghz band – 54Mbps • IEEE – 802.11h – 5Ghz band – 54Mbps – enhancement of 802.11a – TPC (limit power) – DFS (protect sensitive freq.) Prepared by : Zuraidy Adnan, FITM UNISEL

  8. 1.2 Wireless Networking Basics (cont.) • Bluetooth & WPAN • Point to point, point to multipoint piconets – adhoc. • Flexible net topology, low energy consumption, robust data capacity, high quality voice transmission. • Speed – 1Mbps, 10 meters • Ultra wideband • UWB – > 100Mbps - < 10 meters. Prepared by : Zuraidy Adnan, FITM UNISEL

  9. 1.2 Wireless Networking Basics (cont.) • Security for WLANs • 802.11i – security standard for 802.11a,b,g. • Replace WEP with TKIP, AES, and 802.1 x authentication. • Incorporated into IEEE 802.11-2007 standard. • Wi-Fi alliance – Wi-Fi Protected Assets (WPA), before 802.11i finalized. • WEP – 40bit, 60bit, 128bit encryption key. • All devices has to be set to use same encryption key. • Slow data transfer rate – up to 30% Prepared by : Zuraidy Adnan, FITM UNISEL

  10. 1.2 Wireless Networking Basics (cont.) • SSID – method to identify or name an individual WLAN • Service Set Identifier – 32 char unique identifier. • Device level pass – connect to BSS – diff 1 WLAN to another – known also as network name. • Step to secure WLAN • See page 17 & 18 chapter 1. Prepared by : Zuraidy Adnan, FITM UNISEL

  11. 1.2 Wireless Networking Basics (cont.) • WLANs performance • Transmission speed – file size, number of users, distance from access points. • Performance vary – number of users, local environment, obstructions that are in the way. • WLAN implementation concerns • Planning – Floor plan, site survey • Capacity – 1 access point, 15-20 users Prepared by : Zuraidy Adnan, FITM UNISEL

  12. 1.2 Wireless Networking Basics (cont.) • Performance – 802.11b, 350 meters outdoors, very much reduce indoors. • Interference – bluetooth connectivity (handheld device, mobile phones in the same area) • Building work – installation of metal storage cabinets, microwave ovens, fish tanks. • Power consumption – 802.11a, limited power output. • Power over Ethernet (PoE) – removing the need to install additional power cabling. Prepared by : Zuraidy Adnan, FITM UNISEL

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