Your 802.11 Wireless Network has No Clothes *

1. Your 802.11 Wireless Network has No Clothes* William A. Arbaugh, Narendar Shankar Y.C. Justin Wan University of Maryland • Presentation by Eddy Purnomo, email: epur008@ec.auckland.ac.nz

2. Outline • Introduction • overview of the 802.11 • 802.11 Standard Security Mechanisms • Shared Key Authentication Flaw • Conclusion • Question

3. Introduction • 802.11 standard provides only limited support for confidentially. • 802.11 has many security issues such as key management and robust authentication mechanism • Deployment of a wireless network opens a “back door” into the internal network. • Use of encryption prevents an adversary from gaining immediate access, but the weaknesses found in WEP will provides such access.

4. 802.11 wireless standard Ad-hoc network Infrastructure network Independent Basic Service Set (IBSS) Basic Service Set (BSS)

5. 802.11 wireless standard(cont) • wireless clients and access points must establish a relationship, or an association • Only after an association is established can the two wireless stations exchange data. • The association process is a two step process involving • 1. Unauthenticated and unassociated, • 2. Authenticated and unassociated, and • 3. Authenticated and associated • Transition between the states, the communicating parties exchange messages called management frames.

6. 802.11 Standard Security Mechanisms • Wired Equivalent Privacy protocol(WEP) • provide confidentiality for network traffic using the wireless protocol. • Open System Authentication • Authenticates anyone who requests authentication • Access Control Lists • Each access point can limit the clients of the network to those using a listed MAC address. • Key Management • window of four keys • key mappings table

7. Authentication request management frame 5.Encrypted management frame Authentication management frame Shared key Authentication 1. Share key 2. Authenticate request 4. Challenge text copy into management frame 6. Decrypts and And verify. 3. Challenge text Match Challenge text Encrypted with WEP using ‘shared secret’ And new IV OK! WEP pseudo-random number generator + Shared secret & random initialization vector(IV)

8. Shared Key Authentication Flaw • Fixed structure protocol • By capturing the 2nd & 3rd management message: • Authentication management frame • Encrypted management frame • Attacker can derive pseudo-random stream and use it to authenticate.

9. Conclusion • These paper demonstrates serious flaws in the security mechanisms used by the vast majority of access points supporting the IEEE 802.11 wireless standard • ALL of the deployed 802.11 wireless networks are at risk. • Question: Are there any such thing as a perfect security in wireless communication?