1. Privacy and Authentication for Wireless LAN 1 Privacy And Authentication for Wireless Local Area Networks Ashar Aziz Whitfield Diffie Sun Microsystems, Inc Presented by: Naveen Srinivasan.

2. Privacy and Authentication for Wireless LAN 2 OUTLINE Loopholes in wireless Design Goals Design Overview Message Exchange in Protocol Other Issues

3. Privacy and Authentication for Wireless LAN 3 Loopholes in Wireless medium –Wireless receivers –No physical constraints Design Goals –Privacy of wireless data communication and authenticity of the communicating parties –Seamless integration into existing wired network –Mutual authentication –To take advantage of shared key cryptography

4. Privacy and Authentication for Wireless LAN 4 Two ways to achieve security –Secure wireless link Obviates the need for upgrading existing network secured(wired)+secured(wireless) –End-to-End Approach application layer transport layer upgrading existing network

5. Privacy and Authentication for Wireless LAN 5 Public key and shared key cryptographic techniques –Public Key : session key and authentication –Shared Key: privacy CA Pub Key MobileBase Challenge/Response Protocol Design Overview

6. Privacy and Authentication for Wireless LAN 6 Content of the Certificate Contents: Serial Number Validity Period Machine Name Machine Public Key CA Name CA

7. Privacy and Authentication for Wireless LAN 7 MobileBase Cert_Mobile, CH1, Lists of SKCSs Message #1 CH1 128 bit random number List of SK algorithm include algo and key size Base station on receiving could indentify that it received from mobile but it doesn’t know if the certificate belongs to Mobile Certificate Invalid – rejects the connection Valid – Reply to message as mentioned in Message #2

8. Privacy and Authentication for Wireless LAN 8 Issues in choosing the SKCS Why list of SKCSs and CH1 is sent in Msg #2 ? Message #2 MobileBase Cert_Base, E(Pub_mobile, RN1), Chosen SKCS, Sig(Priv_Base, { E(pub_Mobile, RN1), Chosen SKCS, CH1, List of SKCSs })

9. Privacy and Authentication for Wireless LAN 9 Message #3 MobileBase E(Pub_Base, RN2), Sig{ Priv_Mobile, { E(Pub_Base, RN2), E(Pub_Mobile, RN1) } }

10. Privacy and Authentication for Wireless LAN 10

11. Privacy and Authentication for Wireless LAN 11 Data Packet Issues Problems: Packet losses Playback attack Solutions: Message ID Count of no. of 64-bits blocks that have been sent Last 64-bits of the cipher-text of the last packet Assumes taken care by higher layer protocol

12. Privacy and Authentication for Wireless LAN 12 Operation with Multiple CAs Previous protocol description single network wide CA – not feasible Hierarchy of CA s is employed Base Station Not only include the certificate but also the certificate path Mobile Just its own certificate