1. Comparative studies on authentication and key exchange methods for 802.11 wireless LAN Authors: Jun Lei, Xiaoming Fu, Dieter Hogrefe and Jianrong Tan Src: Computers & Security, Vol. 26, 2007, pp. 401-409

2. Outline Introduction 3 Levels AKE Requirements for IEEE 802.11 WLANs AKE Methods overview  Legacy AKE Methods  Layered AKE Methods  Access control-based layered AKE method Comparison results Multi-layer AKE framework Conclusion

3. Introduction Two key security aspects in 802.11  Authentication of the wireless user/device  Data confidentiality between the wireless device and the network Three major issues with today’s authentication mechanisms for wireless networks  Lack of mutual authentication between the user and the network  Shared communication channel could be monitored by any malicious user  Attacker might figure out the password by observing the pair of challenge and response messages

4. 3 Levels AKE Requirements for IEEE 802.11 WLANs Mandatory requirements  Mutual authentication  Credential security.  Resistance to dictionary attack  Man-in-the-middle attack protection  Immune to forgery attacks  Anti-replay  Strong session key Recommended requirements  Management message authentication  Authenticate users  Key integrity check  Weak key protection Additional Operational requirements  No computational burden  Ease implementation  Fast reconnection

5. AKE Methods overview Legacy AKE methods Layered AKE methods  TLS embedded protocol  Layered method with cryptographic design Access control-based layered AKE method  Transitional solution  Long-term scheme

6. Legacy AKE Methods Open System Authentication (OSA)  C  AP: Request & ID  AP  C: Accept/Reject => Simplest & Default Share Key Authentication (SKA)  Challenge/Response => Mutual authentication Wired Equivalent Privacy (WEP)  Pre-shared Key (PSK): Mutually exchange at both endpoints  Weak for the propose of authentication No protection to forgery attacks No replay protection. Misusing RC4 algorithm for the encryption so that the protocol is extremely weak to key attacks Has the security hole that attacker without the encryption key but reusing IV can decrypt the encrypted code

7. Layered AKE Methods (1/2) TLS embedded protocol  EAP-TTLS, EAP-FAST Prevent dictionary attack & replay attack  EAP-TLS Widely deployed Well-formed and reliable mechanism  PEAP Concern credential security & anti-replay protection  All tunneled authentication protocols are potentially venerable to the man-in-the- middle attack

8. Layered AKE Methods (2/2) Layered method with cryptographic design  EAP-PSK Alleviate computational burden WiMAX for device authentication  EAP-PSEKE Simple password authentication Prevent man-in-the-middle and off-line dictionary attacks  Advantage High efficient & easily deployable authentication framework  Disadvantage No identity protection; no protected ciphersuite negotiation; and no fast reconnection capability

9. Access control-based layered AKE method IEEE 802.1X (2004)  Port-based network access control Transitional solution  WPA Authentication: 802.1X & EAP Traffic encryption: Temporal key integrity protocol (TKIP) Variable  T=Temporal Key  I=Intermediate Key  K=Per-packet Key  A=802 MAC address of the local Wireless interface Steps  I=T  A  K=B  I  Streamkey =RC4(IV, K)

10. Long-term scheme 3 components of 802.11  802.1X for authentication  Robust Security Network (RSN) for keeping the track of associations  Advanced Encryption Standard-based Counter Mode CBC-MAC Protocol (AES-CCMP) to provide integrity, replay protection and confidentiality 802.11i :  4 way handshake authentication  Security enhancements to 802.11  Complete protection of the Layer 2 packet  Unavoidable weaknesses & Complicated to implement

11. Comparison results

12. Multi-layer AKE framework 3 components  Access control 802.1X  Mutual authentication & Key distribution EAP+TLS  New functionalities Based on TLS-EAP in higher layer

13. Conclusion EAP-based layered AKE methods  More promising since provide the strong security by EAP-TLS as well as some complementary features Multi-layered AKE framework Future works  New functionalities provided by other high-layer protocols  Extensions to the proposed framework for the purpose of efficiency  Support sufficiently fast handovers among access points  How to handle fast-roaming users by these AKE methods