Edith C.H. Ngai and Michael R. Lyu

1. An Authentication Service Based on Trust and Clustering in Wireless Ad Hoc Networks: Description and Security Evaluation Edith C.H. Ngai and Michael R. Lyu Department of Computer Science and EngineeringThe Chinese University of Hong Kong 5 Jun 2006 The IEEE International Conference on Sensor Networks, Ubiquitous, and Trustworthy Computing (SUTC 2006)

2. Outline • Introduction • Related Work • Architecture and Models • Trust- and Clustering-Based Authentication Service • Simulation Results • Conclusion Dept. of Computer Science & Engineering, CUHK

3. Mobile Ad Hoc Network • An ad-hoc network (of wireless nodes) is a temporarily formed network, created, operated and managed by the nodes themselves. • It is also often termed an infrastructure-less, self-organized, or spontaneous network. Dept. of Computer Science & Engineering, CUHK

4. Mobile Ad Hoc Network • Connected with wireless communication • Dynamic Topology • Nodes are often mobile • Vulnerable to security attacks • Applications • Military: for tactical communications • Rescue missions : in times of natural disaster • Commercial use: for sales presentations or meetings Dept. of Computer Science & Engineering, CUHK

5. Vulnerabilities • Security in wireless ad hoc network is hard to achieve due to the vulnerabilities of its links, limited physical protection, and the absence of centralized management point • Unlike conventional networks, nodes of ad hoc networks cannot be secured in locked cabinets • Risk in being captured and compromised • Wireless communications are vulnerable to eavesdropping and active interference Dept. of Computer Science & Engineering, CUHK

6. Security Mechanisms • Popular network authentication architecture include X. 509 standard and Kerberos systems • Pretty Good Privacy (PGP) functions by following a web-of-trust model and using digital signatures • Authentication service establishes the valid identities of communicating nodes • In reality, a node may turn from trustworthy to malicious under a sudden attack • We provide a secure authentication service that can defend against malicious nodes Dept. of Computer Science & Engineering, CUHK

7. Related Work • Partially-distributed certificate authority byZhou and Hass • Mobile Certificate Authority (MOCA) by Yi and Kravets • Fully-distributed certificate authority by Kong et. al. Dept. of Computer Science & Engineering, CUHK

8. Related Work • Pretty Good Privacy (PGP) • following a web-of-trust authentication model • Self-issued certificatesby Hubaux et. al. • distribute certificates by users themselves without the involvement of any certificate authority Dept. of Computer Science & Engineering, CUHK

9. Our Work • Propose a secure public key authentication service in mobile ad hoc networks with malicious nodes • Prevent nodes from obtaining false public keys of the others • Engage a network model and a trust model • Design security operations including public key certification, identification of malicious nodes, and trust value update Dept. of Computer Science & Engineering, CUHK

10. Trust- and Clustering-Based Authentication Service Architecture Dept. of Computer Science & Engineering, CUHK

11. The Network Model • Clustering-based network model obtains a hierarchical organization of a network • Limit direct monitoring capability to neighboring nodes • Allow monitoring work to proceed more naturally • Improve network security Dept. of Computer Science & Engineering, CUHK

12. The Trust Model • This model uses digital signatures as its form of introduction. Any node signs another's public key with its own private key to establish a web of trust • Define the authentication metric as a continuous value between 0.0 and 1.0 • Define a direct trust relationship as the trust relationship between two nodes in the same group and a recommendation trust as the trust relationship between nodes of different groups. Dept. of Computer Science & Engineering, CUHK

13. Clustering Structure Maintenance • Maintain a balanced clustering structure for supporting our trust model and security operations • Adapt to the mobility of nodes • Handle leave and join of nodes from one cluster to another • Each node requests for the cluster ID of its neighboring nodes periodically • In each cycle, a node collects this information and updates its cluster ID Dept. of Computer Science & Engineering, CUHK

14. Clustering Structure Maintenance A node joins the neighbouring cluster with minimum size only if it leaves the original cluster or the sizes of the neighbouring clusters are not within a certain range Dept. of Computer Science & Engineering, CUHK

15. Evolution of Cluster Size It keeps balance cluster sizes Dept. of Computer Science & Engineering, CUHK

16. Authentication Service Selects a number of trustable nodes as introducers • Public key certification • Identification of malicious nodes • Trust value update Sends out request messages to introducers Collects and compares all the public key certificates received Selects the public key of t with majority votes Discovers malicious introducer? Isolates malicious introducer Calculates trust value of t Updates trust table Dept. of Computer Science & Engineering, CUHK

17. Public Key Certification • Authentication in our network relies on the public key certificates signed by some trust-worthy nodes • Nodes in the same group always know each other better by means of their monitoring components and their short distances • Every node is able to request for the public key certificates of other new nodes • Nodes in the same cluster are assumed to know each other by means of their mutual monitoring components Dept. of Computer Science & Engineering, CUHK

18. Public Key Certification • We focus on public key certification, wheres and t belong to different groups • Nodes, which are in the samecluster as t and have already built up a trust relationshipwith s, can be introducers Dept. of Computer Science & Engineering, CUHK

19. Public Key Certification Send request to neighbors if target node in same cluster Send request to introducers if target node in different cluster Dept. of Computer Science & Engineering, CUHK

20. Identification of Malicious Nodes • Identify malicious neighboring nodes by monitoring their behaviors • Identify introducers who provide public key certificates different from the others • Identify a target node as malicious if the trust values provided from the introducers indicate that Dept. of Computer Science & Engineering, CUHK

21. Trust Value Update Dept. of Computer Science & Engineering, CUHK

22. Parameters Setting • Network simulator Glomosim • Evaluate the effectiveness in providing secure public key authentication in the presence of malicious nodes Dept. of Computer Science & Engineering, CUHK

23. Simulation Metrics Possible Cases with 3 Introducers • Successful rate • Fail rate • Unreachable rate • False-positive error rate • False-negative error rate Dept. of Computer Science & Engineering, CUHK

24. Effectiveness of Neighbor Monitoring Rates to No. of Cycles with n=40, r=100, (left) m=0.3 (right) m=0.7 Dept. of Computer Science & Engineering, CUHK

25. ID Cases 0 Not enough Introducers 1 OOO 2 OOX 3 OXX 4 XXX 5 OO 6 OX 7 XX 8 O 9 X 10 No Reply Isolation of Malicious Nodes Rates to No. of Cycles with n=40, r=100, and Isolation of Suspicious Nodes in Cases 2,3,4,6,7 (left) m=0.3 (right) m=0.7 Dept. of Computer Science & Engineering, CUHK

26. ID Cases 0 Not enough Introducers 1 OOO 2 OOX 3 OXX 4 XXX 5 OO 6 OX 7 XX 8 O 9 X 10 No Reply Isolation of Malicious Nodes Rates to No. of Cycles with n=40, r=100, and Isolation of Suspicious Nodes in Cases 2,4,7 (left) m=0.3 (right) m=0.7 Dept. of Computer Science & Engineering, CUHK

27. Conclusions • We developed a trust- and clustering-based public key authentication mechanism • We defined a clustering-based network model with a balanced structure and a trust model that allows nodes to monitor and rate each other with quantitative trust values • The authentication protocol proposed involves new security operations on public key certification, update of trust table, discovery and isolation of malicious nodes • We conducted security evaluation to demonstrate the effectiveness of our solution Dept. of Computer Science & Engineering, CUHK