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Dr. Kemal Akkaya E-mail: kemal@cs.siu

Department of Computer Science Southern Illinois University Carbondale CS 591 – Wireless & Network Security Lecture 12: Trust. Dr. Kemal Akkaya E-mail: kemal@cs.siu.edu. Trust. Definition: The belief that an entity is capable of acting reliably, dependably, and securely in a particular case

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Dr. Kemal Akkaya E-mail: kemal@cs.siu

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  1. Department of Computer ScienceSouthern Illinois University CarbondaleCS 591 – Wireless & Network SecurityLecture 12: Trust Dr. Kemal Akkaya E-mail: kemal@cs.siu.edu Wireless & Network Security 1

  2. Trust Wireless & Network Security 2 • Definition: • The belief that an entity is capable of acting reliably, dependably, and securely in a particular case • A well studied concept in sociology and psychology. • Need for trust • Traditional schemes focus on preventing attackers from entering the network through security protocols. • Those schemes, however, are not effective when: • Malicious nodes have gained access to the network • Some nodes in the network have been compromised • Trust function: • Provide an incentive for good behavior. • Provide a prediction of one’s future behavior. • Detect malicious and selfish entities. • Examples: • E-commerce : risk estimation • P2P : reducing free riding • Mobile ad hoc networks: mitigating nodes selfish behavior

  3. Trust Models • Trust models entails collecting the information necessary to establish a trust relationship and dynamically monitoring and adjusting the existing truth relationship. • Two models: • Policy-based Trust • Based on access control • Restricting access to resources according to application-defined policies • PolicyMaker, Keynote, REFEREE • Reputation-based Trust • a peer requesting a resource may evaluate its trust in the reliability of the resource and the peer providing the resource • Trust value assigned to a trust relationship is a function of the combination of the peer’s global reputation • SPORAS, HISTOS, XREP, NICE, DCRC/CORC, Beta, EigenTrust • Others: Social network-based Trust • Utilize social relationships between peers when computing trust and reputation values Wireless & Network Security 3

  4. Policy-based Trust Wireless & Network Security 4

  5. Policy-based Trust: virtual • Problems • They do not provide a complete generic trust management solution for all decentralized applications • Scalability Wireless & Network Security 5

  6. Reputation-based Trust • Community of cooks (200 people) • Need to interact with someone you don’t know, • To extablish trust: • you ask your friends • and friends of friends • ... • some recommendations are better than other • you check the record (if any) • After success trust increases • p2p community of hackers (2000 people) • Exchange programs & scripts • Need to interact with someone you don’t know, • ... • Difference with concrete community: • Larger, faster • Trust establishment has to be to some extent automatic Wireless & Network Security 6

  7. Challenges • Trust metrics • How to model and compute trust • Evaluating initial trust value • Combining evidences, recommendations, reputation • Management of reputation data • Secure & efficient retrieval of reputation data • Automating trust based decision • Closing the circle: using experience as feedback Wireless & Network Security 7

  8. open system (different security domains) trust is a measure & changes in time risk-based recommendation based (NOT identity-based) peers are not continuously available Some systems: PGP TBD open system (different security domains) trust is boolean & less time-dependent no risk rule (credential) based (NOT identity-based) peers are not continuously available Some systems: keynote, Trust-X Reputation vs Policy-based Trust Wireless & Network Security 8

  9. Distributed Trust Models • Distributed Trust: • The representation of inputs to, and the process of making, trust decisions based on resources shared among multiple entities • Without Trust, either parties refuse to interact or require severe restrictions and complex controls – increased costs. • Trust is required for multiple entities to co-operate and share resources, and thus achieve some application value. • Conditional transitivity of trust • if A trusts B & B trusts C then A trusts C if • B recommends its trust in C to A explicitly • A trusts B as a recommender • A can judge B’s recommendation and decide how much it will trust C, irrespective of B’s trust in C • Will look at different models separately • MANETs • P2P Networks Wireless & Network Security 9

  10. Comparison of TM Approaches Wireless & Network Security 10

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