1. STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions April 2006 Daniele Quercia, Manish Lad, Stephen Hailes, Licia Capra, and Saleem Bhatti CS department University College London {d.quercia}@cs.ucl.ac.uk SAC

2. Daniele Quercia SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions 2 Outline Novel and existing mechanisms to support those features To avoid tragedy, STRUDEL supports 4 features Mesh Net and its tragedy How STRUDEL supports them? State machine One experiment & Conclusion

3. Daniele Quercia3 Mesh net and its tragedy Mesh nodes form a peering coalition  Result: SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions Free-riders join the coalition  Result: Bandwidth sharing Tragedy (of the commons)

4. Daniele Quercia4 To avoid tragedy, STRUDEL supports 4 Features SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions STRUDEL needs distributed mechanisms to: form peering coalitions; detect free-riders; manage (trust) info; decide such that free-riders excluded.

5. Daniele Quercia5 Novel and existing work to support... SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions formdetect managedecide

6. Daniele Quercia6 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions STRUDEL needs to form peering coalitions. How? Common (Connection sharing in MANETs) : Each device in turn acts as a gateway formdetect managedecide pxpx pypy pzpz

7. Daniele Quercia7 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions Novel (Connection sharing in Mesh Nets) : Devices share multiple connections simultaneously formdetect managedecide pxpx pypy pzpz CPD M. Lad, S. Bhatti, S. Hailes, and P. Kirstein. Enabling Coalition-Based Community Networking. In Proc. of the London Communications Symposium. 2005.

8. Daniele Quercia8 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions STRUDEL needs to detect free-riders. How? 2-ACK scheme: formdetect managedecide pxpx pypy pzpz One-hop ACKTwo-hop ACK packet If p x does not receive: one-hop ACK  retransmits two-hop ACK  is suspicious about p y

9. Daniele Quercia9 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions STRUDEL needs to manage trust info. How? formdetect managedecide Existing distributed trust management Fine- grained trust metric 2+ Trust Sources TimeFormalization Abdul-Rahmal [2]  XX Confidant [4] X  ? 

10. Daniele Quercia10 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions formdetect managedecide How ?Fine- grained trust metric 2+ Trust SourcesTimeFormalization B-trust  n-level  Direct experiences & Recommendations  Aging  Bayesian Quercia; Hailes; Capra B-trust: Bayesian Trust Framework for Pervasive Computing Proceedings of the 4 th International Conference on Trust Management. LNCS. 2006.

11. Daniele Quercia11 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions Upon trust info, STRUDEL (p x ) needs to decide whether to exclude (cooperate). How? For each next-hop p y, p x has a table: formdetect managedecide Quercia ; Hailes Risk Aware Decision Framework for Trusted Mobile Interactions Proceedings of the 1 st IEEE SECOVAL Workshop (in conjunction with SECURECOMM). (b) py’s actions Send now Send Don’t send Send Just- in-time Send Out- of-time Sent Sent just- in-time Sent out- of-time Not sent (a) px’s actions (c) Expected Outcomes

12. Daniele Quercia12 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions CPD2-ACK B-trustUtility Support of the 4 Features How ?

13. Daniele Quercia13 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions How? State Machine! Wait  Ready Next Hop: p x selects whether to send packets and, if so, chooses its next-hop Update: p x updates its direct trust and recommended trust in its next-hops

14. Daniele Quercia14 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions How? State Machine Send: p x sends packets without 2- ACK scheme; Slow Start: p x sends q packets (initially, q=1). If it receives 2-hop ACK, p x increases its sending window by q. Maliciousness avoidance: p x increases linearly its sending window

15. Daniele Quercia15 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions One experiment When using STRUDEL, p x successfully sent. 67% of the packets on average (if n=2),. 84% (if n=4), in contrast to 42% when using random selection. pxpx fm m b fb 100% 70% 30% 15%

16. Daniele Quercia16 SAC STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions Conclusion STRUDEL forms peering coalitions detects free-riders manages trust info, upon which it teams up only with trustworthy peers Future work: Fully implement STRUDEL