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 SAC

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

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)

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.

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

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

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

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

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  ? 

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

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

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

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

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

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%

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