1. Muppet Reputation Mechanism Juho Heikkilä 16.3.2007 H ELSINKI I NSTITUTE FOR I NFORMATION T ECHNOLOGY H ELSINKI U NIVERSITY OF T ECHNOLOGY

2. 2007-03-13Muppet Reputation Mechanism – Muppet/Juho Heikkilä2 Muppet in Nutshell Managing Privacy and Trust in P2P Communication Cases: Online trading / Media production Human centered mobile devices/services Distributed, no central trust server Peer reputation (human/service/media) –Past actions as a basis for trust Economic and security

3. 2007-03-13Muppet Reputation Mechanism – Muppet/Juho Heikkilä3 What is (our) reputation? Reputation is information about prior acts It is subjective and incomplete –Subjective in use case and in social context –Incompleteness is not a flaw but a natural phenomenan Personalized estimation on known data –How does it look to this user and in this context

4. 2007-03-13Muppet Reputation Mechanism – Muppet/Juho Heikkilä4 Goals of Reputation In financial scenarios maximizing trade Basically we want to encourage –Producing media –That others are interested in too Reputation works by giving ’points’ Spam / Building anti-spam incentives –Spam is annoying to see –It can ruin your whole media/channel

5. 2007-03-13Muppet Reputation Mechanism – Muppet/Juho Heikkilä5 Formation: First Persistent Object Reputation should primarily be gained by the nearest object that is persistent –Trade is not persistent, seller/buyer is –Book is persistent –Song is persistent, performance is not Recording of a performance is, however Multiple different recordings of one event Persistence is not always trivial

6. 2007-03-13Muppet Reputation Mechanism – Muppet/Juho Heikkilä6 Inheritance of Reputation… Things are easier to evaluate than people Even in eBay we evaluate trade, not partner –We do not know anything else about him/her –Even traitors do good deals (and vice versa) Single action does not fully present anyone Reputation is inherited from things –Higher level entities inherit from basic blocks –Event  FPO  Combinatory entity