The objective of this course is: The objective of this course is

The fear of retaliation prevent source agents to provide their real feedback [Resnick, 2002], [ebay.com, 2008]

A privacy preserving trust system protects the user from unwanted information disclosure (~personalization vs privacy dilemma)

A privacy preserving reputation system protects a feedback provider by hiding either the feedback value or the identity of the user (~anonymization)

Issue : anonymity => risk of attacks

• Sybil attack (attacker creates multiple identities)
• Self-promotion, ballot stuffing, slandering (in coalition or not)
• Whitewashing
• Oscillation

Agent q needs to learn rt =  li

• Agent q needs to learn rt =  li

• Privacy of li must be preserved

• Need efficient computation

The Semi-Honest Model

• The Semi-Honest Model

• Follow the protocol according to the specification
• Passively attempt to learn the inputs of honest agents
•