%0 Thesis %1 DistributedReputation_Engler_2007 %A Engler, Michael %D 2007 %K algorithms distributed recommendation reputation systems trust %T Fundamental Models and Algorithms for a Distributed Reputation System %U http://elib.uni-stuttgart.de/opus/volltexte/2008/3401/ %X With the increased significance of the Internet in our everyday lifes, we embrace its benefits as seemingly unlimited information source, warehouse and general communication medium, but sometimes fall prey to its predators. Outside the online world, social network structures of friends or colleagues allow to identify malicious and reputable entities and to communicate recommendations or warnings accordingly. When interacting through open computer networks, these traditional mechanisms used in the physical world for establishing trust are adapted by reputation systems that allow to build trust in entities and create social network structures on a much larger scale. In this dissertation, we investigate various models and algorithms required for realizing a fully decentralized reputation system with enhanced privacy properties and fine-grained trust modeling. To ensure the former, we bind trust to virtual identities instead of real identities and present extended destination routing, an approach that allows anonymous communication between pseudonyms without exposing any link to a real identity. To enable the latter, we introduce a generic trust model that allows to model trust in various context areas in addition to expressing context area dependencies that are taken into account when updating trust. The model definition permits incorporating several well-known trust update algorithms from the related work. Subjecting the algorithms to a set of evaluation scenarios gives valuable inputs regarding their specific performance. In order to capture the transitivity of trust, we present algorithms to simplify trust networks and then compute the transitive trust with subjective logic operators. Finally, we propose mechanisms to protect trust by firstly laying its foundation in trusted hardware and secondly ensuring the authenticity of recommendations through the integration of an originality statement. This reputation system can be utilized by users and relying applications alike to determine the trustworthiness of other entities. While these building blocks are all essential for our system, many contributions can be applied to other reputation systems and even to other research areas as well.

@phdthesis{DistributedReputation_Engler_2007, abstract = {With the increased significance of the Internet in our everyday lifes, we embrace its benefits as seemingly unlimited information source, warehouse and general communication medium, but sometimes fall prey to its predators. Outside the online world, social network structures of friends or colleagues allow to identify malicious and reputable entities and to communicate recommendations or warnings accordingly. When interacting through open computer networks, these traditional mechanisms used in the physical world for establishing trust are adapted by reputation systems that allow to build trust in entities and create social network structures on a much larger scale. In this dissertation, we investigate various models and algorithms required for realizing a fully decentralized reputation system with enhanced privacy properties and fine-grained trust modeling. To ensure the former, we bind trust to virtual identities instead of real identities and present extended destination routing, an approach that allows anonymous communication between pseudonyms without exposing any link to a real identity. To enable the latter, we introduce a generic trust model that allows to model trust in various context areas in addition to expressing context area dependencies that are taken into account when updating trust. The model definition permits incorporating several well-known trust update algorithms from the related work. Subjecting the algorithms to a set of evaluation scenarios gives valuable inputs regarding their specific performance. In order to capture the transitivity of trust, we present algorithms to simplify trust networks and then compute the transitive trust with subjective logic operators. Finally, we propose mechanisms to protect trust by firstly laying its foundation in trusted hardware and secondly ensuring the authenticity of recommendations through the integration of an originality statement. This reputation system can be utilized by users and relying applications alike to determine the trustworthiness of other entities. While these building blocks are all essential for our system, many contributions can be applied to other reputation systems and even to other research areas as well.}, added-at = {2010-02-04T01:07:04.000+0100}, author = {Engler, Michael}, biburl = {https://www.bibsonomy.org/bibtex/221835bc381dc3c4b308b42909d642b17/gwpl}, interhash = {079b02891e1660b55228194aeb4e6add}, intrahash = {21835bc381dc3c4b308b42909d642b17}, keywords = {algorithms distributed recommendation reputation systems trust}, month = {December}, school = {University of Stuttgart}, timestamp = {2010-02-04T01:07:04.000+0100}, title = {Fundamental Models and Algorithms for a Distributed Reputation System}, url = {http://elib.uni-stuttgart.de/opus/volltexte/2008/3401/}, year = 2007 }