International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Towards a Theory of Trust Based Collaborative Search

Yacov Yacobi
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Abstract: Trust Based Collaborative Search is an interactive metasearch engine, presenting the user with clusters of results, based not only on the similarity of content, but also on the similarity of the recommending agents. The theory presented here is broad enough to cover search, browsing, recommendations, demographic profiling, and consumer targeting. We use the term search as an example. We developed a novel general trust theory. In this context, as a special case, we equate trust between agents with the similarity between their search-behaviors. The theory suggests that clusters should be close to maximal similarity within a tolerance dictated by the amount of uncertainty about the vectors of probabilities of attributes representing queries, pages and agents. In addition, we give a new theoretical analysis of clustering tolerances, enabling more judicial decisions about optimal tolerances. Specifically, we show that tolerances should at least be divided by a constant>1 as we descend from one layer in the hierarchical clustering to the next. We also show a promising connection between collaborative search and cryptography: A query plays the role of a cryptogram, the search engine is the cryptanalyst, and the user's intention is the cleartext. Shannon's unicity distance is the length of the search. It is needed to quantify the clustering-tolerance.
  title={Towards a Theory of Trust Based Collaborative Search},
  booktitle={IACR Eprint archive},
  keywords={foundations / trust, collaboration, search, cryptography},
  note={This paper has not been published elsewhere. 14733 received 29 Apr 2010, last revised 3 May 2010},
  author={Yacov Yacobi},