Lightweight Distributed Trust Propagation

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Lightweight Distributed Trust Propagation

  1. 1. Lightweight Distributed Trust Propagation (daniele quercia & stephen hailes & licia capra) U C L
  2. 2. What I do...
  3. 3. Research @ ...
  4. 5. What I research...
  5. 6. Reputation Systems for Mobiles
  6. 7. Daniele Quercia Situation : People exchange digital content
  7. 8. Daniele Quercia Problem : Content overload
  8. 9. Daniele Quercia Proposal: Accept content only from reputable people
  9. 10. Daniele Quercia Take two devices… A B
  10. 11. Daniele Quercia A B Shall I accept content from B ?
  11. 12. Daniele Quercia A B A should set its initial trust for B
  12. 13. Daniele Quercia A B A should set its initial trust for B Yes, but how?
  13. 14. Daniele Quercia <ul><li>Traditional way: </li></ul><ul><li>Trust propagation </li></ul>? A B C
  14. 15. Daniele Quercia <ul><li>That way works on the Web and </li></ul><ul><ul><li>has been tested on “binary” ratings </li></ul></ul>
  15. 16. Daniele Quercia <ul><ul><ul><li>If that way is tested on </li></ul></ul></ul><ul><ul><ul><li>3-level ratings </li></ul></ul></ul>
  16. 17. Conclusion: A needs a new way for propagating its trust in B
  17. 18. Conclusion: A needs a new way for propagating its trust in B But which way?
  18. 19. Our proposal
  19. 20. Daniele Quercia 1 ? A B C 2 A  B A  C C  B
  20. 21. Daniele Quercia 1 ? A B C 2 ? Put trust relationships in a new graph & label graph nodes 1 2 A  B A  C C  B
  21. 22. Daniele Quercia 1 ? A B C 2 ? Put trust relationships in a new graph & label graph nodes Define a “good” function that rates A  B f 1 2 A  B A  C C  B
  22. 23. Daniele Quercia 1 ? A B C 2 ? build_graph ( trust_relationships, A  B ) f find_f 1 2 A  B A  C C  B
  23. 24. <build_graph>
  24. 25. A B D C 3 2 1 1 2 ? A  B ? ? 2 3 1 0.5 1 M M
  25. 26. A B D C 3 2 1 1 2 ? A  B ? ? 2 3 1 0.5 1 M M What are those ?
  26. 27. Remember, we’ll define f We will see that f rates neighbouring nodes alike It’s a neighbour of A  B; therefore, it rates as A  B does ?
  27. 28. Remember, we’ll define f We will see that f rates neighbouring nodes alike It’s a neighbour of A  B; therefore, it rates as A  B does ? Find relationships that rate as A  B does
  28. 29. Remember, we’ll define f We will see that f rates neighbouring nodes alike It’s a neighbour of A  B; therefore, it rates as A  B does ?
  29. 30. 2 Types of those relationships
  30. 31. 1. The relationships with same rater ( A ) A B D C 3 2 1 1 2 As long as B and D behave alike
  31. 32. A B D C 3 2 1 1 2 2. The relationships with same rated node ( B ) As long as A and C rate alike
  32. 33. OK, 2 Types
  33. 34. Taking those relationships, one comes up with …
  34. 35. <ul><ul><ul><ul><li>… a graph! </li></ul></ul></ul></ul>A  C A  B A  D C  B 2 3 1 0.5 1 M M
  35. 36. </build_graph>
  36. 37. <find_f>
  37. 38. A  C A  B A  D C  B 2 3 1 0.5 1 M M
  38. 39. <ul><ul><li>Take f that returns </li></ul></ul><ul><ul><ul><li>the ratings already there ( ) </li></ul></ul></ul><ul><ul><ul><li>& similar ratings for neighbouring nodes </li></ul></ul></ul>A  C A  B A  D C  B 2 3 1 0.5 1 M M 2 3
  39. 40. More formally, …
  40. 41. We find f that minimizes that loss!
  41. 42. </find_f>
  42. 43. Daniele Quercia 1 ? A B C 2 ? build_graph f find_f 1 2 A  B A  C C  B
  43. 44. <ul><li>Does it work? </li></ul>Useful, Robust, Fast, “Light”?
  44. 45. Daniele Quercia <ul><li>Useful? Tested on real data </li></ul><ul><li>(Advogato: > 55K user ratings) </li></ul>
  45. 46. Daniele Quercia <ul><li>Useful? Tested on real data </li></ul><ul><li>(Advogato: > 55K user ratings) </li></ul>
  46. 47. Daniele Quercia Robust?
  47. 48. Daniele Quercia Robust?
  48. 49. Daniele Quercia Fast and “ Light ”?
  49. 50. Daniele Quercia Fast and “ Light ”? <ul><ul><li>For propagating A  B </li></ul></ul><ul><ul><li>(worst case) </li></ul></ul><ul><ul><li> Transmit 30KB </li></ul></ul><ul><ul><li>& run for 2.8ms </li></ul></ul>
  50. 51. Daniele Quercia All this on …
  51. 52. Daniele Quercia All this on …
  52. 53. Daniele Quercia

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