SDSIrep: A Reputation System Based on SDSI

  • Ahmed Bouajjani
  • Javier Esparza
  • Stefan Schwoon
  • Dejvuth Suwimonteerabuth
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4963)


We introduce SDSIrep, a reputation system based on the SPKI/SDSI authorization system. It is well-known that a system of SPKI/SDSI certificates corresponds to the formal model of a pushdown system (PDS). Our system, SDSIrep, allows principals to express trust and recommendations in the form of so-called certificates with weights. By interpreting weights as probabilities, we obtain a random-walk model of the reputation of a principal. Thus, SDSIrep represents an application of the theory of probabilistic PDSs to the field of computer security. We present an algorithm to compute the reputation of each principal. An extension of SDSIrep also provides for so-called intersection certificates, by which, loosely speaking, a principal gains reputation if recommended by all members of a given group of principals. On a formal-methods level, this extension makes SDSIrep correspond to probabilistic alternating PDSs, and we extend the underlying theory of PDSs to handle this case. As an example we sketch a small academic reputation system that combines information from different reputation sources, like conferences, coauthors, and rankings.


Markov Chain Equation System Reputation System Reachability Problem Trust Problem 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Ahmed Bouajjani
    • 1
  • Javier Esparza
    • 2
  • Stefan Schwoon
    • 2
  • Dejvuth Suwimonteerabuth
    • 2
  1. 1.LIAFAUniversity of Paris 7Paris cedex 13France
  2. 2.Technische Universität MünchenGarchingGermany

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