How to Work with Honest but Curious Judges? (Preliminary Report)

Jun Pang
(University of Luxembourg)
Chenyi Zhang
(University of Luxembourg)

The three-judges protocol, recently advocated by Mclver and Morgan as an example of stepwise refinement of security protocols, studies how to securely compute the majority function to reach a final verdict without revealing each individual judge's decision. We extend their protocol in two different ways for an arbitrary number of 2n+1 judges. The first generalisation is inherently centralised, in the sense that it requires a judge as a leader who collects information from others, computes the majority function, and announces the final result. A different approach can be obtained by slightly modifying the well-known dining cryptographers protocol, however it reveals the number of votes rather than the final verdict. We define a notion of conditional anonymity in order to analyse these two solutions. Both of them have been checked in the model checker MCMAS.

In Michele Boreale and Steve Kremer: Proceedings 7th International Workshop on Security Issues in Concurrency (SECCO 2009), Bologna, Italy, 5th September 2009, Electronic Proceedings in Theoretical Computer Science 7, pp. 31–45.
Published: 23rd October 2009.

ArXived at: bibtex PDF

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