Fair and Efficient Secure Multiparty Computation with Reputation Systems.

A reputation system for a set of entities is essentially a list of scores that provides a measure of the reliability of each entity in the set. The score given to an entity can be interpreted (and in the reputation system literature it often is [12]) as the probability that an entity will behave honestly. In this paper, we ask whether or not it is possible to utilize reputation systems for carrying out secure multiparty computation. We provide formal definitions of secure computation in this setting, and carry out a theoretical study of feasibility. We present almost tight results showing when it is and is not possible to achieve fair secure computation in our model. We suggest applications for our model in settings where some information about the honesty of other parties is given. This can be preferable to the current situation where either an honest majority is arbitrarily assumed, or a protocol that is secure for a dishonest majority is used and the efficiency and security guarantees (including fairness) of an honest majority are not obtained.