Collusion-Free Multiparty Computation in the Mediated Model

Collusion-free protocols prevent subliminal communication (i.e., covert channels) between parties running the protocol. In the standard communication model, if one-way functions exist, then protocols satisfying any reasonable degree of privacy cannot be collusion-free. To circumvent this impossibility, Alwen, shelat and Visconti (CRYPTO 2008) recently suggested the mediated model where all communication passes through a mediator. The goal is to design protocols where collusionfreeness is guaranteed as long as the mediator is honest, while standard security guarantees hold if the mediator is dishonest. In this model, they gave constructions of collusion-free protocols for commitments and zeroknowledge proofs in the two-party setting. We strengthen the definition of Alwen et al., and resolve the main open questions in this area by showing a collusion-free protocol (in the mediated model) for computing any multi-party functionality.

• Type: Conference
• Year: 2009
• Where: CRYPTO
• Authors: Joël Alwen, Jonathan Katz, Yehuda Lindell, Giuseppe Persiano, Abhi Shelat, Ivan Visconti
• Keywords: Collusion-free Protocol, CRYPTO 2009, Cryptology, Mediated Model, Standard Communication Model