Rafail Ostrovsky - Publications

Near-Linear Unconditionally-Secure Multiparty Computation with a Dishonest Minority

Eli Ben-Sasson, Serge Fehr, Rafail Ostrovsky

Abstract:

In the setting of unconditionally-secure MPC, where dishonest players are unbounded and no cryptographic assumptions are used, it was known since the 1989′s that an honest majority of players is both necessary and sufficient to achieve privacy and correctness, assuming secure point-to point and broadcast channels. The main open question that was left is to establish the exact communication complexity.

We settle the above question by showing an unconditionally-secure MPC protocol, secure against a dishonest minority of malicious players, that matches the communication complexity of the best known MPC protocol in the honest-but-curious setting. More specifically, we present a new n-player MPC protocol that is secure against a computationally-unbounded malicious adversary that can adaptively corrupt t N K bits per multiplication gate. For any k polynomial in n , the amortized communication cty of our protocol matches the O( n log N) bit communication complexity of the best known MPC protocol with passive security.

We introduce several novel techniques that are of independent interest and we believe will have wider applicability. One is a novel idea of computing authentication tags by means of mini MPC, which allows us to avoid expensive double-sharings; the other is a batch-wise multiplication verification that allows us to speedup Beaver′s ″multiplication triples″.

comment: CRYPTO 2012 PP:663-680

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