Round-Optimal Token-Based Secure Computation.

Secure computation in the presence of tamper-proof hardware tokens is proven under the assumption that the holder of the token is only given black-box access to the functionality of the token. Starting with the work of Goldreich and Ostrovsky [GO96], a long series of works studied tamper-proof hardware for realizing two-party functionalities in a variety of settings. In this work we focus our attention on two important complexity measures of stateless token-based secure computation: round complexity and hardness assumptions and present the following results in the two-party setting: • A round optimal generic secure protocol in the plain model assuming one-way functions, where the tokens are created by a single party. • A round optimal generic UC secure protocol assuming one-way functions. Our constructions are proven in the real/ideal paradigm with security in the presence of static malicious adversaries. As a side contribution, we identify a flaw in one of the feasibility results regarding UC secure protocols in the tamper proof model proved in the work of Goyal, Ishai, Sahai, Venkatesan and Wadia (TCC 2010) and correct history by attributing the work of Choi, Katz, Schrooder, Yerukhimovic and Zhou (TCC 2014) to establishing the (same) feasibility result.