Adaptively Secure Two-Party Computation from Indistinguishability Obfuscation

© International Association for Cryptologic Research 2015. We present the first two-round, two-party general function evaluation protocol that is secure against honest-but-curious adaptive corruption of both parties. In addition, the protocol is incoercible for one of the parties, and fully leakage tolerant. It requires a global (nonprogrammable) reference string and is based on one way functions and general-purpose indistinguishability obfuscation with sub-exponential security, as well as augmented non-committing encryption. A Byzantine version of the protocol, obtained by applying the Canetti et al. [STOC 02] compiler, achieves UC security with comparable efficiency parameters, but is no longer incoercible.1

Adaptively Secure Two-Party Computation from Indistinguishability Obfuscation

We present the first two-round, two-party general function evaluation protocol that is secure against honest-but-curious adaptive corruption of both parties. In addition, the protocol is incoercible for one of the parties, and fully leakage tolerant. It requires a global (non-programmable) reference string and is based on one way functions and general-purpose indistinguishability obfuscation with sub-exponential security, as well as augmented non-committing encryption. A Byzantine version of the protocol, obtained by applying the Canetti et al. [STOC 02] compiler, achieves UC security with comparable efficiency parameters, but is no longer incoercible

Two-Round MPC without Round Collapsing Revisited -- Towards Efficient Malicious Protocols

Recent works have made exciting progress on the construction of round optimal, *two-round*, Multi-Party Computation (MPC) protocols. However, most proposals so far are still complex and inefficient. In this work, we improve the simplicity and efficiency of two-round MPC in the setting with dishonest majority and malicious security. Our protocols make use of the Random Oracle (RO) and a generalization of the Oblivious Linear Evaluation (OLE) correlated randomness, called tensor OLE, over a finite field $\mathbb{F}$, and achieve the following: - MPC for Boolean Circuits: Our two-round, maliciously secure MPC protocols for computing Boolean circuits, has overall (asymptotic) computational cost $O(S\cdot n^3 \cdot \log |\mathbb{F}|)$, where $S$ is the size of the circuit computed, $n$ the number of parties, and $\mathbb{F}$ a field of characteristic two. The protocols also make black-box calls to a Pseudo-Random Function (PRF). - MPC for Arithmetic Branching Programs (ABPs): Our two-round, information theoretically and maliciously secure protocols for computing ABPs over a general field $\mathbb{F}$ has overall computational cost $O(S^{1.5}\cdot n^3\cdot \log |\mathbb{F}|)$, where $S$ is the size of ABP computed. Both protocols achieve security levels inverse proportional to the size of the field $|\mathbb{F}|$. Our construction is built upon the simple two-round MPC protocols of [Lin-Liu-Wee TCC\u2720], which are only semi-honest secure. Our main technical contribution lies in ensuring malicious security using simple and lightweight checks, which incur only a constant overhead over the complexity of the protocols by Lin, Liu, and Wee. In particular, in the case of computing Boolean circuits, our malicious MPC protocols have the same complexity (up to a constant overhead) as (insecurely) computing Yao\u27s garbled circuits in a distributed fashion. Finally, as an additional contribution, we show how to efficiently generate tensor OLE correlation in fields of characteristic two using OT