Payman Mohassel

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We study efficiency tradeoffs for secure two-party computation in presence of malicious behavior. We investigate two main approaches for defending against malicious behavior in Yao’s garbled circuit method: (1) Committed-input scheme, (2) Equality-checker scheme. We provide asymptotic and concrete analysis of communication and computation costs of the(More)
Secure function evaluation (SFE) allows a set of mutually distrustful parties to evaluate a function of their joint inputs without revealing their inputs to each other. SFE has been the focus of active research and recent work suggests that it can be made practical. Unfortunately, current protocols and implementations have inherent limitations that are hard(More)
Recently, Aumann and Lindell introduced a new realistic security model for secure computation, namely, security against covert adversaries. The main motivation was to obtain secure computation protocols which are efficient enough to be usable in practice. Aumann and Lindell presented an efficient two party computation protocol secure against covert(More)
We revisit the problem of general-purpose private function evaluation (PFE) wherein a single party P1 holds a circuit C, while each Pi for 1 ≤ i ≤ n holds a private input xi, and the goal is for a subset (or all) of the parties to learn C(x1, . . . , xn) but nothing else. We put forth a general framework for designing PFE where the task of hiding the(More)
We initiate the study of secure multi-party computation (MPC) in a server-aided setting, where the parties have access to a single server that (1) does not have any input to the computation; (2) does not receive any output from the computation; but (3) has a vast (but bounded) amount of computational resources. In this setting, we are concerned with(More)
We examine the feasibility of private set intersection (PSI) over massive datasets. PSI, which allows two parties to find the intersection of their sets without revealing them to each other, has numerous applications including to privacy-preserving data mining, location-based services and genomic computations. Unfortunately, the most efficient constructions(More)
Most implementations of Yao’s garbled circuit approach for 2-party secure computation use the free-XOR optimization of Kolesnikov & Schneider (ICALP 2008). We introduce an alternative technique called flexible-XOR (fleXOR) that generalizes free-XOR and offers several advantages. First, fleXOR can be instantiated under a weaker hardness assumption on the(More)
We introduce the notion of adaptive trapdoor functions (ATDFs); roughly, ATDFs remain one-way even when the adversary is given access to an inversion oracle. Our main application is the black-box construction of chosenciphertext secure public-key encryption (CCA-secure PKE). Namely, we give a black-box construction of CCA-Secure PKE from ATDFs, as well as a(More)
We consider secure delegation of linear algebra computation, wherein a client, privately and verifiably, outsources tasks such as matrix multiplication, matrix inversion, computing the rank and determinant, and solving a linear system to a remote worker. When operating on n×n matrices, we design non-interactive, and secure protocols for delegating matrix(More)
Applying cut-and-choose techniques to Yao’s garbled circuit protocol has been a promising approach for designing efficient Two-Party Computation (2PC) with malicious and covert security, as is evident from various optimizations and software implementations in the recent years. We revisit the security and efficiency properties of this popular approach and(More)