### Salus: A System for Server-Aided Secure Function Evaluation

Seny Kamara, Payman Mohassel, and Ben Riva

##### Abstract

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 to overcome using standard and practical techniques. Among them are: (1) requiring participants to do work linear in the size of the circuit representation of the function; (2) requiring all parties to do the same amount of work; and (3) not being able to provide complete fairness. A promising approach for overcoming these limitations is to augment the SFE setting with a small set of untrusted servers that have no input to the computation and that receive no output, but that make their computational resources available to the parties. In this model, referred to as server-aided SFE, the goal is to tradeoff the parties' work at the expense of the servers. Motivated by the emergence of public cloud services such as Amazon EC2 and Microsoft Azure, recent work has explored the extent to which server-aided SFE can be achieved with a single server. In this work, we revisit the sever-aided setting from a practical perspective and design single-server-aided SFE protocols that are considerably more efficient than all previously-known protocols. We achieve this in part by introducing several new techniques for garbled-circuit-based protocols, including a new and efficient input-checking mechanism for cut-and-choose and a new pipelining technique that works in the presence of malicious adversaries. Furthermore, we extend the server-aided model to guarantee fairness which is an important property to achieve in practice. Finally, we implement and evaluate our constructions experimentally and show that our protocols (regardless of the number of parties involved) yield implementations that are 4 and 6 times faster than the most optimized two-party SFE implementation when the server is assumed to be malicious and covert, respectively.

Available format(s)
Category
Cryptographic protocols
Publication info
Published elsewhere. Full version of the paper that appears in ACM CCS 2012
Keywords
secure multi-party computationserver-aided computationcloud-assisted MPC
Contact author(s)
pmohasse @ cpsc ucalgary ca
History
Short URL
https://ia.cr/2012/542

CC BY

BibTeX

@misc{cryptoeprint:2012/542,
author = {Seny Kamara and Payman Mohassel and Ben Riva},
title = {Salus: A System for Server-Aided Secure Function Evaluation},
howpublished = {Cryptology ePrint Archive, Paper 2012/542},
year = {2012},
note = {\url{https://eprint.iacr.org/2012/542}},
url = {https://eprint.iacr.org/2012/542}
}

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