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1. The More The Merrier: Reducing the Cost of Large Scale MPC

   Gordon, S. Dov; Starin, Daniel; Yerukhimovich, Arkady (January 2021, Eurocrypt)

   Canteaut, Anne; Standaert, Francois-Xavier (Ed.)

   Secure multi-party computation (MPC) allows multiple par-ties to perform secure joint computations on their private inputs. To-day, applications for MPC are growing with thousands of parties wish-ing to build federated machine learning models or trusted setups for blockchains. To address such scenarios we propose a suite of novel MPC protocols that maximize throughput when run with large numbers of parties. In particular, our protocols have both communication and computation complexity that decrease with the number of parties. Our protocols build on prior protocols based on packed secret-sharing, introducing new techniques to build more efficient computation for general circuits. Specifically, we introduce a new approach for handling linear attacks that arise in protocols using packed secret-sharing and we propose a method for unpacking shared multiplication triples without increasingthe asymptotic costs. Compared with prior work, we avoid the log|C|overhead required when generically compiling circuits of size |C| for use in a SIMD computation, and we improve over folklore “committee-based” solutions by a factor of O(s), the statistical security parameter. In practice, our protocol is up to 10X faster than any known construction, under a reasonable set of parameters. 

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2. The More The Merrier: Reducing the Cost of Large Scale MPC

   Gordon, S. Dov; Starin, Daniel; Yerukhimovich, Arkady (January 2021, Eurocrypt)

   Canteaut, Anne; Standaert, Francois-Xavier (Ed.)

   Secure multi-party computation (MPC) allows multiple par-ties to perform secure joint computations on their private inputs. To-day, applications for MPC are growing with thousands of parties wish-ing to build federated machine learning models or trusted setups for blockchains. To address such scenarios we propose a suite of novel MPC protocols that maximize throughput when run with large numbers of parties. In particular, our protocols have both communication and computation complexity that decrease with the number of parties. Our protocols build on prior protocols based on packed secret-sharing, introducing new techniques to build more efficient computation for general circuits. Specifically, we introduce a new approach for handling linear attacks that arise in protocols using packed secret-sharing and we propose a method for unpacking shared multiplication triples without increasingthe asymptotic costs. Compared with prior work, we avoid the log|C|overhead required when generically compiling circuits of size |C| for use in a SIMD computation, and we improve over folklore “committee-based” solutions by a factor of O(s), the statistical security parameter. In practice, our protocol is up to 10X faster than any known construction, under a reasonable set of parameters. 

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3. Multiparty Private Set Intersection Cardinality and Its Applications

   https://doi.org/10.56553/popets-2024-0041  

   Gao, Jiahui; Trieu, Ni; Yanai, Avishay (April 2024, Proceedings on Privacy Enhancing Technologies)

   We describe a new paradigm for multi-party private set intersection cardinality (PSI-CA) that allows $$n$$ parties to compute the intersection size of their datasets without revealing any additional information. We explore a variety of instantiations of this paradigm. By operating under the assumption that a particular subset of parties refrains from collusion, our protocols avoid computationally expensive public-key operations and are secure in the presence of a semi-honest adversary. We demonstrate the practicality of our PSI-CA with an implementation. For $n=16$ parties with data-sets of $$2^{20}$$ items each, our server-aided variant takes 71 seconds. Interestingly, in the server-less setting, the same task takes only 7 seconds. To the best of our knowledge, this is the first `special purpose' implementation of a multi-party PSI-CA from symmetric-key techniques (i.e. an implementation that does not rely on a generic underlying MPC).We study two interesting applications -- heatmap computation and associated rule learning (ARL) -- that can be computed securely using a dot-product as a building block. We analyse the performance of securely computing heatmap and ARL using our protocol and compare that to the state-of-the-art. 

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4. Arithmetic and Boolean Secret Sharing MPC on FPGAs in the Data Center

   Patel, Rushi; Wolfe, Pierre-Francois; Munafo, Robert; Varia, Mayank; Herbordt, Martin (September 2020, IEEE Conference on High Performance Extreme Computing)

   Multi-Party Computation (MPC) is an important technique used to enable computation over confidential data from several sources. The public cloud provides a unique opportunity to enable MPC in a low latency environment. Field Programmable Gate Array (FPGA) hardware adoption allows for both MPC acceleration and utilization of low latency, high bandwidth communication networks that substantially improve the performance of MPC applications. In this work, we show how designing arithmetic and Boolean Multi-Party Computation gates for FPGAs in a cloud provide improvements to current MPC offerings and ease their use in applications such as machine learning. We focus on the usage of Secret Sharing MPC first designed by Araki et al to design our FPGA MPC while also providing a comparison with those utilizing Garbled Circuits for MPC. We show that Secret Sharing MPC provides a better usage of cloud resources, specifically FPGA acceleration, than Garbled Circuits and is able to use at least a 10x less computer resources as compared to the original design using CPUs. 

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5. Distributed Learning without Distress: Privacy-Preserving Empirical Risk Minimization

   Bargav Jayaraman, Lingxiao Wang (December 2018, Advances in neural information processing systems)

   Distributed learning allows a group of independent data owners to collaboratively learn a model over their data sets without exposing their private data. We present a distributed learning approach that combines differential privacy with secure multi-party computation. We explore two popular methods of differential privacy, output perturbation and gradient perturbation, and advance the state-of-the-art for both methods in the distributed learning setting. In our output perturbation method, the parties combine local models within a secure computation and then add the required differential privacy noise before revealing the model. In our gradient perturbation method, the data owners collaboratively train a global model via an iterative learning algorithm. At each iteration, the parties aggregate their local gradients within a secure computation, adding sufficient noise to ensure privacy before the gradient updates are revealed. For both methods, we show that the noise can be reduced in the multi-party setting by adding the noise inside the secure computation after aggregation, asymptotically improving upon the best previous results. Experiments on real world data sets demonstrate that our methods provide substantial utility gains for typical privacy requirements. 

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