webSPDZ: Versatile MPC on the Web

Thomas Buchsteiner; Karl W. Koch; Dragos Rotaru; Christian Rechberger

Paper 2025/487

webSPDZ: Versatile MPC on the Web

Thomas Buchsteiner, Graz University of Technology

Karl W. Koch

, Graz University of Technology, Secure Information Technology Center Austria (A-SIT)

Dragos Rotaru

, Gateway

Christian Rechberger

, Graz University of Technology

Abstract

Multi-party computation (MPC) has become increasingly practical in the last two decades, solving privacy and security issues in various domains, such as healthcare, finance, and machine learning. One big caveat is that MPC sometimes lacks usability since the knowledge barrier for regular users can be high. Users have to deal with, e.g., various CLI tools, private networks, and sometimes even must install many dependencies, which are often hardware-dependent. A solution to improve the usability of MPC is to build browser-based MPC engines where each party runs within a browser window. Two examples of such an MPC web engine are JIFF and the web variant of MPyC. Both support an honest majority with passive corruptions. $\texttt{webSPDZ}$: Our work brings one of the most performant and versatile general-purpose MPC engines, MP-SPDZ, to the web. MP-SPDZ supports ≥40 MPC protocols with different security models, enabling many security models on the web. To port MP-SPDZ to the web, we use Emscripten to compile MP-SPDZ’s C++ BackEnd to WebAssembly and upgrade the party communication for the browser (WebRTC or WebSockets). We call the new MPC web engine webSPDZ. As with the native versions of the mentioned MPC web engines, MPyC-Web and JIFF, webSPDZ outperforms them in our end-to-end experiments. We believe that webSPDZ brings forth many interesting and practically relevant use cases. Thus, webSPDZ pushes the boundaries of practical MPC: making MPC more usable and enabling it for a broader community.

Note: webSPDZ source code @ GitHub: https://github.com/tbuchs/webSPDZ

Metadata

Available format(s): PDF
Category: Implementation
Publication info: Preprint.
Keywords: Privacy-Enhancing Technology Private Computations Multi-Party Computation MP-SPDZ MPC Web Engine webSPDZ
Contact author(s): thomas buchsteiner @ gmail com
karl koch @ tugraz at
dragos @ mygateway xyz
christian rechberger @ tugraz at
History: 2025-03-17: approved; 2025-03-14: received; See all versions
Short URL: https://ia.cr/2025/487
License: CC BY

BibTeX

@misc{cryptoeprint:2025/487,
      author = {Thomas Buchsteiner and Karl W. Koch and Dragos Rotaru and Christian Rechberger},
      title = {{webSPDZ}: Versatile {MPC} on the Web},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/487},
      year = {2025},
      url = {https://eprint.iacr.org/2025/487}
}