YOSO: You Only Speak Once - Secure MPC with Stateless Ephemeral Roles

Craig Gentry, Shai Halevi, Hugo Krawczyk, Bernardo Magri, Jesper Buus Nielsen, Tal Rabin, Sophia Yakoubov

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


The inherent difficulty of maintaining stateful environments over long periods of time gave rise to the paradigm of serverless computing, where mostly stateless components are deployed on demand to handle computation tasks, and are torn down once their task is complete. Serverless architecture could offer the added benefit of improved resistance to targeted denial-of-service attacks, by hiding from the attacker the physical machines involved in the protocol until after they complete their work. Realizing such protection, however, requires that the protocol only uses stateless parties, where each party sends only one message and never needs to speaks again. Perhaps the most famous example of this style of protocols is the Nakamoto consensus protocol used in Bitcoin: A peer can win the right to produce the next block by running a local lottery (mining) while staying covert. Once the right has been won, it is executed by sending a single message. After that, the physical entity never needs to send more messages. We refer to this as the You-Only-Speak-Once (YOSO) property, and initiate the formal study of it within a new model that we call the YOSO model. Our model is centered around the notion of roles, which are stateless parties that can only send a single message. Crucially, our modelling separates the protocol design, that only uses roles, from the role-assignment mechanism, that assigns roles to actual physical entities. This separation enables studying these two aspects separately, and our YOSO model in this work only deals with the protocol-design aspect. We describe several techniques for achieving YOSO MPC; both computational and information theoretic. Our protocols are synchronous and provide guaranteed output delivery (which is important for application domains such as blockchains), assuming honest majority of roles in every time step. We describe a practically efficient computationally-secure protocol, as well as a proof-of-concept information theoretically secure protocol.

Original languageEnglish
Title of host publicationAdvances in Cryptology - CRYPTO 2021 - 41st Annual International Cryptology Conference, CRYPTO 2021, Virtual Event, August 16-20, 2021, Proceedings, Part II
EditorsTal Malkin, Chris Peikert
PublisherSpringer Berlin
Number of pages30
ISBN (Electronic)9783030842451
ISBN (Print)9783030842444
Publication statusPublished - 11 Aug 2021

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume12826 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


  • Blockchains
  • Secure MPC
  • Stateless Parties
  • YOSO


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