## Abstract

We consider the fundamental problem of designing classical consensus-related distributed abstractions for large-scale networks, where the number of parties can be huge. Specifically, we consider tasks such as Byzantine Agreement, Broadcast, and Committee Election, and our goal is to design scalable protocols in the sense that each honest party processes and sends a number of bits which is sub-linear in n, the total number of parties. In this work, we construct the first such scalable protocols for all of the above tasks. In our protocols, each party processes and sends Õ (√n) bits throughout Õ (1) rounds of communication, and correctness is guaranteed for at most 1/3-ϵ fraction of static byzantine corruptions for every constant ϵ>0 (in the full information model). All previous protocols for the considered agreement tasks were non-scalable, either because the communication complexity was linear or because the computational complexity was super polynomial. We complement our result with a matching lower bound showing that any Byzantine Agreement protocol must have ω(√n) complexity in our model. Previously, the state of the art was the well-known ω(3√n) lower bound of Holtby, Kapron, and King (Distributed Computing, 2008).

Original language | English |
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Title of host publication | STOC 2024 - Proceedings of the 56th Annual ACM Symposium on Theory of Computing |

Editors | Bojan Mohar, Igor Shinkar, Ryan O�Donnell |

Publisher | Association for Computing Machinery |

Pages | 411-422 |

Number of pages | 12 |

ISBN (Electronic) | 9798400703836 |

DOIs | |

State | Published - 10 Jun 2024 |

Event | 56th Annual ACM Symposium on Theory of Computing, STOC 2024 - Vancouver, Canada Duration: 24 Jun 2024 → 28 Jun 2024 |

### Publication series

Name | Proceedings of the Annual ACM Symposium on Theory of Computing |
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ISSN (Print) | 0737-8017 |

### Conference

Conference | 56th Annual ACM Symposium on Theory of Computing, STOC 2024 |
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Country/Territory | Canada |

City | Vancouver |

Period | 24/06/24 → 28/06/24 |

### Bibliographical note

Publisher Copyright:© 2024 Owner/Author.

## Keywords

- Broadcast
- Byzantine Agreement
- Consensus
- Leader Election