Context: Modern distributed systems, such as blockchain consensus and secure multiparty computation protocols, relies on a fundamental primitive: byzantine reliable broadcast.

It allows a set of processes to agree on a message broadcasted by a dedicated process, even when some of them are malicious (byzantine). It relies on quorum systems to prevent correct processes from delivering two different messages: each message needs to be certified by a majority (a quorum) of processes before delivery.

Byzantine reliable broadcast needs to maintain low latency and small communication complexity, but its efficiency depends on the number of processes constituting a majority. It was proposed in [1] to validate each message by smaller quorums such that 2 quorums for 2 different messages will intersect only with high probability.

 
This technique is not yet secure against fully rushing-adaptive adversaries: a malicious entity can learn the processes constituting a small quorum and corrupt them to force the validation of 2 conflicting messages. This research internship seeks to explore how to secure byzantine reliable broadcast against this adversary. A promising direction involves using secret quorums, a new abstraction introduced in [2] which hides processes composing small quorums. The intern will be advised by authors of [1] and [2].

[1] João Paulo Bezerra, Veronika Anikina, Petr Kuznetsov, Liron Schiff, and Stefan Schmid. Dynamic Probabilistic Reliable Broadcast. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 31:1-31:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024) https://doi.org/10.4230/LIPIcs.OPODIS.2024.31 

[2] Maxence Perion, Sara Tucci-Piergiovanni, and Rida Bazzi. StealthDust: Secret Quorums for Faster Fractional Spending. In arXiv preprint arXiv:2412.16648 (2025). https://arxiv.org/pdf/2412.16648

Objective: This research internship is dedicated to secure byzantine reliable broadcast in the presence of a well-defined rushing-adaptive adversary. The primary goals include the creation of a communication-efficient protocol, the rigorous verification of its correctness, the prototyping of the protocol, its practical evaluation and the subsequent preparation of a research paper.

Methodology: The intern will have the following responsibilities:

1. Prepare a state-of-the-art on similar solutions (this would be part of the state of art section for a research paper).
2. Become familiar with protocols already proposed in [1] and [2].
3. Specify a new distributed protocol solving the problem and proving its correctness.
4. Code a prototype and evaluate its practical relevance.
5. Prepare a research paper.

Competences:

• Being Master 1 or 2 in Computer Science/Engineering.
• Knowledge about distributed systems in general.
• Have an interest in theoretical computer science.
• Basic Rust abilities.