Broadcast with unknown participants and any number of corruptions

Σκουμιός, Νικόλαος Άγγελος; Skoumios, Nikolaos Angelos

dc.contributor.author	Σκουμιός, Νικόλαος Άγγελος	el
dc.contributor.author	Skoumios, Nikolaos Angelos	en
dc.date.accessioned	2025-03-19T11:33:59Z
dc.date.available	2025-03-19T11:33:59Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/61373
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.29069
dc.rights	Default License
dc.subject	Distributed algorithms	en
dc.subject	Byzantine agreement	en
dc.subject	Unknown participants	en
dc.subject	Any number of corruptions	en
dc.title	Broadcast with unknown participants and any number of corruptions	en
heal.type	bachelorThesis
heal.classification	Κρυπτογραφία	el
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2024-10-14
heal.abstract	The byzantine agreement problem is one of the most fundamental research areas in the field of fault-tolerant distributed algorithms. While the problem has attracted the interest of the scientific community the last years due to the development of blockchain technologies and cryptocurrencies, the bulk of the literature studies the cases of static participation and honest majority. In this work, we present the first, to our knowledge, byzantine Broadcast protocol (where the parties shall agree on the input value of designated sender), which tolerates any number of corruptions in the unknown participants model, where the parties have no clue about the set of actual participants nor for their number. Our solution is based on the main idea of the corresponding protocol in the known participants model, where in every round the parties accept an input value of the sender only if they receive as many signatures in support of it as the round number. In particular, we modify appropriately this protocol, so then in every round the parties accept the active participation of some other party only it they receive as many signatures in support of it from as many parties as the round number, but only from parties that they have already accepted in the previous rounds. Hence, we we construct a new protocol in the unknown participants model which achieves agreement among the parties on a subset of them, which contains all honest parties (the ones which do not deviate from the protocol). In addition, we extend our protocol, so then the parties agree on an input value for each one of the parties of this commonly agreed party set. In this way, our solution of byzantine Broadcast is an immediate application of this extended protocol. Finally, relying once again on corresponding results in the known participants model, we prove that any protocol that solves byzantine Broadcast in the unknown participants model with the same resilience requires as many communication rounds in the worst case as the number of active parties. Thus, we show that our protocol, which requires the same number of rounds as the number of parties, is optimal in terms of its worst-case round complexity	en
heal.advisorName	Παγουρτζής, Αριστείδης	el
heal.committeeMemberName	Παγουρτζής, Αριστείδης	el
heal.committeeMemberName	Ζήκας, Βασίλειος	el
heal.committeeMemberName	Λεονάρδος, Νικόλαος	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών	el
heal.academicPublisherID	ntua
heal.fullTextAvailability	false