--- _id: '10553' abstract: - lang: eng text: The popularity of permissioned blockchain systems demands BFT SMR protocols that are efficient under good network conditions (synchrony) and robust under bad network conditions (asynchrony). The state-of-the-art partially synchronous BFT SMR protocols provide optimal linear communication cost per decision under synchrony and good leaders, but lose liveness under asynchrony. On the other hand, the state-of-the-art asynchronous BFT SMR protocols are live even under asynchrony, but always pay quadratic cost even under synchrony. In this paper, we propose a BFT SMR protocol that achieves the best of both worlds -- optimal linear cost per decision under good networks and leaders, optimal quadratic cost per decision under bad networks, and remains always live. article_processing_charge: No author: - first_name: Rati full_name: Gelashvili, Rati last_name: Gelashvili - first_name: Eleftherios full_name: Kokoris Kogias, Eleftherios id: f5983044-d7ef-11ea-ac6d-fd1430a26d30 last_name: Kokoris Kogias - first_name: Alexander full_name: Spiegelman, Alexander last_name: Spiegelman - first_name: Zhuolun full_name: Xiang, Zhuolun last_name: Xiang citation: ama: 'Gelashvili R, Kokoris Kogias E, Spiegelman A, Xiang Z. Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol. In: Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing. Association for Computing Machinery; 2021:187-190. doi:10.1145/3465084.3467941' apa: 'Gelashvili, R., Kokoris Kogias, E., Spiegelman, A., & Xiang, Z. (2021). Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol. In Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing (pp. 187–190). Virtual, Italy: Association for Computing Machinery. https://doi.org/10.1145/3465084.3467941' chicago: 'Gelashvili, Rati, Eleftherios Kokoris Kogias, Alexander Spiegelman, and Zhuolun Xiang. “Brief Announcement: Be Prepared When Network Goes Bad: An Asynchronous View-Change Protocol.” In Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing, 187–90. Association for Computing Machinery, 2021. https://doi.org/10.1145/3465084.3467941.' ieee: 'R. Gelashvili, E. Kokoris Kogias, A. Spiegelman, and Z. Xiang, “Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol,” in Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing, Virtual, Italy, 2021, pp. 187–190.' ista: 'Gelashvili R, Kokoris Kogias E, Spiegelman A, Xiang Z. 2021. Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol. Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing. PODC: Principles of Distributed Computing, 187–190.' mla: 'Gelashvili, Rati, et al. “Brief Announcement: Be Prepared When Network Goes Bad: An Asynchronous View-Change Protocol.” Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing, Association for Computing Machinery, 2021, pp. 187–90, doi:10.1145/3465084.3467941.' short: R. Gelashvili, E. Kokoris Kogias, A. Spiegelman, Z. Xiang, in:, Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing, Association for Computing Machinery, 2021, pp. 187–190. conference: end_date: 2021-07-30 location: Virtual, Italy name: 'PODC: Principles of Distributed Computing' start_date: 2021-07-26 date_created: 2021-12-16T13:20:19Z date_published: 2021-07-21T00:00:00Z date_updated: 2023-09-04T11:42:10Z day: '21' department: - _id: ElKo doi: 10.1145/3465084.3467941 external_id: arxiv: - '2103.03181' isi: - '000744439800018' isi: 1 keyword: - optimal - state machine replication - fallback - asynchrony - byzantine faults language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/2103.03181 month: '07' oa: 1 oa_version: Preprint page: 187-190 publication: Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing publication_identifier: isbn: - 9-781-4503-8548-0 publication_status: published publisher: Association for Computing Machinery quality_controlled: '1' scopus_import: '1' status: public title: 'Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol' type: conference user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 year: '2021' ... --- _id: '6931' abstract: - lang: eng text: "Consider a distributed system with n processors out of which f can be Byzantine faulty. In the\r\napproximate agreement task, each processor i receives an input value xi and has to decide on an\r\noutput value yi such that\r\n1. the output values are in the convex hull of the non-faulty processors’ input values,\r\n2. the output values are within distance d of each other.\r\n\r\n\r\nClassically, the values are assumed to be from an m-dimensional Euclidean space, where m ≥ 1.\r\nIn this work, we study the task in a discrete setting, where input values with some structure\r\nexpressible as a graph. Namely, the input values are vertices of a finite graph G and the goal is to\r\noutput vertices that are within distance d of each other in G, but still remain in the graph-induced\r\nconvex hull of the input values. For d = 0, the task reduces to consensus and cannot be solved with\r\na deterministic algorithm in an asynchronous system even with a single crash fault. For any d ≥ 1,\r\nwe show that the task is solvable in asynchronous systems when G is chordal and n > (ω + 1)f,\r\nwhere ω is the clique number of G. In addition, we give the first Byzantine-tolerant algorithm for a\r\nvariant of lattice agreement. For synchronous systems, we show tight resilience bounds for the exact\r\nvariants of these and related tasks over a large class of combinatorial structures." alternative_title: - LIPIcs article_processing_charge: No author: - first_name: Thomas full_name: Nowak, Thomas last_name: Nowak - first_name: Joel full_name: Rybicki, Joel id: 334EFD2E-F248-11E8-B48F-1D18A9856A87 last_name: Rybicki orcid: 0000-0002-6432-6646 citation: ama: 'Nowak T, Rybicki J. Byzantine approximate agreement on graphs. In: 33rd International Symposium on Distributed Computing. Vol 146. Schloss Dagstuhl - Leibniz-Zentrum für Informatik; 2019:29:1--29:17. doi:10.4230/LIPICS.DISC.2019.29' apa: 'Nowak, T., & Rybicki, J. (2019). Byzantine approximate agreement on graphs. In 33rd International Symposium on Distributed Computing (Vol. 146, p. 29:1--29:17). Budapest, Hungary: Schloss Dagstuhl - Leibniz-Zentrum für Informatik. https://doi.org/10.4230/LIPICS.DISC.2019.29' chicago: Nowak, Thomas, and Joel Rybicki. “Byzantine Approximate Agreement on Graphs.” In 33rd International Symposium on Distributed Computing, 146:29:1--29:17. Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2019. https://doi.org/10.4230/LIPICS.DISC.2019.29. ieee: T. Nowak and J. Rybicki, “Byzantine approximate agreement on graphs,” in 33rd International Symposium on Distributed Computing, Budapest, Hungary, 2019, vol. 146, p. 29:1--29:17. ista: 'Nowak T, Rybicki J. 2019. Byzantine approximate agreement on graphs. 33rd International Symposium on Distributed Computing. DISC: International Symposium on Distributed Computing, LIPIcs, vol. 146, 29:1--29:17.' mla: Nowak, Thomas, and Joel Rybicki. “Byzantine Approximate Agreement on Graphs.” 33rd International Symposium on Distributed Computing, vol. 146, Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2019, p. 29:1--29:17, doi:10.4230/LIPICS.DISC.2019.29. short: T. Nowak, J. Rybicki, in:, 33rd International Symposium on Distributed Computing, Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2019, p. 29:1--29:17. conference: end_date: 2019-10-18 location: Budapest, Hungary name: 'DISC: International Symposium on Distributed Computing' start_date: 2019-10-14 date_created: 2019-10-08T12:41:38Z date_published: 2019-01-01T00:00:00Z date_updated: 2021-01-12T08:09:38Z ddc: - '004' department: - _id: DaAl doi: 10.4230/LIPICS.DISC.2019.29 ec_funded: 1 external_id: arxiv: - '1908.02743' file: - access_level: open_access checksum: 2d2202f90c6ac991e50876451627c4b5 content_type: application/pdf creator: jrybicki date_created: 2019-10-08T12:47:19Z date_updated: 2020-07-14T12:47:44Z file_id: '6934' file_name: LIPIcs-DISC-2019-29.pdf file_size: 639378 relation: main_file file_date_updated: 2020-07-14T12:47:44Z has_accepted_license: '1' intvolume: ' 146' keyword: - consensus - approximate agreement - Byzantine faults - chordal graphs - lattice agreement language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ oa: 1 oa_version: Published Version page: 29:1--29:17 project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: 33rd International Symposium on Distributed Computing publication_identifier: eisbn: - 978-3-95977-126-9 publication_status: published publisher: Schloss Dagstuhl - Leibniz-Zentrum für Informatik quality_controlled: '1' scopus_import: 1 status: public title: Byzantine approximate agreement on graphs tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: conference user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 146 year: '2019' ...