Nakamoto’s consensus protocol works in a permissionless model, where nodes can join and leave without notice. However, it guarantees agreement only probabilistically. Is this weaker guarantee a necessary concession to the severe demands of supporting a permissionless model? This paper shows that, at least in a benign failure model, it is not. It presents Sandglass, the first permissionless consensus algorithm that guarantees deterministic agreement and termination with probability 1 under general omission failures. Like Nakamoto, Sandglass adopts a hybrid synchronous communication model, where, at all times, a majority of nodes (though their number is unknown) are correct and synchronously connected, and allows nodes to join and leave at any time.
@InProceedings{pu_et_al:LIPIcs.DISC.2022.33, author = {Pu, Youer and Alvisi, Lorenzo and Eyal, Ittay}, title = {{Safe Permissionless Consensus}}, booktitle = {36th International Symposium on Distributed Computing (DISC 2022)}, pages = {33:1--33:15}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-255-6}, ISSN = {1868-8969}, year = {2022}, volume = {246}, editor = {Scheideler, Christian}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2022.33}, URN = {urn:nbn:de:0030-drops-172246}, doi = {10.4230/LIPIcs.DISC.2022.33}, annote = {Keywords: Consensus, Permissionless, Nakamoto, Deterministic Safety} }
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