eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2020-10-07
48:1
48:3
10.4230/LIPIcs.DISC.2020.48
article
Brief Announcement: Multi-Threshold Asynchronous Reliable Broadcast and Consensus
Hirt, Martin
1
Kastrati, Ard
1
Liu-Zhang, Chen-Da
1
https://orcid.org/0000-0002-0349-3838
Department of Computer Science, ETH Zurich, Switzerland
Classical protocols for reliable broadcast and consensus provide security guarantees as long as the number of corrupted parties f is bounded by a single given threshold t. If f > t, these protocols are completely deemed insecure. We consider the relaxed notion of multi-threshold reliable broadcast and consensus where validity, consistency and termination are guaranteed as long as f ≤ t_v, f ≤ t_c and f ≤ t_t respectively. For consensus, we consider both variants of (1-ε)-consensus and almost-surely terminating consensus, where termination is guaranteed with probability (1-ε) and 1, respectively. We give a very complete characterization for these primitives in the asynchronous setting and with no signatures:
- Multi-threshold reliable broadcast is possible if and only if max{t_c,t_v} + 2t_t < n.
- Multi-threshold almost-surely consensus is possible if max{t_c, t_v} + 2t_t < n, 2t_v + t_t < n and t_t < n/3. Assuming a global coin, it is possible if and only if max{t_c, t_v} + 2t_t < n and 2t_v + t_t < n.
- Multi-threshold (1-ε)-consensus is possible if and only if max{t_c, t_v} + 2t_t < n and 2t_v + t_t < n.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol179-disc2020/LIPIcs.DISC.2020.48/LIPIcs.DISC.2020.48.pdf
broadcast
byzantine agreement
multi-threshold