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DTEND:20200110T120000Z
UID:80551673b2f7b13a32c37e85e5bd6458-44
DTSTAMP:19700101T120011Z
DESCRIPTION:Communication Complexity of Byzantine Agreement, Revisited
URL;VALUE=URI:https://www.csa.iisc.ac.in/newweb/event/44/communication-complexity-of-byzantine-agreement-revisited/
SUMMARY:As Byzantine Agreement (BA) protocols find application in largescale decentralized cryptocurrencies, an increasingly important problem is to design BA protocols with improved communication complexity. A few existing works have shown how to achieve subquadratic BA under an adaptive adversary. Intriguingly, they all make a common relaxation about the adaptivity of the attacker, that is, if an honest node sends a message and then gets corrupted in some round, the adversary cannot erase the message that was already sent — henceforth we say that such an adversary cannot perform “after-the-fact removal”. By contrast, many (super-)quadratic BA protocols in the literature can tolerate after-the-fact removal. It turns out, as shown in our work, that disallowing after-the-fact removal is necessary for achieving subquadratic-communication BA.

In this talk, I will first present a simple quadratic BA protocol. Next, I will show a new subquadratic binary BA construction (of course, assuming no after-the-fact removal) that achieves near-optimal resilience and expected constant rounds under standard cryptographic assumptions and a public-key infrastructure (PKI). In comparison, all known subquadratic protocols make additional
strong assumptions such as random oracles or the ability of honest nodes to erase secrets from memory, and even with these strong assumptions, no prior work can achieve the above properties.
DTSTART:20200110T120000Z
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