arXiv subjects

Ivan Klianev

Publications and source records attributed to Ivan Klianev.

5 recordsLinked to original sources

arXiv2026

Consensus In Asynchrony: Strictly Formal

In this paper, we resolve the apparent contradiction between the proven possibility of deterministic crash-tolerant consensus in a fully asynchronous environment and the reconfirmation of the FLP impossibility result by Attiya, Casta\~neda, and Rajsbaum. With the use of a strictly formal framework that extends their reasoning, we close this fundamental gap in theory. Specifically, we demonstrate that a single protocol phase separates their findings from reaching the exact opposite conclusion. Another important outcome is a novel algorithm with ability to tolerate multiple crash faults. We provide a rigorous, strictly formal proof of correctness to validate our results.

cs.DC↗

arXiv2026

Consensus In Asynchrony

We demonstrate sufficiency of events-based synchronisation for solving deterministic fault-tolerant consensus in asynchrony. Main result is an algorithm that terminates with valid vector agreement, hence operates with safety, liveness, and tolerance to one crash. Reconciling with the FLP impossibility result, we identified: i) existence of two types of agreements: data-independent and data-dependent; and ii) dependence of FLP theorem correctness on three implicit assumptions. Consensus impossibility with data-dependent agreement is contingent on two of them. The theorem-stated impossibility with every agreement type hinges entirely on the third. We provide experimental results showing that the third assumption has no evidence in support.

cs.DC↗

arXiv2025

Different Perspectives on FLP Impossibility

We demonstrate termination of binary consensus under the model and conditions used by Fischer, Lynch, and Patterson (FLP) to prove impossibility of binary agreement - in complete asynchrony and a possible process crash - in two steps. First, we introduce a new paradigm for consensus termination and show that impossibility of agreement is not evidence for impossibility to terminate. Next, we present a consensus algorithm that ensures termination with agreement about the initial input from the processes.

cs.DC↗

arXiv2024

Synchronous Consensus in Partial Synchrony

We demonstrate a deterministic Byzantine consensus algorithm with synchronous operation in partial synchrony. It is naturally leaderless, tolerates any number of $ f<n/2 $ Byzantine processes with 2 rounds of exchange of originator-only signed messages, and terminates within a bounded interval of time. The algorithm is resilient to transient faults and asynchrony in a fraction of links with known size per number of faulty processes. It circumvents asynchronous and faulty links with 3-hop epidemic dissemination. Key finding: the resilience to asynchrony of links and the enabled by it leaderless consensus in partial synchrony ensure algorithm operation with simultaneous validity, safety, and bounded liveness.

cs.DC↗

arXiv2022

Synchronous Consensus During Incomplete Synchrony

We present an algorithm for synchronous deterministic Byzantine consensus, tolerant to links failures and links asynchrony. It cares for a class of networks with specific needs, where both safety and liveness are essential, and timely irrevocable consensus has priority over highest throughput. The algorithm operates with redundant delivery of messages via indirect paths of up to 3 hops, aims all correct processes to obtain a coherent view of the system state within a bounded time, and establishes consensus with no need of leader. Consensus involves exchange of 2*n*n*n asymmetrically authenticated messages and tolerates up to < n/2 faulty processes. We show that in a consensus system with known members: 1) The existing concepts for delivery over a fraction of links and gossip-based reliable multicast can be extended to also circumvent asynchronous links and thereby convert the reliable delivery into a reliable bounded delivery. 2) A system of synchronous processes with bounded delivery does not need a leader - all correct processes from connected majority derive and propose the same consensus value from atomically consistent individual views on system state. 3) The required for bounded delivery asymmetric authentication of messages is sufficient for safety of the consensus algorithm. Key finding: the impossibility of safety and liveness of consensus in partial synchrony is not valid in the entire space between synchrony and asynchrony. A system of synchronized synchronous processes, which communicate with asymmetrically authenticated messages over a medium susceptible to asynchrony and faults, can operate with: 1) defined tolerance to number of asynchronous and/or faulty links per number of stop-failed and/or Byzantine processes; 2) leaderless algorithm with bounded termination; and 3) conceptually ensured simultaneous safety and bounded liveness.

cs.DC↗