The Finality Calculator: Analyzing and Quantifying Filecoin's Finality Guarantees

TL;DR

This paper introduces a dynamic method for assessing Filecoin's finality guarantees, significantly reducing confirmation times and improving network usability by providing more accurate probabilistic assessments.

Contribution

It presents a novel dynamic analysis algorithm for Filecoin's finality, enabling more efficient and accurate probabilistic guarantees without altering the existing consensus.

Findings

Achieves error probability of 2^-30 in about 30 rounds

Provides a 30x faster confirmation compared to the fixed 900-round threshold

Enables practical, off-chain finality assessment for clients

Abstract

In this paper, we analyze the finality of the Filecoin network, focusing on dynamic probabilistic guarantees of tipset permanence in the canonical chain. Our approach differs from static analyses that consider only the worst-case scenario; instead, we dynamically compute the error probability at each round using the live chain history, providing a more accurate and efficient assessment. We provide a practical algorithm that only requires visibility into the blocks produced by honest participants, which can be implemented by clients or off-chain applications without any change to Filecoin's consensus mechanisms.We demonstrate that, under typical operating conditions, the sought-after error probability of $2^{-30}$ is achievable in approximately 30 rounds, a 30x improvement over the 900 rounds that the network currently encodes as a fixed threshold. This finding immediately expedites transactions and enhances usability of the Filecoin network, while laying the foundation for further analysis of other DAG-structured blockchains.