Achieving Instantaneous Blockchain Finality by Resolving the Availability-Finality Dilemma ∞ Research

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Briefing

The core research problem is the inherent trade-off in hybrid consensus protocols like Gasper, which sacrifice rapid finality for dynamic availability, leaving a 64-to-95 slot window for short-term chain reorganizations and Maximum Extractable Value (MEV) exploits. The breakthrough is a non-blackbox protocol that tightly integrates a synchronous dynamically available ledger (a modified LMD-GHOST) with a partially synchronous finality gadget (Casper-FFG) in a “confirm-finalize” paradigm. This novel combination achieves single-slot finality under synchronous conditions, fundamentally enhancing the economic security of the base layer by eliminating the non-finalized chain prefix and enforcing immediate, economically-backed settlement.

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Context

Before this work, established Byzantine Fault Tolerance (BFT) protocols faced the Availability-Finality Dilemma, which dictates that a single consensus mechanism cannot simultaneously guarantee both liveness under dynamic validator participation and safety during network partitions. This led to hybrid designs, where an available chain (like LMD-GHOST) was layered with a slow finality gadget (like Casper-FFG), resulting in a probabilistic chain that required dozens of slots to achieve economic finality, a major vulnerability for transaction security and user experience.

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Analysis

The protocol operates by introducing a tight, non-blackbox coupling between the fork-choice rule and the finality mechanism. Validators use a variant of LMD-GHOST, called RLMD-GHOST, to maintain an available chain head. In the same slot, they cast “head votes” and attempt to “fast confirm” the proposed block.

Fast confirmation occurs when the block’s subtree receives votes from a two-thirds supermajority of the validator set. This immediate, supermajority-backed confirmation is then used as the direct input to the finality gadget, ensuring that the block is justified and finalized within the same slot under ideal network conditions, conceptually collapsing the two-step process into a single, atomic operation.

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Parameters

Current Finality Time ∞ 64 to 95 slots (The current delay for a block to be finalized on the existing Gasper protocol, approximately 15 minutes).
Target Finality ∞ 1 slot (The goal of the new protocol under synchronous network conditions).
Required Supermajority ∞ 2/3 (The fraction of the validator set required to fast confirm a block and achieve finality).

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Outlook

This research opens the path for a new era of decentralized applications that rely on immediate, cryptographically-backed settlement guarantees, which is critical for cross-chain bridging and high-frequency DeFi. In 3-5 years, this foundational work is expected to be integrated into major Proof-of-Stake architectures, creating a base layer that is resilient to all short-range reorgs and nearly eliminates MEV extraction via chain manipulation. Future research will focus on optimizing the parallel voting and communication overhead necessary to achieve the two-thirds supermajority within the tight time constraints of a single slot.

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Verdict

This protocol represents a fundamental architectural advancement in Proof-of-Stake systems, transforming probabilistic safety into deterministic, near-instantaneous economic finality.

Single slot finality, Consensus mechanism design, Dynamic availability, Partially synchronous model, Ebb-and-flow protocols, Accountable safety, Finality gadget, Fork choice rule, Validator set economics, Transaction ordering security, Proof of Stake upgrade, Byzantine fault tolerance, Economic security, Chain reorganization risk, Liveness guarantee Signal Acquired from ∞ arxiv.org