EigenLayer is an Ethereum re-staking framework that enables validators to pool security across different blockchain modules, protocols, and applications. Validators that opt to re-stake ETH into EigenLayer can provide validation services to Actively Validated Services (AVS) and earn additional returns beyond consensus rewards. In exchange, re-stakers are subject to slashing conditions imposed by the AVS modules they opt into. This pooled security model allows new innovations to leverage Ethereum's cryptoeconomic guarantees, strong security, and decentralization.

One proposed application of EigenLayer is providing single-slot finality for transactions or blocks. Under a basic SSF model, a set of validators re-staked on an EigenLayer AVS module could attest that they will never vote for a chain that reverses or excludes a block after it has been proposed. This would finalize the block in a single slot rather than waiting for probabilistic finality. However, several challenges exist with this approach:

First, a majority of Ethereum validators would likely need to re-stake into this EigenLayer SSF module for the guarantees to be meaningful. Otherwise, the minority SSF validators may be forced to violate their attestations or face inactivity penalties from the Ethereum base layer for failing to build on the canonical chain. Reaching this threshold for a new opt-in module presents difficulties.

Second, bolting SSF onto Ethereum in a minority way risks creating coordination failures, chain splits, or breaking consensus incentives if the minority SSF validators clash with the majority. Careful cryptoeconomic protections are needed to align incentives.

Third, providing SSF at the transaction level via tips or fees faces challenges around fairly compensating SSF re-stakers and block proposers without enabling MEV manipulation or requiring non-EigenLayer stakers to opt-in to some extra rule or code. Preventing oligopolistic behavior is also difficult in a minority SSF system.

Overall, while EigenLayer's pooled security model offers intriguing possibilities, implementing strong SSF guarantees for Ethereum without majority adoption or base layer modifications remains challenging. A better pathway may be using EigenLayer to facilitate fast finality sidechains. If EigenLayer is able to reach a supermajority of validators, then a SSF AVS could be enabled, and SSF could be implemented much more quickly and without a change to the core protocol. This would provide valuable data while limiting disruption risks to Ethereum's core consensus.