Ethereum co-founder Vitalik Buterin has unveiled a new framework for the security of Layer-2 (L2) rollups, which aims to enhance both the speed of finality and the trust guarantees within Ethereum’s scaling ecosystem.
In a recent proposal, Buterin laid out a roadmap focused on a hybrid-proof architecture that integrates zero-knowledge proofs, optimistic rollups, and trusted execution environments (TEEs), while minimizing dependence on any single solution.
This proposal comes at a time when the L2 landscape for Ethereum is advancing. Numerous rollups have achieved Stage 1 on the scaling roadmap, with forthcoming upgrades—like Pectra and Fusaka—expected to greatly increase the availability of data blobs for rollup utilization.
Buterin emphasized that the current objective is to advance these rollups to Stage 2, necessitating a greater degree of trustlessness and quicker transaction finality. He believes that a three-prover system—where at least two out of three validation mechanisms must confirm a rollup’s state root to attain finality—represents the most effective immediate approach.
In this system, if both a ZK prover and a TEE prover verify a state root, it is finalized instantly. If only one approves, the process defaults to an optimistic model that introduces a seven-day challenge phase.
The optimistic framework serves as a final adjudicator, ensuring that semi-trusted systems do not override decisions when there is a disagreement with more trustless systems.
### Trustless Finality
Buterin noted that this architecture is meticulously crafted to fulfill the security and decentralization aspirations set for Stage 2 rollups.
It enables quick finality during standard operations, guarantees that trust-minimized proof systems cannot be overridden by less reliable components, and minimizes reliance on the current generation of ZK systems, which are still at risk from bugs and shared-code vulnerabilities.
He also proposed the establishment of a security council to act as a protective measure. This council would have the capacity to immediately update the TEE logic in the event of a failure and implement delayed modifications to the ZK or optimistic systems.
In unusual circumstances—such as when provers yield conflicting results—the council would hold the power to intervene swiftly, maintaining the system’s integrity.
Buterin insists that the combination of one ZK prover, one optimistic prover, and one TEE is the sole feasible strategy to reach Ethereum’s Stage 2 objectives without compromising speed or security.
ZK and optimistic systems are based on fundamentally different mathematical principles, significantly reducing the chances of shared vulnerabilities. Therefore, combining them with a TEE provides a practical balance that is unlikely to fail together.
### Scaling with Blobs and Aggregated Proofs
In addition to the proof architecture, Buterin also discussed the progression of Ethereum’s data layer. He highlighted the upcoming Pectra upgrade, which is expected to roll out in a few weeks and will expand the blob space to six units per block.
Following that, the Fusaka upgrade might increase that number to as many as 72, vastly enhancing the data bandwidth accessible to rollups. More blob space decreases congestion, making L2 transactions more affordable and scalable.
The roadmap also pointed out a critical gap within Ethereum’s infrastructure: the absence of a standardized, ecosystem-wide proof aggregation layer. Buterin argued that various applications across the Ethereum spectrum—ranging from rollups and privacy protocols to wallet recovery tools—should not need to submit individual zero-knowledge proofs.
Instead, a collective aggregation mechanism would enable all these applications to merge their outputs into one cohesive proof. This strategy would significantly reduce gas costs by distributing the approximately 500,000 gas load of proof submissions among all participants.
Buterin remarked that the Ethereum community is already making progress towards developing ZK-EVMs capable of producing proofs within a single slot, even in the most challenging scenarios.
As these systems advance and critical bugs are resolved, TEEs could eventually become obsolete. In such a scenario, Ethereum rollups would achieve complete trustlessness, enabling instant finality with no dependence on semi-trusted components.