Multi-proof design in the OP Stack

You’ve heard about the security benefits of multi-client networks, but what if your favorite L2  could incorporate multiple proof schemes into its design? This is exactly what’s in store for OP Mainnet after it upgrades to Bedrock.

Following the logic that client diversity is healthy for a blockchain ecosystem, the OP Stack turns OP Mainnet into a modular blockchain that is capable of proof-scheme diversity as well. Builders will soon be able to utilize any type of existing proof when working with the OP Stack, and the modular design of Bedrock and ensures that the system can adapt to accommodate future innovations in proving.

Let’s delve into the technical aspects of this unique feature and discuss the broader implications for the ecosystem.

The Problem: Rigid Proof Schemes in Rollup Design

Previous iterations of rollup design focused on creating a proof and fitting the system to it. This approach resulted in limited flexibility and adaptability to changing technology. Because of this type of design, contentious debates over optimistic proofs versus validity proofs dominate the conversation in the L2 space.

When designing Bedrock, we wanted to change this narrative. With modularity as a key design principle for the Bedrock upgrade, we built a system that can fit many types of proofs, providing a more secure and future proof solution for builders.

The Solution: Modular Design, Flexibility, and Security

The ability to incorporating multiple proofs into the OP Stack offers numerous benefits, with security being the most notable. Having multiple proofs prevents a bug in any one of them from becoming the canonical truth. This is similar to how multiple implementations of L1 clients provide better overall security. Vitalik has written about how Ethereum’s multi-client philosophy might interact with ZK-EVMs. In that article he notes that multi-client implementations are a form of technical decentralization, the main benefit of which is the resilience it brings against bugs in the network. It also results in a form of social decentralization if multiple independent teams/stakeholders maintain an implementation. The interests of each team goes into the calculation of the roadmap for the network.

Bedrock’s modular design has already enabled multiple implementations of L2 clients to emerge in the Optimism ecosystem, a first for an L2. Like Vitalik and Ethereum, we’re extending this philosophy to allow the OP Stack to incorporate multiple proofs. This leaves the door open for adding zero-knowledge (ZK) validity proofs to OP Mainnet, or another OP Chain like Base, and ensures compatibility with future advancements. The OP Stack's modular design allows it to easily adopt new technologies when they become secure and battle-tested, without requiring significant changes to the codebase.

How Does It Work?

The proof system in the OP Stack achieves modularity through standardized on-chain APIs and off-chain actors. This allows for mixing and matching of dispute contracts, facilitating easy swapping of proof schemes.

Standardized Onchain APIs

By standardizing on-chain APIs, Bedrock makes it possible to swap proof schemes as long as they implement the standardized API. This means that new proof schemes can be added on the fly and we can even create a m of n scheme where multiple proof schemes are required for operation of the bridge.

Standardized Offchain Actors

Offchain actors, or bots, communicate with the dispute contracts. This system creates a Maximal Extractable Value (MEV) opportunity that incentivizes honest behavior and secures the system, while maintaining the principle that playing the dispute game should always be profitable as an incentive to ensure its continual play. With this model, we are creating an open network of monitoring actors that can step in to resolve disputes to secure the system.

Two implementations of standardized offchain actors are being worked on here and here.

The Future is Super… chain.

The Bedrock upgrade and its support for multiple proofs aligns with our vision for a scalable network of chains that doesn't fracture our ecosystems, applications, or ability to work together. As the only L2 ecosystem designed for multi-client, multi-proof simplicity, Optimism will lead industry into a more secure, adaptable, collaborative, and ✨ optimistic ✨ future.