Polymer x EigenDA: Open, Neutral Interoperability for Ethereum

EigenDA is a data availability store made by EigenLabs and built on top of EigenLayer. Currently live on the Goerli testnet, EigenDA is on a path to launch on mainnet later this year, with support for up to 10 MB/s in write throughput. As a rollup developer, if you'd like to learn more about EigenDA, read the Intro Blog Post and Litepaper, check out the Rollup User Guides and Documentation, and submit your information via https://contact.eigenda.xyz/. We provide integrated partners with both technical and ecosystem support. We'll be in touch soon!

Introduction to Polymer

Polymer, the "Interoperability Hub of Ethereum", is paving the way for collaboration among Ethereum rollups through its native IBC (Inter-blockchain Communication) technology. As the Ethereum ecosystem grapples with scaling challenges and the need for composability, Polymer emerges with a customizable model of interoperability that connects Ethereum with its integrated Layer 2 solutions.

Since 2015, Ethereum has faced scalability issues, despite the success of its Layer 2 solutions. While these layers improve scalability and user experience, they introduce execution environments that hinder liquidity and complicate the developer journey. Ensuring composability across Layer 2s remains a challenge due to the absence of a standardized native message-passing solution that the Polymer team is tackling using IBC.

Understanding IBC

IBC has several properties that distinguish it as an interoperability standard versus alternatives.

• Credible neutrality. It is not primarily associated with any one company or any DeFi products.
• Large contributor base. IBC currently has 17+ different companies and 120+ individual contributors.
• No token or value capture at the protocol level. Interoperability standards with a token or encoded value capture may affect credible neutrality and be unsuitable for enshrinement or native integrations.
• Application composability. IBC has a solid core feature set with opt-in middleware that extends its core functionality for building composable applications.

Polymer positions itself not as a bridge but as a Layer 2 dedicated to serving as Ethereum's Interoperability Hub. Polymer provides IBC execution to connected Layer 2s without requiring a native IBC integration, enabling new L2s to permissionlessly connect to the IBC network.

Polymer enhances composability between Ethereum rollups while leveraging IBC’s expanding network of applications. Although initially focused on the Ethereum ecosystem, the Polymer network looks to scale and connect all major blockchains.

Polymer will support various modes of verification or IBC clients between connected rollups. The default mode of verification will be to use the Ethereum L1 for verification. Additionally, any AVS that performs state transition verifications of rollups can be turned into an IBC client and used for pre-confirmations. 

Key Elements of Polymer

Polymer's modular stack consists of a few main building blocks.

• Settlement (OP Stack). Provides settlement and chain derivation logic to and from Ethereum.
• Execution (Cosmos SDK). Polymer’s virtual IBC protocol enables developers to build application-specific rollups with the Cosmos SDK on Ethereum providing builders with more optionality.
• Data Availability (EigenDA). Ensures scalable, secure, and cheap data availability.
• Proving (OP Stack’s Fault Proof System).
  • Interactive Fraud Proofs (IVG) for secure verification games.
  • ZK Validity Proofs using Rust ZK program by RiscZero.

Using EigenDA for Security and Scalability

The core insight of EigenDA is that the problem of data availability does not require independent consensus to solve. If we are building a decentralized transient data store for Ethereum, we can use Ethereum for aspects of coordination required, and for everything else address EigenDA operators directly.

EigenDA has the following characteristics:

• Scalable. EigenDA write throughput scales linearly with its number of operators. On mainnet launch EigenDA will provide 10 MB/s of write throughput.
• Secure. EigenDA is made up of hundreds of operators registered in EigenLayer, whose delegated stake imposes an economic cost to misbehavior. EigenDA expects to have billions of dollars of economic security at launch.
• Cheap. The abundance of L2 blockspace provided by EigenDA will demand a new kind of pricing model. Where the pricing of L1 blockspace is primarily constrained by supply, EigenDA blockspace pricing is primarily constrained by cost-of-security, which is shared with Ethereum and other EigenLayer AVSs. As a result we expect EigenDA to be orders of magnitude cheaper than alternatives.
• Ethereum-centric. EigenDA's design is inspired by Danksharding, which promises to scale Ethereum-native DA beyond EIP-4844. EigenDA blob writes are registered with contracts on Ethereum, which natively subject operators to certain slashing risks. Ethereum L2s using EigenDA avoid any trust assumption on another chain's light client.

Choosing EigenDA aligns with Polymer's commitment to security and scalability, taking advantage of security measures from Ethereum staking and the validator set. The flexible cost model of EigenDA ensures affordable data availability services, crucial for high throughput applications like cross-chain interoperability.

Integrating EigenDA with OP Stack

Polymer is building on top of Optimism's OP Stack. EigenLabs recently announced integration support of EigenDA with OP Stack! Let's understand briefly how the integration works.

The components of OP Stack fall into four categories:

1. L1 Contracts: These contracts manage bridging to and from Ethereum. In the future, they will include logic to verify fraud proofs.
2. Node Components: OP Stack nodes are responsible for scaling L2 reads and verifying that the sequencer is acting honestly. They scale L2 reads by having verifier nodes independently derive the L2 chain state from the DA layer and serving read traffic. In the future, they will be able to challenge a sequencer on-chain if their derived state root does not match the state root posted on-chain by the sequencer.
3. Sequencer Components: The sequencer is a node that has two additional jobs: to post batches of transactions to DA, and to post state roots of executed transactions to Ethereum.
4. Execution Component: The execution engine of the OP stack is by default op-geth. Polymer replaces op-geth with the Cosmos SDK for execution instead which comes with native IBC interoperability and Polymer’s virtual IBC protocol for permissionless IBC network expansion.

The OP Stack batcher is the sequencer module responsible for posting batches of L2 transaction data to DA. We modified this component to write batches to EigenDA instead of Ethereum. When a batch is successfully written to EigenDA, the disperser returns a unique blob key (4), which can be used to later retrieve the data that was written. The batcher then posts this blob key to Ethereum calldata (4), so that Ethereum remains the source of truth for the L2 ordering of EigenDA blobs.

Importantly, the OP Stack x EigenDA fork supports writing each batch to multiple EigenDA quorums, enabling redundant security and mitigating data withholding attacks.

Node EigenDA Reads

OP Stack full nodes derive the L2 state from transaction data posted to DA, downloading batches and executing them. We modified the OP Stack node to seamlessly handle retrieving EigenDA blobs using blob keys indexed in the Ethereum calldata. This involves a set of scatter-gather requests to EigenDA Operators storing chunks of the requested blob. If the retrieval of the blob from one quorum fails, the next will be tried, until the blob is retrieved or there are no more quorums to try.

Limitations

At the time of writing, OP Stack does not support fraud proofs, and neither does the EigenDA x OP Stack fork. When fraud proofs are enabled for OP Stack, we plan to update the contracts in OP Stack to support verifying the correctness and availability of L2 inbox data using KZG verification and calls to EigenDA contracts.

Polymer Innovates on Cutting-Edge Technology

Polymer combines OP Stack’s settlement capabilities, Cosmos SDK’s interoperability, and EigenDA’s data availability solution. In doing so, Polymer is delivering a leading hub for domain-specific interoperability, which improves the developer experience, facilitates interconnectivity, and prioritizes security across Ethereum.

Not only is Polymer addressing Ethereum's current challenges, but it also facilitates collaboration with Cosmos. By bringing IBC to Ethereum and allowing for direct connectivity and standardized composability between the two ecosystems, Polymer unites the strengths of both platforms. Ethereum and Cosmos, previously built in siloes, now share innovations, accelerating advancements for both chains.

In summary, Polymer is leading the way toward achieving interoperability and scalability for Ethereum and its Layer 2 chains. It tackles composability issues while fostering collaboration among ecosystems. And finally, by using EigenDA, it is able to achieve greater security, scalability, and cost-effectiveness in achieving its mission.