Overview of Data Availability Solutions

In the blockchain field, Layer 2 (L2) faces data availability (DA) issues that mainly involve a trade-off between security and cost. To address this problem, two main solutions have emerged in the industry: on-chain and off-chain.

On-chain Solutions: Proto-Danksharding

On-chain solutions refer to L2 continuing to use Ethereum as the DA layer and relying on Ethereum to reduce data availability costs. Proto-Danksharding (EIP-4844) is Ethereum's solution to reduce DA costs, which introduces a new transaction format called Blob. The transaction data uploaded by L2 will be non-permanently stored in Blob format on the Ethereum consensus layer, providing L2 with more cost-effective data availability.

This means that Ethereum will become a real-time bulletin board in the future, where the data on the bulletin board will be deleted after a period of time, and L2 will need to store backups of all data on its own. Proto-Danksharding is expected to be launched in Ethereum's Cancun upgrade at the end of this year.

Off-chain Solutions

Off-chain solutions no longer use Ethereum as the DA layer, but seek more cost-effective data availability methods. Depending on the level of decentralization and security, off-chain solutions can be divided into four categories:

1. Validium

Validium is a highly centralized DA solution. In this model, transaction data is managed by a centralized operator and published off-chain. Although this approach maximizes the protection of transaction party privacy and minimizes DA costs, it also brings the highest risk. If the off-chain operator fails or engages in malicious behavior, user funds may be unrecoverable.

2. Data Availability Committee (DAC)

To reduce the risk of single points of failure caused by a single operator, Validium is usually used in conjunction with DAC. DAC is similar to a consortium chain, consisting of multiple trusted nodes. These nodes keep copies of transaction data and make the data public in case of operator issues, facilitating users to withdraw funds.

The operating costs of DACs are relatively low, but from a security perspective, small DACs (8-10 people ) are still prone to private key theft or collective malicious behaviors, which may lead to on-chain funds being frozen or stolen.

3. Volition

Volition is a hybrid model that allows users to choose whether the data for a single transaction is published on-chain or off-chain. For example, in a DEX that adopts this model, users can control multiple accounts and move assets to an off-chain data account for frequent and low-cost trading, and after the trading is completed, they can move the assets back to the on-chain data account.

Compared to pure Validium, Volition can partially inherit the security of Ethereum.

4. General DA Solution

In addition to the DA solutions in the Ethereum ecosystem, there is a type of generic DA solution. These solutions not only provide data availability for Ethereum's L2 but can also serve more chains and projects.

The general idea of the generic DA scheme is to enhance the security of data availability to achieve public chain-level security. They have independent verification nodes, block producers, and consensus mechanisms, but do not support smart contracts.

Introduction to DA Layer Projects

In the development of modular blockchain, Ethereum occupies almost 90% of the consensus layer and settlement layer, while the execution layer has formed a "four-legged balance" pattern after fierce competition. The DA layer is still in its infancy, and here are a few popular DA layer projects:

StarkEx

StarkEx is a framework developed by the StarkWare team that provides scalability solutions for specific applications, as well as data availability solutions. StarkEx offers three data availability modes: on-chain, Validium, and Volition. Its Validium solution integrates DAC to enhance security.

Currently, projects using StarkEx for data availability include dYdX v3, Immutable, Sorare, DeversiFi, and others.

zkPorter

zkPorter is an off-chain DA solution proposed by Matter Labs, the development team of zkSync, in April 2021. It is an independent chain specifically for L2 to publish transaction data, maintained securely through a PoS consensus mechanism. zkSync token holders can stake their tokens to become guardians of zkPorter to verify and sign blocks.

In the vision of Matter Labs, accounts on zkPorter can seamlessly interact with accounts or contracts on ZK Rollup (zkSync Era). From the user's perspective, the only noticeable difference may be that the fees for zkPorter accounts are much cheaper.

However, despite zkPorter being proposed a few years ago, there has been no significant progress, and Matter Labs has not disclosed any information about the zkPorter testnet and development progress.

EigenDA

EigenDA is a DA layer project developed based on EigenLayer. Unlike general DA projects, EigenDA is a middleware that does not have its own consensus mechanism; its security is obtained through the re-staking model of Ethereum validators in EigenLayer.

EigenDA is the first Active Verification Service (AVS) on EigenLayer. Re-stakers re-stake ETH into EigenDA to execute data verification services for rewards, while buyers (L2) publish data to EigenDA to achieve lower transaction costs and higher TPS.

Although EigenDA has not yet launched its testnet, multiple teams are planning to integrate it into L2, such as Mantle, Layer N, Offshore, and others.

Celestia

Celestia is a general-purpose DA public chain that has its own validation nodes and PoS consensus mechanism. Although the cost is higher compared to other off-chain DA solutions, the security is significantly enhanced.

Celestium is an Ethereum L2 chain that uses Celestia as the DA layer and Ethereum as the settlement and consensus layer. Celestium implements data availability in the following way:

1. Celestium will upload proof data to Ethereum, but will publish transaction data to Celestia;
2. The Celestia validator nodes send data availability proof signatures to the DA Bridge Contract on Ethereum for verification and storage.
3. L2 contracts on Ethereum can access this data at any time.

Celestia has completed two rounds of financing and announced on September 26 that it will airdrop TIA (Celestia's native asset) to developers and specific on-chain addresses.

Avail

Avail was originally a project founded by Polygon Labs in 2020, aimed at solving data availability issues. In March of this year, Avail became independent from Polygon and operates as a standalone DA public chain, no longer limited to the Polygon or Ethereum ecosystems.

Technically, Avail is more complex than Celestia. Its mainnet is expected to launch in the first quarter of 2024 and is currently in the second phase of the testnet. Users can participate in various ways, including obtaining testnet tokens, developing applications or chains integrated with Avail, or joining the testnet as validators or light clients.

Summary

As the Ethereum Cancun upgrade approaches, off-chain DA layer projects may directly face business competition with Ethereum. In addition to focusing on lower costs, these projects also need to consider how to enhance their competitiveness. For users, it is worth paying attention to whether significant projects similar to Optimism and Arbitrum will emerge in the DA layer competition.