Intro

After Celestia’s latest roadmap was released, several community members posted questions on social media regarding the role of ZK in the network’s development. This inspired a deep dive into understanding how the Celestia DA Layer interacts with ZK projects and what’s being built within the Celestia ecosystem using ZKPs.

In the following paragraphs, we will first examine the various types of identities by creating a comprehensive taxonomy. Then, we will delve into some of the projects that aim to address the challenges that have hindered the growth of decentralized digital identities in the past.

First, the status of the network

Celestia launched on October 2023. Since then, many projects have started interacting with the network. Here’s a quick summary with some stats on the general state of the network as of December 2024: 

• A total of 20 rollups are active. 
• There have been 25.3M transactions recorded in the network. 
• A total of 204 GB have been posted. 
• Eclipse is the most active rollup, with 47% of the data posted to Celestia, which accounts for 84.1GBs. It’s followed by LightLink (16.4%) and B3 (11.7%).

Now, what’s the State of ZK on Celestia?

To better understand the intersection of the ZK space with Celestia, we will categorise the different projects that are using or have announced an integration with the network. 

Let’s start with Celestia’s own 

There are currently three ZK initiatives within the Celestia Network. First, there’s the Blobstream data availability solution. Then, led by the ZK Working Group (ZKWG), a community initiative, ZK Accounts is developed. Finally, there is research on using recursive ZKPs to improve light nodes’ sync speed and portability. 

Blobstream 

Blobstream is an Ethereum data availability solution that integrates with Celestia’s modular data availability (DA) layer. It allows other chains, currently Ethereum mainnet and its Layer 2 (L2) rollups, to leverage Celestia’s highly scalable DA layer while maintaining settlement on Ethereum using Zero Knowledge Proofs (ZKPs). It verifies that Celestia validators, operating under the CometBFT consensus protocol, have reached consensus on a block, thus ensuring the integrity and availability of data on Celestia. 

There are two implementations: SP1 Blobstream (in production) and Blobstream Zero (under development). 

Blobstream’s TL;DR by @jadler0 from @CelestiaOrg pic.twitter.com/1zZI49o39Q

— ZKV (@zkv_xyz) November 8, 2023

ZK Accounts 

Core contributors in the ZK Working Group are building ZK accounts. They leverage ZKPs to enhance blockchain expressivity without requiring full general execution on the base layer. This innovation allows Celestia to verify transactions based on ZK proofs, offering flexibility for creating highly customisable accounts that execute complex logic while avoiding direct integration of each feature into the protocol.

This functionality aims to provide more advanced functionalities (e.g., multisig, conditional spending) without being explicitly encoded in the blockchain protocol. This allows for more scalable and secure Layer 2 (L2) solutions and more versatile account designs.

Here’s a quick overview of how they work: 

Each account is associated with a verification key in a ZK account system. This key represents a program, defined by the user, that validates whether a transaction meets specific conditions. The process follows these steps:

• State of ZK Account: The account holds a current state, typically tied to balances or other assets.
• Transaction Proof: To execute a transaction, a user submits a ZK proof that validates the proposed state change (e.g., spending funds or updating account logic).
• Verification: The blockchain’s state machine only verifies the validity of this proof. If it passes, the transaction is executed according to the predefined conditions.

This design allows users to define flexible spending rules without requiring protocol-level changes, simplifying blockchain architecture while enhancing account control and security. 

Prototyping has begun, with a PoC implementation in development.

Recursive Proofs of Consensus History 

Recursive ZK proofs of consensus history are being prototyped to improve synchronisation performance. as. This primitive can significantly reduce the resources needed to run light nodes, fostering their broader adoption. 

By creating a proof of the entire blockchain history in each new block header, users can sync by verifying just one proof. This method, used by Celo’s Plumo and expanded by Mina, improves efficiency but doesn’t solve all issues, such as data availability (DA) sampling. Recursive syncing can cut bandwidth by up to 99%, but proving times remain slow. Solutions like folding schemes could address this, allowing proof aggregation without falling behind block times, making light clients even more efficient.

Cross-chain

One of the use cases where ZK and Celestia interface the most is the interoperability or the cross-chain space. At least two relevant integrations have been announced to leverage Celestia’s DA layer and ZKPs in this space. 

Zeko

Zeko is a modular rollup built on Mina Protocol that utilises ZKPs to ensure transaction integrity and privacy. It leverages Celestia’s data availability (DA) layer to enhance scalability and security by separating transaction execution from data storage. The DA layer stores all transaction data off-chain, ensuring it is publicly accessible for verification without overloading the main blockchain.

Union

Union is a sovereign interoperability protocol that integrates with Celestia’s modular architecture to support cross-chain communication. Utilising Celestia’s data availability (DA) layer, Union’s zk-IBC bridge facilitates secure and decentralised asset transfers between IBC-enabled chains and Ethereum, without relying on intermediaries like multisigs. 

ZK Rollups

Polygon CDK

The integration of Celestia’s data availability (DA) layer with Polygon Chain Development Kit (CDK) enables the development of zero-knowledge (ZK)-powered Layer 2 (L2) chains on Ethereum. By incorporating Celestia’s DA layer, developers can leverage an easily pluggable solution for scalable data availability. The integration also allows for broader interoperability between ZK-powered L2s in the Polygon CDK ecosystem. 

ZK L1s

Mina

An efficient and secure DA solution becomes critical as Mina’s zkApps scale, particularly those requiring large amounts of off-chain data. Celestia addresses this and allows Mina participants to verify the availability of transaction data without needing to download the entire block. The integration enables zkApps on Mina to offload data to Celestia’s DA layer, ensuring that large-scale data is available while maintaining Mina’s minimal on-chain footprint. Additionally, by relying on Celestia’s modular architecture, Mina can focus on its zero-knowledge proof verification, while Celestia ensures the availability and verifiability of the data.

In this integration, BlobstreamX plays a key role by optimising the transfer of large data sets between Mina and Celestia’s data availability layer. 

Opportunities for ZK in Celestia

In his talk, ZK-based Improvements to Celestia at Research Day 2023, Nick White, COO of Celestia, explored several potential improvements to the network using ZKPs. Here are the ideas mentioned in the talk: 

Proving the Correctness of Block Data Encoding 

A key improvement to Celestia could be proving the correctness of block data encoding. Currently, block producers can encode blocks incorrectly, leading to difficulties in reconstructing the block. Celestia addresses this issue through a bad encoding fraud-proof, which alerts light nodes when an improperly encoded block is detected. However, this solution has latency drawbacks, requiring waiting for the fraud-proof to propagate. This latency issue is akin to delays seen in optimistic rollups, where time is needed to generate and circulate fraud proofs before action can be taken. To solve the encoding issue more efficiently, ZK proofs could be applied from the outset to prove that block encoding is correct. By doing so, block producers would provide a ZKP alongside the block itself, allowing the network to instantly verify its correctness without needing fraud-proof. This approach significantly reduces latency and enhances the system’s trust minimisation, as nodes would no longer need to wait to detect fraud before verifying the integrity of blocks.

ZK-friendly Data Root

Celestia could improve block data verification by introducing a ZK-friendly data root. This would involve restructuring how data is encoded and stored in a format easily proven using ZKPs. A ZK-friendly data root would allow nodes to verify block data availability without downloading or verifying the entire block themselves. This would enhance scalability and allow faster, more efficient verification, reducing the load on light nodes while maintaining security guarantees.

Nick also shared ideas during his talk about Increasing Censorship Resistance, In-Protocol MEV Support, and Restaking Support for Shared Sequencer Networks. 

Conclusion

Although many of the initiatives involving ZK in Celestia are still being developed, this ecosystem has the potential to adopt many use cases powered by ZKPs and produce some innovations in the ZK field. In the coming months, it will be gratifying to see new ZK rollups launching on Celestia and the intersection between privacy protocols such as Namada, Penumbra or Aztec and the modular ecosystem.