Data Availability by Celestia

What is Celestia

Celestia is a modular data availability (DA) network that securely scales with the number of users, making it easy for anyone to launch their own blockchain.

Rollups and L2s use Celestia as a network for publishing and making transaction data available for anyone to download. For them, Celestia provides high-throughput DA that can be verified easily with a light node.

And by making the blockchain stack modular, anyone can launch their own blockchain without needing a validator set.

Two key features of Celestia's DA layer are:

• Data availability sampling (DAS)

• Namespaced Merkle trees (NMTs).

Both features are novel blockchain scaling solutions: DAS enables light nodes to verify data availability without needing to download an entire block; NMTs enable execution and settlement layers on Celestia to download transactions that are only relevant to them.

Data availability sampling

Celestia employs light nodes for data availability and integrity, utilizing a novel approach called Data Availability Sampling (DAS). Light nodes perform random sampling, facilitated by a 2D Reed-Solomon encoding scheme, multiple times across block segments.

Each successful sample boosts confidence in data availability by 50%, reaching a validity threshold of 99% for the entire block.

Think of it like this: There are two coins where one always lands on heads, and the other has a 50% probability of landing on heads or tails. You are given one of these two coins. Now, how do you figure out which coin you have? You keep flipping. You likely have the heads-only coin if the coin keeps landing on heads.

This approach to data availability is scalable. As more light nodes join the network to sample data, the block size increases, which allows for more throughput.

Namespaced Merkle trees

Celestia serves as a rollup-agnostic DA layer by allowing rollup nodes to download transaction data that is relevant to them for execution and settlement. This partition of different rollup data on Celestia is done through Namespaced Merkle Trees (NMTs).

An NMT helps Celestia organize data into different categories called namespaces. Each namespace represents a data set associated with one application or rollup. The Merkle Tree is used to index the contents of the data set, and then the DA layer sends the application with the requested data and proofs.