Polygon Avail

Polygon Avail is a modular blockchain component, specifically a data availability (DA) layer, that provides a secure and scalable foundation for other blockchains to verify that transaction data is published and accessible. It solves the core data availability problem by using advanced cryptographic techniques like KZG polynomial commitments and data availability sampling (DAS). This allows light clients to efficiently and trustlessly confirm that all data for a block is available without downloading the entire dataset, a critical requirement for rollups and other modular execution layers to operate securely.

The architecture of Avail is purpose-built for high-throughput data publishing. It functions as a blobspace, a term for a blockchain optimized for storing large amounts of data (blobs) from other chains. Its consensus mechanism, based on Proof-of-Stake (PoS) and Nominated Proof-of-Stake (NPoS), secures this data. By offloading the costly task of data publication and verification, execution layers (like optimistic rollups or zk-rollups) can post their transaction data to Avail, drastically reducing their operational costs and increasing transaction throughput while maintaining the security guarantees of data availability.

A key innovation is its light client protocol, which enables even resource-constrained devices to participate in the network's security. Through DAS, these clients randomly sample small pieces of published block data. Statistically, if enough samples are successful, the client can be confident the entire data is available. This creates a highly decentralized and robust security model. Furthermore, Avail provides data availability proofs, which other chains can use to verify data was published correctly, forming a trustless bridge between the execution and data availability layers.

The primary use case for Polygon Avail is serving as the data availability layer for modular blockchain stacks. For example, a sovereign rollup or a validium can use Avail to ensure its data is available, enabling faster and cheaper transactions than if it were posted to a monolithic chain like Ethereum Mainnet. It also enables the creation of new, application-specific blockchains that do not need to worry about the complexities of achieving consensus on data availability, allowing developers to focus solely on execution logic and state transitions.

In the broader Polygon 2.0 vision, Avail is one pillar of a unified ecosystem of ZK-powered L2 chains. It interoperates with other Polygon components like the Polygon zkEVM and the Polygon CDK (Chain Development Kit). By providing a scalable, secure, and dedicated data layer, Avail aims to be a foundational piece of infrastructure for the next generation of scalable blockchain networks, facilitating the transition from monolithic to modular blockchain design across the industry.

Polygon Avail operates as a data availability layer, a specialized blockchain whose primary function is to guarantee that transaction data for other chains is published and accessible. It uses advanced cryptographic techniques like KZG polynomial commitments and data availability sampling (DAS). Validators on Avail order transactions into blocks and generate a short cryptographic commitment, while light clients can efficiently verify data availability by randomly sampling small pieces of the block without downloading it entirely.

The core innovation is its decoupling of data availability from execution. A rollup or standalone chain (often called a sovereign rollup) posts its compressed transaction data to Avail. By using Avail's secure and scalable ledger as a data source, these chains no longer need to rely on a monolithic Layer 1 for data publishing. This separation allows execution layers to achieve higher throughput and lower costs, as their scalability is no longer bottlenecked by the data capacity of their settlement layer.

Developers interact with Avail by submitting data blobs via a simple transaction. The network orders these blobs, provides a cryptographic proof of their inclusion, and makes the data available for a verifiable period. Clients, including rollup provers or bridge watchers, can then use the data availability proofs to reconstruct the state of the connected chain or verify fraud proofs, ensuring security without trusting a central party.

Key technical components enabling this include erasure coding, which redundantly encodes block data so it can be recovered even if some parts are missing, and the aforementioned DAS protocol. This combination allows the network to maintain security with a high number of light clients, creating a robust and trust-minimized foundation for the modular blockchain stack. Avail is optimized purely for data, not smart contract execution, which is its defining architectural advantage.

Polygon Avail's foundation is a KZG polynomial commitment scheme, a cryptographic primitive that allows a prover (the sequencer) to commit to a large block of data by representing it as a polynomial and publishing a single, short KZG commitment. This commitment acts as a succinct cryptographic fingerprint, binding the prover to the data without revealing it. The scheme's key property is that it enables efficient generation of proofs for any specific piece of data within the committed block, allowing light clients to verify data inclusion without downloading the entire block.

To verify data availability, Avail employs Data Availability Sampling (DAS), a probabilistic technique where light clients randomly sample small, unique chunks of the block data. Using the KZG commitment, a client can request a proof for each sampled chunk to verify it is part of the originally committed block. By successfully sampling a sufficient number of random chunks, a client can achieve statistical certainty that the entire dataset is available. This process is highly scalable, as clients only need to download a tiny fraction of the total block data to participate in network security.

The interaction between KZG commitments and DAS creates a powerful security model. The KZG commitment provides binding and enables efficient proofs, while DAS provides probabilistic guarantee of availability. If a malicious sequencer withholds even a small portion of data, the probability that a sampling client will detect the missing data increases exponentially with each sample. This design allows a large network of light clients to securely and trustlessly monitor data availability, forming the backbone of Avail's security without requiring any single node to reconstruct the full block.

From an implementation perspective, block data is arranged into a two-dimensional matrix, with each cell representing a data chunk. The KZG commitment is generated for each row and column of this matrix, creating a structure that supports efficient sampling and fraud proofs. This 2D Reed-Solomon encoding adds redundancy, ensuring data can be recovered even if a significant portion of chunks are missing, provided enough samples are collected. This redundancy is crucial for the data recovery process if the original block publisher becomes unavailable.

The security and efficiency of this system enable key blockchain scaling properties. By offloading data availability verification to light clients via DAS, full nodes are not a bottleneck, allowing block sizes to increase significantly. This architecture is foundational for modular blockchain designs, where execution layers (like rollups) can post their transaction data to Avail, relying on its cryptographic guarantees instead of replicating data across all nodes in their own network.