PeerDAS: The What

Introduction

PeerDAS stands for Peer Data Availability Sampling. It is an upgrade designed to enhance Ethereum's scalability by improving how data availability is handled on the network, particularly for Layer 2 (L2) solutions like rollups. PeerDAS builds on the foundation laid by earlier upgrades, such as EIP-4844 (Proto-Danksharding), and is part of Ethereum's long-term roadmap to achieve full Danksharding, a comprehensive scaling solution.

What is Data Availability Sampling (DAS)?

Data Availability Sampling (DAS) is a technique that allows nodes in a blockchain network to verify that all the data associated with a block (e.g., transaction data or "blobs" used by rollups) is available without requiring every node to download and store the entire dataset. Instead, nodes sample small, random portions of the data. If these samples are successfully retrieved, it provides high confidence that the full data is accessible to the network. This approach relies on erasure coding, a method that adds redundant data so that the original dataset can be reconstructed even if only a portion (e.g., 50%) is available.

DAS is crucial for scaling because it reduces the storage and bandwidth burden on individual nodes, enabling Ethereum to process more transactions while maintaining decentralization and security.

What is PeerDAS?

PeerDAS is a specific implementation of DAS tailored for Ethereum's peer-to-peer (P2P) network. It was introduced as part of EIP-7594 and is expected to be integrated into Ethereum's consensus layer in an upcoming upgrade, such as the Pectra hard fork (slated for late 2025 or beyond, based on current development discussions). Here’s how PeerDAS works:

  1. Blob Data Extension: PeerDAS builds on the "blobs" introduced in EIP-4844. Blobs are large chunks of data (up to 1MB per blob initially) used by rollups to post transaction data to Ethereum Layer 1 (L1) cheaply. PeerDAS extends these blobs using one-dimensional erasure coding, transforming them into an expanded matrix of data (e.g., rows and columns) with redundancy.
  2. Distributed Custody: Instead of every node storing all blob data, PeerDAS assigns each node custody of a small subset of the data—specifically, certain "columns" of the extended matrix. Nodes are responsible for maintaining and sharing their assigned columns with peers via the P2P network.
  3. Sampling Process: To verify data availability, nodes request random samples (e.g., specific columns) from their peers. If a node can consistently retrieve its samples, it assumes the full dataset is available. If more than 50% of the data is accessible, the entire blob can be reconstructed due to erasure coding.
  4. P2P Components: PeerDAS leverages Ethereum’s existing P2P infrastructure, including gossip protocols (for broadcasting data), peer discovery (to find nodes holding specific data), and peer requests (to fetch samples). This makes it a practical "intermediate" solution, bridging the gap between EIP-4844 and full Danksharding.

PeerDAS: The Why