Owner: @Daniel Sanchez Quiros

Reviewers: 🟢@Álvaro Castro-Castilla 🟢@Daniel Kashepava 🟢@Gusto Bacvinka

Introduction

NomosDA is the scalability solution protocol for data availability within the Nomos network. This document delineates the protocol's structure at the network level, identifies participants, and describes the interactions among its components.

Please note that this document does not delve into the cryptographic aspects of the design. For comprehensive details on the cryptographic operations, refer to the Encoding Specification.

Objectives

NomosDA was created to ensure that data from Nomos zones is distributed, verifiable, immutable, and accessible. At the same time, it is optimised for the following properties:

• Decentralization: NomosDA’s data availability guarantees must be achieved with minimal trust assumptions and centralised actors. Therefore, permissioned DA schemes involving a Data Availability Committee (DAC) had to be avoided in the design. Schemes that require some nodes to download the entire blob data were also off the list due to the disproportionate role played by these “supernodes”.
• Scalability: NomoDA is intended to be a bandwidth-scalable protocol, ensuring that its functions are maintained as the Nomos network grows. Therefore, NomosDA was designed to minimise the amount of data sent to participants, reducing the communication bottleneck and allowing more parties to participate in the DA process.

To achieve the above properties, NomosDA splits up data submitted to it and distributes it among network participants, with cryptographic mechanisms used to verify the data’s integrity. A major feature of this design is that parties who wish to receive an assurance of data availability can do so very quickly and with minimal hardware requirements. However, this comes at the cost of additional complexity and resources required by more integral participants.

Requirements

In order to ensure that the above objectives are met, the NomosDA network requires a group of participants that undertake a greater burden in terms of active involvement in the protocol. Recognising that not all node operators can do so, NomosDA assigns different roles to different kinds of participants, depending on their ability and willingness to contribute more computing power and bandwidth to the protocol. It was therefore necessary for NomosDA to be implemented as an opt-in Service Network.

Because the NomosDA network has an arbitrary amount of participants, and the data is split into a fixed number of portions (see the Encoding & Verification Specification), it was necessary to define exactly how each portion is assigned to a participant who will receive and verify it. This assignment algorithm must also be flexible enough to ensure smooth operation in a variety of scenarios, including where there are more or fewer participants than the number of portions.

Overview

Network Participants

The NomosDA network includes three categories of participants:

• Encoders: Tasked with the encoding and dispersal of data blobs.
• DA Nodes: Receive and verify the encoded data, subsequently temporally storing it for further network validation through sampling.
• Light Nodes: Employ sampling to ascertain data availability.

Network Distribution