Information Dispersal with Provable Retrievability for Rollups

TL;DR

This paper introduces Semi-AVID-PR, an efficient, privacy-preserving data dispersal protocol for rollups that ensures data retrievability without comprehensive termination, suitable for blockchain scalability solutions.

Contribution

It presents Semi-AVID-PR, a novel verifiable information dispersal scheme optimized for rollups, with provable retrievability, privacy, and no need for on-chain contract modifications.

Findings

Disperses 22 MB among 256 nodes with up to 85 adversaries

Requires approximately 70 MB total communication and storage

Completes in under 41 seconds on a standard server

Abstract

The ability to verifiably retrieve transaction or state data stored off-chain is crucial to blockchain scaling techniques such as rollups or sharding. We formalize the problem and design a storage- and communication-efficient protocol using linear erasure-correcting codes and homomorphic vector commitments. Motivated by application requirements for rollups, our solution Semi-AVID-PR departs from earlier Verifiable Information Dispersal schemes in that we do not require comprehensive termination properties. Compared to Data Availability Oracles, under no circumstance do we fall back to returning empty blocks. Distributing a file of 22 MB among 256 storage nodes, up to 85 of which may be adversarial, requires in total ~70 MB of communication and storage, and ~41 seconds of single-thread runtime (<3 seconds on 16 threads) on an AMD Opteron 6378 processor when using the BLS12-381 curve. Our solution requires no modification to on-chain contracts of Validium rollups such as StarkWare's StarkEx. Additionally, it provides privacy of the dispersed data against honest-but-curious storage nodes. Finally, we discuss an application of our Semi-AVID-PR scheme to data availability verification schemes based on random sampling.