Walrus: An Efficient Decentralized Storage Network

TL;DR

Walrus is a decentralized storage system that combines high security, efficient recovery, and low overhead through innovative erasure coding and epoch protocols, suitable for scalable, high-integrity applications.

Contribution

Walrus introduces RedStuff, a novel 2D erasure coding protocol supporting asynchronous networks and low bandwidth recovery, along with a multi-stage epoch change protocol for node churn.

Findings

Achieves 4.5x replication with high security.

Supports recovery bandwidth proportional to lost data.

Maintains availability during node churn.

Abstract

Decentralized storage systems face a fundamental trade-off between replication overhead, recovery efficiency, and security guarantees. Current approaches either rely on full replication, incurring substantial storage costs, or employ trivial erasure coding schemes that struggle with efficient recovery especially under high storage-node churn. We present Walrus, a novel decentralized blob storage system that addresses these limitations through multiple technical innovations. At the core of Walrus is RedStuff, a two-dimensional erasure coding protocol that achieves high security with only 4.5x replication factor, while enabling self-healing recovery that requires bandwidth proportional to only the lost data $(O(|blob|/n)$ versus $O(|blob|)$ in traditional systems). Crucially, RedStuff is the first protocol to support storage challenges in asynchronous networks, preventing adversaries from exploiting network delays to pass verification without actually storing data. Walrus also introduces a novel multi-stage epoch change protocol that efficiently handles storage node churn while maintaining uninterrupted availability during committee transitions. Our system incorporates authenticated data structures to defend against malicious clients and ensures data consistency throughout storage and retrieval processes. Experimental evaluation demonstrates that Walrus achieves practical performance at scale, making it suitable for a wide range of decentralized applications requiring high-integrity, available blob storage with reasonable overhead.