Walrus Point of Availability: The On-Chain Proof Every Blob Needs
A Proof of Availability (PoA) is Walrus's on-chain anchor. It transforms decentralized storage from a handshake—"we promise to store your data"—into a mathematical guarantee: "we have committed to storing your data and Sui has finalized this commitment."
The PoA contains critical information. It lists the blob ID, the cryptographic commitment (hash), and the threshold of validators who signed storage attestations. Most importantly, it records the epoch in which the storage obligation began. This timestamp becomes crucial for enforcement.
The PoA has immediate effects. Once finalized on-chain, smart contracts can reference it with certainty. An application can call a contract function saying "verify blob X exists according to PoA Y" and receive cryptographic proof without trusting any single validator. The contract enforces that only PoAs matching the commitment hash are valid.
The PoA also enables enforcement. If a validator that signed a PoA later fails to serve the blob when requested, the client can prove misbehavior on-chain. The validator's signature is evidence of acceptance. Its later unavailability is provable dishonesty. Slashing and penalties follow automatically.
The PoA transforms storage from a best-effort service into a verifiable obligation. Validators cannot silently lose data—the PoA proves they accepted responsibility. Clients cannot dispute commitments—the PoA proves what was agreed. Disputes are resolved mathematically, not through negotiation.
Every blob written to Walrus gets one PoA. That single on-chain record becomes the source of truth.
