Proof of Indexing

A PoI is a Merkle root hash that cryptographically commits to the exact state of an indexer's database for a specific subgraph deployment and block. It is generated by hashing the ordered set of entity operations (creates, updates, deletions) processed up to that point. This deterministic nature means any indexer processing the same data with the same rules must produce an identical PoI, enabling objective verification.

The primary function of a PoI is to provide a cryptographic proof that an indexer's served data is correct. Consumers or verifiers can challenge an indexer by requesting a fraud proof. The indexer must then provide the PoI and the underlying data, allowing anyone to recompute the hash and confirm a mismatch, proving the indexer served incorrect information.

Each PoI is uniquely scoped. It is tied to:

• A specific subgraph manifest (defining the data schema and mapping logic).
• A specific Ethereum block number (or block hash). This granular scoping prevents ambiguity and allows for precise pinpointing of which data slice is being proven, enabling efficient partial verification and dispute resolution.

In networks like The Graph, PoIs are the core input for the Dispute Resolution layer (e.g., the Arbitration Charter). When a query dispute is raised, arbitrators compare the PoIs from the challenged and honest indexers. A divergence in PoIs serves as incontrovertible evidence of a fault, allowing for the slashing of the malicious indexer's stake and rewarding the challenger.

PoIs allow the network to decentralize trust. Consumers do not need to trust an indexer's claim; they can cryptographically verify it. This enables a marketplace where multiple, untrusted indexers can compete to serve data, with PoIs providing the mechanism to economically punish bad actors and reward honest ones, aligning incentives without a central authority.

Unlike Proof of Work (securing consensus) or Proof of Stake (validating blocks), Proof of Indexing is a Proof of Correct Execution. It proves the correctness of off-chain computation (data indexing) rather than the right to produce a block. It's a verifiable state transition proof for a specific application logic, making it a critical primitive for decentralized oracle and data networks.

The core security of PoI lies in its deterministic execution. Given the same block hash and subgraph manifest, any honest indexer must produce an identical Merkle root for the processed data. This allows verifiers (e.g., Fishermen) to re-execute queries off-chain and challenge mismatched proofs, slashing the indexer's stake.

Indexers must stake the network's native token (e.g., GRT) to participate. This stake acts as a security bond that can be slashed for provable misbehavior, such as:

• Serving incorrect query results.
• Failing to submit a valid PoI.
• Engaging in malicious indexing. The threat of financial loss disincentivizes attacks and ensures network reliability.

Token holders who do not run infrastructure can delegate their stake to an indexer, earning a share of query fees and inflation rewards. This pools security but introduces risks:

• Delegator slashing: A portion of a delegator's stake can be slashed if their chosen indexer is penalized.
• Reward cuts: Indexers can set a commission rate on delegated rewards. Delegators must assess indexer performance and reliability.

Fishermen are network participants who verify PoI attestations and query responses. They can submit fraud proofs to a dispute resolution layer (like an Arbitrum-style rollup). Successful challenges reward the fisherman with a portion of the slashed stake, creating a crypto-economic game that continuously audits indexer honesty.

PoI cryptographically ties indexed data to its on-chain source. It proves that the data:

• Originated from a specific block hash.
• Was transformed according to the declared subgraph logic. This prevents indexers from inventing or tampering with data, as any alteration would produce a different, invalid proof.

The requirement for substantial, slashable stake provides Sybil resistance. An attacker cannot cheaply create many fake indexer identities to corrupt the network. The cost of attack is tied to the total value staked, making it economically irrational to attempt to manipulate the indexed data at scale.

The open-source data specification that defines what data to index and how to transform it. A subgraph manifest specifies the smart contract, events of interest, and mapping logic. The Proof of Indexing is a unique hash derived from the subgraph's deployment ID and the specific block range it has processed.

A broader cryptographic concept of which PoI is a specific type. An attestation is a verifiable claim or proof about a statement. In decentralized systems, attestations (like PoIs) allow independent verification of work without needing to trust the entity providing the data, forming the basis for cryptographic guarantees.

The network operator responsible for ingesting blockchain data. An indexer runs a node that processes events from a subgraph, stores the resulting data in a queryable database, and serves GraphQL queries. They periodically generate and submit Proof of Indexing to the network to prove faithful execution and earn rewards.

A cryptographic function that requires a prescribed amount of sequential computation to evaluate. Some decentralized oracle and indexing designs propose using VDFs in conjunction with or as an alternative to PoI schemes to create time-based proofs that certain data was available or an event was processed at a specific point in time.