0007-separate-slashing-percentages

Abstract

This proposal introduces two different slashing percentages, one for indexing disputes and another for query disputes. This change allows slashing percentages to be set in such a way that accounts for the different risks of producing slashable faults while indexing and querying.

Motivation

One of the security mechanisms in The Graph relies on filing disputes whenever an Indexer presents a wrong Proof of Indexing (PoI) or if it returns a query with inaccurate data.

After any participant files a dispute, the Arbitrators will decide if the dispute is valid according to norms established via protocol governance. If the Arbitrator accepts the dispute, the offending Indexer's stake is slashed according to a governance parameter called slashingPercentage.

The issue with having a single slashingPercentage parameter for both indexing and query disputes is that an Indexer, in the regular day-to-day operation, will return a disproportionately higher amount of queries than PoIs. As a result, servicing queries is a higher-risk activity than indexing.

This proposal allows two different slashing percentages to balance the risk, one for indexing disputes and another for query disputes.

Detailed Specification

All the changes required to implement this proposal are related to the DisputeManager contract.

Current Behavior

By default, every time disputes are accepted, indexers get slashed on the their total stake using the single slashingPercentage protocol parameter, both for indexing dispute and query disputes.

Proposed Changes

1) Introduce separate protocol parameters for query and indexing slashing

Change set slashing percentage signature to accept two different parameters.

function setSlashingPercentage(uint32 _qryPercentage, uint32 _idxPercentage)

Add two state variables in the contract storage:

uint32 public qrySlashingPercentage;
uint32 public idxSlashingPercentage;

2) Add dispute type when created

Whenever a new dispute is created we store the dispute type. This way the contract can resolve using the appropiate slashing percentage.

enum DisputeType { Null, IndexingDispute, QueryDispute }

// Disputes contain info necessary for the Arbitrator to verify and resolve
struct Dispute {
    address indexer;
    address fisherman;
    uint256 deposit;
    bytes32 relatedDisputeID;
    DisputeType disputeType;
}

3) Dispute resolution

Update the acceptDispute function to slash based on the dispute type.

Backwards Compatibility

The current solution changes the getter of the previous slashingPercentage variable. Anyone doing an integration with the contracts need to take special care to call the proper idxSlashingPercentage or qrySlashingPercentage according to their needs.

Additionally, the function setSlashingPercentage(uint32 _percentage) changed to setSlashingPercentage(uint32 _qryPercentage, uint32 _idxPercentage).

Validation

Audits

An audit of the changes described in this document has been performed by OpenZeppelin.

Testnet

The implementation is yet to be deployed to testnet and the source code verified in Etherscan.

Copyright Waiver

Copyright and related rights waived via CC0.