ERC-1497: Evidence Standard

The V1 evidence standard defining how arbitrable contracts share MetaEvidence and Evidence with Kleros arbitrators via IPFS and event logs.

ERC-1497 is the V1 evidence standard. Kleros V2 replaces MetaEvidence with Dispute Templates registered in the DisputeTemplateRegistry, and extends evidence to support cross-chain submission. See the Architecture guide for V2 details.

Overview

ERC-1497 standardizes how DApps share context and evidence during dispute resolution. It defines two categories of information:

• MetaEvidence: The context of a dispute: the agreement, parties involved, ruling options, and the question jurors need to answer. Each dispute has one piece of MetaEvidence, created at the same time as the agreement.
• Evidence: Proof submitted by any party to support their position in a dispute.

Both are stored off-chain (typically on IPFS) and referenced on-chain through event logs.

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Interface

ERC-1497 introduces three events:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "../IArbitrator.sol";

interface IEvidence {
    /// @dev Emitted when meta-evidence is submitted.
    /// @param _metaEvidenceID Unique identifier of meta-evidence.
    /// @param _evidence IPFS path to metaevidence JSON.
    event MetaEvidence(
        uint256 indexed _metaEvidenceID,
        string _evidence
    );

    /// @dev Emitted when evidence is submitted.
    /// @param _arbitrator The arbitrator for the dispute.
    /// @param _evidenceGroupID Unique identifier of the evidence group
    ///        (typically the dispute ID or external ID).
    /// @param _party The address submitting the evidence.
    /// @param _evidence IPFS path to evidence JSON.
    event Evidence(
        IArbitrator indexed _arbitrator,
        uint256 indexed _evidenceGroupID,
        address indexed _party,
        string _evidence
    );

    /// @dev Emitted when a dispute is created to link meta-evidence
    ///      and evidence group to the dispute.
    /// @param _arbitrator The arbitrator for the dispute.
    /// @param _disputeID ID of the dispute in the Arbitrator contract.
    /// @param _metaEvidenceID ID to look up the MetaEvidence event.
    /// @param _evidenceGroupID ID for the evidence group.
    event Dispute(
        IArbitrator indexed _arbitrator,
        uint256 indexed _disputeID,
        uint256 _metaEvidenceID,
        uint256 _evidenceGroupID
    );
}

---

MetaEvidence JSON

MetaEvidence is a JSON file hosted on IPFS that provides dispute context:

{
  "category": "Escrow",
  "title": "Payment for website development",
  "description": "Alice hired Bob to develop an e-commerce website...",
  "question": "Should the payment be released to the developer?",
  "rulingOptions": {
    "type": "single-select",
    "titles": ["Refund Buyer", "Pay Developer"],
    "descriptions": [
      "Return the funds to the buyer",
      "Release the funds to the developer"
    ]
  },
  "fileURI": "/ipfs/QmContractTerms...",
  "fileHash": "0x...",
  "evidenceDisplayInterfaceURI": "/ipfs/QmEvidenceDisplay..."
}

Field	Description
title	Short title for the dispute
description	Detailed context for jurors
question	The question jurors must answer
rulingOptions	Labels and descriptions for each ruling choice
fileURI	IPFS path to the agreement or contract document
fileHash	Hash of the linked file for integrity verification
evidenceDisplayInterfaceURI	Optional custom UI for displaying evidence

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Evidence JSON

Each piece of evidence is a JSON file:

{
  "name": "Delivery confirmation email",
  "description": "Email from the developer confirming delivery of the website",
  "fileURI": "/ipfs/QmEvidence...",
  "fileHash": "0x...",
  "fileTypeExtension": "pdf"
}

---

Integrity Verification

The JSON for both MetaEvidence and Evidence contains fileHash fields. Arbitrators use these hashes to verify that files have not been tampered with after submission. IPFS content-addressing provides built-in integrity for files hosted on IPFS, since the CID itself is derived from the file content.

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Usage in a V1 Contract

contract SimpleEscrowWithERC1497 is IArbitrable, IEvidence {
    // Emit MetaEvidence at contract creation
    constructor(string memory _metaEvidence) {
        emit MetaEvidence(0, _metaEvidence);
    }

    // When creating a dispute, link it to the meta-evidence
    function raiseDispute() external payable {
        uint256 disputeID = arbitrator.createDispute{value: msg.value}(
            numberOfChoices, extraData
        );
        emit Dispute(arbitrator, disputeID, 0, 0);
    }

    // Allow parties to submit evidence
    function submitEvidence(string calldata _evidence) external {
        emit Evidence(arbitrator, 0, msg.sender, _evidence);
    }
}

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V2 Replacement

In V2, ERC-1497 is replaced by:

• Dispute Templates: Registered in DisputeTemplateRegistry with Mustache-style variable interpolation. Templates define the dispute question, ruling options, and policy reference.
• DisputeRequest event: Replaces the Dispute event, linking disputes to templates by templateId.
• Cross-chain evidence: Evidence can be submitted on either the home or foreign chain, with the Court UI consolidating from both.

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References

• ERC-1497 on GitHub
• Reference implementation
• Archon library JavaScript library for fetching and validating evidence