Add Custom Metadata Signature Structure

To authorize the addCustomMetadata operation within the Name Service, the user who currently owns the username must generate a cryptographic signature compliant with the EIP-191 standard using the Ethereum Signed Message format.

The signature verification process uses the SignatureRecover library. This signature proves the current username owner's intent and authorization to add or update a specific custom metadata field (_value) associated with their identity (_identity).

Signed Message Format

The signature verification uses the SignatureRecover.signatureVerification function with the following structure:

SignatureRecover.signatureVerification(
    Strings.toString(evvmID),                           // EVVM ID as string
    "addCustomMetadata",                                // Action type
    string.concat(                                      // Concatenated parameters
        _identity,
        ",",
        _value,
        ",",
        Strings.toString(_nameServiceNonce)
    ),
    signature,
    signer
);

Internal Message Construction

This results in a message format:

"{evvmID},addCustomMetadata,{identity},{value},{nameServiceNonce}"

Message Components

1. EVVM ID (String):

• The result of Strings.toString(evvmID)
• Purpose: Identifies the specific EVVM instance

2. Action Type (String):

• Fixed value: "addCustomMetadata"
• Purpose: Identifies this as an add custom metadata operation

3. Concatenated Parameters (String):

3.1. Target Identity (String):

• The _identity string itself
• Purpose: Specifies the identity (username) to which this custom metadata applies

3.2. Metadata Value (String):

• The _value string itself, exactly as provided by the user
• Purpose: Represents the custom data being associated with the identity

3.3. Name Service Nonce (String):

• The result of Strings.toString(_nameServiceNonce)
• Purpose: Provides replay protection for metadata operations

Example

Scenario: Owner wants to add custom metadata to their identity "alice"

Parameters:

• evvmID: 1
• _identity: "alice"
• _value: "https://alice.example.com/profile"
• _nameServiceNonce: 12

Signature verification call:

SignatureRecover.signatureVerification(
    "1",
    "addCustomMetadata",
    "alice,https://alice.example.com/profile,12",
    signature,
    signer
);

Final message to be signed:

1,addCustomMetadata,alice,https://alice.example.com/profile,12

EIP-191 formatted message hash:

keccak256(abi.encodePacked(
    "\x19Ethereum Signed Message:\n59",
    "1,addCustomMetadata,alice,https://alice.example.com/profile,12"
))

Technical Details

• Message Format: "{evvmID},{functionName},{parameters}"
• EIP-191 Compliance: Uses "\x19Ethereum Signed Message:\n" prefix with message length
• Authorization: Only the current owner of the identity can add custom metadata
• Flexible Data: _value can contain any string data (URLs, descriptions, custom information)
• Metadata Management: Allows users to associate additional information with their identities
• Replay Protection: _nameServiceNonce prevents replay attacks
• EVVM ID: Identifies the specific EVVM instance for signature verification