Make Offer Signature Structure

To authorize the makeOffer operation within the Name Service, the user (the offeror) 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 offeror's intent and authorization to place a specific offer on a target username under the specified terms (amount, expiration).

Signed Message Format

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

SignatureRecover.signatureVerification(
    Strings.toString(evvmID),                           // EVVM ID as string
    "makeOffer",                                        // Action type
    string.concat(                                      // Concatenated parameters
        _username,
        ",",
        Strings.toString(_dateExpire),
        ",",
        Strings.toString(_amount),
        ",",
        Strings.toString(_nameServiceNonce)
    ),
    signature,
    signer
);

Internal Message Construction

This results in a message format:

"{evvmID},makeOffer,{username},{dateExpire},{amount},{nameServiceNonce}"

Message Components

The signature verification takes three main parameters:

1. EVVM ID (String):

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

2. Action Type (String):

• Fixed value: "makeOffer"
• Purpose: Identifies this as a make offer operation

3. Concatenated Parameters (String): The parameters are concatenated with comma separators:

3.1. Target Username (String):

• The _username string itself
• Purpose: Specifies the username on which the offer is being placed

3.2. Offer Expiration Date (String):

• The result of Strings.toString(_dateExpire)
• Purpose: Unix timestamp indicating when this offer expires

3.3. Offer Amount (String):

• The result of Strings.toString(_amount)
• Purpose: The quantity of tokens being offered in exchange for the username

3.4. Name Service Nonce (String):

• The result of Strings.toString(_nameServiceNonce)
• Purpose: Provides replay protection for make offer actions

Example

Here's a practical example of constructing a signature message for making an offer:

Scenario: User wants to make an offer on username "alice"

Parameters:

• evvmID: 1 (EVVM instance ID)
• _username: "alice"
• _dateExpire: 1735689600 (Unix timestamp for January 1, 2025)
• _amount: 1000 (tokens)
• _nameServiceNonce: 5

Signature verification call:

SignatureRecover.signatureVerification(
    "1",  // evvmID as string
    "makeOffer", // action type
    "alice,1735689600,1000,5",
    signature,
    signer
);

Final message to be signed (after internal concatenation):

1,makeOffer,alice,1735689600,1000,5

EIP-191 formatted message hash:

keccak256(abi.encodePacked(
    "\x19Ethereum Signed Message:\n36",
    "1,makeOffer,alice,1735689600,1000,5"
))

Concatenated parameters breakdown:

1. alice - The username being offered on
2. 1735689600 - Unix timestamp when the offer expires
3. 1000 - Amount of tokens being offered
4. 5 - The offeror's name service nonce

Technical Details

• Message Format: "{evvmID},{functionName},{parameters}"
• EIP-191 Compliance: Uses "\x19Ethereum Signed Message:\n" prefix with message length
• Expiration Logic: _dateExpire must be a future Unix timestamp
• Token Amount: _amount represents the total tokens offered for the username
• Replay Protection: _nameServiceNonce prevents replay attacks for offer actions
• EVVM ID: Identifies the specific EVVM instance for signature verification

tip

• The function selector d82e5d8b is the first 4 bytes of the keccak256 hash of the function signature for verifyMessageSignedForMakeOffer
• Strings.toString converts a number to a string (standard OpenZeppelin utility)
• The signature verification uses the EIP-191 standard for message signing
• The _dateExpire parameter should be a Unix timestamp representing when the offer expires
• The _amount represents the total amount of tokens being offered for the username