Cancel Order Signature Structure

To authorize order cancellation operations, users 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 which implements the standard Ethereum message signing protocol. The message is constructed by concatenating the EVVM ID, action type, and parameters, then wrapped with the EIP-191 prefix.

Signed Message Format

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

SignatureRecover.signatureVerification(
    Strings.toString(evvmID),        // EVVM ID as string
    "cancelOrder",                   // Action type
    string.concat(                   // Concatenated parameters
        Strings.toString(_nonce),
        ",",
        AdvancedStrings.addressToString(_tokenA),
        ",",
        AdvancedStrings.addressToString(_tokenB),
        ",",
        Strings.toString(_orderId)
    ),
    signature,
    signer
);

Internal Message Construction

Internally, the SignatureRecover.signatureVerification function constructs the final message by concatenating:

string.concat(evvmID, ",", functionName, ",", inputs)

This results in a message format:

"{evvmID},cancelOrder,{nonce},{tokenA},{tokenB},{orderId}"

EIP-191 Message Hashing

The message is then hashed according to EIP-191 standard:

bytes32 messageHash = keccak256(
    abi.encodePacked(
        "\x19Ethereum Signed Message:\n",
        Strings.toString(bytes(message).length),
        message
    )
);

This creates the final hash that the user must sign with their private key.

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: "cancelOrder"
• Purpose: Identifies this as an order cancellation operation

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

3.1. Nonce (String):

• The result of Strings.toString(_nonce)
• Purpose: Provides replay protection for the P2P Swap transaction

3.2. Token A Address (String):

• The result of AdvancedStrings.addressToString(_tokenA)
• Purpose: Identifies the token that was offered in the original order

3.3. Token B Address (String):

• The result of AdvancedStrings.addressToString(_tokenB)
• Purpose: Identifies the token that was requested in the original order

3.4. Order ID (String):

• The result of Strings.toString(_orderId)
• Purpose: Specifies the unique ID of the order to be cancelled

Example

Here's a practical example of constructing a signature message for cancelling a swap order:

Scenario: User wants to cancel their order #3 in the USDC/ETH market

Parameters:

• evvmID: 1 (EVVM instance ID)
• _nonce: 25
• _tokenA: 0xA0b86a33E6441e6e80D0c4C6C7527d72E1d00000 (USDC)
• _tokenB: 0x0000000000000000000000000000000000000000 (ETH)
• _orderId: 3

Signature verification call:

SignatureRecover.signatureVerification(
    "1",  // evvmID as string
    "cancelOrder", // action type
    "25,0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000,0x0000000000000000000000000000000000000000,3",
    signature,
    signer
);

Final message to be signed (after internal concatenation):

1,cancelOrder,25,0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000,0x0000000000000000000000000000000000000000,3

EIP-191 formatted message hash:

keccak256(abi.encodePacked(
    "\x19Ethereum Signed Message:\n134",
    "1,cancelOrder,25,0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000,0x0000000000000000000000000000000000000000,3"
))

Concatenated parameters breakdown:

1. 25 - P2P Swap nonce for replay protection
2. 0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000 - USDC token address (tokenA from original order)
3. 0x0000000000000000000000000000000000000000 - ETH address (tokenB from original order)
4. 3 - Order ID to be cancelled

Example with Different Token Pair

Scenario: User wants to cancel their order #7 in the MATE/USDC market

Parameters:

• evvmID: 1
• _nonce: 42
• _tokenA: 0x0000000000000000000000000000000000000001 (MATE)
• _tokenB: 0xA0b86a33E6441e6e80D0c4C6C7527d72E1d00000 (USDC)
• _orderId: 7

Final message to be signed:

1,cancelOrder,42,0x0000000000000000000000000000000000000001,0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000,7

Concatenated parameters breakdown:

1. 42 - P2P Swap nonce
2. 0x0000000000000000000000000000000000000001 - MATE token address
3. 0xa0b86a33e6441e6e80d0c4c6c7527d72e1d00000 - USDC token address
4. 7 - Order ID to cancel

Signature Implementation Details

The SignatureRecover library performs signature verification in the following steps:

1. Message Construction: Concatenates evvmID, functionName, and inputs with commas
2. EIP-191 Formatting: Prepends "\x19Ethereum Signed Message:\n" + message length
3. Hashing: Applies keccak256 to the formatted message
4. Signature Parsing: Splits the 65-byte signature into r, s, and v components
5. Recovery: Uses ecrecover to recover the signer's address
6. Verification: Compares recovered address with expected signer

Signature Format Requirements

• Length: Exactly 65 bytes
• Structure: [r (32 bytes)][s (32 bytes)][v (1 byte)]
• V Value: Must be 27 or 28 (automatically adjusted if < 27)

Security Considerations

Order Ownership Validation

The signature alone does not prove order ownership. The contract performs additional validation:

1. Signature Verification: Confirms the user signed the cancellation request
2. Order Existence: Verifies the order exists in the specified market
3. Ownership Check: Confirms the signer is the original order creator
4. Nonce Validation: Ensures the nonce hasn't been used before

Market Identification

The token pair (tokenA, tokenB) must match the original order exactly:

• Token Addresses: Must be identical to the original order
• Market Resolution: Used to find the correct market for the order
• Order Lookup: Combined with orderId to locate the specific order

Technical Details

• Message Format: The final message follows the pattern "{evvmID},{functionName},{parameters}"
• EIP-191 Compliance: Uses "\x19Ethereum Signed Message:\n" prefix with message length
• Hash Function: keccak256 is used for the final message hash before signing
• Signature Recovery: Uses ecrecover to verify the signature against the expected signer
• String Conversion:
  • AdvancedStrings.addressToString converts addresses to lowercase hex with "0x" prefix
  • Strings.toString converts numbers to decimal strings
• Order Identification: Requires both token pair and order ID to uniquely identify the order
• Nonce Independence: P2P Swap nonces are separate from EVVM payment nonces