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Withdrawal Signature Structure

To authorize withdrawal operations from the EVVM protocol, the user whose funds are being withdrawn (from) must generate a cryptographic signature compliant with the EIP-191 standard.

This signature proves the user's intent and authorization to withdraw a specific amount of a token to a designated external addressToReceive (if any), according to the parameters included in the signed message.

Signed Message Format​

The message is constructed by concatenating the following components as strings, separated by commas (,):

string.concat(
  _priority_boolean ? "920f3d76" : "52896a1f",
  ",",
  AdvancedStrings.addressToString(addressToReceive),
  ",",
  AdvancedStrings.addressToString(_token),
  ",",
  Strings.toString(_amount),
  ",",
  Strings.toString(_priorityFee),
  ",",
  Strings.toString(_nonce),
  ",",
  _priority_boolean ? "true" : "false"
)

1. Withdrawal Identifier (Hex String):

  • Value: Depends on the _priority_boolean flag indicating the intended nonce type:
    • 920f3d76: Used for asynchronous withdrawals (_priority_boolean is true).
    • 52896a1f: Used for synchronous withdrawals (_priority_boolean is false).

2. Recipient Address (String):

  • Value: The result of AdvancedStrings.addressToString(addressToReceive).
  • Purpose: The string representation of the destination address on the external network where the withdrawn tokens should be sent via the bridge.

3. Token Address (String):

  • Value: The result of AdvancedStrings.addressToString(_token).
  • Purpose: The string representation of the ERC20 token contract address being withdrawn.

4. Amount (String):

  • Value: The result of Strings.toString(_amount).
  • Purpose: The string representation of the quantity (uint256) of the token the user authorizes to be withdrawn.

5. Priority Fee (String):

  • Value: The result of Strings.toString(_priorityFee).
  • Purpose: The string representation of the fee (uint256) included in the transaction authorization. (Note: Whether this fee is paid to an executor depends on the specific withdrawal function called, e.g., NoMateStaking versions typically do not pay this to the executor).

6. Nonce (String):

  • Value: The result of Strings.toString(_nonce).
  • Purpose: The string representation of the user's (from address's) nonce required for replay protection. This must match the user's expected synchronous nonce if _priority_boolean is false, or be an unused asynchronous nonce if _priority_boolean is true.

7. Priority Flag (String):

  • Value: The literal string "true" if _priority_boolean is true (asynchronous), or "false" if _priority_boolean is false (synchronous).
  • Purpose: Explicitly includes the intended nonce context (sync/async) in the signed message, aligning with the chosen Withdrawal Identifier.
tip
  • addressToString converts an address to a lowercase string
  • Strings.toString converts a number to a string
  • _priority_boolean indicates whether the payment will be executed asynchronously (true) or synchronously (false)
  • The function selector (4faa1fa2 for synchronous or f4e1895b for asynchronous) is determined by the _priority_boolean value