Register accounts using EVM Wallets

In this section, we will create a module that enables user account registration using EVM (Ethereum Virtual Machine) wallets. This functionality allows users to sign in with EVM-compatible wallets like MetaMask and can be extended to include features such as payments.

Conceptual design

Users will register an account by signing a message with MetaMask. We achieve this by utilizing the open account registration strategy from the ft library. The following sequence diagram illustrates the registration flow:

Implementation in Rell

We will implement the registration flow by creating a new module called registration. This separation allows easy inclusion or removal of account registration features and supports multiple registration methods. Follow these steps for implementation:

1. Create a folder named registration, and within it, add a file called module.rell.

2. Add the following definitions to registration/module.rell:

src/registration/module.rell

module;

import ^.news_feed.*;
import lib.ft4.accounts.strategies.open;
import lib.ft4.accounts.strategies.{ register_account };

operation register_user(name) {
    val account = register_account();
    val user = create user ( name, account.id, account );
    create follower ( user = user, follower = user );
}

• The open strategy allows users to register themselves.
• The register_user operation registers an account, creates a user, and establishes follower information.
• The register_account function ensures that the transaction is signed by a unique EVM account.

3. In your chromia.yml file, add an exclusion for this operation to notify the ft library that the register_user operation is safe to use:

chromia.yml

blockchains:
  my_news_feed:
    module: development
    test:
      modules:
        - test
    moduleArgs:
      lib.ft4.core.admin:
        admin_pubkey: x"023BEE5A479CE5AF31F6F64EDE7BEAD394E92E4D973E1727782DB577A55E878563"
      lib.ft4.core.auth:
        evm_signatures_authorized_operations:
          - register_user

For more details on configuring your chromia.yml file, refer to the Chromia Project Configuration documentation.

4. In your main.rell file, include an import statement for the new registration module:

src/main.rell

module;

import news_feed.*;
import registration.*;

caution

While the register_user operation requires a valid EVM signature, it can expose a potential DDOS attack vector since each account corresponds to a row in the database. To mitigate this risk, consider the following strategies:

• Implement rate limiting for the operation.
• Enforce payments during registration.
• Establish an authentication layer as an intermediary.