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Use Resource Accounts in Apps

A resource account is a developer feature used to manage resources independent of an account managed by a user, specifically publishing modules and automatically signing for transactions. For example, a developer may use a resource account to manage an account for module publishing, say managing a contract. The contract itself does not require a signer post initialization. A resource account gives you the means for the module to provide a signer to other modules and sign transactions on behalf of the module.

Typically, a resource account is used for two main purposes:

  • Store and isolate resources; a module creates a resource account just to host specific resources.
  • Publish module as a standalone (resource) account, a building block in a decentralized design where no private keys can control the resource account. The ownership (SignerCap) can be kept in another module, such as governance.

Restrictions​

In Aptos, a resource account is created based upon the SHA3-256 hash of the source's address and additional seed data. A resource account can be created only once. An entity may call create_account in an attempt to claim an account ahead of the creation of a resource account. But if a resource account is found, Aptos will transition ownership of the account over to the resource account. This is done by validating that the account has yet to execute any transactions and that the Account::signer_capbility_offer::for is none. The probability of a collision where someone has legitimately produced a private key that maps to a resource account address is improbably low.

Setup​

To properly set a resource account up, you will need to initialize the mint_nft module and retrieve the signer capability from both the resource account and module account. To do so, call create_resource_account_and_publish_package to publish the module under the resource account's address.

You have three options for creating a resource account:

  • create_resource_account_and_publish_package - creates the resource account and results in loss of access to the resource account by design, because resource accounts are used to make contracts autonomous and immutable.
  • create_resource_account_and_fund - creates the resource account and funds it, retaining access to the resource account's signer until explicitly calling retrieve_resource_account_cap.
  • create_resource_account - merely creates the resource account but doesn't fund it, retaining access to the resource account's signer until explicitly calling retrieve_resource_account_cap.

Follow these steps and examples, which assume use of create_resource_account_and_publish_package:

  1. Initialize the module as shown in the minting.move example.
  2. Call create_resource_account_and_publish_package to publish the module under the resource account's address, such as in the mint_nft.rs end-to-end example.
  3. Retrieve the signer cap from the resource account + module account as shown in the minting.move example.

Note, if the above resource_account signer is not already set up as a resource account, retrieving the signer cap will fail. The source_addr field in the retrieve_resource_account_cap function refers to the the address of the source account, or the account that creates the resource account.

For an example, see the SignerCapability employed by the mint_nft function in minting.move.

For more details, see the "resource account" references in resource_account.move and account.move.