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Interacting with the Aptos Blockchain

The Aptos blockchain uses the Move virtual machine (VM) for executing operations. While many blockchains implement a set of native operations, Aptos delegates all operations to Move, including: account creation, fund transfer and publishing Move modules. To support these operations, blockchains built on top of Move must provide a framework (akin to an operating system for a computer or a minimal viable set of functions) for interacting with the blockchain. In this section, we discuss these functions, exposed via the Aptos Framework's script functions.

This guide (in concert with the Move module tutorial) will unlock the minimal amount of information required to start building rich applications on top of the Aptos blockchain. Note: the Aptos Framework is under heavy development and this document may not be up to date. The most recent framework can be found in the source code, here.

The core functions provided to users within the Aptos Framework include:

  • Sending and receiving the network coin Coin<AptosCoin>
  • Creating a new account
  • Publishing a new Move module

Note: this document assumes readers are already familiar with submitting transactions, as described in the Your first transaction tutorial.

Sending and Receiving the network coin Coin<AptosCoin>

Coin<AptosCoin> is required for paying gas fees when submitting and executing transactions. Coin<AptosCoin> can be obtained by calling the Devnet Faucet. See the Your first transaction tutorial for an example.

The payload for instructing the blockchain to perform a transfer is:

{
"type": "entry_function_payload",
"function": "0x1::Coin::transfer",
"type_arguments": ["0x1::aptos_coin::AptosCoin"],
"arguments": [
"0x737b36c96926043794ed3a0b3eaaceaf",
"1000",
]
}

This instructs the VM to execute the script 0x1::Coin::transfer with a type argument of 0x1::aptos_coin::AptosCoin. Type is required here as Coin is our standard module that can be used to create many types of Coins. See the Your first coin tutorial for an example of creating a custom Coin. The first argument is the recipient address, 0x737b36c96926043794ed3a0b3eaaceaf, and the second is the amount to transfer, 1000. The sender address is the account address that sent the transaction querying this script.

Creating a new account

The payload for instructing the blockchain to create a new account is:

{
"type": "entry_function_payload",
"function": "0x1::AptosAccount::create_account",
"type_arguments": [],
"arguments": [
"0x0c7e09cd9185a27104fa218a0b26ea88",
"0xaacf87ae9d8a5e523c7f1107c668cb28dec005933c4a3bf0465ffd8a9800a2d900",
]
}

This instructs the Move virtual machine to execute the script 0x1::AptosAccount::create_account. The first argument is the address of the account to create and the second is the authentication key pre-image (which is mentioned in Accounts). For single signer authentication, this is the public key concatenated with the 0 byte (or pubkey_A | 0x00). This is required to prevent account address land grabbing. The execution of this instruction verifies that the last 16-bytes of the authentication key are the same as the 16-byte account address. We are actively working on improving this API to support taking in a 32-byte account address that would eliminate concerns around land grabbing or account manipulation.

Publishing a new Move module

The payload for publishing a new module is:

"type": "module_bundle_payload",
"modules": [
{"bytecode": "0x..."},
],

This instructs the VM to publish the module bytecode under the sender's account. For a full length tutorial see Your first move module.

It is important to note that the Move bytecode must specify the same address as the sender's account, otherwise the transaction will be rejected. For example, assuming account address 0xe110, the Move module would need to be updated as such module 0xe110::Message, module 0xbar::Message would be rejected. Alternatively an aliased address could be used, such as module HelloBlockchain::Message but the HelloBlockchain alias would need to updated to 0xe110 in the Move.toml file. We are working with the Move team and planning on incorporating a compiler into our REST interface to mitigate this issue.