Starknet’s Account Abstraction Workshop

In this workshop you will learn how to create an account contract with a single signer that uses the STARK-friendly elliptic curve to sign transactions. The final code is inspired by Open Zeppelin’s account contract.

After completing each step, run the associated script to verify it has been implemented correctly.

Setup

Install Scarb 2.3.1 with asdf (instructions)
Install Starknet Foundry v0.10.2 (instructions)

curl -L https://raw.githubusercontent.com/foundry-rs/starknet-foundry/master/scripts/install.sh | sh
snfoundryup -v 0.10.2

Clone this repository
Create a new file called account.cairo inside the src folder.
Copy the following code into the file.

#[starknet::contract]
mod Account {
    #[storage]
    struct Storage {}
}

Run scarb build to verify the project is setup correctly

Note: You'll be working on the account.cairo file to complete the requirements of each step. The file prev_solution.cairo will show up in future steps as a way to catch up with the workshop if you fall behind. Don't modify that file.

Step 1

Checkout the step1 branch to enable the verification tests for this section.

git switch step1

Goal

Collect the public_key associated with a signer that is passed to the constructor, and make it public through a function also called public_key.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

A public_key is defined with a single felt

Step 2

Checkout the step2 branch to enable the verification tests for this section.

git switch step2

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Implement the function is_valid_signature as defined by the SNIP-6 standard.

Requirements

If the signature was created by the signer associated with the account contract the function should return the short string 'VALID'.
If the signature was created by a signer not associated with the account contract, the function should return any other felt that is not the short string 'VALID'.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

Use the stored public_key to check the signature.
A "short string" is just an ascii representation of a single felt.
You can check signatures on the STARK-friendly curve with the syscall check_ecdsa_signature available in the ecdsa module.
The short string 'VALID' can be hardcoded or read from the module starknet::VALIDATED.

Step 3

Checkout the step3 branch to enable the verification tests for this section.

git switch step3

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Implement the function __validate__ as defined by the SNIP-6 standard. This function is similar to is_valid_signature but instead of expecting the signature to be passed as an argument it verifies the transaction's signature.

Requirements

If the transaction signature was created by the signer associated with the account contract the function should return the short string 'VALID'.
If the transaction signature was created by a signer not associated with the account contract, the transaction should be halted and reverted with an error message.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

You can read the transaction details which includes the transaction signature using the syscall get_tx_info from the starknet module.
You can stop and revert a transaction with an error message using the assert function.
The Call struct can be found in the module starknet::account.

Step 4

Checkout the step4 branch to enable the verification tests for this section.

git switch step4

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Protect the __validate__ function by making it callable only by the protocol which uses the zero address.

Requirements

If the function is invoked by any other address, the transaction should be halted and reverted with an error message.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

You can read who the caller is by using the syscall get_caller_address available in the starknet module.

Step 5

Checkout the step5 branch to enable the verification tests for this section.

git switch step5

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Implement the functions __validate_declare__ and __validate_deploy__ with the exact same logic as __validate__ and make them publicly accessible. The signature of both functions is shown below.

fn __validate_declare__(
    self: @ContractState,
    class_hash: felt252
) -> felt252

fn __validate_deploy__(
    self: @ContractState,
    class_hash: felt252,
    salt: felt252,
    public_key: felt252
) -> felt252

Requirements

The return value of both functions is the same as __validate__ ('VALID' or halted transaction).
Both functions should only be callable by the Starknet protocol (same as __validate__).

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

Create a private function to encapsulate the logic of __validate__ so it can be reused by __validate_declare__ and __validate_deploy__.
By grouping private functions into its own trait they can be called as methods of self and the smart contract state doesn’t need to be explicitly passed.
You can auto generate a trait from an implementation using the attribute generate_trait.

Step 6

Checkout the step6 branch to enable the verification tests for this section.

git switch step6

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Implement the function __execute__ as defined by the SNIP-6 standard.

Requirements

The function should be able to handle a single contract call or multiple contract calls in sequence.
The result of each call should be collected and returned as an array.
If an empty array of calls is passed, the function should halt and revert the transaction.
The function should only be called by the protocol (the zero address).

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

You can call other contracts using the low level syscall call_contract_syscall available in the starknet module.
You can iterate over an array by using the loop keyword and the array method pop_front.

Step 7

Checkout the step7 branch to enable the verification tests for this section.

git switch step7

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Implement the function supports_interface from the SNIP-5 standard for the SNIP-6 interface.

Requirements

When providing the interface_id of the SNIP-6 trait the function should return true.
When providing any other value for interface_id the function should return false.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

The interface_id of the SNIP-6 trait is 1270010605630597976495846281167968799381097569185364931397797212080166453709

Step 8

Checkout the step8 branch to enable the verification tests for this section.

git switch step8

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Limit execution of the functions __execute__, __validate__, __validate_declare__ and __validate_deploy__ to transactions of the latest version.

Requirements

Attempting to execute an invoke, declare, and deploy_account transaction that is not of the latest version should result in the transaction being halted and reverted.
Simulated transactions should be supported.

Verification

When completed, execute the test suite to verify you've met all the requirements for this section.

scarb test

Hints

Simulated transactions use the same version as their real counterpart but offset by 2^128.

Step 9 (Final)

Checkout the step9 branch to enable the verification tests for this section.

git switch step9

If you fell behind, the file prev_solution.cairo contains the solution to the previous step.

Goal

Check that you have correctly created an account contract for Starknet by running the full test suite:

scarb test

If the test suite passes, congratulations, you have created your first custom Starknet account contract thanks to account abstraction.

Bonus: Deploying to Testnet

You can deploy your account contract to Starknet testnet in two ways, using Starkli (CLI) or using Starknet.js (SDK).

Using Starkli to deploy an account contract is a "manual" process but you can follow this tutorial to learn how to do it. On the other hand, with an SDK like Starknet.js you can automate the process of declaring, deploying and testing an account contract.

The following bonus steps will show you how to configure and use the deploy.ts script found in the scripts folder to deploy your account contract to Starknet testnet.

Dependencies

Install the dependencies required to run the deployer script.

Steps

Install Nodejs 20 or higher on your computer. You can use asdf for that too.
Once you have Nodejs, install the script dependencies by running npm install from the project's root folder.

Deployer Wallet

Create a wallet that the script can use to pay for the declaration of your account contract.

Steps

Create a wallet on Starknet testnet using the Argent X or Braavos browser extension.
Fund the wallet by using the Faucet or the Bridge.
Create a file in the project's root folder called .env
Export the private key of the funded wallet and paste it in the .env file using the key DEPLOYER_PRIVATE_KEY.

DEPLOYER_PRIVATE_KEY=<YOUR_FUNDED_TESTNET_WALLET_PK>

RPC Endpoint

Provide an RPC URL that the script can use to interact with Starknet testnet.

Steps

Create an account on Infura.
Create a new API Key for a Web3.
Copy the RPC URL for Starknet's testnet.
Paste the RPC URL in the .env file using the key RPC_ENDPOINT.

DEPLOYER_PRIVATE_KEY=<YOUR_FUNDED_TESTNET_WALLET_PK>
RPC_ENDPOINT=<YOUR_RPC_URL_FOR_STARKNET_TESTNET>

Run the Script

Run the script that will declare, deploy and use your account contract to send a small amount of ETH to another wallet as a test.

Steps

From project's root folder run npm run deploy
Follow the instructions from the terminal

If the script finishes successfully your account contract is ready to be used on Starknet testnet.

0xLucqs/aa-workshop

Starknet’s Account Abstraction Workshop

Setup

Step 1

Goal

Verification

Hints

Step 2

Goal

Requirements

Verification

Hints

Step 3

Goal

Requirements

Verification

Hints

Step 4

Goal

Requirements

Verification

Hints

Step 5

Goal

Requirements

Verification

Hints

Step 6

Goal

Requirements

Verification

Hints

Step 7

Goal

Requirements

Verification

Hints

Step 8

Goal

Requirements

Verification

Hints

Step 9 (Final)

Goal

Bonus: Deploying to Testnet

Dependencies

Steps

Deployer Wallet

Steps

RPC Endpoint

Steps

Run the Script

Steps