ERC-4337 Account Abstraction

Question 1

What is Account Abstraction (ERC-4337)

Answer 1

A system that enables the use of smart contract wallets with arbitrary logic instead of EOAs, without changing the blockchain.

Question 2

What is a UserOperation

Answer 2

A structure describing a user’s transaction, including calldata, gas info, signature, and more. It allows complex instructions from a smart contract wallet.

Question 3

What is the EntryPoint contract in ERC-4337

Answer 3

A singleton smart contract that validates and executes bundles of UserOperations.

Question 4

Who or what is a Bundler

Answer 4

A node that collects UserOperations, creates a transaction with handleOps(), and submits it to the blockchain via the EntryPoint.

Question 5

What is a Paymaster

Answer 5

A smart contract that sponsors the gas fee for a UserOperation.

Question 6

What is a Factory in ERC-4337?

Answer 6

A contract that deploys smart accounts using CREATE2, allowing precomputed addresses and wallet creation on demand.

Question 7

What is an Aggregator

Answer 7

A contract that validates aggregated signatures from multiple UserOperations using the same scheme.

Question 8

What does CREATE2 enable in wallet creation?

Answer 8

Deployment of smart wallets at predictable addresses, enabling users to receive funds before wallet deployment (counterfactual address).

Question 9

What happens in the Verification phase of handleOps()?

Answer 9

• Create the sender Smart Contract Account if it does not yet exist.
• Calculate the fee the sender must add to its “deposit” in the EntryPoint
• Call validateUserOp on the sender contract
• When using paymaster: check that the paymaster has enough ETH deposited with the EntryPoint to pay for the UserOperation, and then call validatePaymasterUserOp on the paymaster to verify that the paymaster is willing to pay for the UserOperation.
• Validate the account’s deposit in the EntryPoint is high enough to cover the max possible cost

Question 10

What happens in the Execution phase?

Answer 10

• Call the account with the UserOperation’s calldata.
• After the call, refund the account’s deposit with the excess gas cost that was pre-charged.
• After the execution of all calls, pay the collected fees from all UserOperations to the beneficiary address provided by the bundler.

Question 11

How does a Paymaster handle post-execution logic?

Answer 11

It can use the postOp() function to adjust based on actual gas used (e.g., deduct tokens like USDC).

Question 12

What are Smart Contract Wallets in ERC-4337?

Answer 12

Wallets powered by smart contracts with custom logic (e.g. Soul Wallet, Candide).

Question 13

What restrictions are placed on validateUserOp to prevent simulation attacks?

Answer 13

Limited storage access and restricted opcodes to avoid interference or falsification.