# EIP-3074: AUTH and AUTHCALL opcodes

`EIP-3074: AUTH and AUTHCALL opcodes` represents a significant advancement. It allows users to use some features of smart wallets without paying contract deploy gas fees:

1. Gas sponsor (e.g., paying gas fees using ERC20 tokens without native token).
2. Batch transactions (such as executing token approval and swap in one transaction).
3. Conditional execution (e.g., only allowing transaction to execute when blockNumber < x).

Compared to ERC-4337, EOA wallets can benefit immediately by supporting EIP-3074.

However, since EIP-3074 is based on EOA, it currently does not support exciting features already in ERC-4337, such as 'change owner,' 'use any signature algorithm,' and 'social recovery.'

If you are interested in the specific execution flow of EIP-3074, you can continue reading:

## Verify gas sponsor

1. The user and the `sponsor` negotiate an `invoker contract` that they both support.
2. The user signs the transaction details and sends the data with the signature to the `sponsor`.
3. The `sponsor` verifies off-chain whether the transaction can be sponsored. If approved, the `sponsor` sends the transaction to the `invoker contract`.
4. The `invoker contract` first verifies the user's signature using `AUTH` and then executes the user's transaction using `AUTHCALL`.

In this scenario, the user can 'send a transaction' using their EOA without needing any tokens.

## ERC20 gas sponsor

1. The user and the `sponsor` negotiate an `invoker contract` that they both support.
2. The user signs the transaction details and sends the data with the signature to the `sponsor`.
3. The `sponsor` verifies the data submitted by the user off-chain. If verified, the `sponsor` sends the transaction to the `invoker contract`.
4. The `invoker contract` verifies whether the user's ERC20 tokens are sufficient and transfer the ERC20 tokens in advance. Then, it verifies the user's signature using `AUTH` and executes the user's transaction using `AUTHCALL`. After execution, any excess ERC20 tokens withheld earlier are refunded to the user based on the actual gas cost, and the final ERC20 tokens received are transferred to the address provided by the `sponsor`.

In this scenario, users can pay gas fees using ERC20 tokens.

If you want to know more details, I've also prepared an example `Invoker contract` that supports batch transactions:

[https://github.com/jayden-sudo/InvokerDemo/blob/main/contract/Invoker.sol](https://github.com/jayden-sudo/InvokerDemo/blob/main/contract/Invoker.sol)