> ## Documentation Index
> Fetch the complete documentation index at: https://jiffyscan.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Paymaster

> Description of your new file.

💡 A **Paymaster** defines the gas abstraction logic for a smart contract wallet.

## What is Gas Abstraction?

Gas abstraction enables:

* Gas payment in alternative ERC20 tokens
* Gasless transactions (requiring gas sponsorship from a Paymaster)

## Key Features of Paymasters

1. **Modular Design**: ERC-4337 allows a `UserOperation` to choose any Paymaster by specifying its address and input parameters in the `paymasterAndData` field.

2. **Smart Contract Implementation**: A Paymaster is essentially a smart contract implemented by a dApp. It uses custom logic in the `validatePaymasterOp` function, which the Bundler calls to selectively pay gas for UserOperations.

3. **ETH Deposits**: Paymasters must deposit Ethereum on the Entry Point Contract to pay for gas for UserOperations.

4. **Staking Requirement**: In addition to gas deposits, Paymasters must stake ETH on the Entry Point Contract. This stake acts as an anti-spam measure rather than being slashed.

## Paymaster Interface

The Paymaster interface exposes two crucial functions:

### 1. `validatePaymasterOp`

* Defines the logic for gas abstraction
* Ensures sufficient balance (e.g., checking if the wallet has enough ERC20 tokens for gas payment)
* Called before the execution of a UserOperation
* Follows the principle of separating validation from execution

### 2. `postOp`

* Called at the final step of a smart contract wallet function call
* Can revert the function call if the wallet lacks sufficient ERC20 balance to reimburse the Paymaster
* Double-checks gas sufficiency after function execution
* Gas is still deducted even if a function call fails at this step