Fiat Paymaster

This project is an implementation of an account abstraction paymaster using the ERC-4337 paradigm that was recently deployed throughout the Ethereum ecosystem. Using a PayPal integration, we allow users to pay for any transaction fees with fiat.

This paymaster is generic and can be used by any dapp or wallet by setting the paymasterAndData field to the address of our paymaster.

This project is cross-chain by nature, as it is deployed on many different chains that support AA:

• Optimism Mainnet
• Polygon zkEVM
• Gnosis Chain
• Scroll
• Goerli

You can test it using our PayPal test account:

• email: sb-mx70425265463@personal.example.com
• password: &$}0XzO4

We implemented a TokenPaymaster called FPUSD (short for Fiat Paymaster USD). This paymaster is an ERC-20 token that is used to pay for ERC-4337 transactions, and represents an USD balance in PayPal.

Since there aren't currently many ERC-4337 supporting wallets, we use the high-level @account-abstraction/sdk to create UserOperations and sign them in Metamask, which is later sent to a bundler to be included on the mempool.

We spent some time doing a pull request to add token paymaster support to the trampoline wallet but this wallet was too unstable to complete it.