EOA Based Paymaster

This document introduces a paymaster solution specifically designed for Externally Owned Account (EOA) wallets, differing from the paymaster defined in EIP-4337. With minimal modifications, wallets can integrate this solution to support gas fee sponsorship, significantly enhancing user experience.

What is EOA based Paymaster

The paymaster in EIP-4337 (Account Abstraction via Entry Point Contract Specification) is a crucial component designed to enhance the flexibility and user experience of Ethereum transactions. It allows a third party to pay for a user’s transaction fees, removing the need for users to hold ETH to pay for gas.

While EIP-4337 introduced the revolutionary concept of paymasters for smart contract wallets, a significant portion of the Ethereum ecosystem still relies on EOAs. Recognizing this, this present a groundbreaking paymaster solution specifically designed for EOA wallets. This innovation brings the benefits of transaction sponsorship and enhanced user experience to the broader BNB Chain user base, without requiring a shift to smart contract wallets. The EOA paymaster solution aims to democratize access to sponsored transactions, making blockchain interactions more user-friendly and cost-effective for millions of existing EOA wallet users.

How does it Work

Under BEP322’s Proposer-Builder Separation (PBS) architecture, a significant shift occurs in transaction processing:

1. Validator Role: Validators no longer verify individual transaction gas prices within a block.
2. Transaction Bundling: Private transactions are grouped into bundles and submitted to builders.
3. Prioritization: Builders prioritize based on the aggregate gas price of each bundle.
4. Intra-Bundle Flexibility: Within a single bundle, gas prices can vary, allowing for zero-fee and higher-fee transactions to coexist.

This flexibility enables innovative features such as sponsored gas fees and gasless transactions.

Definitions

Bundle: An ordered array of transactions that execute atomically, ensuring all transactions in the bundle are processed together or not at all.

Builder: A new stakeholder in the MEV supply chain responsible for constructing blocks. Builders package transaction bundles, individual transactions from the public txpool, and private transaction order flow into proposed blocks.

Proposer: A validator who selects the most profitable block from multiple builders’ proposals for inclusion in the blockchain.

Paymaster: An infrastructure component that enables transaction sponsorship, allowing self or third parties to cover gas fees.

Sponsor Policy: A set of rules defined by the gas sponsor to determine which transactions qualify for sponsorship. This may include criteria such as whitelisted transaction senders or specific transaction types.

Overall Workflow

The gas sponsorship process involves several key components and steps:

1. User Initiation:

   • A user prepares a transaction using any compatible wallet.
   • The wallet sets the gas price to zero for potentially sponsored transactions.

2. Paymaster Submission:

   • The wallet submits the zero-gas-price transaction to the Paymaster.

3. Sponsor Policy Verification:

   • The Paymaster checks the transaction against existing sponsor policies.
   • Policies may include criteria such as sender/recipient addresses, token types, or transaction limits.

4. Sponsorship Processing:

   • If the transaction is eligible for sponsorship: a. The Paymaster creates a sponsor transaction with a higher gas price. b. The original user transaction and the sponsor transaction are combined into a bundle.
   • If not eligible, the transaction is rejected or returned to the user for normal processing.

5. Bundle Creation and Submission:

   • This bundle is submitted to multiple MEV builders.

6. Builder Selection and Block Proposal:

   • MEV builders incorporate the bundle into their block proposals.

7. Blockchain Inclusion:

   • Proposers (validators) select the most profitable block from the builders’ proposals.
   • The selected block, containing both the user’s original transaction and the sponsor’s transaction, is added to the blockchain.
   • This ensures atomic execution of both transactions.

8. Post-Transaction Processing:

   • The Paymaster Manager updates the sponsor’s account, deducting the appropriate amount for the sponsored gas.

This solution leverages the BEP322 Proposer-Builder Separation architecture to enable seamless gas sponsorship without requiring significant changes to existing wallet infrastructures. It provides a flexible system that can accommodate various sponsorship models while maintaining the security and integrity of the blockchain network.

Paymaster Infra

Ready to enable gasless experiences in your app or wallet? Here’s some helpful information on paymaster infrastructure that are available on BNB Chain:

• Nodereal. The MegaFuel powered by Nodereal is a paymaster implementation based on BNB Chain Paymaster for EOA Wallet. With minimal modifications, wallets can integrate MegaFuel to support gas fee sponsorship, significantly enhancing user experience. At the same time, sponsors can customize their sponsorship on MegaFuel, allowing sponsored users to send gasless transactions.
• Bitget Wallet. Bitget Wallet has integrated the paymaster on BSC, providing gasless functionality for sponsored user transactions.