Enable Gasless USDC Payments with EIP-7702 and Circle Paymaster

Paymasters enable transaction sponsorship by paying gas fees on behalf of users. The video demonstrates configuring Stack Up's paymaster in config.json, including RPC URL and context settings for different paymaster types. The pay-as-you-go paymaster (context: 'payg') pays gas without requiring payment, while ERC20 token paymasters accept tokens for gas fees. The process involves minting testnet ERC20 tokens to the smart account, approving the paymaster to withdraw tokens for gas, and executing sponsored transactions. The approval transaction itself is paid using the ERC20 tokens being approved, enabling accounts with only ERC20 tokens to send transactions. This mechanism allows seamless sponsored transactions with proper token accounting.

The Paymaster feature on zkSync allows users to pay for gas fees using any ERC-20 token (such as USDT, USDC, or platform-specific tokens like Hold, ZK, or Mute) instead of native ETH, with discounts ranging from 15% to 50% on gas fees; this feature utilizes account abstraction and is integrated across multiple decentralized applications including SyncSwap, Velocore, zkSwap, Mute.io, Zyfi, Orbiter Finance, and HoldStation Futures, making it a valuable tool for both cost-effective transactions and potential airdrop qualification.

Paymaster contracts enable users to pay gas fees using alternative currencies or have fees covered entirely by third parties. This solves the gas payment barrier for new users who may not have native currency. Paymasters can accept stablecoins, cover gas fees as marketing incentives, or implement custom pricing models. The system allows users to specify which Paymaster will handle their transaction, with the Entry Point verifying authorization before execution. This creates economic incentives for user acquisition while simplifying the user experience for non-technical users who previously abandoned Web3 due to gas payment complexity.

A Paymaster is a smart contract that sponsors gas fees for user transactions on Abstract's native account abstraction platform. To build one, you implement the IPaymaster interface with two core functions: validateAndPayForPaymasterTransaction (which validates if the paymaster will cover the fee and calculates the required ETH payment) and postTransaction (optional). The process involves calculating the gas fee as transactionGasLimit × transactionMaxFeePerGas, sending this amount to the bootloader, and optionally withdrawing funds later. The paymaster must have sufficient funds to cover the gas fees it sponsors, and transactions are submitted by including the paymaster address in the customData.paymasterParams field.

Paymasters are smart contracts that abstract gas fees from end users by either sponsoring transactions (where the paymaster pays gas from a gas tank) or allowing users to pay gas with any ERC20 token, enabling seamless user experiences in dApps by removing transaction friction and simplifying the payment process.

Gasless transactions require Biconomy paymaster setup with a funded gas tank on the target network. Developers register a paymaster, deposit native tokens, and integrate the API key into environment variables. The custom ethers provider wraps Particle's AAProvider with gasless transaction mode enabled. Social login integration leverages Particle's authentication system, allowing users to sign in via Google or Twitter. The login flow checks authentication status and retrieves user information, enabling seamless transition from social identity to smart account functionality without cryptographic key management.

Casper Click provides a single SDK for integrating with all Casper ecosystem wallets, reducing development complexity. Features include a polished UI with customizable themes and menu items, Fiat onramps for buying CSpr, single sign-on for cross-app authentication, and social login for easy onboarding without wallet installation. Users get self-custodial wallets through Google or Apple authentication. Transaction approval uses second-factor authentication. The SDK handles all wallet API complexities. Integration is easiest through React templates (under a minute), but also works via script tags for non-React apps. Key features include customizable account menus, theme switching, and event handling for sign-in, account switching, and disconnection.

Account abstraction enables frictionless Web3 onboarding by using biometric authentication to sign transactions without requiring users to manage seed phrases or understand gas fees, maintaining self-custody and privacy while removing traditional barriers that prevent Web2 users from adopting Web3 applications.

Gasless architecture unlocks new application categories by eliminating transaction barriers. For gaming, users can transact freely without pre-funding wallets or relying on vulnerable paymaster accounts. For social apps, posting, liking, sharing, and token transfers become frictionless, enabling decentralized social networks. For DeFi, users can swap tokens and list NFTs without understanding gas fees. This simplification lowers barriers to crypto adoption, transforming complex onboarding processes into seamless user experiences across gaming, social media, and financial applications.

Biconomy SDK is a one-stop Web3 development solution that addresses user experience challenges through integrated features. It enables gasless transactions via meta transactions (EIP-2771) and account abstraction (ERC-4337), allowing users to perform actions without holding native tokens. The SDK integrates social login using Gmail accounts for easier onboarding, cross-chain bridging through Hyphen, and batch transactions for gas optimization. These features abstract away complex blockchain operations, enabling users to focus on Web3 applications without managing multiple tokens, chains, or transactions. The approach follows the principle that users should not need to understand underlying technical details, similar to how they don't need to know which database Facebook uses.

EIP-7702 fundamentally transforms Ethereum by allowing externally owned accounts (EOAs) to have executable code, eliminating the traditional distinction between EOAs and smart contracts. EOAs currently lack on-chain code but possess private keys, preventing batch operations, transaction sponsorship, and alternative signing mechanisms. The EIP introduces a new transaction type (type 4) with an authorization list containing chain ID, address, nonce, and signature, enabling EOAs to delegate to smart account code. Foundry provides cheat codes (sign_delegation, assign_and_attach_delegation) for systematic testing. Early implementations reveal critical vulnerabilities: V0 shows unprotected execute functions allowing fund drainage; V1 demonstrates constructor misuse where initialization logic executes in the wrong context; V2 exposes front-running risks where attackers set unauthorized guardians. These examples illustrate why proper access controls, initialization protection, and context-aware design are essential for secure 7702 accounts.

EIP-7702 introduces significant technical challenges because it changes fundamental EVM assumptions. The EVM's 'origin' variable, which indicates the original signer, was always an EOA because only EOAs can sign executable transactions. Some DeFi protocols used this assumption to prevent reentrancy attacks, though this is considered bad security practice. The mempool relied on the assumption that only EOA-signed transactions could affect EOA accounts. EIP-7702 requires new security rules, particularly nonce validation to prevent spam attacks where attackers could create many delegated accounts and drain balances. Unlike standard smart contracts that cannot sign transactions, 7702 delegated accounts retain the ability to sign transactions, creating a middle ground that maintains EOA functionality while gaining smart contract wallet capabilities.

The speaker provides a comprehensive explanation of the EIP-7702 attack mechanism: users are lured to malicious websites claiming airdrops or NFT mints, which prompt them to sign transactions that appear normal but are actually EIP-7702 transactions. By signing, users unknowingly set malicious smart contracts as temporary account authorities. Once confirmed, these contracts can immediately transfer stablecoins, NFTs, or interact with any protocol. Prevention requires using reputable wallets that warn about authorization changes. The speaker demonstrates two practical revocation methods: using EIP7702.App to detect and revoke EIP-7702 delegations by entering wallet address and confirming revocation through MetaMask account details, and using revoke.cash to revoke token approvals and unlimited delegations by connecting wallet and confirming the revocation transaction.

The EIP-772 proposal introduces delegation designation to improve revocability in Ethereum accounts. The core debate centers on permanent versus temporary delegation: permanent delegation stores targets in account code indefinitely until changed, while temporary delegation only activates within the transaction scope. The proposal moves from storage-slot-based implementation to direct code embedding, making delegation more permanent. This distinction affects user experience, security, and the ability to revoke authorizations. The proposal addresses the gap between traditional EOA wallets and smart contract wallets, creating an experience where authorization is consumed once (requiring a nonce) and the account is delegated to a smart contract wallet in perpetuity until changed. This enables gradual migration while maintaining EOA transaction origination capability. A fundamental challenge with one-time use delegation signatures is the risk of front-running and griefing. When users send 7702 transactions with one-time signatures to the mempool, anyone can extract and use those signatures in their own transactions. Since signatures don't commit to specific transactions, they can be consumed in transactions that don't actually use the account, effectively invalidating the user's intended transaction. This creates a griefing vulnerability.

EIP 7702 enables Externally Owned Accounts (EOAs) to run smart contract code directly from their address through a delegation designator, providing smart account features like sponsored transactions, batch transactions, passkeys, session keys, granular permissions, assets recovery, and revocability. Safe has developed three approaches to integrate with EIP 7702 while preventing front running attacks: (1) Modified Safe Proxy - changes proxy logic with setup data hash verification, requiring proxy deployment but offering wallet compatibility; (2) Modified Safe Singleton - removes proxy entirely, requiring two signatures and infrastructure changes; (3) Safe Light - minimalistic contract supporting only batching and relaying with non-interfering storage slots. Each approach balances complexity, cost, and feature set differently. A critical limitation is that stolen private keys can override smart account logic, as account recovery depends on the user holding the private key.