LinkWallet

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LinkWallet

Account Abstraction Wallet with Off-chain Gas Fee Subscription by Chainlink

User Benefits

• Users can pay the gas fee with an off-chain subscription
• It enables users to skip "bridge token from the other chain" or "send token from the central exchange," which is the first obstacle for users to start using a blockchain-based app
• It brings excellent onboarding, especially for the new user

What it does

1. User can pay the gas fee by credit card with a stripe subscription
2. After the user subscription, a webhook is called from Stripe, and the webhook sends a tx to request Chainlink
3. Chainlink gets the payment status from the off-chain stripe API, then stores it in the on-chain paymaster contract
4. Paymaster contract verifies the payment status with the user address, then pays the gas fee for paid users when sending tx.

How we built it

• Chainlink and Account Abstraction is the primary implementation of the hackathon
• Payment status is integrated securely with Chainlink
• Verification is implemented in an Account Abstraction way which brings better flexibility than the average meta transaction

Chainlink Integration

• This is to integrate stripe payment status into the Account Abstraction Paymaster
• The Main reference of the integration
• (Contract)[https://github.com/taijusanagi/chainlink-aa-paymaster-wallet/blob/main/packages/contracts/contracts/ChainlinkStripePaymaster.sol#L68]
• (Backend)[https://github.com/taijusanagi/chainlink-aa-paymaster-wallet/blob/main/packages/app/src/pages/api/stripe/checkout-callback-to-request-chainlink.ts#L13]

Polygon Integration

• ChainlinkStripePaymaster https://mumbai.polygonscan.com/address/0xbb0447c7194fb0e99213ad140d0dff4c82fbb9ca#code

• EntryPoint https://mumbai.polygonscan.com/address/0xf317c52db727f9d8a3ac04304cb34a297bffef9a#code

• WalletFactory https://mumbai.polygonscan.com/address/0x5352d8704b9a251d46aa4674e3215fc6d7baa80a#code

Quicknode

• Using Quicknode RPC for better performance
• Used in deploy script and Account Abstraction Bundler
  • https://github.com/taijusanagi/chainlink-aa-paymaster-wallet/blob/main/package.json#L22
  • https://github.com/taijusanagi/chainlink-aa-paymaster-wallet/blob/main/packages/contracts/network.json#L9

Challenges we ran into

• This is my first to build an Account Abstraction paymaster, and significantly less documentation is available for this implementation. I had to debug so many times to complete the whole process.

Accomplishments that we're proud of

• Now I can use paymaster for any Account Abstraction tx. This is good progress.
• I believe this is the first implementation of integrating Account Abstraction and Chainlink. There should be excellent business opportunities too.
• Automated chainlink integration, and it works very well

What we learned

• How to use Chainlink and Account Abstraction

What's next for LinkWallet

• Run own bunder
• This off-chain payment method can be used in cross-chain payment too. This enables user not to need to bridge and swap to use the dApp. Users can pay the fee in any chain.

Built With

• accountabstraction
• chainlink
• polygon
• quicknode
• stripe