trusted-gateway-token

Trusted gateway ERC20 token example

Summary

This example showcase a simple token airdrop usecase using a trusted gateway model where a gateway signs responses with a private key and the contract verifies the data using the signing account's address.

The flow

Showing the token balance

• An ERC20 token on L1 has signer field and the token owner can set an Ethereum address.
• The gateway server has a flat file contains the list of ethereum address and how many tokens to airdrop.
• When a client calls token.balanceOf(address) on L1, it throws OffchainLookup error with the gateway server url.
• When the client calls the token gateway server, it checks the file to see if the address qualifies for the airdrop and how many, signs the message of balance and address with the private key of the signer, and returns balance and signature.
• The client then calls token.balanceOfWithSig() with the proof.
• The L1 token verifies that the message was signed by token.signer and returns the balance.

Claiming and transferring tokens

Becuase Token.balanceOf shows the balance of the both L1 and off chain information, users don't need to explicitly claim tokens. When a user transfers tokens from an account for the first time, the airdrop balance is automatically claimed for them.

• When the client calls token.transfer(recipient, amount) on L1, it throws OffchainLookup error with the gateway server url.
• When the client calls the token gateway server, it checks the file to see if the from address qualifies for the airdrop and how much, signs the message of balance and address with the private key of the signer, and returns balance and signature.
• The client then calls token.transferWithSig() with the proof.
• The L1 token verifies that the message was signed by token.signer, mints new token for the balance , then transfers the amount to the recipient.

Running the example

1. Clone the repo and copy the .env file

git clone https://github.com/smartcontractkit/ccip-read
cd ccip-read
yarn install
cd packages/examples/trusted-gateway-token
cp .env.local .env

2. Start local Ethereum node

cd contracts
npx hardhat node

5. Deploy the contract

$ yarn deploy
yarn run v1.22.10
$ npx hardhat run --network localhost scripts/deploy.js
Token deployed to: 0x5FbDB2315678afecb367f032d93F642f64180aa3
The signer is set to: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
Saving as TOKEN_ADDRESS to: ../.env
✨  Done in 1.90s.

This will add TOKEN_ADDRESS to the .env file

6. Run the server

cd ../server
yarn start

7. Run the client

cd ../client
yarn start

If successful, the client will output the following messages demonstrating that SENDER had tokens to claim and transferred 1 of the tokens to RECIPIENT.

SENDER 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 balance 1000000000000000000000
RECIPIENT 0x8626f6940e2eb28930efb4cef49b2d1f2c9c1199 balance 1000000000000000000000
TRANSFER 1 from 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 to 0x8626f6940e2eb28930efb4cef49b2d1f2c9c1199
SENDER 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 balance 999999999999999999999
RECIPIENT 0x8626f6940e2eb28930efb4cef49b2d1f2c9c1199 balance 1000000000000000000001