This package simplifies the process of signing permit messages for Ethereum tokens.
Permit is a technique for metatransaction token transfers. Using permit can allow a contract
to use a user's tokens without the user first needing to first to send an approve() transaction.
Permit was first introduced in the Multi-Collateral Dai token contract.
The permit technique is being standardized as part of ERC-2612. This standard (which has already been implemented in projects like Uniswap V2) is slightly different than the implementation used by Dai. Therefore, this library provides functions for signing both types of messages.
Install the package eth-permit using npm or yarn.
import { signDaiPermit } from 'eth-permit';
// Sign message using injected provider (ie Metamask).
// You can replace window.ethereum with any other web3 provider.
const result = await signDaiPermit(window.ethereum, tokenAddress, senderAddress, spender);
await token.methods.permit(senderAddress, spender, result.nonce, result.expiry, true, result.v, result.r, result.s).send({
from: senderAddress,
});import { signERC2612Permit } from 'eth-permit';
const value = web3.utils.toWei('1', 'ether');
// Sign message using injected provider (ie Metamask).
// You can replace window.ethereum with any other web3 provider.
const result = await signERC2612Permit(window.ethereum, tokenAddress, senderAddress, spender, value);
await token.methods.permit(senderAddress, spender, value, result.deadline, result.v, result.r, result.s).send({
from: senderAddress,
});The library now supports Ethers.js Wallet signers:
import { signERC2612Permit } from 'eth-permit';
const value = web3.utils.toWei('1', 'ether');
const wallet = new ethers.Wallet(privateKey, new ethers.providers.JsonRpcProvider(rpcUrl));
const senderAddress = await wallet.getAddress();
const result = await signERC2612Permit(wallet, tokenAddress, senderAddress, spender, value);
await token.methods.permit(senderAddress, spender, value, result.deadline, result.v, result.r, result.s).send({
from: senderAddress,
});
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