You are already aware that executing transactions on the Ethereum network (including Polygon, Arbitrum, and Optimism) requires #Gas fees.What is Gas and Gas Fee? Please read here: <a href="http://shorturl.at/nLWZ7">shorturl.at/nLWZ7</a>Now when the price of the Native Token is “affordable”, there is not much noise around gas fees; however, as soon as the price of the Native Token starts climbing your Twitter feeds will be filled with the high gas fee hue and cry. For obvious reasons.Add to the above, we have the fact that interacting with certain smart contracts, for example, the Uniswap Router Contract (Uniswap App), a user has to make 2 transactions:<ol><li>first the <code>approve</code> function to allow a fixed number of tokens that can be used by the other smart contract in a transaction and</li><li>second, the smart contract call which will then call the<code>transferFrom</code>.</li></ol>It is easy to guess that this increases the overall gas costs for doing transactions.While there are multiple methods in which the “high” gas fees issue has been tackled by the industry, this article is just focusing on, probably the first large-scale implementation: the DAI Smart Contract’s Permit Function.If you are designing your smart contracts that will require the issuance and management of ERC20 Tokens, it will be in your interest to design your ERC20 Token Smart Contract with this function.While in theory, we could be writing for a lot more, instead we are doing a quick demo of the use case of the <code>Permit function</code> in the Smart Contract for the <code>DAI Stablecoin</code>.<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*82fd7p9rL32eIc3XoPxoMQ.png" alt="" loading="lazy"></figure><h1 style="margin-left:0px;">Let's get our hands dirty</h1>(A) Local Set-upYou can clone the tutorials repo from here: <a href="https://github.com/BuildBearLabs/Tutorials">Github</a> and then progress to the eip-2612 folder(B) InstallationOnce the code is set up on your local system, you need to make sure you install all the dependencies using <code>npm i</code> or <code>yarn install</code> depending on your personal preference.(C) What is happening in the CodeLines 1 to 17 are straightforward; so are lines 19 to 21.Lines 18: <code>nonce</code>This is NOT the nonce of any wallet address. This is the nonce that is maintained by the DAI Contract independently. Reason: imagine if I were to grant an signed message, approving your address to use my DAI. This message is used by you, but not once, but twice → this would technically qualify as “Double Spending” and hence the maintenance of an independent <code>nonce</code> by the DAI Smart ContractLine 63: The signing of the message. Type: <code>_signTypedData</code>Now, DAI follows the EIP712 standard for typed message signing. I will not complicate this (unless someone really wants, then just mention it in the comment below). In simple terms, it is a standard that needs to be adopted for the purpose of signing a message that can be put into “execution” by the Smart Contract and in this case, the DAI Smart Contract.As you can see, the <code>_signTypedData</code> requires 3 parameters:<ul><li>domain: think of these as the details of the smart contract for which this message is intended to be</li><li>types: defines the names and types of the individual items of the message</li><li>message: literally the message that you would like to pass to the smart contract.</li></ul><h1 style="margin-left:0px;">Seeing the above in action</h1>(a) Run the script: <code>node scripts/sign.js</code><ul><li>Yes, I am not using Hardhat, cause I do not need to. You can get the job done by using Ethers alone. It is just generating the signature.</li><li>For convenience, I have set the nonce to the value that the contract returns. That is to say, it will automatically fetch the correct nonce, based on the value stored in the contract.</li><li>For security purposes, I am setting the deadline to be 15 seconds from the current block. timestamp. That is to say that this signature must be lodged with the Smart Contract in 15 seconds of generation. Then, I will deliberately fail to register this signature in 15 seconds and lodge a transaction. It should fail</li></ul>(b) Once it is run after using your environment variables, you will get something similar to the below image in your console:<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*ls5kQv24_hBsBpRXjswcZg.png" alt="" loading="lazy"></figure>(c) Testing if the approval went through:— creating a Private Testnet on <a href="http://buildbear.io/">buildbear.io</a>, forking from the Ethereum Mainnet<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*9a0eDvckdnn_GNIFfPmZ9w.png" alt="" loading="lazy"></figure>— first getting some tokens into a different account from the BuildBear Faucet:<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*olveW01Ae1RouXS0t1Q1cg.png" alt="" loading="lazy"></figure>—Visiting the DAI Smart Contract in my Private Testnets Explorer:<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*FQjLQ8BQqdVBn6fbx9U1LA.png" alt="" loading="lazy"></figure>— Using the Permit Function (in the Write Contract part): 📝<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*RTcRVnGNPQeGHcphbjM7Nw.png" alt="" loading="lazy"></figure>— Executing the transaction (Obviously failed transaction): ❌<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*Al98skxn8CUn2J8W7R4AYQ.png" alt="" loading="lazy"></figure>— checking why it failed by visiting the trace of the tx: 🤯<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*6-Sp8eQajKNEW62jZ7Tfdg.png" alt="" loading="lazy"></figure>and voila! I was able to see what happened inside the transaction and not just the revert reason.Trying to run the same script but this time with 2 mins as the expiry and re-doing everything for a successful tx will lead to:<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*5usX-Adr2Seq3aMOVA2k5g.png" alt="" loading="lazy"></figure>Obviously, if you notice that I lodged the above transaction from a completely different account, which would otherwise be known as the ‘relayer’. This account paid the gas price for submitting to the blockchain that the account <code>0xD31950cD762281b9849c33bfa5CE9A42B756155</code> shall have permission to transfer my DAI tokens.Proof:<figure class="image image_resized" style="width:679.997px;"><img src="https://miro.medium.com/v2/resize:fit:706/1*rh-GMU6tPIuNq9MerZN8Bw.png" alt="" loading="lazy"></figure>And that is all in relation to how to use the <code>Permit Function</code> in the DAI contract.About BuildBearBuildBear provides you with a private test node, making the testing process smooth and efficient.To learn more about BuildBear, read here <a href="https://bit.ly/bb-notion-docs">docs</a>Get the above Github code from <a href="https://github.com/BuildBearLabs/Tutorials">here</a>. 👈If you appreciate what we are doing, please follow us on <a href="https://twitter.com/_BuildBear">Twitter</a> and <a href="https://t.me/+6mjOnBFUR9xjN2U1">Join the Telegram</a> group if you haven’t done yet.And please give us a clap 👏 if you like our work and please do share this article.Thank you.Author:Dipesh (<a href="https://linktr.ee/d_sukh">https://linktr.ee/d_sukh</a>) and Shivam (<a href="https://twitter.com/shivam___ag">Twitter</a> || <a href="https://www.linkedin.com/in/shivam---agrawal/">LinkedIn</a>)

Learn how to use the Permit function of the DAI Stablecoin

Let’s get started then, Shall we?

Let’s get started then, Shall we?

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