Signing

Simple orders / Basic orders

Part 1/ Basic orders/Signing

Here we will build on the previous tutorial and sign the quote we got from the quote tutorial, so that we can place an order on CoW Protocol.

Intents and signatures

CoW Protocol uses intents to represent orders. An intent is a signed message. Most intents are signed using the EIP-712 signing scheme, and this is what we will use in this tutorial.

Signing an order

In the previous tutorial, we received an OrderQuoteResponse object. This object contains all the data that we need to sign an order.

Types and utilities

For signing, we will use the UnsignedOrder type from the SDK, along with the OrderSigningUtils utility.

import type { Web3Provider } from '@ethersproject/providers';
import { OrderBookApi, SupportedChainId, OrderQuoteRequest, OrderQuoteSideKindSell, OrderSigningUtils, UnsignedOrder } from '@cowprotocol/cow-sdk';


	

export async function run(provider: Web3Provider): Promise<unknown> {
  // ...

	// Use the original sellAmount, which is equal to quoted sellAmount added to quoted feeAmount
	// sellAmount === BigNumber.from(quote.sellAmount).add(BigNumber.from(quote.feeAmount)).toString()

	// And feeAmount must be set to 0
	const feeAmount = '0'

	const order: UnsignedOrder = {
	  ...quote,
	  sellAmount,
	  feeAmount,
	  receiver: ownerAddress,
	}
}

The OrderQuoteResponse type contains a receiver field, however the type of this field is not compatible with the UnsignedOrder type. This is why we need to override the receiver field with the ownerAddress (which is the address of the wallet we are using).

Sign the order

Now that we have the UnsignedOrder, we can sign it:

import type { Web3Provider } from '@ethersproject/providers';
import { OrderBookApi, SupportedChainId, OrderQuoteRequest, OrderQuoteSideKindSell, OrderSigningUtils, UnsignedOrder } from '@cowprotocol/cow-sdk';

export async function run(provider: Web3Provider): Promise<unknown> {
  // ...

  return OrderSigningUtils.signOrder(order, chainId, signer);
}

Run the code

To run the code, we can press the "Run" button in the bottom right panel (the web container).

When running the script, we may be asked to connect a wallet. We can use Rabby for this.

1. Accept the connection request in Rabby
2. Press the "Run" button again
3. Observe the SigningResult object returned to the output panel

An example signing result should look like:

{
  "signature": "0x98ac143acad82e3908489ac8ca3f908cb49b0a861f15a51fc0a79bdea6dcca0212403f419ed8b022881a7cecf7358a69c2cfa9596e877fc67bea5be6d9981cf51b",
  "signingScheme": "eip712"
}

In the above case, we can see the signature returned is the ECDSA signature of the EIP-712 hash of the UnsignedOrder. Now this can be used to place an order on CoW Protocol.