> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Signing

> TypeScript signing module API for CoW Protocol order signatures

# Signing

The signing module provides utilities for various signature schemes used in CoW Protocol order signing.

## Signing Schemes

```typescript theme={null}
enum SigningScheme {
  EIP712 = 0,
  ETHSIGN = 1,
  EIP1271 = 2,
  PRESIGN = 3,
}
```

| Scheme      | Description                                                                 |
| ----------- | --------------------------------------------------------------------------- |
| **EIP712**  | Recommended. Provides structured data to wallets about what is being signed |
| **ETHSIGN** | Uses the `eth_sign` RPC call for legacy wallet compatibility                |
| **EIP1271** | For smart contract wallets like Gnosis Safe                                 |
| **PRESIGN** | On-chain pre-authorization before settlement                                |

## Signature Types

### EcdsaSignature

```typescript theme={null}
interface EcdsaSignature {
  scheme: SigningScheme.EIP712 | SigningScheme.ETHSIGN;
  data: string; // ECDSA signature (r, s, v)
}
```

### Eip1271Signature

```typescript theme={null}
interface Eip1271Signature {
  scheme: SigningScheme.EIP1271;
  verifier: string; // Smart contract address
  data: string; // Signature bytes
}
```

### PreSignSignature

```typescript theme={null}
interface PreSignSignature {
  scheme: SigningScheme.PRESIGN;
  signer: string; // Signer address
}
```

## Functions

### signOrder

Signs orders using externally owned accounts with either EIP-712 or ETHSIGN schemes.

```typescript theme={null}
async function signOrder(
  domain: TypedDataDomain,
  order: Order,
  signer: Signer,
  scheme: SigningScheme.EIP712 | SigningScheme.ETHSIGN
): Promise<EcdsaSignature>;
```

**Parameters:**

| Name     | Type              | Description               |
| -------- | ----------------- | ------------------------- |
| `domain` | `TypedDataDomain` | EIP-712 domain separator  |
| `order`  | `Order`           | Order to sign             |
| `signer` | `Signer`          | ethers.js Signer instance |
| `scheme` | `SigningScheme`   | EIP712 or ETHSIGN         |

### encodeEip1271SignatureData

Encodes EIP-1271 signature components into hex format.

```typescript theme={null}
function encodeEip1271SignatureData(signature: {
  verifier: string;
  data: string;
}): string;
```

### decodeEip1271SignatureData

Reverses the encoding to retrieve original signature components.

```typescript theme={null}
function decodeEip1271SignatureData(encodedSignature: string): {
  verifier: string;
  data: string;
};
```

## Example

```typescript theme={null}
import { domain, signOrder, SigningScheme, Order, OrderKind } from "@cowprotocol/contracts";
import { ethers } from "ethers";

const settlementDomain = domain(1, "0x9008D19f58AAbD9eD0D60971565AA8510560ab41");
const wallet = new ethers.Wallet("YOUR_PRIVATE_KEY");

const order: Order = {
  // ... order fields
  kind: OrderKind.SELL,
  partiallyFillable: false,
};

// EIP-712 signing (recommended)
const signature = await signOrder(
  settlementDomain,
  order,
  wallet,
  SigningScheme.EIP712
);
```

<Tip>
  EIP-712 is the recommended signing scheme for optimal user experience, as it shows users a structured representation of the order data in their wallet.
</Tip>