---
title: "✍️ Create Order Signature"
description: >-
  Learn how to create and sign Forkast orders using EIP-712 typed data,
  including domain setup, order structure, and amount calculations.
---

> **For AI agents:** the complete documentation index is at [llms.txt](/llms.txt). Append `.md` to any page URL for its markdown version.

Orders on Forkast use **EIP-712 typed data signing**. The signature proves the order was authorized by the wallet owner without exposing the private key.

## 1️⃣ Step 1: Construct the EIP-712 Domain

```javascript
{
  "name": "CTF Exchange",
  "version": "1",
  "chainId": 42161,
  "verifyingContract": "0x2D7aa09fe8a9Af205aD6E0Fef1441834c4250cdc"
}
```

## 2️⃣ Step 2: Define the Order Type Structure

```javascript
{
  "Order": [
    { "name": "salt",          "type": "uint256" },
    { "name": "maker",         "type": "address" },
    { "name": "signer",        "type": "address" },
    { "name": "taker",         "type": "address" },
    { "name": "tokenId",       "type": "uint256" },
    { "name": "makerAmount",   "type": "uint256" },
    { "name": "takerAmount",   "type": "uint256" },
    { "name": "expiration",    "type": "uint256" },
    { "name": "nonce",         "type": "uint256" },
    { "name": "feeRateBps",    "type": "uint256" },
    { "name": "side",          "type": "uint8" },
    { "name": "signatureType", "type": "uint8" }
  ]
}
```

## 3️⃣ Step 3: Build the Order Message

| Field         | Type    | Description                                                                                                                              |
| ------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| salt          | uint256 | A unique value per order. Generate by hashing order fields + random entropy + timestamp using SHA-256, then convert to a uint256integer. |
| maker | address | The **proxy wallet** (Gnosis Safe) address — not the EOA. |
| signer | address | The user's **EOA wallet** address (the key that signs). |
| taker         | address | 0x0000000000000000000000000000000000000000 (public order, anyone can fill).                                                              |
| tokenId       | uint256 | The CTF ERC-1155 token ID of the outcome being traded.                                                                                   |
| makerAmount   | uint256 | See calculation below. Scaled to 6 decimals (USDC precision).                                                                            |
| takerAmount   | uint256 | See calculation below. Scaled to 6 decimals.                                                                                             |
| expiration    | uint256 | "0" (no expiration).                                                                                                                     |
| nonce         | uint256 | "0".                                                                                                                                     |
| feeRateBps    | uint256 | "0".                                                                                                                                     |
| side          | uint8   | 0 = Buy, 1= Sell.                                                                                                                        |
| signatureType | uint8   | 3 (EIP-712 with Gnosis Safe proxy — signer is EOA, maker is proxy).                                                                      |

### 🧮 Calculating makerAmount and takerAmount

Amounts are scaled by 1e6(USDC has 6 decimals):

**Buy order** (side = 0)

```javascript
makerAmount = floor(amount × price × 1,000,000)   // TC you pay
takerAmount = floor(amount × 1,000,000)            // outcome tokens you receive
```

**Sell order** (side = 1)

```javascript
makerAmount = floor(amount × 1,000,000)            // outcome tokens you sell
takerAmount = floor(amount × price × 1,000,000)    // TC you receive
```

**Example** — buying 50 shares at a price of 0.80:

$$
\text{makerAmount} = \text{floor}(50 \times 0.80 \times 1000000) = 40000000 \newline \text{takerAmount} = \text{floor}(50 \times 1000000) = 50000000
$$

## 4️⃣ Step 4: Generate a Unique Salt

```javascript
import crypto from "crypto";

const raw = [
  signerAddress.toLowerCase(),
  makerAddress.toLowerCase(),
  tokenId,
  side,
  type,
  price,
  amount,
  (BigInt(Date.now()) * BigInt(1_000_000)).toString(),
  crypto.randomBytes(16).toString("hex"),
].join("|");

const digest = crypto.createHash("sha256").update(raw).digest("hex");
const salt = BigInt("0x" + digest).toString();
```

## 5️⃣ Step 5: Sign with EIP-712

```javascript
import { ethers } from "ethers";

const domain = {
  name: "CTF Exchange",
  version: "1",
  chainId: 42161,  // or 421614 for testnet
  verifyingContract: "0x2D7aa09fe8a9Af205aD6E0Fef1441834c4250cdc",
};

const types = {
  Order: [
    { name: "salt", type: "uint256" },
    { name: "maker", type: "address" },
    { name: "signer", type: "address" },
    { name: "taker", type: "address" },
    { name: "tokenId", type: "uint256" },
    { name: "makerAmount", type: "uint256" },
    { name: "takerAmount", type: "uint256" },
    { name: "expiration", type: "uint256" },
    { name: "nonce", type: "uint256" },
    { name: "feeRateBps", type: "uint256" },
    { name: "side", type: "uint8" },
    { name: "signatureType", type: "uint8" },
  ],
};

const message = {
  salt: salt,
  maker: proxyWalletAddress,
  signer: walletAddress,
  taker: ethers.ZeroAddress,
  tokenId: tokenId,
  makerAmount: "40000000",
  takerAmount: "50000000",
  expiration: "0",
  nonce: "0",
  feeRateBps: "0",
  side: 0,
  signatureType: 3,
};

const wallet = new ethers.Wallet(privateKey);
const signature = await wallet.signTypedData(domain, types, message);
```

## ✅ Validation Rules

| Field         | Constraint                                 |
| ------------- | ------------------------------------------ |
| side          | Must be 0 (Buy) or 1 (Sell)                |
| amount        | Must be > 0, max 2 decimal places          |
| price         | Must be > 0 and \< 1, max 2 decimal places |
| signer        | Must match the private key used to sign    |
| signatureType | Must be 3 (EOA signer + Gnosis Safe maker) |