[Python] Bitunix API returns "Signature Error" (code 10007) when placing an order using...

I'm trying to integrate with the Bitunix API (https://openapidoc.bitunix.com/doc/common/introduction.html) using Python and aiohttp. I implemented authentication and signature generation as per the documentation, but when I try to place an order, the API always responds with:

{
"code": 10007,
"data": null,
"msg": "Signature Error"
}


Code (Relevant Part)

import aiohttp, hashlib, uuid, time, json
import logging

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

class BitunixClient:
def __init__(self, api_key, secret_key, base_url="https://fapi.bitunix.com"):
self.api_key = api_key
self.secret_key = secret_key
self.base_url = base_url
self.session = aiohttp.ClientSession()

async def place_order(self, order_data):
method = "POST"
endpoint = "/api/v1/futures/trade/place_order"
url = f"{self.base_url}{endpoint}"

nonce = uuid.uuid4().hex[:32]
timestamp = str(int(time.time() * 1000))

# Signature step 1: sorted params (none here)
query_params = ""

# Signature step 2: sorted, no-whitespace body
body = json.dumps(order_data, separators=(',', ':'), sort_keys=True)

# Signature step 3: double SHA256
digest_input = f"{nonce}{timestamp}{self.api_key}{query_params}{body}"
digest = hashlib.sha256(digest_input.encode()).hexdigest()
sign_input = digest + self.secret_key
sign = hashlib.sha256(sign_input.encode()).hexdigest()

headers = {
"api-key": self.api_key,
"nonce": nonce,
"timestamp": timestamp,
"sign": sign,
"Content-Type": "application/json"
}

logger.debug(f"Request URL: {url}")
logger.debug(f"Headers: {headers}")
logger.debug(f"Body: {body}")
logger.debug(f"Digest Input: {digest_input}")
logger.debug(f"Signature: {sign}")

async with self.session.request(method, url, data=body, headers=headers) as resp:
resp_json = await resp.json()
logger.info(f"Response: {resp_json}")
return resp_json


Test Case

import asyncio

async def test_order():
client = BitunixClient("YOUR_API_KEY", "YOUR_SECRET_KEY")
order_data = {
"symbol": "BTCUSDT",
"side": "BUY",
"orderType": "LIMIT",
"qty": "0.001",
"price": "50000",
"tradeSide": "OPEN",
"effect": "GTC"
}
result = await client.place_order(order_data)
print(result)

asyncio.run(test_order())


❌ What I’ve Tried

• Double-checked api_key and secret_key
• Sorted and compacted body correctly with sort_keys=True
• Switched from json=data to data=body
• Ensured system time sync

Logs (Excerpt)

Request URL: https://fapi.bitunix.com/api/v1/futures/trade/place_order
Headers: {'api-key': '...', 'nonce': '...', 'timestamp': '...', 'sign': '...', 'Content-Type': 'application/json'}
Body: {"effect":"GTC","orderType":"LIMIT","price":"50000","qty":"0.001","side":"BUY","symbol":"BTCUSDT","tradeSide":"OPEN"}
Signature: ...
Response: {'code': 10007, 'data': None, 'msg': 'Signature Error'}


What am I missing in the signature generation for Bitunix API? Is there any undocumented quirk with how the request body or headers should be constructed?

Has anyone successfully placed an order using Bitunix's futures API and aiohttp? There are same issues like this in other questions. Is there probality of the issue is about the exchage api not our codes?

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