问Allcoin签名POST请求失败

EN

import hashlib
import keys
import requests

KEY = keys.allcoin["key"]
API_SECRET = keys.allcoin["secret"]

msg = "api_key='{}&secret_key={}".format(KEY, API_SECRET)
signature = hashlib.md5(msg.encode("utf-8")).hexdigest()

parameters = {
    "api_key": KEY,
    "sign": signature.upper(),
}

params = "&".join("{}={}".format(a, b) for a, b in parameters.items())
url = "http://www.allcoin.ca/Api_User/userBalance"
r = requests.post(
    headers={
        "Content-Type": "application/x-www-form-urlencoded",
        'user-agent': 'my-app/0.0.1'
    },
    url=url,
    params=parameters
)
print(r.json())