prepare_headers_bfx

import json
import base64
import hashlib
import hmac

def _prepare_headers(payload, api_key, api_secret):
    # payload = parameters-dictionary -> JSON encode -> base64
    payload_json = json.dumps(payload)
    payload_encoded = base64.encodestring(payload_json)
    # signature = HMAC-SHA384(payload, api-secret) as hexadecimal
    encryptor = hmac.new(payload_encoded, api_secret, hashlib.sha384)
    signature = encryptor.hexdigest()
    
    # send (api-key, payload, signature)
    headers = {"X-BFX-APIKEY" : api_key,
               "X-BFX-PAYLOAD" : payload_encoded,
               "X-BFX-SIGNATURE": signature 
               }
    return headers