# To find `media_key` and `media_iv`, see: /bq/stories documentation
import requests
import base64
import mcrypt

res = requests.post(...)  # POST /bq/stories and ensure res is a dict.
data = requests.get(...)  # GET /bq/story_blob?story_id=XXXXX from result
key = base64.b64decode(res[...]["media_key"])
iv = base64.b64decode(res[...]["media_iv"])

m = mcrypt.MCRYPT("rijndael-128", "cbc")
m.init(key, iv)
dedata = m.decrypt(data)  # Boom.