Looking for help: how to verify if a Hive message is signed correctly in Python Beem. UPDATED!

The story so far.... my Python/Flask website now manages to fire up Hive Keychain thanks to help from @rishi556. I even manage to get the answer in the form of a json response back into the Python Flask back end:

As JSON that looks like this:

{ 
  "data": { 
    "key": "posting", 
    "message": "{\"signed_message\":{\"type\":\"login\",\"address\":\"brianoflondon\",\"page\":\"http://127.0.0.1:5000/podcaster/login\"},\"timestamp\":1613710433}", 
    "method": "Posting", 
    "request_id": 3, 
    "type": "signBuffer", 
    "username": "brianoflondon" 
  }, 
  "error": null, 
  "message": "Message signed succesfully.", 
  "publicKey": "STM7B1eanwUQhXa8tdabTi2RxHnXWtyMBd6iJDZ3Z2QA6rKHQY2WJ", 
  "request_id": 3, 
  "result": "2031e828c6673b945a14489e23a90d5502238d56fb4df568e6ab88af703a9e3bba14ea410bed5afcb42b3d164c976a49645ee2848a8b65fbd9cc77cbc574ae2ffd", 
  "success": true 
}

Shhh don't tell anyone but right now the only bit my server looks at is the "success":true.

I've taken a look at the Beem Docs and even searched all of github, but there's minimal explanation here.

Can anyone else help with the python to do this?

Thanks in wondrous anticipation! I fully intent to make a very simple, reference and open source implementation of this kind of Hive Keychain interaction with Python Flask.

And huge thanks again to @crokkon:

I will publish the entire system including the javascript and the server side code when I get a chance.

#!/usr/bin/python 
from beemgraphenebase.account import PublicKey 
from beemgraphenebase.ecdsasig import verify_message 
from binascii import hexlify, unhexlify 
 
def validate_hivekeychain_ans(ans): 
    """ takes in the answer from hivekeychain and checks everything """ 
    """ http://bit.ly/keychainpython """ 
 
    acc_name = ans['data']['username'] 
    pubkey = PublicKey(ans['publicKey']) 
    enc_msg = ans['data']['message'] 
    signature = ans['result'] 
 
    msgkey = verify_message(enc_msg, unhexlify(signature)) 
    pk = PublicKey(hexlify(msgkey).decode("ascii")) 
    if str(pk) == str(pubkey): 
        print("SUCCESS: signature matches given pubkey") 
        acc = Account(acc_name) 
        match = False, 0 
        for key in acc['posting']['key_auths']: 
            match = match or ans['publicKey'] in key 
        if match: 
            print('Matches public key from Hive') 
            mtime = json.loads(enc_msg)['timestamp'] 
            time_since = time.time() - mtime 
            if time_since < 30: 
                return True , time_since 
            else: 
                print("ERROR: answer took too long.") 
    else: 
        print("ERROR: message was signed with a different key") 
        return False, 0

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