Why do i keep getting invalid token when i've validated that the tokens are the exact same? Cryptography Fernet : Invalid Token

Question

So the message is supposed to be decrypted here:

def recv_message(self):
        while True:
            try:

                data = self.socket.recv(1024)
                # converting values from raw string into dictionary with json
                formatted_data = json.loads(data)

                # check the content of the recived data for the type of state that it is
                if formatted_data["state"] == "keyexchange":

                    # store the public key send from the server in an array
                    # needed to generate the secret for encryption

                    Client.server_public_key.append(int(
                        formatted_data["content"]))

                    # add the secret to the array for the client to generate fernet
                    Client.secret.append(
                        (Client.server_public_key[0] ** Client.c_private_key) % Client.prime)

                    # generate fernet to encrypt and decrypt
                    Client.fernet = Fernet(base64.urlsafe_b64encode(
                        f"{Client.secret[0]:032d}".encode(FORMAT)[:32]))

                if formatted_data["state"] == "message":

                    # standard state of messages
                    # assign all the values to variables from the formatted data locally to be used when necessary
                    address = formatted_data["address"]
                    data = formatted_data["content"]
                    data = self.decrypt(data)

                    # print the message and the address that it came from
                    print(f"{address}: {data}")

            except:
                print(traceback.format_exc())
                print("[CONNECTION ENDED]")
                break

After the server broadcasts the messages back to the clients - This supposed to be a chat app with the CLI

However i get this error

cryptography.fe.net.InvalidToken`

Note all messages are formatted into JSON in this code before sending to the server:

` def send_message(self, data, state): # function to send message to server # format all messages through this function try: # make dictionary to format all messages

        if state == "keyexchange":
            d = {"state": state, "address": None, "content": data}
            # dump into a formatted string with json.dumps

            formated_data = json.dumps(d)
        if state == "message":

            # dump into a formatted string with json.dumps
            d = {"state": state, "address": None,
                 "content": str(data)}
            formated_data = json.dumps(d)
    except:
        print(traceback.format_exc())

    # return the formatted values passed into the function
    return self.socket.send(formated_data.encode(FORMAT))

`

Also the value for the key is generated from Diffie Hellman exchange in the recv message function

• Ive tried converting the data into the correct format using encode and decode - this as far as i can tell isn't the issue
• Ensured the token is the same on client and server side
• Ensured the data is being loaded by the JSON formatter
• Checked that the data is not being altered on either socket server or client

Answer 1

it might be becz the Fe.net object is unable to decrypt the data because it is not a valid token. There are a few cause for this i guess

Make sure that the key used to initilize the Fe.net obj on the client side is the same as the key used on the server side.

Make sure that the data being passed to the Fe.net obj is in the corct frmt. it seems like you are using base64.urlsafe_b64encode to encode the key, so make sure that the data being passed to the Fe.net object is also in this format.

Make sure that the data is not being modified or corrupted during the transmission between client & server. could be an issue with the.netwrk conxtion or a problem with the JSON formatting.

Check the value of formated_data that is being sent to the server,I think it should be a bytes object not a string.

Make sure that the dumps and loads are using the same format utf-8 or utf-16

see if you are using the correct method of fe.net, you might be using encrypt method instead of decrypt or vice-versa.

Try these steps, see which one resolves the issue.

Here are a few suggestions for improving the code and troubleshooting the

Verify that the key being passed to Fe.net is the correct length and format. The key must be 32 bytes long and ensure it is encoded in base64 URL-safe format. Check that the data being passed to Fe.net for encryption/decryption is also in the correct format. It should be bytes-like and not to be encoded before passing it to Fe.net. Make sure that the same key is being used for encryption and decryption on both the client and the server. If the keys are different, the encryption/decryption process will not work properly. Also check the key is not getting expired during the communication process.