Secure iFrame URL Retrieval
To securely retrieve the iFrame URL, follow these steps for each request:

Generate RSA Key Pair
For every request, a new RSA key pair (4096-bit) must be generated.
YOU CANNOT USE TWICE THE SAME KEYS !!!

Send the Public Key
The public key must be Base64-encoded and sent as a request parameter. Use https://www.base64encode.org/ to test your encode.

Decrypt the Response
Decrypt the response using your private key with the following RSA cipher configuration: RSA/NONE/OAEPWithSHA1AndMGF1Padding

For testing or verification purposes, you can use the following RSA tool:
https://8gwifi.org/RSAFunctionality?keysize=4096