Absolutely amazing work. I've got to go over this a few times because, whilst I managed to get my thing working, I never actually got into understanding the cryptography and that is super interesting.
P.S. I just tipped you 5000 sats as Hive via @v4vapp
RE: [SOLVED!] PHP Native - Hive Signature Validation - and the Hive+WordPress SSO (single sign on)