It's not just KYC; security in Bitcoin is currently based largely on obscurity. On not talking about the fact that you own BTC. On hiding. According to Auguste Kerckhoffs, a cryptographic system must be secure even if everyone knows how it works, except for the secret key. I found this interesting protocol: https://ugc.production.linktr.ee/dfb2dee7-917b-451d-9c80-1b088de2b546_gw-light-deck.pdf