A user definitely receives 2FA code—Nobody can control or restrict their account. The blockchain verifies OTP delivery.
Send 2FA codes with blockchain transactions, encrypted with Diffie-Hellman Curve25519, Salsa20, Poly1305 algorithms and signed by SHA-256 + Ed25519 EdDSA. Exclude MITM attacks, and guarantee authenticity.
Receive a code on any device—in a browser, or use iOS, Android, Windows, Linux, macOS app. And you can create your own.
Your users remain privacy. No emails and phone numbers. IPs are hidden. The Tor app.
Feel free to deploy packages and revise the software code—including Blockchain node, communication protocol and client apps.