Probably to help define what is it is, uses:

• Slave to master authentication
• Application to mariadb server authentication for web scripts etc

Rough thoughts:

Registration:

1. Using modern authentication, the first use creates a registration with the server with the server and saves one side of the authentication (as a local file) and the server saves the other side (in the users table).
2. The user is created without permissions
3. A server administrator with existing permissions creates grants for the user
4. "Change Master TO" could also use the same registration if PASSWORD was made optional (could help simplify the easiest part of MDEV-7502)
5. Todo - optional MITM registration protection
   ( Assumptions: database servers are installed in network environments where the risk of a DoS though registration is low, however its not totally risk free and a post process to enable the registration is required )

Connection:

1. The client connection will mmap the file used in registration and will use DH aspects of a key exchange to prevent MITM
2. A shared secret will be provided to the client and stored in shared memory (mmap MAP_SHARED) with the other process by the client plugin using the same user (i.e. php-fpm, and equivalent for other languages)

Subsequent connections:

1. use a HMAC based authentication from the shared secret in shared memory (for CPU speed in computation and less exchanges compared to DH)

I'm currently just looking to replace SHA1-based password auth. So the new one should do the same — get the password from the client to the server, so that the server could compare it, without actually seeing or storing the password.

I'd rather avoid saving files on the server or client side, I think it complicates usage.

btw, my working prototype uses ed25519.