The Xiaomi Authorized Flash Tool is an official service tool developed by Xiaomi Inc. Unlike the common Mi Flash Tool used by enthusiasts, the Authorized version connects directly to Xiaomi’s authentication servers. This allows authorized service centers and technicians to flash Fastboot ROMs on devices that are:
As of my last update, here are the general steps to download and use the tool: Xiaomi Authorized Flash Tool 6.1.1 Download - Google