If your phone is hard-bricked (no display, no vibration, only detected as “MediaTek USB Port”), the BootROM is still active. Flashing without auth will fail. With auth, you can write a full stock ROM.

Click "Choose" on the line and select your MT6785 auth file.

The Auth File is a tool of efficiency. ODM factories use reverse-engineered or legitimately licensed Auth files to flash the initial firmware onto millions of blank MT6785 eMMCs. Here, it prevents rogue operators from injecting malware into the supply chain.

This is why professional repair guides almost universally recommend mode rather than "Format All + Download" when working with Secure Boot devices. The latter erases authentication-related partitions, making recovery exponentially more difficult.

The Auth File is the Holy Grail. Developers on forums like XDA-Developers painstakingly extract leaked Auth files from factory dumps. The existence of a valid MT6785_Authentication_File.bin for a specific device (e.g., the Xiaomi Camellia) dictates whether custom ROM development is feasible. Without it, the bootloader is a digital fortress.

: Tools like the MTK Auth Bypass Tool v13 allow you to disable the Secure Boot/DA authentication.