[GUIDE] Backup TA/DRM Keys before Unlocking Bootloader

[boylush]

Unlocking the Bootloader the Correct Way!

I've realised there is a lack of proper steps that shows how to unlock BL + backup TA properly, here it is.

FOR WINDOWS ONLY (Dependencies)
First, download the following dependencies:
1. Backup TA ( https://github.com/DevShaft/Backup-TA/releases )
2. Root ( http://forum.xda-developers.com/crossdevice-dev/sony/root-how-to-root-5-0-lollipop-t3212108 )
3. FlashTool ( http://www.flashtool.net/index.php )
4. Kanuti Drivers ( http://developer.sonymobile.com/downloads/drivers/xperia-m4-aqua-driver/ )

Secondly, install 1, 3 dependencies from step 1.
If you are using Windows 8 and above, disable driver signing enforcement (If you are using Windows 7 and below, you can ignore this step)
Then, install 'FlashMode' and 'Fastboot' drivers from FlashTool/drivers/Flashtool-drivers.exe
Also, install Kanuti drivers.

Thirdly, revert your firmware (equivalent for model) to one of those supported for rooting (BACKUP YOUR DATA)

M4 Aqua Dual E2363 - 26.1.B.1.85
M4 Aqua E2303 - 26.1.A.1.128

You can download the required firmware in FlashTool's XperiFirm downloader. (You can download other region specific firmwares and flash, there is no harm, try not to cross flash other model's FTF)

Forth, enable usb debugging in phone, then root phone using the 2nd dependency.

Fifth, Backup TA using the bat file provided in the 1st dependency.
Keep the zip safe on cloud storage or somewhere you won't lose it, if you require to service your phone, restore this zip and flash stock ftf, your phone would be as good as new, no traces of unlocked bootloader could be found.

Sixth, After Backup TA, unlock BL using FlashTool.
Request code from http://developer.sonymobile.com/unlockbootloader/unlock-yourboot-loader/ (Click either M/M2 and key in your IMEI for unlock code)

AND, you are done!