Note: Since lowtraxx's guide has included how to get back to stock rom since the time this post was made, I strongly suggest to follow his guide instead.
- I make no claims to any of the codes, scripts and programs listed in this post. Credit goes to the creators.
- This serves as a extension of lowtraxx's guide (which left your device on a rooted SGP621 on a D6603 system).
- These are what I did to get stock rooted firmware on my SGP621 while keeping the bootloader locked and most importantly, the DRM keys intact. I make no guarantees that you will not brick your device, but I did quite a lot of trial and error flashing without messing things up, so if you know what you are doing, these steps should be relatively safe.
- Backup TA by DevShaft
- Flashtool by Androxyde
- Stock SGP621 FTF (I compiled my own by downloading the firmware using XperiFirm by laguCool and bundling the FTF using Flashtool. Alternatively, you can just use the one provided in lowtraxx's guide.)
- Advanced Stock Kernel by krabappel2548
- PRFCreator by zxz0O0
- SuperSU by Chainfire
- SonyRICDefeat by dosomder
- Follow lowtraxx's guide to completion.
- Backup TA partition using Backup TA.
- Return to stock unrooted by flashing the SGP621 FTF using Flashtool.
- Unlock the bootloader (You'll lose the DRM keys here, but it doesn't matter anymore since you already have them backed up using Backup TA).
- Flash the Advanced Stock Kernel using Flashtool in FastBoot mode. At this point your device will be unlocked, with DRM keys lost, and rooted with custom recovery.
- Using PRFCreator on the SGP621 FTF and the SuperSU zip, create a rooted stock firmware flashable zip. Note: Be sure to check all the checkboxes under the "Include" section.
- Copy the resulting zip onto your device's internal storage or external SD card.
- Also copy the SonyRICDefeat zip to the same location.
- Boot into TWRP on your device (Boot up the device and press the Volume down key when the purple LED lights up on the Sony boot screen).
- Flash the rooted stock firmware zip followed by the SonyRICDefeat zip.
- Once complete, reboot into system and set up the device for USD Debugging.
- Restore the TA partition using Backup TA.
- Reboot the device again and you now have the device on rooted stock firmware, with DRM keys intact.