Sometimes the nvram or nvdata inside the BLU Advance 5.2 mobile gets corrupted, due to which problems like "invalid IMEI" or "null baseband" arise in the mobile. It is not possible to repair them manually unless the mobile allows access in brom mode. DA Auth File comes in handy at this point which gives SP Flash Tool access to nv sections. With its help, not only IMEI can be written but also Wi-Fi MAC address, Bluetooth ID, and other security attributes can be restored. If this process is performed correctly, the mobile is restored with its original network functions..
There are some new series of BLU Advance 5.2 mobiles which have customized bootchain along with secure boot. That is, every part of the firmware is encrypted and any unauthorized access immediately shuts down the mobile. Flashing them is not possible for a common person. DA Auth File decodes these custom bootchains and allows the mobile to accept specific signed images. When you use the right scatter file and specific DA file, it becomes possible to bypass these complex protection layers, and thus you can not only install firmware but also restore the broken or dead state of the mobile.