Nexus 6P appears to use e-fuse to store permanent record of unlocked bootloader
There’s a battle going on in Android-land right now, one that threatens to ostracize users power users in the name of security. It seems that with every major of revision of Android, Google makes its mobile platform less appealing to the mod community, and especially with the emphasis on Verified Boot in Android Marshmallow, it can feel like there’s no longer a place in Android for users who want their phones to run “unapproved” software. And while it’s no surprise that mainstream devices may arrive with their firmware thoroughly locked down, Google’s Nexus line has long been a bastion of developer support. With the new Nexus 6P, though, devs are wondering just how friendly the phone really is, as it appears to arrive with a hardware “feature” that may scare away potential ROM flashers.
Unlocking your phone’s bootloader may sound a little intimidating to the uninitiated, but it’s par for the course when preparing to load a new ROM image on a device. And while there’s a small amount of risk involved, users have always taken heart in knowing that they could restore their hardware to a previous state by flashing the old software and re-locking the bootloader – just like new.
At least, that’s the way things work for many phones, but today we hear that the Nexus 6P is equipped to carry a permanent record of any bootloader fiddling.
When unlocking the bootloader for the first time, the phone reportedly marks an area of one-time programmable memory with a flag that indicates the hardware’s been unlocked. The presence of this “electronic fuse” is visible above in the Qfuse section of the Nexus 6P’s fastboot menu.
And much like a physical fuse, once that e-fuse is blown, it’s blown for good: no matter what you do, restoring factory images and re-locking the bootloader, the Nexus 6P’s going to remember that it was previously unlocked.
What are the consequences of that “I was once unlocked” flag being set? As of right now, that’s not yet clear. Could Google deny access to features like Android Pay, just like if you’d rooted a phone? It may not be long before we find out.