The feature is an upgrade on security standards first implemented on Android 6.0 Marshmallow, in which the system would notify users of malicious software, but would still boot up to a user’s’ typical settings. A phone with errors running Nougat won’t boot up, but will offer the user an option to boot into a limited functionality mode (possibly safe mode, which has existed for years). Android will also be able to correct errors, but this will cause some headaches for modders.
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The new version of the operating system will also feature “forward error correction”, or redundant code that it can use to fix the critical parts of the OS, to ensure that Android 7.0+ devices don’t lock-up because of random software corruption.
So, let’s say you want to root or install Xposed. Users will be able to root and customize unlocked bootloader devices as usual. A device with a locked bootloader will (probably) fail the hash check and won’t boot normally. Typically, developers and tech savvy users get devices with unlocked bootloaders or unlock the bootloaders on their smartphones to make customization easier. That’s where you may run into problems with Nougat.
In the changes we made to dm-verity for Android 7.0, we used a technique called interleaving to allow us to recover not only from a loss of an entire 4 KiB source block, but several consecutive blocks, while significantly reducing the space overhead required to achieve usable error correction capabilities compared to the naive implementation.
In this day and age where security breaches are everywhere and everybody is vulnerable in one way or another, it should be of no surprise that Android will start enforcing secure, verified boot on devices that ship with Android 7.0 (Nougat).
Even a single-byte error could prevent the phone from booting. You will most likely notice error-related corruption, since the verification could stop access to data blocks and trigger unusual behavior.
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The Android developer team detailed the new Android Nougat feature in a blog post Tuesday.
