‘Verified boot’ is one of the many layers of protection that Android uses to keep its users safe and ensure that rootkits or other forms of malware don’t operate on your device unnoticed. Android verified boot makes use of cryptographic integrity checking to detect changes to the operating system. While users have been notified about their system security since Marshmallow, with the Android 7.0 (Nougat OS), Android will strictly apply verified boot.
In other words, it means that if a device is found with a corrupt boot image or verified partition, it will not boot at all or will boot only in a limited capacity with user consent. This will act as a safeguard to prevent viruses and malware from taking advantage of the corrupted software.
While enforcing verified boot is definitely a good move by Google greater security for Android users, but it could also lead to more problems on devices suffering from software and/or hardware issues.
According to the Android Developers blog, “Such strict checking, though, means that non-malicious data corruption, which previously would be less visible, could now start affecting process functionality more.”
Enforcing verified boot could possibly make it difficult to install custom ROMs. You will most likely notice error-related corruption, since the verification could stop access to data blocks and trigger unusual behavior. The downside is it could make custom software more difficult to create.
Meanwhile, according to Google, devices with a locked bootloader on Android 7.0 Nougat will utilize this new security to check for modifications. However, the good news is that the Nexus line or smartphones that come with unlocked bootloaders will remain the same.
Source: Android Developers Blog