Anti-rollback/ARB for device firmware

Anti-rollback, or ARB, for device firmware is a feature of some devices that prevents the device from booting if it detects that the device has been downgraded to an older, unapproved software build. This prevents attackers from loading older software on a device that’s susceptible to an exploit. However, some people prefer to use an older version of the firmware, and many support the ability to backtrack or downgrade to a previous build or edition. However, many companies have created devices that prevent rolling back to the previous firmware.

In the case of Xiaomi Verified Boot has a rollback index which is compared with the rollback index of the ROM that you are about to flash.^[1] If the current rollback index on your device is less than the rollback index in the ROM to be flashed, then the ROM will be flashed without any issues and the current rollback index will be increased to match the new rollback index [of the just flashed ROM].^[1] If the current rollback index on your device is equal to the rollback index in the ROM to be flashed, then the ROM will be flashed and there will be no change in the rollback index.^[1] If the current rollback index is greater than the rollback index in the ROM to be flashed, then the ROM will be rejected. But this will only happen if you’re flashing via fastboot or Mi Flash.^[1]

1. Denys users from being able to willingly downgrade to previous firmware
2. If the new firmware creates problems, the ability to fix the problem through rollback is unavailable

• Oneplus phone update introduces hardware anti-rollback

• Secure boot