We have explained about Xiaomi’s Anti-rollback Protection in our previous post. There are still readers asking about “what can I do and what I shouldn’t do with my MIUI device?“. Before we get into that, let us have a refresh about what is the Anti-rollback Protection (ARB) built in recent MIUI devices.
ARB is basically a new security mechanism introduced by Google within Android 8.1 Oreo. However, it is not mandatorily activated. OEM manufacturers can opt whether to use or not to use this feature on all shipped Android Oreo devices. In the case of Xiaomi, the company has decided to enable the feature on several devices. Several MIUI phones known to have the ARB activated are Redmi Note 5 Global/Pro (whyred), Mi 6X (wayne), Mi 8 (dipper), Mi Max 3 (nitrogen), Redmi S2 (ysl/ysl_global), and Redmi 6 Pro (sakura).
Check also: ARB Bypasser and Fastboot Unlocker.
ARB makes use of Android Verified Boot 2.0 (also known as Verified Boot). This prevents the device from booting if it detects that the device has been downgraded to an older, unapproved software build. However, there is a major difference between what Xiaomi and Google have. While Google’s anti-rollback protection can be disabled if you unlock the bootloader, the Xiaomi’s can’t be disabled even if the bootloader has been unlocked.
ARB is a really big thing especially for ROM adventurous and root addicts. Users are no longer be able to flash a custom recovery and hence cannot root with Magisk as usual. Otherwise, the device may cause a thermonuclear war. No! What we mean is a bricked device.
Here are several things of what you can and cannot do on devices with ARB enabled.
- Do not downgrade from MIUI with ARB 4 to ARB 3, or ARB 5 to ARB 3.
- Do not switch from China to Global MIUI ROM or vice versa if the ARB of the new ROM is lower.
- Do not flash a custom recovery (TWRP/RWRP) without flashing dummy image.
You can do the following things:
- You can flash TWRP again.
- You can Root Anti ROMs with Magisk or Disable Encryption.
- You can switch from China to Global builds or vice versa but make sure the ARB index is not lower.
- You can switch between all ROMs with ARB 4 builds just fine, like from 8.7.12 to 126.96.36.199 or anything with anti 4.
- You can flash any AOSP/LOS-based ROM.
- You can flash fastboot ROMs with ARB 4.
What is ARB? ARB is just an abbreviation of Anti-rollback Protection. Nevertheless, this abbreviation also refers to the ARB index. This is useful to find out whether your phone runs MIUI with ARB enabled or not.
How to check for ARB on Mi/Redmi Devices?
- Disable Windows Driver Signature Enforcement on your computer – read here.
- Install Mi Flash tool – download here.
- Enable Developer Options. Go to Settings > About phone > tap the MIUI version several times until the developer options being enabled.
- Also, enable USB Debugging through Settings > Additional Settings > Developer Options > USB Debugging > toggle it on
- Turn off your device completely.
- Press the Power button and Volume Down (-) buttons simultaneously to enter bootloader mode (fastboot).
- Connect your phone to your computer.
- Launch Command Prompt window or Windows PowerShell. You can search for it in the Cortana search bar.
- Type the following command and hit Enter on your keyboard: fastboot getvar anti
Sample output will look like this:
- Any MIUI ROMs with ARB 4 (or greater) have Anti-rollback Protection Enabled.
- Any MIUI ROM with ARB 3 has no Anti-rollback Protection enabled.
You can read the full tutorial on how to check the ARB Index for any Xiaomi devices here.
Anti-rollback Protection on Redmi Note 5
In the case of Redmi Note 5 (Pro/AI/Global/China), the following rules of thumb may help you:
Global Beta ROM
- If you have updated to MIUI 10 Beta ROM 8.7.6 or above, you can flash all ROMs after MIUI 8.7.6 (including 8.7.6), but you can not downgrade to Beta ROM 8.7.5 or ROM previously.
- If you are on Beta ROM 8.7.5 or ROM previously, you can flash your device using all those previous ROMs.
Global Stable ROM
- If you are on Stable ROM V 9.5.19 (it will be released soon) or ROM above, you can flash all Stable ROMs after V 9.5.19 (including V 9.5.19), but you can not flash your device to Stable ROM V 9.5.17 or ROM previously.
- If you are on Stable ROM 9.5.17 or ROM previously, you can flash your device using all those ROMs.
— Source: MIUI Forum.
In short, MIUI Global Stable ROM v9.5.17 is the last version known to have ARB 3 (without ARB protection enabled).