Android utilizes a so-called “crypto footer” format that stores encryption-related parameters. It’s very similar to an encrypted header for partitions used in LUKS (Linux Unified Key Setting); however, it’s more compact and does not include many LUKS features. While LUKS allows multiple key slots and allows encryption with different passwords, the crypto footer on Android only holds a single copy of the master key that is encrypted and supports only one encryption passphrase.
Furthermore, while LUKS breaks the encrypted key into multiple stripes to lower the chances of recovering the full key once it’s deleted from the disk, Android doesn’t have such a feature. Additionally, LUKS includes a master key checksum (derived from using the master key in PBKDF2) that lets you verify that the password entered is valid without encryption of any disk information.
The Android crypto footer does not have the master key checksum. The only way to determine if the passphrase entered is correct is to mount encrypted files. If the mount is successful, then the passphrase is believed to be valid.
Crypto Footer looks like:
In Android 4.3 the Crypto footer looks like:
unsigned char crypto_type_name[MAX_CRYPTO_TYPE_NAME_LEN];
The structure includes the version of the FDE scheme, the key size, some flags, and the name of the actual disk encryption cipher mode (as-CBC-essive:sha256). The crypto footer is then followed by an encrypted key and the random salt of 16 bits. In the initial version, many elements are not explicit and therefore are not included within the footer of cryptography.
The 128 bit AES key encrypts master keys (key-encryption key, also known as the KEK) created from a passphrase supplied by the user, using a 2000 iteration of PBKDF2. The derivation process also produces an IV that is used to decrypt your master keys in CBC mode.
How to fix: Unable to find crypto footer:
If you try to download Open Beta 7 (OTA_011) zip using TWRP on your Android and it fails, it will break everything. The flash usually worked as it did with the last updates, but this time, you could not install SuperSU onto it. So you rebooted and hoped it would work.
The screen displayed was the “Decryption failed” screen, with the only option being a factory reset.
The problem is that you don’t have backups of your data because FolderSyncLite does not work in any way. When you returned to TWRP, the data partition was not mounted; with an error, TWRD displays the data partition as having 0 MB. So it’s not like the data could disappear overnight.
The user data partition was corrupted, and as it was encrypted, the entire division became unusable. TWRP’s fsck.f2fs cannot function with an error of 254 (glitched error number -1? ).
Do you have any way you can do to salvage your information? For example, could you copy the raw partition onto your computer and then process it there? Do you have the ability to repair the damaged header or footer manually? If you have the pattern or PIN. Use the mega unbrick guidebook, and everything will work fine.
You must change the partition for data to the format ext4. This should work since often; the partition is formatted with a corrupted copy of F2FS. If this doesn’t work, erase user data, then try it again. The chances are it will be working. Don’t be surprised. It occurs.
How to fix: Unable to Mount Data:
All your mobile data will be deleted. Make a backup of your data before moving on to the second step.
Suppose you are experiencing issues with your laptop or computer. In that case, it is recommended to try Restore Repair, which can scan the repositories and repair the missing or corrupted files. This is a good option in most cases where the problem originates from a corrupted system.
- The first thing you should test is to see if the internal storage got encrypted using the security method for screen locks.
- Visit your Android screen lock in the Settings menu, Security, and change the screen lock’s way of locking to the Pass option or pin. Create a new screen lock.
- Reboot TWRP, and it will prompt you to enter a password. Enter the pass or pin that you have made.
- TWRP attempts to unlock your device’s internal storage. If it succeeds, then you should not encounter any issues. If, however, you are still unable to resolve your issue with “unable to mount data, internal storage 0MB”, proceed to the next step in this tutorial.
- Reboot your device into TWRP again.
- Go to Wipe > Advance Wipe > Data and select Repair or Change File System.
- Click Repair File System to check whether this resolves the problem. If not, go on.
- Click the Change File System button, select Ext2, and move your finger to confirm.
- Then switch over Ext4 to Ext4 with a swipe for confirmation.
- Return to the TWRP the main menu and then go to the Mount menu. You can then check whether your partitions can be mounted as of now.
- If you’re still unable to mount your partitions, you should repair your Internal sections, likely erasing the internal storage.
If none of the Methods have resolved the issue for you, you can use the Restore Repair Tool to scan the repositories to replace corrupt and missing files. These methods implement in most cases, where the issue is originated due to system corruption. Restoring the data will also optimize your system for maximum performance.