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Since I still encounter issues with modified boot images and recovery images I want to remove the device encryption from my Nexus 4 (running 4.3).

I known that there is no "official" way to to this but since this is an encryption it can be reverted. So please don't tell me that it is impossible (I already know that android don't want you to do this).

So I came up with two ideas but I could not find anyone who already did this and want to be sure before wiping my data partition. My device is not rooted but the bootloader is unlocked.

  1. Making a backup with adb backup, format the data partition and restore the backup. But I could imagine that adb is unable to restore backups on non-encrypted devices if they were made on an encrypted on. (Can tell me for sure?)

  2. Starting a modified boot image with fastboot that just decrypts the data partition (should be perfectly possbile but I havn't seen such a tool)

  3. Any other idea?

Chris
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    Factory reset is the only way to remove the encryption from the device, you will lose all your data. – Ryan Conrad Aug 26 '13 at 20:35
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    @RyanConrad It is not for sure. If android can decrypt /data than any other code that is running on the cpu can too. It is only a questions of whether of not someone already coded something like that. You can always revert an encryption. Only because android has no option for it does not mean you can't. – Chris Aug 26 '13 at 20:49
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    Decrypting data is not the same as removing the encryption. Your statement about "if android can decrypt /data, any other code running on the cpu can too" is not true. Android system level applications can have more permissions than non-system applications, they can also access things that non-system apps cannot. If you are asking, "Can this be done", Yes, in theory it is possible, but just about everything "is possible". That doesn't mean anyone has done it. How to do it would be outside the scope of this site. The only real way to do it is to do a factory reset. – Ryan Conrad Aug 26 '13 at 21:15

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I did manage to turn my device back to an unencrypted state. If you do a device backup via the adb backup command you get a nice .ab file. There exists at least DroidExplorer that can convert these backups into .tar files: How do you extract an App's data from a full backup made through "adb backup"?

I'm not realy sure why there are some apps that did not get backed up but I think this migth have to do with the market license stuff. Only some bougth apps were not backed up. If you want to make sure that all your important apps got backet up use DroidExplorer to check it out.

Then you have to perform a factory reset in order to get it back in an unencrypted state. Now you can eigther use adb restore or Titanium Backup(which also allows to only restore some data) to restore the backup.

Even if this is an answer to my question i will not mark it as one for now since I'm still convinced that you could also load a custom software via fastboot to encrypt the data partition without a factory wipe.

I also found a tecnical description from google: http://source.android.com/devices/tech/encryption/android_crypto_implementation.html

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Chris
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I just removed my Android encryption. I plugged my Android into my computer to back it up. Then, I did a factory reset. After that, I copied all of the files onto it WITHOUT DELETING ANY FILES ON THE PHONE, and I merged the folders + copied over files. If it doesn't let you copy a certain file, skip it. I then unlocked my phone, it didn't change the lock or the main screen back, or keep my texts, but it did back up my apps with all of the app data. I put my main screen back how it was, and the encryption was removed.

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