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I think about the following use cases:

  • 'Perfectly' reverse encryption without losing settings
  • Update ROMs. Even if /system, /data, /sdcard (internal) are encrypted
  • Low level Backups with CWM. When SDCARD partition is also encrypted.
  • Emergency access to my data (screen broken, soft bricked...)
  • How to mount crypted dumps on linux (knowing the passphrase)

Is there some salt value going into the key together with the passphrase stored on the device?

I currently use a tmpfs mount to /sdcard and 'adb push update.zip' on my Nexus S to update the ROM. I've been told that the Galaxy Nexus also has an encrypted /system which would prevent all that (see Nexus S solution here: Broken screen while debug mode was disabled. How can I re-enable adb? )

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  • For the record: I will investigate and answer myself as soon as i find the time
    – ce4
    Jun 15, 2012 at 19:55
  • CM9 nightly here: updates work fine when encrypted. Backups need to backup /data which is encrypted so they don't work. The way I have been doing it is to use Mybackup Root to create a backup of my apps and settings and restoring that after I move from one major revision to another (such as I will be doing soon from ICS to JB).
    – warsong
    Jul 16, 2012 at 8:34
  • 2
    I use a tmpfs mount on /sdcard and 'adb push update.zip /sdcard' ATM for updates (the normal /sdcard partition is also encrypted on a Nexus S, so that doesn't work!). I'm mostly interested in accessing data post-mortem (aka. how does the enc work, how could I mount it using standard linux and access my data in emergencies and so on. Just for knowing what I could do if something goes titsup)
    – ce4
    Jul 16, 2012 at 8:39
  • I had this issue right now: broken screen but device functional. I managed to decrypt and backup my data with TWRP recovery, with a little help from the TWRP IRC channel: android.stackexchange.com/a/125155/130726
    – personne3000
    Oct 6, 2015 at 16:34

3 Answers 3

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I don't know of any implementation for non-android devices for accessing the data, although it should be fairly easy to port / implement. For an explanation how the encryption works I recommend reading the following article:

http://nelenkov.blogspot.de/2014/10/revisiting-android-disk-encryption.html

I really doubt the Galaxy Nexus has an encrypted /system. And starting from Android 5.0 it could be almost impossible to read the data on other devices than the android device itself because parts of the key are stored in otherwise unaccessible DRM areas of the system board / SoC --- not the eMMC flash (on Qualcomm devices and possibly also Intel).

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Download the latest cwm philz touch recovery{Install} and then look in philz settings or recovery options for the clone current rom to zip option then do that, or could be complicated to get that kind of backup from a dead or broken device so just clone current rom to zip file or modify your rom on computer to your liking then save to sdcard for safe keeping, hope this helped.

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I think encrypted device backups will work on that device only as long as the used passphrase does not change between the backups. If this is not the case, I think adb backups are the best, at least for apps and settings. Google remembers system settings, and backing up apps via MTP or adb or TB,etc. is possible. Keep your personal data in an encrypted archive backup. If all this is a bit too complicated, use TWRP, I'm pretty sure the latest versions support encrypted partitions in Nandroid. The encryption format has to be understood before the image backups can be decrypted on Linux.

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