Reading Pro encrypted files

madonnell

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Been waiting for the encrypted filesystem support so that the Pro would meet requirements for corporate email since I got my Pro in Dec. Upgraded to 3.8.7 when it came out, and turned on device and SD encryption.

Oddities ...

(OK, the oddities came out a questions. But these are more rhetorical - not really needing an answer)

Why per-file encryption and not device encryption?

Why leave old files or those copied from PC unencrypted, and only encrypt new files created on the phone?

Given the mix of encrypted and unencrypted files, why no method for seeing their state or converting to/from encryption?

Why encrypt files but retain the original filename, so you can't tell by looking at a file in the filesystem whether it has been encrypted or not?

Seems like a pretty marginal half-a$%ed encryption implementation.

The real question ...

How do I access a decrypted copy of the files from the PC USB interface?

USB Mass Storage mode mounts the sd card with a drive letter, and lets me see the files, but in their encrypted form. It basically mounts the SD card as a 'dumb' usb drive. (If you view a '.txt' file, you see the encrypted binary)

USB PC Mode makes the droid look like a music player to the PC - you see a 'droid' device which has media syncing and such. I believe that this show the unencrypted view of the files, since it is being interpreted and exported through the OS (wow, that was a horrible explanation). BUT, PC Mode only appears to show certain media file types (mp3, jpeg, etc) and their associated directories, so most of the directories and files are totally inaccessible. (even renaming junk.xls to junk.jpeg and putting it in the 'downloads' directory does not seem to work).

Dropbox, or email, or some other indirect solution is not acceptable, since the whole idea of encryption is to keep my unencrypted files out of the porous cloud. Plus, it would be annoying and awkward.

So, sub-questions ...

Does the Droid use a standard encryption algorithm like AES/256, and can we get/find/see the encryption key on the phone, such that I could use USB Mass Storage mode and a PC-side decrypter with that key to see the file?

Alternatively, is there a way to make USB PC Mode show other files types and directories? Hypothesize it could be a rooted phone and I am totally comfortable poking around the linux underpinnings of the phone.

 
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madonnell

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Painful hack

OK, I did discover one really crude way to get a file off the phone when the file was encrypted. Pain in the a$%, but it does work.

On the phone, in a file explorer
- make a copy of the file (if desired)
- add a '.jpeg' extension to it (fake that it is a media file).
Plug in the usb, and set to PC Mode
- Browse to the folder on the phone where your file was.
- you should see <yourfile>.jpeg
- copy it to your computer
- remove the .jpeg from the filename (restore the old extension)
Open the file!

I tried this originally and did not think I saw the file. But it was there today. So it is possible this did not work until some later time / action (like that I rebooted the phone!).

Easy!

(I originally posted this at http://www.droidforums.net/forum/mo...d-pro-encryption-honeycomb-2.html#post1546179, but meant to do it here)
 
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