[O] mobileorg encryption in iOS vs. Android

[John Hendy]

See this thread on the Android mobileorg mailing list for reference:
- https://groups.google.com/forum/#!topic/mobileorg-android/IELoLsOCvos

I was having issues with org-mobile-use-encryption, and think it ended
up being that this variable is only for the iOS version. It encrypts
with openssl (at least from what I could tell) evidenced by this in
org-mobile.el:
----------
(defun org-mobile-encrypt-file (infile outfile)
  "Encrypt INFILE to OUTFILE, using `org-mobile-encryption-password'."
  (shell-command
   (format "openssl enc -aes-256-cbc -salt -pass %s -in %s -out %s"
           (shell-quote-argument (concat "pass:"
                                         (org-mobile-encryption-password)))
           (shell-quote-argument (expand-file-name infile))
           (shell-quote-argument (expand-file-name outfile)))))
----------

The Android version integrates encryption via Android Privacy Guard
(http://thialfihar.org/projects/apg/), which decrypts gpg files. Thus,
the Android procedure is:

1) Encrypt the desired org files:
$ gpg -c file.org

2) Get org-mobile-files to update by either:
- Adding file.org.gpg (or whatever you renamed the encrypted file to)
to org-agenda-files
- Adding the encrypted gpg file to org-mobile-files

3) M-x org-mobile-push

4) I was asked for the password three times; looks like once to
decrypt and then twice for a new password to re-encrypt when pushing

5) Make sure Android Privacy Guard is installed on phone

6) Setup sync settings and syncronize

7) A popup via APG should ask for symmetric password

Also, add this text at the top of the file so that emacs knows this is
an orgmode file even thought it ends in .gpg:
-*-mode:org-*-

I'm wondering if there's a way to add some sort of variable, say
`org-mobile-os` that could take "ios" or "android" as the inputs so
that org-mobile-use-encryption worked more as expected for Android
users?

Just a thought and wanted to inquire about this. At the very least, it
looks like the manual should be updated to reflect that the process is
not the same for both mobileorg's when it comes to encryption.


Thanks for any feedback,
John