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I'm looking for a way to share a very sensitive document between Windows (read and write access) and Android (read access at least, writing appreciated but not immediately necessary). What I considered already:

  1. Veracrypt. Works for the Windows part, but people say that the only relevant Android app (EDS Lite) has been having issues on recent versions of Android for years. Not reliable.

  2. An encrypted archive like WinRAR has. Sadly, it has never been meant for my use case: WinRAR, for instance, decrypts and unpacks a file to be viewed to a temporary file on disk and keeps it as plaintext until WinRAR is closed. WinRAR not closed nicely, plaintext sits there forever. An absolute no go.

  3. Encrypted PDF. Would work if not for the necessity to copy out some text from time to time. PDF is notoriously unreliable at this.

Overall, I'm at a loss and would appreciate some ideas.

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  • what have you finally chosen?
    – Suncatcher
    Commented Aug 4 at 1:53
  • 1
    Finally I chose not to use Windows; not just because of this problem but for many reasons. Switched to Linux and happy.
    – sigil
    Commented Aug 5 at 10:24

3 Answers 3

1

You could go with gocryptfs:

It's a FBE (file based encryption) inspired by EncFS. I use it on Linux, and it works fine. Files are only stored in encrypted form, their decrypted "presence" is established via FUSE (Filesystem in Userspace) on-the-fly, and shown like a "mount point" (i.e. a "virtual directory").

This should fit all your requirements, comes for free, and even is open-source so you can inspect if it does what it claims.

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  • Sadly, the Android part of scheme you suggest has the same issue as Veracrypt: it relies on just one app that can go broken, unmaintained, etc. any moment. Moreover, the app is not available through the official app store, which is suspicious in itself.
    – sigil
    Commented Apr 23, 2021 at 15:58
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    What is "the official app store"? F-Droid is a place where open-source apps are published. Nothing suspicious about that. It's the "official app store" on my devices (I solely use F-Droid as I don't like Google tracking me or having a bunch of trackers in security-sensitive apps). IMHO F-Droid is a much safer place than Google, not a single piece of "bad stuff" has ever been found there. As for "single app": most of such solutions rely on "one single thing", especially the commercial ones (and those you cannot fix as you don't have the source).
    – Izzy
    Commented Apr 25, 2021 at 0:01
  • Official app store for Android is exactly this: play.google.com Anyway, I think I found... now an actionable answer yet, but an approach that seems to lead somewhere - encrypted Word files. Thank you very much for your desire to help.
    – sigil
    Commented Apr 26, 2021 at 13:37
  • I won't ask what the official shop for food stuff is then ;) Glad you found something that works for you! Maybe my suggestion works for someone else then.
    – Izzy
    Commented Apr 26, 2021 at 16:54
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meanwhile....

I found out and implemented "AESCrypt" on all my systems - fedora Linux, Archlinux, Windows 11, Android 12 (with added Crypt4All app) - and it works very well for my needs. With exchange via my own Nextcloud on a Debian server in a data center.

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  • Crypt4All seems like shady app: it was delisted from Play Store and I found no official page for this app. Was it ever security audited at all? I would avoid using it for encrypting the sensitive data
    – Suncatcher
    Commented Aug 4 at 1:53
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You could always plug the Android device into your computer with a charger cable to pull the file over from the device directly. If you're worried about the file having something happen to it, like being stolen from the computer, encrypt it on the Windows end.

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