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I want to store an encrypted .txt file (encrypted with a password, with AES for example) in the interal SD memory or µSD card of my phone. I want to be able to read it every now and then, but:

  • I don't want the unencrypted plain text file to be extracted and stored in the SD card (even as a temp file).

  • I don't want the unencrypted plain text file to transit via network (internet, etc.)

Is there a solution / app that would display an encrypted text file?

PS: I already tried full encryption of the phone, it's not what I'm looking for (other reasons, off topic here)

PS2: I don't want to use an online service

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  • While app recommendations are off-topic here (there's SoftwareRecs.SE for that), you might wish to take a look at my list of encryption apps. I vaguely remember some of them described exactly your use-case.
    – Izzy
    Oct 29, 2017 at 18:03
  • Thanks @Izzy. Is there one which is open-source, ad-free, and that uses no permission except reading a file on sd card (I don't want it to access internet)?
    – Basj
    Nov 6, 2017 at 10:40
  • See the list – or use the search, which allows you to exclude apps requesting given permissions. For open source, watch out for the F-Droid and IzzyOnDroid icons next to the app name. Ad modules (and other trackers) are often indicated by "monitor icons", but that information is not complete (not known for all apps).
    – Izzy
    Nov 6, 2017 at 10:54
  • Thanks for your list of apps @Izzy. It's very useful, and all the little icons (0, 2, etc.) for the number of required permissions are very helpful to see what we're looking for.
    – Basj
    Nov 7, 2017 at 17:48

1 Answer 1

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Thanks to this list of encryption apps, I found Encrypt It MkII which does exactly when I need:

The only problem I still have, is that I don't know how to decrypt it on Windows. (Does anyone have any idea for this?)

As an example the plain-text

COUCOU
COMMENT CA VA?

was encrypted by Encrypt It MkII with password abcdef as:

9XWIf05d8m2+1lhdJa+mzhChq6+8SmMu6D5UsWNFNcCNmE0fcPZghaR3C7VZVlTDxHcqazBUwBcs
6Ts2R81cfCo=
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  • That app uses AES256 to encrypt your text with a salted password – so without the "salt", you won't be able to decrypt it. Apart from which, that app was last updated in 2013. Maybe SealNote would be a better option? Open source, also AES256 (but no salt – so knowing the password, you should be able to decrypt on your Windows machine with an appropriate program), and (as that seems important to you as it is to me): no Internet permission. Oh, and more up-to-date (3/2017).
    – Izzy
    Nov 7, 2017 at 18:34
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    Thanks @Izzy. So it seems that this app (Encrypt It) is finally still not exactly what I'm looking for ;) SealNote isn't the one either because it has a "notes" structure, and I just want to open a single encrypted (possibly large) .txt file. I posted a Software Rec question here: softwarerecs.stackexchange.com/questions/46932/…
    – Basj
    Nov 7, 2017 at 20:56

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