[talk] passwd entropy and strength

Jim B. jpb at jimby.name
Mon Nov 6 15:10:21 EST 2017

* Thomas Levine <_ at thomaslevine.com> [2017-11-06 11:22]:
> I am very satisfied with my password management approach, and
> I keep debating whether it is safe to share. On one hand,
> I theoretically think that sharing it would not provide an adversary
> with enough information to guess my passwords or otherwise bother me,
> but I also wonder whether it would tell the adversary enough to study
> the relevant approaches/software enough to come up with a vulnerability.
> Does anyone have any commentary on my concern?

Like many valuable things, it depends on your risk model.
Who is your adversary?  A 3LA?  Large well funded criminal
enterprise?  A really good hacker?  Random scripty?

For most folks, I suspect it is the latter.  On the other hand,
it doesn't matter who it is - personally I want to keep my shit
safe from *all* prying eyes.  It may not be great shit but it's
*my* shit, and I want to keep it that way.

You could of course, follow the web of trust model - share
individually with those you trust and gain feedback to improve
your defenses.

That said, I'll share my approach.  Just don't hack me and steal
all my shit :-)  I'm going to number all the elements below
to allow for easy commentary.  I welcome all comments and
suggestions on how to improve this setup.

1. My "password vault" is just a text file on my TrueOS laptop.

2. The file (in some directory)  is encrypted with gpg2(1) with a
   strong password.  I do not keep a clear text version on hard

3. To edit the file, I create a memory disk, format it with newfs(8)
   mount it, and lock down the mountpoint.
4. I copy the encrypted file to the memory disk, decrypt, edit,
   save, and re-encrypt it all on the memory disk.  Lastly, I
   use "rm -P" to "securely delete" the decrypted copy that
   I edited.

5. The encrypted file is copied back to my hard disk.

6. The memory disk is unmounted and deleted.

7. The ASCII-armored file is then steganographically embedded
   inside a JPEG file.  I use outguess(1) (by Niels Provos)
   for the steganography operations.  This operation has a
   completely different password.

8. The .JPG file is copied to a secure location online.

Thus, I have a local ASCII armored encrypted file on my disk,
and I have a copy of that file embedded inside a JPEG file
on my disk, and also somewhere online.

9. If I just want to view the file, I open up a new terminal,
   cat the encrypted file and pipe it to "gpg2 -d" which
   outputs the clear text to the terminal window.  I
   copy/paste whatever I need, and delete the terminal window
   when done.  pinentry(1) is used for passing the password
   to gpg2 in this step.

That's it.

Comments welcome!
Jim B.


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