usb flash disk, ext3 file systems, enforcing rights, security

Paul Johnson pauljohn32 at gmail.com
Tue Dec 11 17:26:53 UTC 2007


How do you secure privacy of files on a USB stick?

The usb flash memory stick works fine if it is VFAT, but what if you
are worried you might lose it and then anybody could read your
secrets.  Or, if you need to share a file to somebody, but don't want
them to read everything else, what do you do?

I thought I could fix that by putting  on an ext3 file system. But it
doesn't help. Windows users with IExplore can see all the files, no
matter who owns them.

On a Linux system, the owners of the files are not recognized.  I had
forgotten that ext3 uses user numbers, rather than user names, for
ownership information.  So when I take a disk from one system to the
next, then the user is either unrecognized or wrong.  Here's a case
where it is unrecognized:

drwxr-xr-x 3 29999 29999  4096 2007-11-26 19:50 Booger

I've seen other cases where another user who happens to have the same
user number is given ownership of my files.

So, apparently I can't rely on the file system permissions to give me
any security.

Aside from tarring up stuff that I don't want to be public and
encrypting with a gpg signature, I'm stumped on what I should do.

Can you put an encrypted file system on a usb flash disk? How?

-- 
Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas




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