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

[Mike Wright]

Paul Johnson wrote:
> 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?
> 

Hi Paul,

Have you looked at ecryptfs?  It lays on top of the underlying 
filesystem so the files would be visible but their contents would 
require a key or passphrase to decrypt.

http://ecryptfs.sourceforge.net/ecryptfs_design_doc_v0_1.pdf

:m)