shredding files on a flash drive

[D. Hugh Redelmeier]

I was using sneakernet to transfer confidential files.  In particular,
I put them on a "USB key" flash memory.

That got me thinking.  I would like to remove those files from the USB
device.  How can I do that?  As I understand it, flash memory devices
use "wear leveling".  I think that this is done by always writing to a
new physical flash block, leaving the old physical block fallow until
its turn comes.

This means that shred(1) won't do the job unless it is told to
rewrite a great number of times, something that is quite hard on flash
units.  It isn't even clear that we could guess what that number would
have to be.

(It is likely that shred would also not work on a journalling file
system.)

Any recommendation?  Perhaps one should never consider a flash device
cleaned.
--
The Toronto Linux Users Group.      Meetings: http://gtalug.org/
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists