FreeBSD's GBDE (GEOM Based Disk Encryption) has the capability to have
multiple users access an encrypted drive in a reasonably secure fashion. It
also provides (via the command line interface) the ability to destroy all
keys associated with the GBDE partition, and the ability to use detached
lockfiles.
These abilities make the creation of a "dead-man-switch" trivial; I already
keep my private keys for asymmetric crypto on a USB key in my pocket; It
would be reasonably trivial to create a shell script and store it on the USB
drive which would create an in-memory file system, copy the keys to that
filesystem and use that. If the system is every powered down then the keys
should be essentially unrecoverable.
http://phk.freebsd.dk/pubs/bsdcon-03.gbde.paper.pdf
<-- Excerpt from paper -->
The ever increasing mobility of computers has made protection of data on
digital storage media an important
requirement in a number of applications and situations. GBDE is a strong
cryptographic facility for denying unauthorised access to data stored on a
''cold'' disk for decades and longer. GBDE operates on the disk(-partition)
level allowing any type of file system or database to be protected. A
significant focus has been put on the practical aspects in order to make it
possible to deploy GBDE in the real world.
-----Original Message-----
From: Glenn_Everhart@bankone.com [mailto:Glenn_Everhart@bankone.com]
Sent: Wednesday, October 20, 2004 9:37 AM
To: volker.tanger@detewe.de; forensics@securityfocus.com
Subject: RE: Ever seen a dead-man switch?
<snip>
Interestingly, if a cryptodisk ever got to be part of the OS, or any one
cryptodisk package became overwhelmingly dominant, it might be expected that
part of the routine for powering down a box would be to check for the
package and attempt to grab its keys from memory. As it is, there are enough
different packages that this activity is probably not widely done.
<snip>
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