From: Dave Emery <die@die.com>
Date: Tue, 1 Dec 1998 04:14:50 +0800
To: lcs Mixmaster Remailer <mix@anon.lcs.mit.edu>
Subject: Re: Securing data in memory (was "Locking physical memory (fwd)
In-Reply-To: <19981130180002.17576.qmail@nym.alias.net>
Message-ID: <19981130143320.A2756@die.com>
MIME-Version: 1.0
Content-Type: text/plain



On Mon, Nov 30, 1998 at 06:00:02PM -0000, lcs Mixmaster Remailer wrote:
> 
> But speaking of using passwords to protect data, how about an encrypted
> swapfile for a PC?  There are fast enough ciphers today that the virtual
> memory system could encrypt data as it swaps to the disk, and decrypt
> as it loads back into memory.  You'd type in the passphrase at boot time.

	Why the hell would you need a passphrase or any persistant security
for something transient like the swap ?   Might just as well choose a
completely random key (from /dev/urandom perhaps) and make every effort
to erase and forget it on system shutdown or crash.  In fact an algorithm
that initialized a crypto engine and then forgot the key used would
be ideal, provided only that it remains possible to recover blocks of
swap out of order from the order they were written in (they are quite
likely to get swapped back in a very different order than they were
written out, so simple stream ciphers are hard to use).

	There is nothing in a swapfile of value beyond an instantation
of the OS, except of course for snooping and debugging crashes.

	The only real hastle with doing this in real OS's is that the
swap may get initialized before a lot of randomness gets collected on
startup.   One might have to start encrypting swap after it was enabled
(but probably before much actual swapping).



-- 
	Dave Emery N1PRE,  die@die.com  DIE Consulting, Weston, Mass. 
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88 C3 18