Subject: zero'd swap & encrypted swap
To: None <>
From: Darren Reed <>
List: tech-kern
Date: 06/05/2001 00:39:54
Woops we seem to have gotten off the rails.

1. zero'ing out swap.
This helps even with encrypted swap because it can't (easily) be
retrieved for later cryptoanalysis.  I think as time goes by, old
mechanisms which relied on residual magnetic fields be left polarised
one way or the other will become less effect as the size of the
magnetic area gets smaller.

There is an added benefit that if I do "reboot", to boot my laptop up
into Windows, my swap isn't exposed.  Same for booting off a floppy.

2. encrypting swap
I seriously doubt CPU is an issue here, except maybe for the likes of
sun2.  If possible, it would be nice if there was a way to not store
key material for swap on disk anywhere.  Writing out of kernel memory
on a panic to generate a crash dump should be disabled if encrypted
swap is in use.

Neither of these are being put forward as features which are on all the time.