swap?

[killermoehre]

Probably the udev rule you want is something like this:

$ /etc/udev/rules.d/99-hide-luks.rules
KERNEL=="mapper/luks-*", OPTIONS+="ignore_device"

Theoretical, this should match against all /dev/mapper/luks-* devices 
and set them to be ignored. I didn't test it. I don't guarantee 
anything. Your milage may vary. If your computer changes into a 
plutonium powered toaster, you have a plutonium powered toaster.
Have fun!

Regards