[dm-crypt] Hosed encrypted drive. Is disaster recovery possible?

["Willie" <tumbleweed@fastmail.net>]

Evening all,

I'm not very hopeful of a positive response, but having just made my
worst mistake in thirty years of computing I thought this would be where
most of the relevant knowledge is.

I have an external 1.5TB Seagate drive, encrypted with dm-crypt/luks and
formatted xfs.

In a state of dog-tiredness, thinking I was pointing at a USB stick, I
have inadvertently wiped a few hundred MB of the beginning of this disk
with:

   dd if=./archlinux-2010.05-netinstall-i686.iso of=/dev/sdc

My question, as you might guess - is there any possibility of recovering
the vast amount of data still on the drive? I could do it with an
unencrypted disk, but I have no idea how to proceed in this case.

Thanks for any suggestions. (I've managed not to cry so far...)

Willie


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