GPG error for clam-av in sources.list

["IT-Support@AStA TU Darmstadt" <it-support@asta.tu-darmstadt.de>]

Hello,

I put the clam-av volatile mirror for etch/testing in my sources list
and now I'm getting the following error, when I do "apt-get update":

GPG error: http://secure-testing.debian.net etch/security-updates
Release: The following signatures couldn't be verified because the
public key is not available: NO_PUBKEY 946AA6E18722E71E

What do I have to do? Importing the key? Where can I get the gpg-key for
clam-av volatile mirror?

Didn't find any hints at the web-pages for configuring clam-av with
testing/etch.

Thanks!

Ivan