If you want to get rid of the error message, I suspect you would have to manually add the security key for the Knoppix repository, not that I know how to do that or what the key is(or why Klaus Knopper didn't include the key in the Knoppix images). Since the Knppix repository is the only unofficial debian repository in my sources.list, I just tell Aptitude to continue anyway whenever it gives me the untrusted error. That said, if you boot Knoppix in normal, desktop mode, your really don't need any of the adriane packages.