On Fri, 30 Sep 2011 16:59:24 -0700, Greg KH wrote: 
> 2. Verify that your package signatures match what your package manager thinks
>    they are.

<snip>

> To do this on a Debian based system, run the following bash snippet:
> 	dpkg -l \*|while read s n rest; do if [ "$s" == "ii" ]; then echo $n;
> 	fi; done > ~/tmp.txt
> 	for f in `cat ~/tmp.txt`; do debsums -s -a $f; done

At least since squeeze, debsums defaults to checking all packages, so
the following is sufficient:
	debsums -as

It may also be worth checking the output of:
	debsums --list-missing

Matthew W.S. Bell