squeeze-lts problem with debian's keyrings or apt

[Tobias Weiß <tobias-weiss@outlook.com>]

Hello world,

my apt on squeeze-lts complains that the updates could not be verified. This happens since the updates for apache were made a few days ago.

I got the latest keyring package debian, at least I think so:
root@web1-tk2:~# dpkg -l | grep keyring
ii  debian-archive-keyring              2010.08.28+squeeze1          GnuPG archive keys of the Debian archive


I have the following keys within the keyring

oot@web1-tk2:~# apt-key list
/etc/apt/trusted.gpg
--------------------

[..., those vor Lenny. ..]

/etc/apt/trusted.gpg.d//debian-archive-squeeze-automatic.gpg
------------------------------------------------------------
pub   4096R/473041FA 2010-08-27 [verfällt: 2018-03-05]
uid                  Debian Archive Automatic Signing Key (6.0/squeeze) <ftpmaster@debian.org>

/etc/apt/trusted.gpg.d//debian-archive-squeeze-stable.gpg
---------------------------------------------------------
pub   4096R/B98321F9 2010-08-07 [verfällt: 2017-08-05]
uid                  Squeeze Stable Release Key <debian-release@lists.debian.org>

/etc/apt/trusted.gpg.d//debian-archive-wheezy-automatic.gpg
-----------------------------------------------------------

[..., those of Wheezy, ...]

And this is what happens:

root@web1-tk2:~# apt-get dist-upgrade 
[...]
The following packages will be upgraded:
  apache2 apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common libapache2-mod-php5 php5
  php5-cli php5-common php5-gd php5-mysql
11 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
[...]
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
  apache2 apache2-mpm-prefork apache2.2-common apache2.2-bin apache2-utils php5-cli php5-mysql php5-gd
  libapache2-mod-php5 php5-common php5
Install these packages without verification [y/N]? n

I have no idea what wrent wrong, but something is obviously wrong here. Could anybody help me out, please?

Thank you.
Tobias