Hi, while updating I get this error:

Code:
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.kali.org kali/updates Release: The following signatures were invalid: BADSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>

W: Failed to fetch http://security.kali.org/kali-security/dists/kali/updates/Release  

W: Some index files failed to download. They have been ignored, or old ones used instead.
I tried to import the gpg key like described here and also followed the instructions regarding gpg key import published here. Also an
Code:
aptitude reinstall kali-archive-keyring
was not successful, still getting this error on update.

What is going on here? Is this a MIM-attack on network site that tries to inject poisened kali packages on my machine?

Thanks for your attention,
Kalimero