What lately lead to some confusion on the side of Linux users:
We changed the software signing GPG key, but this was news not updated on the Debian repository instruction page. So some users got an error while verifying the GPG signature, while we on our side could not see any problem. This is fixed now, please follow these instructions to get and use the new verification key:
The change of the key was necessary in order to separate it from the general e-mail and support key, so that developers and the support team do not need to share the same key. Moreover, the key has a greater cryptographic strength now.