No, they key did not change. Any key changes are
broadcasted to all lists
including trinity-announce.
The error message you posted refers to
ppa.launchpad.net; TDE is hosted on
oops
ppa.quickbuild.pearsoncomputing.net. Did you add a
Launchpad PPA recently
without adding its signing key?
Right I did so and because I could not receive the key I deleted the
relevant ppa and run apt-get update again, but somehow the ppa remains
in the cache...