Hi!

On Debian Stretch, suddenly I have the following messages:
W: GPG error: http://security.debian.org/debian-security stretch/updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9D6D8F6BC857C906 NO_PUBKEY 8B48AD6246925553
W: GPG error: http://http.us.debian.org/debian stretch InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010

I successfully manually (re)imported the keys into gpg, but when I try to pass them to apt, I have the following error:
apt-key adv --keyserver pgpkeys.mit.edu --recv 8B48AD6246925553
Executing: /tmp/tmp.U8J57UUNyV/gpg.1.sh --keyserver pgpkeys.mit.edu --recv 8B48AD6246925553
gpg: key 8B48AD6246925553: public key "[User ID not found]" imported
gpg: Total number processed: 1
gpg: imported: 1
gpg: WARNING: nothing exported
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

I exported to a file and verified that it does contain a proper gpg key. It seems that my apt does not recognize gpg keys anymore. Most probably a package broke something, but after hours trying to figure out how to reset the apt keys, nothing works. Anybody would have an idea?

Thanks,
Mathias

Have you enabled any non-standard repositories, installed any software packages not FROM the standard repos, or otherwise changed the system away form Debian standard?

Keep in mind that Stretch is currently the TESTING version and not as solid as STABLE (Jessie), though FAR more stable than SID. There can be occasional breakages in testing, though the team is SO good that they are rare and seldom last long.

Unfortunately, I haven't enabled any non-standard repositories not installed anything that is not part of them... It is still a pure Debian system. And I tried everything possible to re-import the keys to no avail. Last thing I'm now thinking of: I'll try to force re-install apt.