Following Whonix documentation on Firmware Security and Updates.
Want to install spectre-meltdown-checker. Added buster-backports. Ran apt-get update. As update returned with an error, installed apt-transport-tor first. Ran update again. Still an error:
Err:9 tor+https://deb.debian.org/debian buster-backports InRelease
The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 04EE7237B7D453EC NO_PUBKEY 648ACFD622F3D138
I tried to get the missing public key like so:
gpg --keyserver keyring.debian.org --recv-keys 0x04EE7237B7D453EC
but that results in error also: gpg: no valid OpenPGP data found.
So, how should I proceed given that I still want to install the meltdown checker and why do I get an error if I want to import the given public keys?