[ Thanks to jhansonxi for this link.
]
“The “–no-default-keyring” and “–keyring” tells gpg
to use only the specified apt trusted keyring. Next, find the key
you want to export from the list and specify either the key ID or
user ID with the following command:gpg --no-default-keyring --keyring /etc/apt/trusted.gpg --armor --export A1F196A8>pidgin.gpg“The “–armor” tells gpg to output an encoded text key instead
of binary one. The Pidgin package signing key ID is A1F196A8 and it
is captured to a “pidgin.gpg” file in the current directory. Then
you copy the key file to your other systems and add it to their apt
keyrings using either Synaptic (Settings > Repositories >
Authentication > Import Key File) or the apt-key command in a
terminal:”