Comment # 1 on bug 1051035 from Andreas Stieger

(In reply to Ralf Friedl from comment #0)
> Each run of "zypper up" leaves one or two processes of gpg-agent running.
> [...]
> Also, why is gpg-agent started at all? It is started with a temporary
> directory as --homedir, and then queries for the existence of keys within
> this newly created directory. 

The execution of gpg in this instance is used for handling the repository
signatures inside zypper/libzypper. This is separate from the user keyring and
root GnuPG directory.

This seems to kick off gpg-agent and leave it running, which appears to be the
bug. So either a problem in libzypper, or gpg2, an incompatibility between them
or a problem from a third element.