qca/plugins/qca-gnupg/gpgproc

GPGProc launches a single instance of GPG and provides a friendly API to
work with all six possible pipe channels.  Theoretically, it should be
possible to build any GPG front end with it, even though qca-gnupg uses it
for only a handful of operations.  If you are writing a Qt-based GPG front
end, please use this class.

GPGProc works on both Windows and Unix platforms.