  We investigate the sensitivity to long-lived dark photons produced in
Higgstrahlung events via the Higgs portal, $H \rightarrow \gamma_{D}
\gamma_{D}$, with the Silicon Detector (SiD) at the International Linear
Collider (ILC). These events provide a useful benchmark for tracking and vertex
detector performance with long-lived particle decays at displaced vertices. The
ILC is one of several Higgs factories proposed by the international community
to study the properties of the Higgs boson at high precision.
