  Dark matter annihilation in Galactic substructure will produce diffuse
gamma-ray emission of remarkably constant intensity across the sky, making it
difficult to disentangle this Galactic dark matter signal from the
extragalactic gamma-ray background. We show that if Galactic dark matter
contributes a modest fraction of the measured emission in an energy range
accessible to the Fermi Gamma-ray Space Telescope, the energy dependence of the
angular power spectrum of the total measured emission could be used to
confidently identify gamma rays from Galactic dark matter substructure.
