  The Hubble constant $H_{0}$ and matter density $\Omega_{m}$ of the Universe
are measured using the latest $\gamma$-ray attenuation results from Fermi-LAT
and Cherenkov telescopes. This methodology is based upon the fact that the
extragalactic background light supplies opacity for very high energy photons
via photon-photon interaction. The amount of $\gamma$-ray attenuation along the
line of sight depends on the expansion rate and matter content of the Universe.
This novel strategy results in a value of
$H_{0}=67.4_{-6.2}^{+6.0}$~km~s$^{-1}$~Mpc$^{-1}$ and
$\Omega_{m}=0.14_{-0.07}^{+0.06}$. These estimates are independent and
complementary to those based on the distance ladder, cosmic microwave
background (CMB), clustering with weak lensing, and strong lensing data. We
also produce a joint likelihood analysis of our results from $\gamma$ rays and
these from more mature methodologies, excluding the CMB, yielding a combined
value of $H_{0}=66.6\pm 1.6$~km~s$^{-1}$~Mpc$^{-1}$ and $\Omega_{m}=0.29\pm
0.02$.
