  The Lunar Lander Neutron and Dosimetry (LND) Experiment aboard the
Chang$'$E-4 Lander on the lunar-far side measures energetic charged and neutral
particles and monitors the corresponding radiation levels. During solar quiet
times, galactic cosmic rays (GCRs) are the dominating component of charged
particles on the lunar surface. Moreover, the interaction of GCRs with the
lunar regolith also results in upward directed albedo protons which are
measured by the LND. In this work, we used calibrated LND data to study the GCR
primary and albedo protons. We calculate the averaged GCR proton spectrum in
the range of 9 368 MeV and the averaged albedo proton flux between 64.7 and
76.7 MeV from June 2019 (the 7th lunar day after Chang$'$E-4$'$s landing) to
July 2020 (the 20th lunar day). We compare the primary proton measurements of
LND with the Electron Proton Helium INstrument (EPHIN) on SOHO. The comparison
shows a reasonable agreement of the GCR proton spectra among different
instruments and illustrates the capability of LND. Likewise, the albedo proton
measurements of LND are also comparable with measurements by the Cosmic Ray
Telescope for the Effects of Radiation (CRaTER) during solar minimum. Our
measurements confirm predictions from the Radiation Environment and Dose at the
Moon (REDMoon) model. Finally, we provide the ratio of albedo protons to
primary protons for measurements in the energy range of 64.7-76.7 MeV which
confirms simulations over a broader energy range.
