A system comprising: a security medium including a reflective volume hologram, said reflective volume hologram being transparent and configured to reflect incident light having a pre-designed diffraction wavelength in a pre-designed diffraction direction; and an authenticity determination device configured to determine authenticity of the security medium, the system comprising: a light source disposed on the front surface side of the reflective volume hologram so that light emitted therefrom is incident on the reflective volume hologram; a first observation device disposed in the pre-designed diffraction direction of the reflective volume hologram; and a second observation device disposed in a direction other than the pre-designed diffraction direction of the reflective volume hologram, wherein the authentication device is configured to determine that the reflective volume hologram is genuine if, when light including the pre-designed diffraction wavelength is emitted from the light source to be incident on the reflective volume hologram, the light amount observed in the first observation device is larger in the diffraction wavelength than in other wavelengths, and the light amount observed in the second observation device is smaller in the diffraction wavelength than in other wavelengths. a security medium including a reflective volume hologram, said reflective volume hologram being transparent and configured to reflect incident light having a pre-designed diffraction wavelength in a pre-designed diffraction direction; and an authenticity determination device configured to determine authenticity of the security medium, the system comprising: a light source disposed on the front surface side of the reflective volume hologram so that light emitted therefrom is incident on the reflective volume hologram; a first observation device disposed in the pre-designed diffraction direction of the reflective volume hologram; and a second observation device disposed in a direction other than the pre-designed diffraction direction of the reflective volume hologram, wherein the authentication device is configured to determine that the reflective volume hologram is genuine if, when light including the pre-designed diffraction wavelength is emitted from the light source to be incident on the reflective volume hologram, the light amount observed in the first observation device is larger in the diffraction wavelength than in other wavelengths, and the light amount observed in the second observation device is smaller in the diffraction wavelength than in other wavelengths. a light source disposed on the front surface side of the reflective volume hologram so that light emitted therefrom is incident on the reflective volume hologram; a first observation device disposed in the pre-designed diffraction direction of the reflective volume hologram; and a second observation device disposed in a direction other than the pre-designed diffraction direction of the reflective volume hologram, wherein the authentication device is configured to determine that the reflective volume hologram is genuine if, when light including the pre-designed diffraction wavelength is emitted from the light source to be incident on the reflective volume hologram, the light amount observed in the first observation device is larger in the diffraction wavelength than in other wavelengths, and the light amount observed in the second observation device is smaller in the diffraction wavelength than in other wavelengths.