Anderson localization of electromagnetic waves incident on a disordered medium manifests itself in exponential decrease of the wave amplitude inwards the medium. Transparency of the medium is exponentially small if the medium thickness is large enough. However, there is a set of frequencies (resonances), specific for every random realization of the disordered medium, for which the medium is almost transparent. These sets are «fingerprints» of the media: every realization is characterized by its own unique set of resonances.
