Examples relate to a concept for anonymous re-identification, more specifically, but not exclusively, to systems, apparatuses, methods and computer programs for performing anonymous re-identification and for training a machine-learning model for use in anonymous re-identification. An apparatus for re-identification comprises processing circuitry configured to obtain media data via an interface. the processing circuitry is configured to generate a re-identification code representing at least a portion of the media data using a hashing algorithm. The processing circuitry is configured to transform the re-identification code using a transformation functionality to obtain a transformed re-identification code. The transformation functionality is configured to transform the re-identification code such that, if the re-identification code is similar to a further re-identification code generated by the hashing algorithm according to a similarity metric, the transformed re-identification code is similar to a further transformed re-identification code being a transformed version of the further re-identification code. The transformation functionality is configured to transform the re-identification code based on a transformation parameter, with the transformation parameter being dependent on a time and/or a location. The processing circuitry is configured to provide the transformed re-identification code.