An embodiment includes a system with a processing unit and a communication unit. The processing unit is configured: to compute a first reference point of a data point that represents a private data item and has a first distance value to the data point, wherein the first distance value is less than a threshold value, to compute a second reference point of the data point different from the first reference point with a second distance value to the data point, wherein the second distance value is less than the threshold value, and to generate hidden reference points from the reference points. The communication unit is configured to send the hidden reference points and distance values to a system.