Abstract: The method and apparatus for copy protecting an optical disk records test data, including modified first signals, on an optical disk such that, when reproduced, random ones of these modified first signals are reproduced as second signals. Both the first and second signals represent data having at least two zeros between successive ones. The method and apparatus for optical disk authentication and reproduction creates a statistical version of the test data through repeated reproduction of the test data. If the test data matches references data, possibly recorded on the optical disk as well, the optical disk is authenticated. Once authenticated, reproduction of the optical disk is permitted. If the test data forms part of the data for reproduction, then the statistical data is output as the reproduced data.