METHOD AND UNIT FOR GENERATING CODE, METHOD AND UNIT FOR DETECTING CODE, WATERMARK BUILT-IN UNIT AND UNIT FOR DETECTING WATERMARK

摘要

PURPOSE: A unit for detecting a watermark is provided to realize firmness regarding a collusion attack, by not increasing a code length of a built-in code as watermark information even if the whole number of users and colluders are large. CONSTITUTION: One code word selected from a plurality of code words forming a single code is outputted in response to an inputted user identification number. A correlation value is obtained between the outputted code word and a content. Whether a code word corresponding to the inputted user identification number based upon the correlation value is in the content is determined. The unit(2) for detecting a watermark detects watermark information including the information of the user identification number from a predetermined content.