Apparatus, computer medium, and method for embedding and extracting a first and second data into a watermark

In an information processing system having a plurality of information processing apparatuses connected through a network, at least one of the plurality of information processing apparatuses can add first additional information to input information as an electronic watermark using a first adding method, and can add second additional information to the input information as an electronic watermark using a second adding method. The first adding method has a higher robustness than the second adding method, and the first additional information can be used for identifying the second adding method.