Methods and systems protect digital content such as premium content like movies, programs, and other types of digital audiovisual content. The process includes depositing a seed layer over the overcoat layer prior to plating a metal mask layer with an opening where the recess is to be formed, wet chemical etching the seed layer through the opening in the mask layer and performing an ion milling process to remove any remaining traces of the seed layer. The slit includes a curved slit, and a plurality of protruding slits spaced from each other in a direction along the curved slit, connected to a protruding portion-side forming edge of the curved slit, and protruding and extending from the protruding portion-side forming edge of the curved slit.