This invention describes a method and apparatus for the increasing the robustness of embedded data. Since many times embedded data is susceptible to removal by an unauthorized person, one preferred embodiment enables an action such that removal of the embedded data provides the attacker no gain. In another preferred embodiment, recording devices are required to embed a registration code in copies, thus aiding in tracing illegal copies. Finally, dynamic locking, including modifying and encrypting the auxiliary data and applicable to all data embedding techniques, is shown to provide this robustness to duplication and modification. The apparatus implements the above two processes with a logic processor and storage unit.