Information capable of tracing a content distribution route, such as a user ID of a content destination, a content ID, a content provider ID, and a service provider ID, is superimposed on the content as additional information for digital watermarking or steganography before delivering the content. For...http://www.google.com/patents/US8171294?utm_source=gb-gplus-sharePatent US8171294 - Additional-information detection processing apparatus and method, content playback processing apparatus and method, and computer program
