Security pitfalls of frame-by-frame approaches to video watermarking
Watermarking digital video material is usually considered as watermarking a sequence of still images. However, such a frame-by-frame approach is very risky since straightforward embedding strategies can result in poor performance in terms of security i.e., against hostile attacks. As examples, two very common video-watermarking systems will be presented as well as the associated intra-video collusion attacks which defeat them. Then, both watermark modulation and embedding strength modulation will be surveyed to design alternative embedding strategies which exhibit superior performance against such attacks. Nevertheless, it will also be shown that an expert attacker can still construct an effective watermark removal attack. Finally, there will be a discussion to assert whether or not security against intra-video collusion can be achieved with such blind frame-by-frame embedding strategies.