  The delay-based fingerprint embedding was recently proposed to support more
users in secure media distribution scenario. In this embedding scheme, some
users are assigned the same fingerprint code with only different embedding
delay. The algorithm's robustness against collusion attacks is investigated.
However, its robustness against common desynchronization attacks, e.g.,
cropping and time shifting, is not considered. In this paper, desynchronization
attacks are used to break the delay-based fingerprint embedding algorithm. To
improve the robustness, two means are proposed to keep the embedded fingerprint
codes synchronized, i.e., adding a synchronization fingerprint and adopting the
relative delay to detect users. Analyses and experiments are given to show the
improvements.
