A desynchronized fingerprinting method and system for identifying collaborators in the making of illegal copies of digital multimedia products. The desynchronized fingerprinting system and method can be used for both audio and video applications. The method and system include an embedding feature and a detection and extraction feature. A different and unique key is assigned to each buyer of a copy of the digital data. The embedding feature includes applying a pseudo-random transformation to selected embedding regions. The key for the pseudo-random transform is user-specific. These regions are chosen by using a secure multimedia hash function. The detection and extraction feature includes a brute-force search in the key space of the buyers. If one of the keys is likely enough, then it can be said that that user was been involved in the production of an illegal copy.