Method and System for Enabling Collusion Resistant Watermarking

摘要

A method and a system for modifying a bitstream signal for enabling collusion resistant bitstream watermarking. The method comprises dividing a bitstream spectral signal X[k] of the bitstream signal bx into a first signal ( 302 ) and a second signal ( 304 ); multiplying the first signal ( 302 ) by a first modification signal ( 306 ) and outputting a modified first signal ( 314 ); performing a transform operation on said second signal ( 304 ) for obtaining a transformed second signal ( 308 ); multiplying said transformed second signal ( 308 ) by a second modification signal ( 310 ) and outputting a second modified signal ( 312 ); subtracting said second modified signal ( 312 ) from said first modified signal ( 314 ) and outputting a modified bitstream spectral signal X'[k] suitable for obtaining a modified bitstream signal b'x of said bitstream signal bx. Thus an efficient manner of applying a collusion resistant property for already encoded contents is provided.