Design of Collusion-Free Hiding Codes using MAI-Free Principle
A new methodology to design collusion-free hiding codes using the multi-access-interference-free (MAI-free) principle is proposed. A precoding technique was recently introduced in orthogonal frequency division multiplexing (OFDM) wireless communication systems to result in MAI-free codes, which simplifies the receiver design greatly. Being motivated by this work, we propose a new class of collusion-free codes called the OSIFT (orthogonal spreading followed by the inverse Fourier transform) codes. It is demonstrated by computer simulation that OSIFT codes have more robust performance against collusion attacks than existing collusion-free codes in an exemplary audio watermarking system.