Steganography for a low bit-rate wavelet based image coder

This approach inserts a hidden steganographic message into a base layer transmission of a zerotree based wavelet coder. The message is hidden in sign/bit values of insignificant children of the detail subbands in nonsmooth regions of the image. The HC-RTOT coder is used to determine what regions of the image that the message can be embedded in. The coder also determines which wavelet coefficients in the detail subbands of these regions are used for messaging by the use of a steganographic mask which can be unique for each transmission occurrence of the image. The advantage of this approach is the ability to send steganographic messages in lossy environments with a robustness against detection or attack. Preliminary results indicate that the message can be sent with a 4%-10% overhead capacity of the base layer bitstream (0.04-0.1 bpp) depending on several variations of the method.