A Covert Communication Scheme for the DCT Based Image Multiple Description Coding System

In this paper, a covert communication scheme is proposed for a discrete cosine transformation (DCT) based image multiple description coding (MDC) system. In our scheme the data to be transmitted is an 8 bits per pixel gray level image. Before transmission, the image is firstly divided into 8x16 pixel blocks, and then each 8x16 pixel block is divided into two 8x8 pixel blocks. For each 8x8 pixel block, the 8x8 DCT is performed to get the 8x8 DCT coefficient block. The 8x8 DCT coefficient block is quantized and Zig-Zag scanned to a vector. The vectors are named as descriptions. The secrete information is embedded in the descriptions. After Huffman coding, the compressed descriptions which contain the secrete information are transmitted through packet based channels. At the receiver side, the inverse procedures are taken to recover the original image and the secrete information.