A high-rate chaotic secured covert channel based on multiple embedding in images

Covert channel is a type of secure communications that provides reliable security in transferring information between entities. Quantization Index Modulation (QIM) technique can be used to embed data in images to implement covert communication channels. In single embedding in QIM, each sample is quantized once to carry a single bit of the secret message. Double embedding in QIM was introduced by Sarkar and Manjunath in 2009, to increase the transferred data rate where a single sample is quantized twice to carry two bits in time. In this paper, a higher data transmission rate covert channel is developed using multiple embedding in the QIM framework with multi quantization vectors. This approach considers the embedding process as a communications problem, that it uses a structured scheme of Multiple Trellis-Coded Quantization jointed with Multiple Trellis-Coded Modulation (MTCQ/MTCM) to generate the stego-space. This technique returns a PSNR ≥ 40 dB. More over, increasing the coding states and/or the coding multiplicity returns an altered space with low correlated coefficients, thus improving the transferred data detection error rate performance. To secure the modulation process, the altered coefficients are chaotic scrambled by the 2-D Arnold Cat Map before embedding to increase the uncertainty in case of an attacker discovered the channel.