Chaotic secure image coding based on SPIHT

From the viewpoint of Shannon¿s information theory, image coding and image encryption both aim at reducing the correlations of pixels. However, current image encoding methods did not take the confidentiality into account. In this paper, a novel chaotic image encryption scheme integrated with the SPIHT wavelet image coding is proposed. Comparing with the existing image encryption schemes, the new method has three prominent advantages: first, only sensitive bits in the coding stream are encrypted, which introduces small overheads to the image codec; second, by introducing a cipher-text feedback mechanism, the scheme can effectively resist the known-plain-text attack; third, by using chaotic pseudo-random bits to mask the SPIHT encoded bitstream, the scheme can truncate the output stream at any position while keeping the image recoverable with different visual qualities. Cryptanalysis and various experiments have been carried out and the results were reported in this paper, which demonstrate the feasibility and flexibility of the proposed scheme.