A Partial Image Encryption Method with Pseudo Random Sequences

摘要

We propose an effective approach for partial image encryption with pseudo random sequences (PRS). It is known that an image can be considered as a combination of correlated and uncorrelated data as well as most of the perceptual information are present in the correlated data rather than the uncorrelated data. Hence, the amount of residual intelligence present in an encrypted image depends on the correlated data. It is, therefore, sufficient to encrypt the correlated data instead of encrypting the entire image in order to speed up the entire operation. From the perception point of view, the most significant bit (MSB) planes have high adjacent correlation between the pixels whereas the least significant bit (LSB) planes contain comparatively more uncorrelated data. PRS with simple hardware like m-sequences and Gold sequences have less correlation between the adjacent bits. These can therefore serve as a good alternative for partially encrypting the MSB planes with low complexity to provide security against casual listeners. It is observed from the results that the new approach is able to reduce the residual intelligence as would have been obtained by encrypting the entire image.