A chaos based partial image encryption scheme

Partial encryption of images can be considered to be better than the existing image encryption techniques in the application areas where computational overhead is the main criterion. In this communication, a chaos based symmetric key partial encryption of gray level images has been proposed. In the proposed algorithm, the plain images, after decomposing them to bitplanes, are first classified into different categories. Next, a threshold based on the autocorrelation of blocks of different bitplanes is used to identify the significant and insignificant bit planes. Following this, the correlated bit planes of an image are encrypted with key stream sequences generated by a chaos based pseudo random binary number generator. The experimental results depict that the proposed algorithm can successfully encrypt and decrypt gray level images with secret keys. The simulation analysis also exhibits that the proposed method is loss-less, secure and efficient in terms of several statistical tests, key sensitivity test, information entropy test and encryption quality tests. From the results it is observed that the new approach is able to hide the residual intelligence with lesser amount of time than that require for encrypting the entire image.