On Perceptual Encryption: Variants of DCT Block Scrambling Scheme for JPEG Compressed Images

In this paper, a perceptual encryption scheme based on scrambling of DCT blocks in JPEG compressed images and its variants are proposed. These schemes are suitable for the environment where perceptual degradation of the multimedia content is required. The security of these techniques is shown to be sufficient against casual attacks. These discussed schemes are kept as light as possible in order to keep the encryption overhead and cost low. Also, an investigation in the progressive degradation of image by increasing the number of the DCT blocks to be scrambled has been carried out. The quality of the degraded multimedia content is measured with objective image quality assessment (IQA) metrics such as SSIM, MS-SSIM, VIF, VIFP and UQI. These IQA metrics provide choice for the selection of control factor.