Perceptual Image Encryption: A Communication Perspective

Due to the popularity of cloud services, privacy sensitive image data is outsourced to avail of third-party owned computation and/or storage resources. In this regard, image encryption is necessary not only to protect identifiable information in them that can lead to privacy concerns, but to protect the data ownership as well. Different from the conventional full image encryption techniques, Perceptual Encryption (PE) algorithm protects only perceivable image contents while leaving its intrinsic characteristics intact to cater for the requirements of multimedia applications. Several techniques (such as the pseudo grayscale representation, processing of each color channel independently, and sub-block processing) have been proposed to achieve an efficient tradeoff between security efficiency and the multimedia application’s performance. This study integrates PE algorithms into the source coding block of an orthogonal frequency-division multiplexing (OFDM) system and analyze their performance in terms of the recovered image quality. Specifically, we have considered four PE schemes, and four modulation schemes and two channel models in the OFDM system. Our analyses have shown that PE methods are robust against wireless communication impairments with a slight difference between the quality of recovered images from plain and PE cipher images over a Rayleigh fading channel.