TPE2: Three-Pixel Exact Thumbnail-Preserving Image Encryption

Facing a large number of personal images and local devices with limited resources, the cloud service plays an increasingly important role in image storage. However, there is no doubt that this will raise a lot of privacy concerns if the image is not under the direct control of the owner. Simply encrypting images utilizing traditional encryption schemes protects the privacy of them, but it sacrifices the usability of image content. Resolving the tension between the usability and privacy risks of images is a critical issue for users. Recently, Tajik et al. proposed the exact thumbnail preserving image encryption (TPE) scheme as a group of two pixels to balance image privacy and usability in the cloud. However, the scheme utilizes the Markov chain to prove the security. The fewer pixels in the group, the worse the connectivity of the chain state. Motivated by this, we further extend the TPE scheme to propose a three-pixel exact TPE scheme, called TPE2. The scheme achieves exact TPE as a group of three pixels. The experimental evaluations show that the image encrypted by the scheme has a good image quality and a satisfactory balance usability and privacy. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This paper discusses the balance between privacy protection and usability of images in the cloud, introduces a new image encryption scheme TPE2 that achieves exact TPE in a group of three pixels, and shows that the encrypted images by the scheme have good image quality and a satisfactory balance of usability and privacy.