A Privacy-Preserving Content-Based Image Retrieval Scheme Allowing Mixed Use Of Encrypted And Plain Images

TL;DR

This paper introduces a content-based image retrieval scheme that efficiently handles both encrypted and plain images using a novel encryption-then-compression method, maintaining retrieval performance across mixed image types.

Contribution

It presents a new retrieval scheme enabling the use of encrypted and plain images together, with image descriptors unaffected by encryption, which is a novel approach.

Findings

Retrieval performance matches conventional methods with plain images.

The scheme supports mixed encrypted and plain images without performance loss.

Encrypted images can be compressed with JPEG like plain images.

Abstract

In this paper, we propose a novel content based-image retrieval scheme allowing the mixed use of encrypted and plain images for the first time. In the proposed scheme, images are encrypted by a block-scrambling method developed for encryption-then-compression (EtC) systems. The encrypted images, referred to as EtC images, can be compressed with JPEG, as well as for plain images. Image descriptors used for the proposed retrieval is designed to avoid the effect of image encryption. As a result, the use of EtC images and the descriptors allows us to carry out retrieval of both encrypted images and plain ones. In an experiment, the proposed scheme is demonstrated to have the same performance as conventional retrieval methods with plain images, even under the mixed use of plain images and EtC ones.