A Block-Permutation-Based Encryption Scheme with Independent Processing of RGB Components

TL;DR

This paper introduces a novel block-permutation encryption scheme that independently scrambles RGB components to enhance security and compression efficiency in image encryption-then-compression systems, especially for JPEG-LS.

Contribution

The scheme uniquely applies independent RGB component processing in block permutation, improving security against JPS and brute-force attacks while maintaining compression performance.

Findings

Increases resistance to jigsaw puzzle solver attacks.

Expands key space exponentially for better security.

Maintains JPEG-LS compression efficiency.

Abstract

This paper proposes a block-permutation-based encryption (BPBE) scheme for the encryption-then-compression (ETC) system that enhances the color scrambling. A BPBE image can be obtained through four processes, positional scrambling, block rotation/flip, negative-positive transformation, and color component shuffling, after dividing the original image into multiple blocks. The proposed scheme scrambles the R, G, and B components independently in positional scrambling, block rotation/flip, and negative-positive transformation, by assigning different keys to each color component. The conventional scheme considers the compression efficiency using JPEG and JPEG 2000, which need a color conversion before the compression process by default. Therefore, the conventional scheme scrambles the color components identically in each process. In contrast, the proposed scheme takes into account the RGB-based compression, such as JPEG-LS, and thus can increase the extent of the scrambling. The resilience against jigsaw puzzle solver (JPS) can consequently be increased owing to the wider color distribution of the BPBE image. Additionally, the key space for resilience against brute-force attacks has also been expanded exponentially. Furthermore, the proposed scheme can maintain the JPEG-LS compression efficiency compared to the conventional scheme. We confirm the effectiveness of the proposed scheme by experiments and analyses.