A Revision of a New Chaos-Based Image Encryption System: Weaknesses and Limitations

TL;DR

This paper critically analyzes a recent chaos-based image encryption system, revealing that its claimed efficiency and security features are insufficient, and highlights the need for multiple iterations and block-level avalanche effects for better cryptographic performance.

Contribution

It provides a detailed critique of a new chaos-based encryption scheme, demonstrating that at least six iterations are necessary for security, contrary to the original claims, and suggests improvements for practical implementation.

Findings

At least 6 iterations are needed for cryptographic security.

Single-round diffusion and permutation are insufficient for desired security.

Block-level avalanche effect reduces error propagation.

Abstract

Lately, multimedia encryption has been the focus of attention in many researches. Recently, a large number of encryption algorithms has been presented to protect image contents.The main objective of modern image encryption schemes is to reduce the computation complexity in order to respond to the real time multimedia and/or limited resources requirements without degrading the high level of security. In fact, most of the recent solutions are based on the chaotic theory. However, the majority of chaotic systems suffers from different limitations and their implementation is difficult at the hardware level because of the non integer operations that are employed requiring huge resources and latency. In this paper, we analyze the new chaos-based image encryption system presented in~\cite{el2016new}. It uses a static binary diffusion layer, followed by a key dependent bit-permutation layer that only iterates for one round. Based on their results in this paper, we claim that the uniformity and avalanche effect can be reached from the first round. However, we tried to verify the results but our conclusion was that these results were wrong because it was shown that at least 6 iterations are necessary to ensure the required cryptographic performance such as the plain-sensitivity property. Therefore, the required execution time must be multiplied by 6 and consequently this will increase the latency. In addition to all aforementioned problems, we find that ensuring the avalanche effect in the whole image introduces a high error propagation. In order to solve this problem, we recommend to ensure the avalanche effect in the level of blocks instead of the whole image.