Rhouma

On the security of a new image encryption scheme based on chaotic map lattices.

This paper reports a detailed cryptanalysis of a recently proposed encryption scheme based on the logistic map [A. Pisarchik et al., Chaos 16, 033118 (2006)]. Some problems are emphasized concerning the key space definition and the implementation of the cryptosystem using floating-point operations. It is also shown how it is possible to reduce considerably the key space through a ciphertext-only attack. Moreover, a timing attack allows for the estimation of part of the key due to the existent relationship between this part of the key and the encryption/decryption time. As a result, the main features of the cryptosystem do not satisfy the demands of secure communications. Some hints are offered to improve the cryptosystem under study according to those requirements.

Security analysis of an image encryption algorithm based on a DNA addition combining with chaotic maps

In this paper, we propose to cryptanalyse an encryption algorithm which combines a DNA addition and a chaotic map to encrypt a gray scale image. Our contribution consists on, at first, demonstrating that the algorithm, as it is described, is non-invertible, which means that the receiver cannot decrypt the ciphered image even if he posses the secret key. Then, a chosen plaintext attack on the invertible encryption block is described, where, the attacker can illegally decrypt the ciphered image by a temporary access to the encryption machinery.

Security analysis of image cryptosystems only or partially based on a chaotic permutation

The paper proposes breaks for the permutation methods adopted in the chaos-based image cryptosystems. By a careful examination on the most chaotic image cryptosystems we can find that the permutation process constitute the main step or, in some cases, the only step to create the confusion. It can be applied on the pixels or on the pixel bits. A recently proposed image encryption scheme based on shuffling the pixel bits inspired from other works is treated as a case study. By applying a chosen plaintext attack, we demonstrate that a hacker can determine the permutation vectors (matrixes) used to permute the pixels bits or the pixels themselves and exploit them to reveal the plain image.

Improvement of an image encryption algorithm based on hyper-chaos

In this paper, we propose to enhance a recently proposed image cryptosystem based on hyper-chaos. The updated version has been builded to resist against attacks made to break the original one and to make it faster. The modification concerns the two Boxes, P-Box and S-Box, which composed the original cryptosystem. Compared with classical encryption schemes, AES and Triple-DES, the new version of the cipher shows a better performances in rapidity, in confusion and in the key sensitivity.

Breaking an image encryption scheme based on a spatiotemporal chaotic system

In this paper, we describe a cryptanalysis of image encryption scheme recently proposed by Chun-Yan Song, Yu-Long Qiao, and Xing-Zhou Zhang. The scheme is based on a spatiotemporal chaos with a dynamic keystream generator, and its security is claimed to rely in utilized the plainimage in the keystream generation process to obtain a different keystream for every plainimage/cipherimage pair. However, two flaws are investigated and prove that the security of the proposal against chosen plaintext attack is groundless. Simulations conducted demonstrate that the plainimage can be recovered under partial attack with an acceptable perceptual quality. Moreover, a total break is possible, but a large number of plain-image/cipher-image pairs is needed. HighlightsA cryptanalysis of an image encryption scheme based on spatiotemporal chaos is presented.We gave a complete and partial break of the cryptosystem under study.We prove that the studied cryptosystem is not sufficiently secure against chosen plaintext attack.Results suggest that a partial attach needs smaller number of plain/ciphered images with acceptable perceptual qualities.

A new color image cryptosystem based on a piecewise linear chaotic map

In this paper a piecewise linear chaotic map (PWLCM) is used to build a new digital chaotic cryptosystem. The characteristics of PWLCM are very suitable for the design of encryption schemes. The implicit digital degradation problem of PWLCM has been eluded through the discretization of the phase space. The accuracy, efficiency and security of the proposed encryption scheme is thoroughly analyzed and its adequacy for image encryption is proved.

On the security of a spatiotemporal chaotic cryptosystem

Recently, Tang et al. [Phys Lett. A 318, 388 (2003)] proposed a spatiotemporal cryptosystem based on one-way coupled map lattices. They claim that it has high security, fast encryption speed, and short synchronization transient. This work proves that this scheme has some security weaknesses. Indeed, we propose an attack which the system cannot withstand.

A novel approach to construct S-box based on Rossler system

The substitution box is an essential element in cryptographic algorithms. Indeed, the S-box guarantees the confusion and nonlinearity properties required by secure block ciphers. In this study, we choose the Rossler system to generate a chaotic S-box. Proposed approach is tested for six criteria, which are bijectivity, nonlinearity, strict avalanche criterion (SAC), input/output XOR distribution and linear approximation probability (LP). In order to test the robustness and the suitability of the proposed S-box in real time application, especially in image encryption, we evaluate the statistical analysis of the substituted image such as, correlation, histogram and information entropy. Comparative studies with some selected S-boxes have been performed to prove the effectiveness of the proposed S-box. Experimental results and simulations show that the proposed Sbox is powerful against attacks.

Selective image encryption scheme based on DWT, AES S-box and chaotic permutation

In this paper, a new selective encryption scheme based on DWT, AES S-box and chaotic permutation is proposed. The new scheme is composed of six steps: Image decomposition, Block permutation, DWT decomposition, substitution phase, chaotic permutation phase and reconstruction phase. Firstly, it generates four subbands, namely cAP, cVP, cHP and cDP, and encrypts only cAP subband, which contains the meaningful part of data. The proposed cryptosystem is evaluated using various security and statistical analysis. The performance tests show that the proposed scheme is secure against statistical and differential attacks.

An eigen value based watermarking scheme for tamper detection in gray level images

Fragile watermarking is used to determine if a digital content has been tampered, and localize tampered regions without referring to the original content. In this paper, we present a novel fragile watermarking technique for tamper detection in gray level images. The proposed method is efficient for simple and intelligent attacks such as collage attack and Vector quantization attack. The embedding process of the watermark starts from computing the Eigen values of the chaotically mixed image and that stands for the watermark, followed by inserting it into the LSBs chosen using the logistic map. The chaotic map is used to improve the security of our algorithm and to contribute with the Eigen values computation by making the watermark as unique as possible in order to face off intelligent attacks. Simulation results show that the presented method is fast, secure and performant in detecting and localising tamper.