A novel colour image encryption algorithm based on chaos

Ultra Wideband Signals and Systems in Communication Engineering

In recent years, various image encryption algorithms based on the permutation-diffusion architecture have been proposed where, however, permutation and diffusion are considered as two separate stages, both requiring image-scanning to obtain pixel values. If these two stages are combined, the duplicated scanning effort can be reduced and the encryption can be accelerated. In this paper, a fast image encryption algorithm with combined permutation and diffusion is proposed. First, the image is partitioned into blocks of pixels. Then, spatiotemporal chaos is employed to shuffle the blocks and, at the same time, to change the pixel values. Meanwhile, an efficient method for generating pseudorandom numbers from spatiotemporal chaos is suggested, which further increases the encryption speed. Theoretical analyses and computer simulations both confirm that the new algorithm has high security and is very fast for practical image encryption.

A new chaos-based fast image encryption algorithm

This paper proposes a novel confusion and diffusion method for image encryption. One innovation is to confuse the pixels by transforming the nucleotide into its base pair for random times, the other is to generate the new keys according to the plain image and the common keys, which can make the initial conditions of the chaotic maps change automatically in every encryption process. For any size of the original grayscale image, after being permuted the rows and columns respectively by the arrays generated by piecewise linear chaotic map (PWLCM), each pixel of the original image is encoded into four nucleotides by the deoxyribonucleic acid (DNA) coding, then each nucleotide is transformed into its base pair for random time(s) using the complementary rule, the times is generated by Chebyshev maps. Experiment results and security analysis show that the scheme can not only achieve good encryption result, but also the key space is large enough to resist against common attacks.

Image encryption using DNA complementary rule and chaotic maps

Color image encryption using spatial bit-level permutation and high-dimension chaotic system

The chaos-based cryptographic algorithms have suggested some new ways to develop efficient image-encryption schemes. While most of these schemes are based on low-dimensional chaotic maps, it has been proposed recently to use high-dimensional chaos namely spatiotemporal chaos, which is modelled by one-way coupled-map lattices (OCML). Owing to their hyperchaotic behaviour, such systems are assumed to enhance the cryptosystem security. In this paper, we propose an OCML-based colour image encryption scheme with a stream cipher structure. We use a 192-bit-long external key to generate the initial conditions and the parameters of the OCML. We have made several tests to check the security of the proposed cryptosystem namely, statistical tests including histogram analysis, calculus of the correlation coefficients of adjacent pixels, security test against differential attack including calculus of the number of pixel change rate (NPCR) and unified average changing intensity (UACI), and entropy calculus. The cryptosystem speed is analyzed and tested as well.

OCML-based colour image encryption

In this work, a new family of spatiotemporal chaotic codes is proposed as an alternative to the Gold codes conventionally used in asynchronous DS/CDMA systems. In addition to their synchronization advantage over the temporal-only chaotic codes, these new codes are shown to have improved performance compared to the Gold codes. The performance criteria used in this study are Multiple Access Interference (MAI), Signal to Noise Ratio (SNR) and Bit Error Probability.

A family of spatiotemporal chaotic sequences outperforming Gold ones in asynchronous DS-CDMA systems

In this study, we address the effect of spreading sequences on the performance of asynchronous direct-sequence (DS) ultra-wideband (UWB) systems. We consider the two cases of short and long sequences in a multipath environment. In particular, we propose the use of sequences generated with a family of spatiotemporal chaotic systems, namely Piecewise Coupled Map Lattices (PCML), as spreading sequences. Such sequences are shown to reduce the MUI variance with regard to i.i.d. and Gold sets for both short and long sequences. Furthermore, simulation results show that the use of long PCML codes improves the average bit error rate (BER) of the system, which hence can accomodate more active users.

Spatiotemporal chaotic sequences for asynchronous DS-UWB systems

It is known that in a direct-sequence (DS) ultrawideband (UWB) system, a single type of UWB pulse is used in all bits for all users. In this paper, we address a method to generate varying waveforms based on spatiotemporal chaotic approach. Regarding spreading sequences, we consider the two cases of short and long sequences. In particular, we propose the use of a family of spatiotemporal chaotic systems, namely Piecewise Coupled Map Lattices (PCML), as spatiotemporal chaotic waveforms and spreading sequences. Such sequences are shown to reduce the multi-user interference (MUI) variance with regard to i.i.d. and Gold sequences for both short and long cases. On the other hand, we evaluate and compare the DS-UWB system performance by using conventional waveform such as Gaussian monocycle pulse and PCML pulses. Finally, we show that the use of long PCML codes with PCML pulses, results in an improvement of the system average BER, hence an increase of the system capacity in terms of number of active users.

Asynchronous DS-UWB communication using spatiotemporal chaotic waveforms and sequences

Software Defined Networking (SDN) has leveraged the recent advances in Artificial Intelligence (AI) techniques to meet the main challenges related to network management complexity. For instance, Reinforcement Learning (RL) algorithms, which address decision-making problems, have been extensively used for routing optimization in SDN networks. Based on the interaction between the controller and the network, the RL algorithm can learn optimal routing policies, hence empowering the controller with intelligence capabilities. In this work, we address latency minimization within a multipath SDN network using the Q-Learning algorithm. Unlike most commonly used approaches, which are based on indirect modeling of the flow routing mechanism as an RL problem, we consider directflow modeling to guarantee flow integrity preservation within a multipath configuration. In particular, we provide a performance evaluation of the Q-Learning algorithm using two different exploration strategies, namely, $\varepsilon$-greedy and softmax, in terms of average flow latency and convergence time for different load levels. We show that, for both strategies, the proposed algorithm performs better than the traditional SPF (Short Path First) routing protocol for almost all load levels. As compared to the softmax strategy, we show that $\varepsilon$-greedy achieves lower levels of average latency and comparable convergence time for the considered topology.

Soumaya Meherzi

Papers

OCML-based colour image encryption

A family of spatiotemporal chaotic sequences outperforming Gold ones in asynchronous DS-CDMA systems

Spatiotemporal chaotic sequences for asynchronous DS-UWB systems

Asynchronous DS-UWB communication using spatiotemporal chaotic waveforms and sequences

ε-QLMR: ε-greedy based Q-Learning algorithm for Multipath Routing in SDN networks