A Chaotic Encryption Algorithm: Robustness against Brute-Force Attack

Image encryption based on chaotic maps is an important method for ensuring the secure communication of digital multimedia on the Internet. To improve the encryption performance and security of image encryption systems, a new image encryption algorithm is proposed that employs a compound chaotic map and random cyclic shift. First, a new hybrid chaotic system is designed by coupling logistic, ICMIC, Tent, and Chebyshev (HLITC) maps. Comparison tests with previous chaotic maps in terms of chaotic trajectory, Lyapunov exponent, and approximate entropy illustrate that the new hybrid chaotic map has better chaotic performance. Then, the proposed HLITC chaotic system and spiral transformation are used to develop a new chaotic image encryption scheme using the double permutation strategy. The new HLITC chaotic system is used to generate key sequences used in the image scrambling and diffusion stages. The spiral transformation controlled by the chaotic sequence is used to scramble the pixels of the plaintext image, while the XOR operation based on a chaotic map is used for pixel diffusion. Extensive experiments on statistical analysis, key sensitivity, and key space analysis were conducted. Experimental results show that the proposed encryption scheme has good robustness against brute-force attacks, statistical attacks, and differential attacks and is more effective than many existing chaotic image encryption algorithms.

A robust and secure chaotic standard map based pseudorandom permutation-substitution scheme for image encryption

A new image cipher in time and frequency domains

In this work, a secure second-order discrete time delta sigma (ΔΣM) modulator is used to securely modulate two physiological signals for e-health applications. The chaotic system used is a new 3D chaotic system that is used to generate random keys for encryption. Quintic nonlinearity is integrated into the existing sprott chaotic system and then studied via nonlinear dynamics tools, which reveal complex dynamics, including the coexistence of three distinct chaotic attractors and the phenomenon of intermittency. A microcontroller implementation of the system is performed to demonstrate its real-life applicability. The bits generated from the chaotic regime of the proposed oscillator are tested successfully via the NIST-800.22 test. The pseudo random bit streams generated from the chaoticity of the oscillator using the system parameters and initial conditions as secret keys are used in a 2-stage confusion process to encrypt two physiological signals. At the receiving end, the physiological signals are successfully recovered, and some standard metrics, such as key space analysis, key sensitivity, and cross-correlation, are applied to verify the strength of the encryption scheme. A comparison with recent and good standing contributions in the literature is also provide at the end of this work, which shows that the proposed scheme is robust against common attacks. The results obtained in this study open the possibility of applying chaos in digital communication systems for the conception of secure e-health services.p. 2Highlights• A new random chaotic system applicable in information protection is conceived and experimented.• Random encryption data are successfully generated from the chaotic system in its confused state and tested statistically. • Patient's ECG signal is securely transferred via a secure and simple communication scheme.

In this paper, a cryptosystem is proposed to encrypt 16-bit monochrome DICOM image using enhanced chaotic economic map. A new enhanced chaotic economic map (ECEM) is designed from the chaotic economic map which has better bifurcation nature and positive Lyapunov exponent values. In order to improve the sternness of the encryption algorithm, the enhanced chaotic map is employed to generate the pixel permutation, masking, and swapping sequences. The substitution operation is introduced in-between the standard permutation and diffusion operations. The robustness of the proposed image encryption algorithm is measured by various analyses such as histogram, key sensitivity, key space, number of pixel change rate (NPCR), unified average change intensity (UACI), information entropy and correlation coefficient. The results of the security analyses are compared with existing algorithms to validate that the proposed algorithm is better in terms of larger key space to resist brute force attacks and other common attacks on encryption.

Exponentially increasing multimedia data over the internet raises concerns over its security. In the current work, we present a new technique for encrypting digital images based upon the pixel shuffling combined with changing pixel values using 128-bit secret key using henon chaotic map. Chaotic maps are characterized by their high sensitivity towards the initial parameters, which makes it a natural choice for developing a dynamic permutation matrix or as it is mostly called, permutation map. So we used chaotic Henon map in order to dynamically generate the permutation matrix. The initial parameters of the chaotic map and the secret key for changing the pixel values are derived from an external secret key. Horizontal and vertical permutations are used to perform pixel shuffling. Shuffling is used to destroy the correlation among the neighbour or adjacent image pixels, also it helps in increasing diffusion in the image. The proposed scheme is tested against a series of tests to measure its performance. Results of such tests indicate that the proposed algorithm is highly sensitive towards the encryption key and showed high resistance against various brute-force or statistical attacks.

Transmission of the information in any form requires security. Security protocols used for communication rely on the use of random numbers. Pseudo-random numbers are required with good statistical properties and efficiency. The use of a single chaotic map may not produce enough randomness. The turbulence is padded into the existing map to improve its chaotic behaviour and increase the periodicity. A Pseudo-random number generator (PRNG) with this architecture is devised to generate random bit sequences from secret keys. The statistical properties of newly constructed PRNG are tested with NIST SP 800–22 statistical test suite and were shown to have good randomness. To ensure its usability in cryptographic applications, we analysed the size of its key space, key sensitivity, and performance speed. The test results show that the newly designed PRNG has a 3.6% increase in key space and a 5% increase in its performance speed compared to existing chaotic PRNGs. The novel PRNG with faster performance is found suitable for lightweight cryptographic applications.

An image encryption scheme based on new spatiotemporal chaos

This paper proposes an image encryption scheme based on chaotic system with changeable parameters depending on plain-image. A generalized Arnold map, whose control parameters are changeable and image-dependent during the iteration procedure, is utilized to generate chaotic orbits applied to permute the pixel positions. A diffusion function is also designed to realize the diffusion effect by piece-wise linear chaotic map. In both the permutation process and the diffusion process, the keystreams generated by chaotic maps are all strongly dependent on plain-image, and thereby can improve the encryption security efficiently. The major merits of the proposed image encryption scheme include a huge key space, good statistical nature resisting statistical analysis attack, differential attack, and good resistance against known-plaintext attack and chosen- plaintext attack, etc. Experimental results have been carried out with detailed analysis to show that the proposed scheme can be a potential candidate for practical image encryption.

The Internet advances in the past decade have been upping at a tremendous pace; especially in the fields like medicine, military, and technology, where lot of internet threats have also been raising, at least at the same rate, if not higher. The communication takes place in the form of text, image, voice, and video signals etc. And we deal with more image-based applications. There are many encryption techniques existing-DES, AES, RSA, etc. but they provide less security and are vulnerable to brute force attacks due to factors like small key space, to avoid which, chaos-based encryption was introduced. Chaotic systems are very sensitive to initial conditions and distort the image to beyond reversible state, except with a protection key with which it is encrypted, which is hard to find in such a large key space. In this paper we will discuss image encryption using combined chaos by combining various chaotic maps like logistics map, singer map, tent map, sine map, piecewise map etc. and attempt to compare the results for better combination for encryption.

Recently, the development of confidentiality and authenticity ensured by image encryption has been one of the key advancements in the field of secured wireless communication. The proposed work focuses on providing confusion, diffusion and permutation inherently in the system. The input grayscale image is shuffled by employing the Henon algorithm and subsequently separated into 8 bit planes. With the aid of a secret key of 256 bits, chaotic sequences are generated for each bit plane. Later, the logistic map is adapted on the chaotic sequences to obtain the scrambled image. Furthermore, this image is shuffled with Zaslavskii and Hilbert Space Filling Curve algorithms, which establishes the confusion stage. To incorporate the diffusion stage, a self-invertible matrix is generated by a latin square image cipher and a secret key. This matrix and the scrambled image underwent the Hill cipher to build the encrypted image followed by a row-column transformation to ensure multifold security. The proposed compound activities of encryption are successfully implemented on the laboratory virtual instrumentation engineering workbench 2013 platform. Noticeably, the established processes of image encryption are tested in the universal software radio peripheral environment and transceived via an additive white Gaussian noise (AWGN) channel. More specifically, the influence of natural and unnatural (cropping attack) noise on the characteristics of the encrypted image while sharing through AWGN channel has been investigated. Security analysis is performed by computing the unified average changing intensity, number of pixels change rate, correlation value, large key space to defy brute force attack, strong key sensitivity and uniform gray value distribution on encryption.

Image encryption with compound chaotic sequence cipher shifting dynamically

Security issues of the physical layer in wireless communications have attracted extensive attention in recent years. Meanwhile, the key space and encryption mechanisms have great impact on the security performance. This paper proposes a novel physical layer encryption scheme based on multi-fold chaotic maps in orthogonal frequency-division multiplexing(OFDM) systems. High security is achieved by performing the chaotic maps on the phase and amplitude of quadrature amplitude modulation(QAM) symbols, and the transmitted subcarrier. The initial conditions of the chaotic maps serve as the secret keys. Mathematical analysis indicates that the proposed scheme can provide a huge key space of 1.5 × 1098, which is much larger than that of the existing solutions. In addition, the transmission performance is evaluated over both AWGN channels and Rayleigh fading channels. The theoretical analysis and simulation results reveal that the proposed scheme significantly outperforms the existing solutions in terms of security. Meanwhile, it can achieve similar transmission performance over different channels.

This paper proposes a novel image block encryption algorithm based on three-dimensional Chen chaotic dynamical system. The algorithm works on 32-bit image blocks with a 192-bit secret key. The idea is that the key is employed to drive the Chen’s system to generate a chaotic sequence that is inputted to a specially designed function G, in which we use new 8x8 S-boxes generated by chaotic maps (Tang, 2005). In order to improve the robustness against differental cryptanalysis and produce desirable avalanche effect, the function G is iteratively performed several times and its last outputs serve as the keystreams to encrypt the original image block. The design of the encryption algorithm is described along with security analyses. The results from key space analysis, differential attack analysis, and information entropy analysis, correlation analysis of two adjacent pixels prove that the proposed algorithm can resist cryptanalytic, statistical and brute force attacks, and achieve a higher level of security. The algorithm can be employed to realize the security cryptosystems over the Internet.

A novel compression-based 2D-chaotic sine map for enhancing privacy and security of biometric identification systems