Abstract This paper proposes an image encryption algorithm based on combined 1D chaotic maps. First, a permutation technique was applied. It was then reorganized into 1D matrices along the rows and columns respectively, which were then shuffled by computing the substituted position indices to obtain the scrambled image. Subsequently, a method of confusion of the scrambled image was used through another generated data map, combined with random sub‐matrices for diffusion, then resulting in an encrypted image. Finally, the proposed cryptosystem was implemented in a single kernel platform developed using the Nios II Software Build Tools processor for Eclipse. A hardware architecture was designed using the Qsys‐built tool which is available in the Quartus II 13.0sp1 environment. The developed single‐core system was implemented using the Cyclone IV EP4CE6E22C8. Robustness evaluation of the cryptosystem was performed through security analysis tests such as histogram analysis, correlation coefficient, differential analysis, and key space analysis to prove that it is of good quality, efficient, fast, and successfully resisting brute force attacks. The hardware performance analysis was also carried out. Then the cryptosystem is compared with those in the literature both in the hardware and security performance aspects.

In this paper, we propose a fusion technique for image encryption combining two maps and generate a new optimized map by fusing Hartley and Duffing chaotic oscillators. In order to measure and quantify the amount of chaos present in data sequences, the resultant map is tested by a new method of nonlinear time series analysis. This test ensures its robustness during its use to construct an encrypted image when combined with some mathematical function that we have designed. The cryptosystem was tested on images such as Lena, Barbara, Mandrill, and Man. The results were compared to those in the literature and proved satisfactory.

This paper introduces a new image encryption scheme using a mixing technique as a way to encrypt one or multiple images of different types and sizes. The mixing model follows a nonlinear mathematical expression based on Cramer’s rule. Two 1D systems already developed in the literature, namely, the May-Gompertz map and the piecewise linear chaotic map, were used in the mixing process as pseudo-random number generators for their good chaotic properties. The image to be encrypted was first of all partitioned into N subimages of the same size. The subimages underwent a block permutation using the May-Gompertz map. This was followed by a pixel-based permutation using the piecewise linear chaotic map. The result of the two previous permutations was divided into 4 subimages, which were then mixed using pseudo-random matrices generated from the two maps mentioned above. Tests carried out on the cryptosystem designed proved that it was fast due to the 1D maps used, robust in terms of noise and data loss, exhibited a large key space, and resisted all common attacks. A very interesting feature of the proposed cryptosystem is that it works well for simultaneous multiple-image encryption.

The need for image encryption is constantly on the rise and has led to the emergence of many techniques in literature. In recent years, many chaos‐based encryption techniques have developed with more or less success. In this study, we suggest one such approach using two oscillators. Mixed chaotic maps from the Colpitts and Duffing oscillators were used to encrypt images, which helped to increase the key space to 2 448 ≃ 7.26 × 10 134 . The authors also succeeded to reduce the encryption time by saving the mixed chaotic maps and reusing them as need arose. The proposed system was tested on well‐known images like Lena, NebulaM83, Mandrill and Clown.