In this paper, an analysis study of two encryption algorithms applied to images is performed in order to assess their robustness in terms of security. The first is the classical cryptosystem known as Advanced Encryption Standard (AES) and the second is issued from the study of chaotic signals called the logistic map. The experimental results and their analysis show that AES encryptions is more secure, but on the other hand the logistic map exhibits good encryption speed.

In this article, a new encryption system that takes as an input an arbitrary size color image (n, m), and generates an encrypted image of the same size at the output, will be proposed. On each three-pixel block, an improvement of the classical HILL method provided by a size matrix (3, 3) invertible in the $Z/256Z$ ring, accompanied by a chaotic translation vector. Then a confusion with the chaotic map is established with the output vector. Finally, a chain with the clear block is performed to increase the avalanche effect. Simulations performed on a large number of images of different sizes and formats, show that our approach can withstand all known attacks.

In this article, we investigate image security for transmission in digital networks using a hybrid coding based on juxtaposed encryption and compression. We have proposed a new approach that integrates a dynamic Hill-Cipher encryption added to the step of quantizing of JPEG compression. A step by step demonstration is given in order to show the functioning of the crypto compression scheme constructed. This explanation justifies how to strategically integrate different operations of our crypto compression system. The effectiveness and robustness of our scheme is validated by measuring its security strength, its computational cost and the quality of reconstructed images (PSNR). The results showed that our new idea by both its generic fast encryption and its simple adaptation provides a reasonable complexity and a good compromise between security and compression rate, this crypto compression scheme is efficient and recommended for networks with low bandwidth especially for low-power devices.