Pseudo-random number sequences which using the form of elliptic curves can be generated efficiently in software or hardware by the same methods that are used for the implementation of elliptic curve (EC) public-key cryptosystems. In this paper, we proposed a secure image encryption scheme using key sequences generated from Chaos-Driven Elliptic Curve Pseudo-random Number Generator (C-D ECPRNG). This key sequences derived from random sequences based on EC points operations driven by a chaotic map. These constructions improve randomness properties of the generated sequences since it combines good statistical properties of an ECPRNG and a Chaotic Pseudo-random Number Generator (CPRNG). Entropy analysis of two test images shows that randomness of the ciphered images with the proposed key schemes are more random than in case of the ECPRNG without modulation by a chaotic map. Statistical and differential analysis demonstrate that the proposed schemes have adequate security for the confidentiality of digital images and the encryption is efficient compared to other competitive algorithms.

We present a new image compression method to improve visual perception of the decompressed images and achieve higher image compression ratio. This method balances between the compression rate and image quality by compressing the essential parts of the image-edges. The key subject/edge is of more significance than background/non-edge image. Taking into consideration the value of image components and the effect of smoothness in image compression, this method classifies the image components as edge or non-edge. Low-quality lossy compression is applied to non-edge components whereas high-quality lossy compression is applied to edge components. Outcomes show that our suggested method is efficient in terms of compression ratio, bits per-pixel and peak signal to noise ratio.

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In this paper, two image encryption schemes are proposed for grayscale and color images. The two encryption schemes are based on dividing each image into blocks of different sizes. In the first scheme, the two dimension (2D) input image is divided into various blocks of size N × N . Each block is transformed into a one dimensional (1D) array by using the Zigzag pattern. Then, the exclusive or (XOR) logical operation is used to encrypt each block with the analogous secret key. In the second scheme, after the transformation process, the first block of each image is encrypted by the corresponding secret key. Then, before the next block is encrypted, it is XORed with the first encrypted block to become the next input to the encrypting routine and so on. This feedback mechanism depends on the cipher block chaining (CBC) mode of operation which considers the heart of some ciphers because it is highly nonlinear. In the case of color images, the color component is separated into blocks with the same size and different secret keys. The used secret key sequences are generated from elliptic curves (EC) over a binary finite field F2m . Finally, the experimental results are carried out and security analysis of the ciphered images are demonstrated that the two proposed schemes had a better performance in terms of security, sensitivity and robustness.