A Robust Chaotic and Fast Walsh Transform Encryption for Gray Scale Biomedical Image Transmission

In this work, a new scheme of image encryption based on chaos and Fast Walsh Transform (FWT) has been proposed. We used two chaotic logistic maps and combined chaotic encryption methods to the two-dimensional FWT of images. The encryption process involves two steps: firstly, chaotic sequences generated by the chaotic logistic maps are used to permute and mask the intermediate results or array of FWT, the next step consist in changing the chaotic sequences or the initial conditions of chaotic logistic maps among two intermediate results of the same row or column. Changing the encryption key several times on the same row or column makes the cipher more robust against any attack. We tested our algorithms on many biomedical images. We also used images from data bases to compare our algorithm to those in literature. It comes out from statistical analysis and key sensitivity tests that our proposed image encryption scheme provides an efficient and secure way for real-time encryption and transmission biomedical images.