CHAOSLET consists in a chaotic encryption scheme for image data. We first extend the definition of the well-known Arnold 2D chaotic map
to the four-dimensional context. By involving the wavelet decomposition filters in the encryption process in addition to the pixel positions and the image gray levels, the 4-D chaotic map is defined in a way that it extends the 3-D chaotic map presented in the literature. This allows to adapt the efficiency of the encryption algorithm to the security needs and the available bandwidth through progressive encryption. In fact, according to the length of the symmetric key, different resolutions of the image can be obtained at the decryption level. Second, we define a secret-sharing technique allowing to enhance the robustness of the chaotic encryption algorithm. Throughout a rigorous
security analysis, we demonstrate that our algorithm outperforms the existing approaches. Concrete results obtained through simulations on real images also confirm the efficiency of our method.

Below is an example of the progressive decryption of a multi-spectral image using chaoslet (press F5 key to replay the progressive decryption process).