Control of multistability with selection of chaotic attractor: application to image encryption

Dynamic systems exhibiting chaos with periodic windows and multistability are not recommended for cryptography due to the lack of security in these regimes. In this work, we use a linear augmentation control scheme to control a periodic attractor in the windows of multistability to a final chaotic attractor which survives to the variation of initial seed useful for image encryption. The empirical Chua’s system with piecewise linear nonlinearity is used as a sample dynamical system but the idea can be applied using any other dynamical system. First, this system is analyzed to reveal multistability dynamics. Second, the technique of linear augmentation combined with the nonlinear system invariant sets like equilibrium points is used to choose a desired survive attractor among the coexisting ones. It is found that annihilation of multistability in the Chua’s system when varying the coupling strength is obtained through several crises among which interior crisis and border collision. Finally, a survived chaotic attractor is jointly used with SHA-512 for image encryption algorithm using a simple diffusion-confusion structure. Security analysis shows that the encryption process based on control theory can resist various forms of attack.