Résumé
Recently, a variety of chaos-based cryptosystems have been proposed. Some of these novel chaotic encryption schemes are not very suitable for image encryption because of their density function which is not uniformly distributed or because of their small key space. Note that for some chaotic map, their control parameters and initial values can be found easily. In this paper, we propose a new scheme for image encryption based on the use of the standard chaotic map with large key space and Engle Continued Fractions (ECF) map. The ECF-map is employed to generate a pseudo random sequence which satisfies uniform distribution, zero co-correlation and ideal nonlinearity to achieve higher level of security. The proposed scheme is resistant to statistic attacks, differential attacks and some other known attacks. Theoretic and numerical simulation analyses on 100 images indicate that our scheme is efficient and satisfies high security.