In this paper, a novel transmission scheme based on the discrete-time fractional-order chaotic system for private digital communications is proposed. The fractional-order Modified-Henon map is used. By adjusting the fractional-orders appropriately, it has been shown that the fractional-order Modified-Henon system possesses a chaotic behaviour. The exact synchronization based on the delayed observer is designed. A detailed study of synchronization and robustness of the proposed scheme is next presented. Simulation results are given to highlight the performances of the proposed method.