Image Encryption Based on Random Fractional Discrete Cosine Transform and Coupling Map Lattices with Hybrid Chaotic Mapping

To improve the security of image encryption based on reality-preserving fractional discrete cosine transform (RPFrDCT), an image encryption scheme based on random fractional discrete cosine transform (RFrDCT) is proposed. Random orders and generating sequences (GS) in RFrDCT not only overcome the weakness of low sensitivity of the fractional orders in RPFrDCT based image encryption, but also enlarge the key space of the encryption scheme. Hybrid chaotic mapping based on Tent and Sine maps is applied to generate the random fractional orders, the random GS and the diffusion matrix. Experimental results show that the encrypted image has better security performance.