Color image encryption by using Arnold and discrete fractional random transforms in IHS space

In this paper, we propose a novel color image encryption method using discrete fractional random transform (DFRNT) and Arnold transform (AT) in the intensity-hue-saturation (IHS) color space. A color image is converted into IHS space from the standard red–green–blue (RGB) space. The intensity component is encrypted by DFRNT, which is a kind of encryption with the secrecy of pixel value and pixel position simultaneously. The hue and saturation components are encrypted using Arnold transform, which is a kind of position scrambling. Comparing to the classical double-random-phase encoding, DFRNT encryption method can save storage space of the encryption keys required to be stored for decryption, meanwhile with the similar security. The fractional order of DFRNT, the random matrix of DFRNT and the iteration numbers of Arnold transform are the encryption keys to enhance the security of the proposed scheme. The performance of the proposed scheme is analyzed against the variation in fractional order, the change of Arnold transform iteration number, known-plaintext attack, noise addition and occlusion of the encrypted image, respectively. Numerical simulation results have demonstrated the feasibility and effectiveness of the proposed method.