Color Image Encryption Algorithm Based On The Spiral Transform

Digital images have become one of the foremost widely distributed forms on the Internet due to their information-rich and visual nature.With numerous digital images,such as medical images,satellite images,military images,domestic images,etc.,in case they are illegally accessed,it will cause damage that cannot be underestimated.Subsequently,it has become a core research goal for scholars to avoid illegal deciphering of information and to adopt fruitful algorithms to encrypt images.The traditional spiral transform is simple and poorly effective,while numerous highlights of chaotic systems can make up for their deficiencies,and the combination of the two can enhance security.Two color image encryption algorithms based on spiral transform are proposed for the problems of poor security and low efficiency of existing color image encryption algorithms,and ignoring the color image features and strong correlation.(1)An image encryption algorithm based on three-dimensional(3D)spiral transform and radial diffusion is proposed.Firstly,in the key generation stage,the hash value of the original color image is output using the hashing algorithm SHA-256,and the initial values and parameters of the chaotic system are calculated by combining the external input parameters.Secondly,in the permutation stage,after a spiral starting point is selected by chaotic sequence,the 3D matrix structure composed of R,G,B planes of the color image is combined with the traditional spiral transform to establish a 3D spiral transform,thus realizing image scrambling.Thirdly,in the diffusion stage,a three-level radial rule is defined with the assistance of the feature that a pixel value has 8 bits,and after determining the diffusion order utilizing chaotic sequences,the cipher image is obtained by bitwise exclusive-OR(XOR)diffusion of the permuted image according to the rule.Finally,in the simulation and experiment stage,eleven metrics such as key space,key sensitivity,and information entropy are evaluated and compared with other algorithms to verify that the proposed algorithm can encrypt color images securely and efficiently.(2)An image encryption algorithm based on cross-spiral transform and partition diffusion is proposed.Firstly,in the key generation stage,the hash value of the plaintext color image and six external parameters are utilized as the key,which can increase the key space and improve the key sensitivity.Secondly,a cross-spiral transform with arbitrary starting points is established by combining the features of color images,and the cross-spiral permutation of the three components is performed by the constructed index matrix.Thirdly,the bit-plane decomposes the scrambled image,divides it into four regions,and performs bitwise XOR operations in different directions for each region to obtain the cipher image.Finally,in the simulation and performance testing stage,several metrics demonstrate that the proposed algorithm is relatively short in time,and is highly resistant to brute-force,statistical,robustness,and chosen-plaintext attacks.Additionally,its performance is more suitable than some algorithms for the encryption transmission of color images of arbitrary size.