Color Image Compression-encryption Algorithm Based On Quaternion Discrete Multi-fractional Random Transform

With the blooming of cloud computing,Internet of Things,big data technologies,et al.,modern information technologies bring great convenience to people.At the same time,how to protect the image information security effectively has been become a research hotspot for many scholars.Traditional text encryption algorithms are no longer suitable for encryption of digital images due to theirs high time costs and poor encryption effects.Therefore,research on safe and efficient image encryption algorithms has important application value.The main research contents are as follows:A color image compression and encryption algorithm based on quaternion discrete multi-fractional random transform and compressive sensing(CS)is designed.The quaternion fractional random transform is extended to the quaternion discrete multi-fractional random transform(QDMFRNT)domain.The fractional order utilized for this transform is generated by a 1D chaotic system,which not only increases the key space,but also greatly improves the sensitivity of the fractional key.The original color image is compressed and encrypted with the assistance of CS,in which the partial Hadamard matrix adopted as measurement matrix is constructed by iterating Chebyshev map instead of utilizing the entire Guassian matrix as a key.In the key generation mechanism,the input of SHA-512 is set to associate with the color plaintext image and the secret keys.The initial keys and parameter of 2D chaotic system are updated via randomly selected hash values,which allows the proposed algorithm to generate different updated keys each time when the color plaintext image and original keys are the same.The proposed strategy further ensures the security of the encryption scheme.In the encryption process,the CS is first used to compress and encrypt the RGB components to reduce the amount of data transmitted.The sparse images are divided into 12 sub-images and then represented as three quaternion signals,which are modulated by the QDMFRNT.The image blocking and quaternion representation make the proposed cryptosystem avoid additional data extension that many transform-based methods yield.To further improve the level of security,the plaintext-related key streams generated by the 2D Logistic-Sine-coupling map areadopted to diffuse and confuse the intermediate results simultaneously.Consequently,the final ciphertext image is attained.Simulation results reveal that the proposed cryptosystem is feasible with high security and has strong robustness against various attacks.