| Currently,multimedia communication is becoming more and more frequent in an open network environment.The privacy of information has received more and more attention on contemporary life.Digital images are an important information carrier for multimedia communications.Image information security has become a highly concerning issue.The digital image has the inherent characteristics of large volume and strong correlation in the spatial domain.The general encryption algorithm is not suitable for image encryption.The chaotic system itself is a complex nonlinear dynamic system,and it has three characteristics: non-periodic,random-like,and non-repetitive.It is very sensitive to initial conditions and chaotic parameters,which makes the generated chaotic sequence have good randomness and complexity.These characteristics are very suitable for the confidential work of image informationTo solve the problem of small key space of low-dimensional chaotic map encryption algorithm,this paper proposes a novel digital image encryption algorithm based on 2D Sine-Chebyshev compound map(2D-SCCM).The algorithm mainly includes two rounds of scram bling-diffusion encryption operations.The addition of the second round of encryption is to further spread and scramble the plaintext,thereby reducing the correlation between the plaintext and the ciphertext.Moreover,the preprocessing part of the key improves the algorithm’s ability to resist differential attack by associating with the plaintext information.Experimental results and security analysis show that the algorithm has sufficient key space and high sensitivity to keys,and can resist various attacks.It is a secure encryption algorithm.However,in the part of resisting tailoring attacks,the algorithm has a mediocre performance,and there is still room for improvement.This paper also proposes a new image encryption algorithm based on two-dimensional compound chaotic map and SHA-2.In order to prevent the encryption algorithm from encountering known plaintext attacks and selected plaintext attacks,the algorithm uses SHA-256 technology to calculate the hash value of the plaintext image.The hash value not only participates in the pre-setting of the key,but also participates in the diffusion part of the algorithm encryption process,so as to make full use of the data disturbance of the plaintext image to affect the entire encryption proce ss.The participating twodimensional compound chaotic map combines the output of Logistic map and Sine map with variable constants β and γ,and then performs cosine transformation in a joint form to generate output.In this way,the complexity of Logistic map and Sine map can be fully mixed,resulting in more complex chaotic behavior.Performance evaluation shows that it has better ergodicity and unpredictability,and has a wider range of chaos than many existing chaotic maps.The scrambling part mainly us es Zigzag technology to scan the plaintext digital image,and then uses the Sort function to scramble the overall pixel position.Diffusion is the key matrix constructed by the chaotic sequence and the pixels of the scrambled image perform BITXOR diffusion operation,and then use the previous pixel and the current pixel to be diffused to perform the BITXOR operation,so that small changes in the current pixel can affect the subsequent pixels.Finally,the experimental results and security analysis show that the algorithm can resist a variety of security attacks,and the part of resisting tailoring attacks has been effectively improved.It is a highly secure image encryption algorithm. |
