Abstract
To protect image information security, we propose an encryption algorithm based on chaotic sequences and bits' cross-diffusion. First, two chaotic sequences are generated by two-dimensional logic-sine coupling mapping, and the original image is scrambled with the two sequences. Secondly, the scrambled image is transformed into a one-dimensional sequence, and the low-order bits between every two pixels are fused to change the detailed information of the image, improved the ability to resist differential attacks. Finally, chaotic sequences are generated by iterative logical mapping to perform pixel replacement and ciphertext diffusion. The known plaintext attack can be effectively resisted because of the stochastic combination of diffusion scheme and chaotic sequence. It also has a significant effect on resisting differential attack. Take Lena image as an example, NPCR and UACI can reach 99.6063% and 33.4477%, respectively, which are very close to the ideal value. The encryption scheme has good key sensitivity and strong ability to resist statistical attacks, which shows that the algorithm has adequate security.
Highlights
It is well known that an effective encryption strategy can better protect the image information
To protect image information security, we propose an encryption algorithm based on chaotic sequences and bits’ cross-diffusion
Transform the original image P into image matrix P1 with the size of M × N: 1) Initial value generation: Input the image matrix P1 into SHA-256 algorithm and output 256 bits hash value H, the chaotic initialization parameters x0, y0, θ 0 and z0 were calculated according to Eq (4) and Eq (5); 2) Pixel scrambling: Iterative 2D-LSCM chaotic mapping produces two chaotic sequences U and V, and processes the data according to Eq (6) and Eq (7) to obtain the sequence U’ and V’
Summary
It is well known that an effective encryption strategy can better protect the image information. Hua et al [12] proposed a twodimensional chaotic sequence generation model combining sine mapping and logistic mapping in 2015, and the model uses sine mapping and parameters to adjust the output of logistic mapping, thereby enhancing the nonlinearity of the two-dimensional chaotic sequence and randomness This method improves the encryption system’s security, but the encryption algorithm cannot effectively resist the differential attack. Because of the limited variety of DNA coding rules and DNA coding operations, these schemes fail to make full use of these limited rules, which weakens the significance of using DNA coding to some extent To solve these problems, this paper proposes an algorithm to encrypt images by two chaotic systems; thereby, there are more key parameters, increasing the key space and better resist brute force attacks.
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