Li-bo Zhang

A novel double-image encryption scheme based on cross-image pixel scrambling in gyrator domains

Recently, a number of double-image cryptosystems have been developed. However, there are notable security performance differences between the two encryption channels in these algorithms. This weakness downgrades the security level and practicability of these cryptosystems, as the cryptosystems cannot guarantee all the input images be transmitted in the channel with higher security level. In this paper, we propose a novel double-image encryption scheme based on cross-image pixel scrambling in gyrator domains. The two input images are firstly shuffled by the proposed cross-image pixel scrambling approach, which can well balance the pixel distribution across the input images. The two scrambled images will be encoded into the real and imaginary parts of a complex function, and then converted into gyrator domains. An iterative architecture is designed to enhance the security level of the cryptosystem, and the cross-image pixel scrambling operation is performed to the real and imaginary parts of the generated complex encrypted data in each round. Numerical simulation results prove that a satisfactory and balanced security performance can be achieved in both channels.

Exploiting self-adaptive permutation–diffusion and DNA random encoding for secure and efficient image encryption

Abstract This paper presents a solution for secure and efficient image encryption with the help of self-adaptive permutation–diffusion and DNA random encoding. The plain image is firstly converted to DNA sequence using random encoding rules, so as to disarrange the bit distribution of the plaintext. A self-adaptive permutation–diffusion procedure is subsequently introduced for further encryption. The quantization processes of the permutation and diffusion procedures are disturbed by the intrinsic features of the plaintext, with the introduced disturbances can be automatically retrieved in the decryption end. The security of the system originates from the plaintext-related quantization of the encryption process which makes the cryptosystem secure against plaintext attack. Besides, the reusability of the random variables can dramatically promote the efficiency of the cryptosystem, which renders great potential for real-time secure image applications.

Cryptanalysis and improvement of an optical image encryption scheme using a chaotic Baker map and double random phase encoding

In this paper, we evaluate the security of an enhanced double random phase encoding (DRPE) image encryption scheme (2013 J. Lightwave Technol. 31 2533). The original system employs a chaotic Baker map prior to DRPE to provide more protection to the plain image and hence promote the security level of DRPE, as claimed. However, cryptanalysis shows that this scheme is vulnerable to a chosen-plaintext attack, and the ciphertext can be precisely recovered. The corresponding improvement is subsequently reported upon the basic premise that no extra equipment or computational complexity is required. The simulation results and security analyses prove its effectiveness and security. The proposed achievements are suitable for all cryptosystems under permutation and, following that, the DRPE architecture, and we hope that our work can motivate the further research on optical image encryption.

An Efficient Diffusion Scheme for Chaos-Based Digital Image Encryption

In recent years, amounts of permutation-diffusion architecture-based image cryptosystems have been proposed. However, the key stream elements in the diffusion procedure are merely depending on the secret key that is usually fixed during the whole encryption process. Cryptosystems of this type suffer from unsatisfactory encryption speed and are considered insecure upon known/chosen plaintext attacks. In this paper, an efficient diffusion scheme is proposed. This scheme consists of two diffusion procedures, with a supplementary diffusion procedure padded after the normal diffusion. In the supplementary diffusion module, the control parameter of the selected chaotic map is altered by the resultant image produced after the normal diffusion operation. As a result, a slight difference in the plain image can be transferred to the chaotic iteration and bring about distinct key streams, and hence totally different cipher images will be produced. Therefore, the scheme can remarkably accelerate the diffusion effect of the cryptosystem and will effectively resist known/chosen plaintext attacks. Theoretical analyses and experimental results prove the high security performance and satisfactory operation efficiency of the proposed scheme.