Abstract
In recent years, with the rapid development of the network communication, information security issues have become increasingly prominent. As an important carrier of information, image plays an important role in the transmission process. Therefore, lots of image encryption algorithms have been proposed. However, these algorithms are not designed in accordance with the unified security standards and requirements, so there may be a lot of security risks, and what is the worst thing is that some encryption algorithms may be cracked in an acceptable time complexity by some cryptographic analysis. This paper focuses on one of the most influential algorithm proposed by Zhang, which improved Zhu’s algorithm. The non-fixed parameter and diffusion-permutation strategy are adopted by Zhang, but there are still problems that cannot resist chosen-plaintext attack and the key space is not enough to resist brute-force attack. We use chosen-plaintext attack to crack Zhang algorithm, and then propose a further improved scheme.
Highlights
In the traditional cryptography research, an image is not considered separately as a special plaintext form
It does not need to consider the specific form of plaintext information, whether it is text or image or video, it is unified as a bit stream
Due to some inherent characteristics of an image, such as the large data volume, two-dimensional spatial distribution of pixel, multiple data redundancy and high correlation between adjacent pixels, if such algorithms as Data encryption standard (DES) and Advanced encryption standard (AES) are used at this time, the encryption performance may not meet the requirements of security or encryption efficiency
Summary
In the traditional cryptography research, an image is not considered separately as a special plaintext form. Zhang analyzed [24] the defects of Zhu et al [3] algorithm, that is, the first pixel in the permutation and diffusion process is unchanged and the security of Arnold permutation is low He cracked the algorithm by chosen-plaintext attack and gave the improved algorithm. When analyzing Zhang’s improved algorithm, it is found that there are still some problems that cannot resist the chosen-plaintext attack and the secret key space is insufficient. Based on the analysis of the Zhang’s algorithm, this paper adopts the chosen-plaintext attack to crack it, and gives a further improved encryption scheme. Kerckhoffs principle is described as follows: all algorithms must be public and the key is secret Based on this principle, four types of attack patterns are proposed, including ciphtext-only attack, known-plaintext attack, chosen-plaintext attack, and chosenciphertext attack. When using the chosen-ciphertext attack, to some extent, the attacker has mastered the equivalent key
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