| Summary: | The security system engaged to transfer securely the sensitive information over wireless channels must posses some innate features such as high resistivity to various cryptographic attacks, high sensitivity to secret key and plaintext, and strong statistical characteristics of encrypted content. Recently, an image cryptosystem is investigated to secure color images while transmission. The cryptosystem is based on permutation only cipher and employed synchronized 4D hyperchaotic systems. The cryptosystem has credibility of providing ample statistical encryption quality of ciphertext. This paper aims to investigate and analyze the security of this image cryptosystem in terms of its defects and attack resistivity. The security analysis uncovers that cryptosystem holds certain serious security defects and incapable to secure encrypted content. To support the claim, the inherent defects are highlighted; thereby an attack procedure is proposed to show that the cryptosystem is breakable under the proposed cryptanalysis. The attacker can recover complete plaintext image from ciphertext image without knowing secret key. Computer simulations are performed to justify the success of cryptanalysis. The image cryptosystem is all insecure for use in practical applications of image-based secure wireless communication. As a remedy, this paper also suggests security enhancements and an enhanced cryptosystem is proposed to make it completely resistive against above and other types of cryptanalytic attacks and increase on its plain image sensitivity and statistical encryption strength.
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