Securing medical images is a great challenge to protect medical privacy. An image encryption model founded on a complex chaos-based Pseudorandom Number Generator (PRNG) and Modified Advanced Encryption Standard (MAES) is put forward in this paper. Our work consists of the following three main points. First, we propose the use of a complex PRNG based on two different chaotic systems which are the 2D Logistic map in a complex set and Henon’s system in the key generation procedure. Second, in the MAES 128 bits, the subbytes’ operation is performed using four different S-boxes for more complexity. Third, both shift-rows’ and mix-columns’ transformations are eliminated and replaced with a random permutation method which increases the complexity. More importantly, only four rounds of encryption are performed in a loop that reduces significantly the execution time. The overall system is implemented on the Altera Cyclone III board, which is completed with an SD card interface for medical image storage and a VGA interface for image display. The HPS software runs on μClinux and is used to control the FPGA encryption-decryption algorithm and image transmission. Experimental findings prove that the propounded map used has a keyspace sufficiently large and the proposed image encryption algorithm augments the entropy of the ciphered image compared to the AES standard and reduces the complexity time by 97%. The power consumption of the system is 136.87 mw and the throughput is 1.34 Gbit/s. The proposed technique is compared to recent image cryptosystems including hardware performances and different security analysis properties, such as randomness, sensitivity, and correlation of the encrypted images and results prove that our cryptographic algorithm is faster, more efficient, and can resist any kind of attacks.

中文翻译：

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改进的医学图像加密和解密安全方法的FPGA实现

保护医学图像是保护医学隐私的巨大挑战。提出了一种基于复杂混沌的伪随机数发生器（PRNG）和改进的高级加密标准（MAES）建立的图像加密模型。我们的工作包括以下三个要点。首先，我们建议使用基于两个不同混沌系统的复杂PRNG，这两个混沌系统是复杂集合中的2D Logistic映射和密钥生成过程中的Henon系统。其次，在MAES 128位中，使用四个不同的S盒执行子字节的操作，从而提高了复杂性。第三，消除了移位行变换和混合列变换，并用随机排列方法代替，这增加了复杂性。更重要的是，循环中仅执行四轮加密，从而大大减少了执行时间。整个系统在Altera Cyclone III板上实现，该板上配有用于医学图像存储的SD卡接口和用于图像显示的VGA接口。HPS软件运行在μ CLinux中并用于控制FPGA加密-解密算法和图像传输。实验结果证明，所使用的映射图具有足够大的密钥空间，并且与AES标准相比，所提出的图像加密算法增强了加密图像的熵，并将复杂度降低了97％。系统的功耗为136.87 mw，吞吐量为1.34 Gbit / s。将该技术与最新的图像密码系统进行了比较，包括硬件性能和不同的安全分析属性，例如随机性，敏感性和加密图像的相关性，结果证明我们的密码算法更快，更有效并且可以抵抗任何类型的攻击。