作者在对当前图像加密技术进行充分分析和研究的基础上,针对X射线图像的特点以及图像评判要求,以混沌理论为基础,设计了双Logistic映射混沌序列发生器并且改进素位置置乱方法来实现了对X射线图像进行加密.新的算法通过双混沌序列发生器产生混沌序列,像素置乱变换与灰度值替换都由这些混沌序列所控制.通过破解实验和性能分析,结果表明该算法安全性很好,能够抵抗一定的恶意攻击,在密文图像缺损的条件下也能很好地还原出原始信息,因此加密效果很好.%On the basis of full analysis and study of the current image encryption technology,we take the X ray detection im?age collected from a detection center of Daqing oilfield as the research object. Aiming at the characteristics of the X ray image and the requirements of the image evaluation,based on the chaos theory,the chaotic sequence generator of the dual Logistic mapping is designed and changed. The scrambling method is used to encrypt X- ray images. The new algorithm generates chaotic sequences through dual chaotic sequence generators,and the pixel scrambling transformation and gray value replacement are controlled by these chaotic sequences. Through theoretical analysis and simulation experiments,it is proved that the key space generated by the multi chaotic sequence is larger than which produced by a single chaotic sequence. Therefore,the algorithm studied in this paper has high encryption strength. After making tiny changes to the key,the encrypted image is decrypted. The decryption failure proves that the algorithm is sensitive to the initial value. Through the experiment and performance analysis,the results show that the algo?rithm is very safe,it can resist a certain malicious attack and restore the original information well in the condition of the image de?fect of the ciphertext,so the encryption effect is excellent.
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