Abstract: In this paper,the methods to measure the scrambling degree of scrambling images are deeply discussed.Then,a new algorithm to measure the scrambling degree of scrambling images is proposed.The algorithm is as follows：first,devising the original image and the scrambling image to sub-block;second,calculating the distance of the according sub-block and get the result as the minimum value of eight valve situation.Finally,the definition of the scrambling degree is given.In order to evaluate the degree of the scrambling,we propose a new definition above it.The experiment results show that the scrambling degree is an efficient metrological method.

Key words: scrambling transformation, encryption, scrambling degree

摘要： 近年来,出现了许多有效的图像置乱加密算法,但却很难找到一种关于置乱加密效果的有效度量方法。对度量置乱加密效果的方法进行了深入的探讨,进而提出了“置乱加密度”的概念,能够客观地反映置乱算法的加密性能,同时兼顾人类的视觉特性,是一种有效的度量方法。算法的执行过程如下：首先,将原始图像和置乱加密后的图像按照同样的方法分割为许多子块;第二步,对于原始图像中的每一块,求出它与置乱加密后的图像各个子块的最小“距离”;最后,给出了“置乱加密度”的定义,用来度量图像的置乱加密程度。实验结果证实了“置乱加密度”能有效地反映算法的置乱加密效果。

关键词: 排列变换, 加密, 置乱加密度