【作者】 何平；

【导师】 彭飞； 胡斌晖；

【作者基本信息】 湖南大学 ， 计算机技术（专业学位）， 2021， 硕士

【摘要】 随着云计算以及物联网技术的快速发展,云制造技术应运而生。二维CAD工程图作为主要的产品设计数据在制造生产过程中存在一系列的安全问题,例如原始的设计数据被恶意修改、图纸遭受非授权拍摄以及实体图纸遭受非法打印扫描等。因此,对遭受媒体转换攻击的二维工程图的版权保护和泄密溯源,是当前研究中亟待解决的课题,且具有实际应用价值。针对屏幕拍摄以及打印扫描两种媒体转换攻击,本文开展了如下研究:(1)提出了基于实体替换的二维工程图抗屏幕拍摄水印算法。首先,选择CAD工程图形中满足条件的直线实体作为嵌入载体。其次,将加密后的水印序列进行分组并生成校验信息,连接原始水印序列和校验序列作为最终水印嵌入序列,通过替换实体来嵌入水印。水印提取过程需要对屏幕拍摄图像进行光照以及畸变校正,识别校正图像中的水印点进行水印提取。实验与分析表明该算法不仅能够抵抗屏幕拍摄过程的多重失真,而且能够抵抗一定程度的裁剪攻击,具有较强的鲁棒性,水印容量较大。同时实现了在矢量图形中嵌入,在栅格图像提取的跨载体应用。(2)提出了基于DCT和置乱的二值工程图像抗打印扫描图像。算法对图像以及计算的可翻转系数矩阵进行置乱,并将相邻分块黑色像素点数量的差值作为特征值,并进行分块DCT(Discrete Cosine Transform,DCT)变换。随后,根据打印扫描前后DCT系数符号变化率低于0.5的特性修改DCT系数,再进行反DCT变换,计算最终分块中黑色像素点的数量。最后,对图像进行逆置乱。实验表明该算法对打印扫描、复印、噪声以及污损攻击都具有较好的鲁棒性,且像素块翻转分布均匀,不可感知性较好。本文提出的二维工程图抗屏幕拍摄水印方案以及抗打印扫描水印方案,有效克服了屏幕拍摄过程以及打印扫描过程中的多重攻击,具有较好的鲁棒性,可用于工程图纸的泄密溯源追踪,提升了二维工程图在跨媒体传输中的数据安全性。更多还原

【Abstract】 With the rapid development of cloud computing and Internet of Things technology,cloud manufacturing technology has emerged.As the main product design data,2D CAD engineering graphics have a series of security problems in the manufacturing process,such as malicious modification of original design data,unauthorized shooting of drawings,and illegal printing and scanning of physical drawings.Therefore,the copyright protection and leak traceability of the 2D CAD engineering graphics attacked by the media conversion is a topic that needs to be solved urgently in the current research,and it has practical application value.This article mainly focuses on the two media conversion attacks of screen shooting and print scanning and The following researches are carried out:(1)A 2D CAD engineering graphics anti-screen shooting watermarking algorithm based on entity replacement.First,select the polyline entities that meet the conditions in the CAD engineering graphics as the embedding carrier.Second,group the encrypted watermark sequence and generate verification information.Then connect the original watermark sequence and the verification watermark sequence as the final embedding sequence,embed the watermark by replacing the entity.The watermark extraction process needs to perform illumination and distortion correction on the screen shot image,and identify the watermark points in the corrected image for watermark extraction.Experimental results show that the algorithm can not only resist multiple distortions in the screen shooting process,but also resist cropping attacks to a certain extent.It has strong robustness and large watermark capacity.At the same time,it realizes the cross-carrier application of embedding in vector graphics and extracting raster images.(2)A binary engineering image anti-printing scanning watermarking algorithm based on eigenvalue matrix block discrete cosine transform and image scrambling.First,perform scrambling and block operations on the image and the flipable coefficients.Use the difference between the number of black pixels in adjacent blocks as the eigenvalue matrix,and perform block DCT transformation on the image.Subsequently,the DCT coefficient is modified according to the characteristic that the rate of change of the DCT coefficient symbol before and after the process of print-scan is less than 0.5,and then perform inverse DCT transformation on the modified coefficients,calculate the number of black pixels in the final block,and flip the corresponding number of pixels.Finally,perform inverse scrambling on the image.Experiments show that the algorithm has good robustness against print-scan,copying,noise,and defacement attacks,and has good imperceptibility.The 2D CAD engineering graphics anti-screen shooting watermark scheme and the anti-print scanning watermark scheme proposed in this paper effectively overcome the multiple attacks in the screen shooting process and the print-scan process.It has good robustness and can be used to trace the source of leaks in engineering drawings,which improves the data security of 2D CAD engineering graphics in cross-media transmission.更多还原