The Research On 2D Engineering Graphics Encryption Technology Based On Chaos

With the development of the information techniques and industrial automation,communication privacy and information security are attracting a lot of attention.Recently,the security of the two-dimensional engineering graphics was also gradually paid attention.But the research on the encryption of the 2D CAD engineering graphics is rare,and most of the existed works are concerned on the encrypt the format of graphics files,which few works have been done to the encryption of the contents.This thesis makes a deep investigation into the encryption techniques of 2D CAD engineering graphics' contents based on chaos scrambling and wavelet domain transform theory.The background,categories and current research status of 2D CAD engineering graphics encryption are presented,and the shortcomings in the existing encryption algorithms are analyzed.And then,the relevant theoretical knowledge,including chaos theory,wavelet transform and scrambling transformation,and their respective features are introduced.Finally,two encryption schemes are proposed,An encryption algorithm is first proposed for 2D engineering graphics based on wavelet descriptors and chaos.The specific coordinates of vertices in the 2D engineering graphics are extracted to form an array,and then they are grouped.Secondly,scrambling is made to each group according to the index vector,which is acquired from the sequence generated by Logistic mapping;After that,Arnold transformation is done to the vertex sequence in each group;Finally,the integer part of the detail coefficient of complex signals are encrypted,which are in turn transformed by wavelet transformation.Experimental results and analysis show that the proposed encryption scheme can obtain good diffusion and confusion.The key space is large,and it is very sensitive to key and ciphertext.The other encryption algorithm is a RST robust encryption scheme for 2D CAD engineering graphics based on chaotic mappings.Firstly,the coordinates of the vertices of 2D CAD engineering graphics are extracted,and a relative distance sequence is obtained by calculating the distance between each vertex and a reference vertex;Secondly,the sequence is grouped,and scrambling is made to each group according to the index vector,which is acquired from the sequence generated by Tent mapping;After that,Fibonacci transformation is done to the vertex sequence in each group;Finally,the integer part of relative distance are encrypted.Experimental results and analysis show that the proposed encryption scheme can obtain good diffusion and confusion.The key space is large,and it is very sensitive to key and ciphertext.Furthermore,the ciphertext is robust against rotation,even scaling,translation and their combination.It has great potential in the application of content protection for 2D CAD engineering graphics.The encryption approaches proposed in this thesis encrypt the contents of the 2D engineering graphics to ensure their safety,and can be used for content protection of 2D engineering graphics.