Research On Perceptual Encryption Of The Vector Map

The country spends a lot of manpower,materials and financial resources to draw vector maps,which completely record the landforms,airports,important bases and other vital data.Most of these important data belong to confidential mapping results.Once being released,,it may have subversive impact on the country and regions.So the security of vector maps is a matter of national security interests.There are two ways to transfer important data of electronic maps from one region to another,one is network transmission and the other is manual transmission.Network transmission is most likely to be monitored by signal,during which time the important documents can be easily stolen by criminals.During manual transmission,important confidential data might also be stolen by hostile molecules.Vector maps in storage are possible to be stolen by browsing the phishing site,computer password cracking and other factors.So the data of vector maps in transmission and storage process is extremely unsafe.It is necessary to conduct encryption for the data of vector maps.The problems are that the speed and security of encryption cannot be compatible in traditional encryption schemes.These two things cannot become true at the same time.Based on this problem,this paper gets an idea from the compression perception theory of remote sensing image map process,and puts forward an encryption scheme,which is applied to the vector map file encryption process.When the system receives a vector map,the whole vector map decomposes into minimum operation objects according to different elements layers,and the data of each minimum operation object is divided into two parts,namely the integer part and the fraction part.A structure of unit compression is defined,and the offset and the direction of the integer part are encrypted based on this structure.The fractional part is parallel computed at the same time.According to different requirements to the accuracy of vector map files,the fractional part is embalmed in accuracy aspect until the requirements can be satisfied.Although data are damaged,the actual results will not be affected.Then new data will be generated after the integer part and the fractional part are combined together.These data through the initial processing will be encrypted again through the information generated during the compression process.In the second encryption,the key borns used is created in the process which creates the structure of unit compression,one is the location key and the other is direction key.The ciphertext is finally generated by these two keys.The decryption scheme can be derived from the reverse.Due to the operation of the program is based on the minimum operation object,so when the files are decrypted,it can be partially decrypted based on minimum object.Keys are generated during files compression and are safer than traditional keys.At the same time,it also makes a special processing to attribute files and topological files,which makes it difficult for the cracker to get the corresponding coordinate files position through the attribute information,thus to ensure the security of the vector map data from multiple aspects.