Selective Encryption Scheme for Vector Map Data in DCT Domain using Shape Components

Abstract

Recently years, vector map has developed, used in many domains, and in most cases vector map data contains confidential information which must be kept away from unauthorized users. Moreover, the producing process of a vector map is considerably complex and the maintenance of a digital map requires substantial monetary and human resources. In addition, widespread of vector map applications, and the rapid development of vector map contents, a large volume of valuable vector map dataset has been distributed illegally. Therefore the problem focuses on how to protect the vector map data for multimedia applications, storage and transmission. At this point, security techniques for vector map focusing on secure network, copyright and data encryption have been studied. This paper presents the selective encryption scheme in DCT domain for vector map security for multimedia applications, storage, transmission and distribution to authorized users. In proposed scheme, polylines and polygons in vector map are targets of selective encryption. Vector map is separated to select polylines and polygons, and then they are randomized vertices by random algorithms before changing them in DCT domain. Here, I present two ways to perform selective encryption in DCT domain. First way, polylines/polygons are classified into groups and then 1D-DCT. Second way, I arrange all coordinates of vertices of polylines/polygons into a two dimensional array and then 2D-DCT. In DCT domain, I select DC values of polylines/polygons to encrypt by random algorithm and cryptography. Experimental results verified that proposed algorithm is effectively and security. Maps are changed whole after encryption process, and unauthorized users cannot access to copy or use them. Encrypted maps do not alter the size of file and it does not have loss accuracy. The error between original map and decrypted map is approximate zero.