JPH0622038B2 - Map drawing data search method - Google Patents

Description

The present invention relates to a map drawing data search method for a map drawing management system that stores a map as vector information.

[Conventional technology]

When the map drawing data is scaled from 1/500 to 1/2500, detailed personal names and road conditions can be recorded, and if anyone can freely view the data, it will violate the privacy of individuals and urban planning, etc. There is a fear that it will be used for land purchase by leaking in advance. Therefore, data encryption is required.

As a method for encrypting data to protect security, for example, as shown in Japanese Patent Laid-Open No. 56-40343, input data is divided into several bits, each of which is arranged in an arbitrary number of bytes, and encrypted, or It is known that the processing time can be shortened by performing the processing in units of more bytes. However, this method is effective when encrypting a communication text that does not need to store data, but has a drawback that the storage capacity becomes large when data needs to be stored, such as a graphic data file.

[Problems to be solved by the invention]

Since the map drawing data uses a magnetic disk device, a magnetic tape device, a floppy disk device, or the like as a storage medium, the data can be easily copied. Therefore, there is a problem in that even if a method of making a search impossible by adding a password is used at the time of data search, the copied data can be freely read and the security cannot be protected.

An object of the present invention is to encrypt map drawing data,
The line data, which is the basis of map data, is divided and rearranged into a plurality of blocks to provide a search method for map drawing data.

[Means for solving problems]

In order to solve the above problems, the present invention divides the map drawing data into a plurality of blocks, and the start and end points of the line segment data span a plurality of blocks, and among them, a road is shown on the map. The parallel lines are extracted, and the coordinates of the start point and the end point of each are converted into another block according to the encryption keyword to be encrypted data.

[Action]

The road figure, which is an important figure identifying condition in the map drawing data, is encrypted so that the map drawing data itself cannot be decrypted without the encryption keyword.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows an example of an encrypted display drawing by coordinate conversion of the map drawing data according to the present invention. In order to encrypt map data of 1/500 or 1/2500 scale, which is the center of map drawing management, a plurality of maps are shown. It shows each intersection point divided into blocks and represented by vector information. FIG. 1 (a) is a map drawing before encryption and shows a road portion which is the most important figure in the map. In order to encrypt data, the point is to perform efficient cryptographic processing in the shortest time. In the present invention, when one map drawing is divided into blocks, line data across a plurality of blocks is extracted and The coordinates of the end point of the line data are converted using the encryption block keyword. FIG. 1 (b) is FIG. 1 (a).
It is a figure which shows the result of having carried out the coordinate conversion by the encryption block keyword point (1st arbitrary reference point) K, a road structure is completely unknown, and drawing encryption can be achieved.

Next, a method for realizing such encrypted data will be described below with reference to FIGS.

FIG. 2 is a diagram showing the structure of the map drawing database. 1 of FIG. 2 is a map drawing, and this drawing data is divided into a plurality of layers according to its graphic configuration, and is composed of a road graphic 2, a house frame graphic 3, a piping graphic 4, and the like. The map drawing database uses a combination of the above layers according to the usage pattern, but the most important part of the map is the road,
For urban planning that carries out this road expansion plan, leaking information on road construction plans in the next few years from now on will lead to price increases at the time of land acquisition, and land will be purchased in advance, which will lead to land purchase. This is an extremely problematic point of interest. Therefore, in order to maintain confidentiality of map drawing data, especially when paying attention to the road part, the line data that is the characteristic point of the road is long, and the point when the line data is almost parallel lines is encrypted. I am trying.

FIG. 3 shows the configuration of a map drawing management system. In FIG. 3, 5 is a CPU for executing processing, 7 is a file device for storing map drawing data, and 6 is for storing a program for executing processing such as drawing data retrieval and edit encryption, and data being processed. Main memory, 9 is a CRT for displaying graphics and characters as a processing result, 10 is a keyboard for inputting commands and encryption keys, 11 is a tablet for selecting menus and inputting coordinate positions, and 12 is a coordinate position. A stylus 8 for scanning is a drawing input device for scanning a drawing to obtain a gray scale, obtaining a digital image, and obtaining coded data. In such a configuration, with respect to the procedure necessary for converting into encrypted data as shown in FIG. 1 (2), how is it encrypted based on the map drawing data in FIG. 4? A process flow chart will be described.

First, the map drawing database stored in advance in the file device 7 of FIG. 3 has one map composed of n pieces of line data as shown in FIG. The position, direction, and size of each data are determined by the coordinates of the start point and the end point.

In the flow chart step S401 of FIG. 5, one map, which is the unit of encryption, is divided into a plurality of blocks (16 divisions in FIG. 1) as shown in FIG. 1, and NO is assigned to each block as 1, 2, 3
…… and sequentially add. In step S402, the start point and end point coordinates are selected from the line data 1 to n in FIG.
It is calculated which block NO is divided by 1, and only those block NOs whose start points and end points are different are extracted. Step S403 is Step S40
Since the end point coordinates of the line segment data extracted in 2 are encrypted, if a block NO including the origin point when the end point coordinates are converted to the origin point is given as the primary conversion cipher keyword k ₁ , the X coordinate of the end point coordinates, Y The coordinates are symmetrically transformed with the first arbitrary reference point as the center point. In this process, when one map is divided into 1 to 16 as shown in FIG. 6, the divided block NO6-1 is assigned to 1 to 16. Now, the starting point coordinates (x ₁ , y ₁ ) and the ending point coordinates (x ₂ , y ₂ )
The line segment data 6-2 across a plurality of blocks will be taken as an example of encrypted data. When the end point coordinates (x ₂ , y ₂ ) to be encrypted are subject to the origin conversion around the origin (x _k1 , y _k1 ) of the block NO6-3 that is the primary conversion cipher keyword k ₁ , the end point coordinates are ( 2x _k1 −x ₂ , 2y _k1 −y ₂ ) and this data becomes the encrypted data by the encryption keyword k ₁ . Step S4
When the encrypted data line data obtained in 03 is a parallel or nearly parallel figure, the figure shape remains even after the encryption, and it is particularly effective for the encryption of road figures featuring parallel line data. Absent. Therefore, step S4
Reference numeral 04 is for extracting line data which is still parallel line data after the primary encryption conversion by the keyword k ₁ . The extraction method is as follows. First, the slope of the line data in which the start point and end point coordinates are passed to a plurality of blocks is sequentially calculated by the following equation (1).

Where ra: slope of a-th line data x _2a-1 , x _2a : start point and end point of x-coordinate of a-th line data y _2a-1 , y _2a : start point of y-coordinate of a-th line data And the end point The slope r _b of the b-th line data is obtained by the formula (1), and if the slope satisfies the following formula (2) or (3), a
It is determined that the 2nd and bth line data are parallel.

r _a = r _b ...... (2) r _a −r _b ε ₀ …… (3) where ε ₀ : allowable tilt error value In step S405, the line data group is selected from the line data group determined to be the same parallel line. The younger one of the array is subjected to the secondary conversion encryption parallel line, and the starting point coordinates of the corresponding line data are converted into encrypted data. That is, in FIG. 7, two line data 7-2,
If 7-6 is parallel line data, this line data is transferred from step S401 to step S403 as in FIG.
Line data 7-
It becomes 5,7-9. However, the encrypted line data 7-
Since 5 and 7-9 remain parallel lines after the primary conversion encryption, it is necessary to reencrypt the younger start point coordinates of the line data array. Starting point coordinates to be encrypted (x _2a-1 ,
y _2a-1 ) is the block N which is the secondary conversion cipher keyword k _2.
O The second arbitrary reference point (x _k2 , y _k2 ) of the work is the center point, and the start point coordinates (x
_2a-1 , y _2a-1 ) becomes (2x _k2- x _2a-1 , 2y _k2- y _2a-1 ), and this data becomes encrypted data by the abbreviation keyword k ₂ . By the above processing, the encryption of the line data is completed,
This result is stored in the file device 7 of FIG. 3 by step STEP406.

The method for searching the encrypted data film thus created and displaying it on the CRT is as follows. In FIG. 3, when a third party who does not know the abbreviation keywords k ₁ and k ₂ searches the encrypted data file using the CRT keyboard 10, the displayed map figure is encrypted and displayed as the coordinates, It becomes unreadable and secure. On the other hand, when an administrator who knew the encryption keywords k ₁ and k ₂ tried to retrieve and display the corresponding map data,
When the next conversion abbreviation keyword k ₁ and the secondary conversion abbreviation keyword k ₂ are input from the CRT keyboard 110, the CPU 5 executes the reverse conversion of the processing shown in the encryption flow of FIG. As a result, the encrypted line data across a plurality of blocks returns to normal coordinates and is displayed on the CRT 9 as a normal figure before encryption.

〔The invention's effect〕

As described above, according to the present invention, when the map drawing database is searched or displayed, even if the corresponding map is displayed without using the encryption keyword, the map becomes completely meaningless and the data can be protected and the file device is also stored. The storage capacity of the encrypted data required is small, and since the encryption is limited to road data, the number of conversion items is small and the search when the encryption keyword is entered can be performed quickly.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an encrypted display drawing of map drawing data according to the present invention, FIG. 2 is a view showing the configuration of a map drawing database, FIG. 3 is a system configuration diagram of an embodiment of the present invention, and FIG. FIG. 5 is a diagram showing the data content of a map drawing, and FIG. 5 is a flow chart of processing. FIG. 6 is a conversion diagram by the primary conversion cryptographic keyword k ₁ , and FIG. 7 is a conversion diagram by the secondary conversion cryptographic keyword k ₂ . 1 ... Map drawing data, 2 ... Road graphic, 3 ... House frame graphic, 4 ... Piping graphic, 5 ... CPU, 6 ... Main memory, 7 ... File device, 8 ... Drawing input device, 9 ……
CRT, 10 ... keyboard, 11 ... tablet, 1
2 ... Stylus.

Claims (1)

[Claims] 1. When map figure data is stored as vector information, when the map drawing data is divided into a plurality of blocks, the start point and the end point of two line segment data indicating a road are divided into a plurality of blocks. The end point coordinates are symmetrically moved with the coordinates of the first arbitrary reference point as a center point, the coordinates of the first arbitrary reference point are used as a primary cryptographic keyword, and the end point coordinates are symmetrically moved by the primary cryptographic keyword. When it is determined that two line segment data are parallel, the start point coordinate of one line segment data is symmetrically moved with the coordinate of the second arbitrary reference point as the center point, and the coordinate of the second arbitrary reference point is changed to the secondary encryption keyword. A method for retrieving map drawing data, characterized in that the vector information of the map figure is retrieved.