CN105488434B - A kind of map vector completeness certification method based on label - Google Patents

Abstract

The present invention provides a kind of map vector completeness certification method based on label.Include the following steps：Identification can be embedded in watermark apex coordinate；It is adaptive to divide pel group；Generate authenticating water-mark；Embedded authenticating water-mark；Mark pel；Watermark authentication and initial data Distortionless.Map vector pel is adaptively divided into different groups by the present invention, under the premise of the trueness error tolerance for considering map vector, the insertion of authenticating water-mark is realized using reversible information hidden method, and based on the method for being inserted into vertex, addition label ensures the correct division of watermark authentication stage diagram tuple to indicate its affiliated pel group in each pel, is accurately positioned while distort pel, with preferable invisibility, and it can tolerate that pel is out of order and vertex backward is attacked；On the other hand the algorithm is in the watermark authentication stage, and after removal marks and extracts authenticating water-mark, lossless reduction map vector initial data can effectively ensure the accurate use of map vector data.

Description

Mark-based vector map integrity authentication method

Technical Field

The invention relates to the fields of geographic information science and information hiding, in particular to a vector map integrity authentication method based on marks.

Background

Nowadays, a two-dimensional vector map is widely used as basic data of a Geographic Information System (GIS) in the fields of city planning, post and telecommunications, transportation, navigation, mapping, and the like. The acquisition of vector data requires a high outlay. However, these vector data can be copied, modified and distributed conveniently and quickly by means of information processing tools and public networks, which makes integrity certification and authenticity identification of two-dimensional vector maps increasingly prominent.

In order to meet the requirements of data integrity authentication and authenticity identification, digital signature technology is proposed. However, this technique can only identify whether data is tampered, and cannot locate the tampered position. Once the data is found to be changed, no matter the tampered data is the required data or the non-required data, the data is considered to be tampered and cannot be used, the data needs to be acquired again, the data acquisition time and cost are increased, and unnecessary delay is caused to some application occasions needing to acquire the data in time. In order to make up for the defects of the digital signature technology, the fragile watermarking technology is generated as an effective means of integrity authentication, and becomes a hot spot of research in the field of integrity authentication of geographic information products in recent years.

In addition, the name of patent application No. CN201210566500 is "a multi-stage authentication method for the integrity of shp line-surface layers"; patent application No. CN201210189469, entitled "a digital vector map integrity protection method"; the patent application number CN201210142896, entitled "a chaotic mapping based shp line-surface layer fragile watermarking technology", also relates to the problem of vector map integrity authentication, but unlike the method adopted in the present patent application, the method cannot have the characteristics of accurate positioning and tampering, recovery of vector map original data after authentication, and tolerance of primitive disorder and vertex reverse-order attack.

The "alternative gate-like multi-level Authentication" and "Authentication method and system" in the U.S. patent library are not specific to the present application, and the specific method is not the same.

Disclosure of Invention

On one hand, the method divides the vector map graphic elements into different groups in a self-adaptive manner, adopts a reversible information hiding method to realize the embedding of authentication watermarks on the premise of considering the precision error tolerance of the vector map, adds marks in each graphic element to indicate the image element group to which the graphic element belongs on the basis of a vertex inserting method, ensures the correct division of the image element group in the watermark authentication stage, has better invisibility while accurately positioning and tampering the graphic elements, and can tolerate the disordered graphic element and the reverse vertex attack; on the other hand, in the watermark authentication stage, after the mark is removed and the authentication watermark is extracted, the original data of the vector map is restored in a lossless manner, and the accurate use of the vector map data can be effectively ensured. Experimental results show that the scheme accurately positions tampered data, and is a practical algorithm for integrity authentication and positioning tampering of the vector map.

Vector map primitives (point, line and surface) are formed by arranging a large number of closely spaced vertices in a particular order, and the map data is a 2-dimensional coordinate sequence of the vertices. The vector map fragile watermarking technology is an important means for solving the problems of integrity authentication and positioning tampering of the vector map. The vector map fragile watermarking strategies which are currently proposed can achieve the aim of authenticating the integrity and the authenticity of data, but the strategies have defects in accurately positioning tampering. Aiming at the problems, the invention provides a vector map integrity authentication method based on a mark, which comprises the following steps:

(1) identifying embeddable watermark vertex coordinates;

identifying the vertex coordinates of the embeddable watermark according to the precision error tolerance of the vector map; suppose that the vector map M contains N line primitives, denoted as P₁,P₂,…,P_N，P_jDenotes the j (j ═ 1,2, …, N) th line element, P_jThe number of coordinates of the embeddable watermark is

(2) Adaptively dividing the graph element group;

adaptively dividing the vector map primitives into non-overlapping groups according to the number of coordinates of the embedded watermark vertices in the primitives; in the invention, the authentication watermark length of each group is L bits, the watermark length embedded by each embeddable watermark vertex coordinate is c (c is 1,2, … bits), and the number of the embeddable watermark vertex coordinates required by each group is LAssume that the number of tuples is N_g(1≤N_gN), ith (i ═ 0,1, …, N_g-1) the groups of graph cells are G_i，G_iContaining embeddable watermark topsNumber of point coordinates ofIf in the group of pixels G_iFully embeds its corresponding L-bit authentication watermark,and N_rIt is necessary to satisfy the following relationship,group of drawing graphs G_iThe included line drawing elements are marked as

(3) Generating an authentication watermark;

generating the authentication watermark of each image element group in the step (2) by using a hash algorithm; group of drawing graphs G_i(i＝0,1,…,N_g-1) authentication watermark is denoted as H_i，H_i＝{h_i,jE {0,1}, j 0,1_iNumber of middle bits, h_i,j(j-0, 1, …, L-1) represents H_iThe jth bit of (1); h is to be_iConversion into a sequence W of watermarks to be embedded_i＝{w_i,j|w_i,j＝0,1,…,2^c–1,j＝0,1,…,N_r–1}，w_i,j＝h_i,j×c×2^c-1+h_i,j×c+1×2^c-2+…+h_i,(j+1)×c-1×2⁰；

(4) Embedding an authentication watermark;

using reversible information hiding method based on interval state value to embed watermark sequence W generated in step (3)_i(i＝0,1,…,N_g-1) embedding into group of primitives G_iFront N of_rEach embeddable watermark vertex coordinate is in the primitive group G_iInto which its corresponding authentication watermark H is embedded_iThen, obtaining the watermark-containing pattern group G_i ^w；

(5) Marking the graphic primitive;

embedding a mark indicating the image group where the watermark-containing primitive is located in each primitive containing the watermark by using a vertex inserting method, wherein the inserted vertex is called as a position vertex, embedding the mark in the primitive containing the watermark to obtain a corresponding primitive containing the mark, correctly identifying the position vertex of the primitive containing the mark according to the characteristics of the primitive containing the mark, obtaining the primitive group where the primitive containing the mark is located, and inserting the mark in each primitive to obtain a vector map containing the mark;

(6) watermark authentication and original data recovery;

according to the primitive marking and reversible information hiding method, vector map data are restored and positioned and tampered, and the specific steps are as follows:

(6.1) identifying an original graph group;

according to the characteristics of the marked primitives contained in the step (5), identifying the original primitive of each primitive group, and deleting the inserted position vertex;

(6.2) watermark extraction and original data recovery;

identifying the watermark-containing embeddable watermark vertex coordinates of the image group by using the embeddable watermark vertex coordinate judgment method in the step (1), extracting the watermark and recovering the original data of the vector map, and recovering the watermark-containing image group G after the data is recovered_i ^w(i＝0,1,…,N_g-1) is denoted as G_i', from G_i ^wThe watermark sequence extracted from the sequence is recorded as W_i'＝{w_i,j'|w_i,j'＝0,1,…,2^c–1,j＝0,1,…,N_r-1}, using the following formula, W is expressed_i' conversion to binary sequence H_i'＝{h_i,j'|h_i,j'∈{0,1},j＝0,1,…,L–1}，

(6.3) generating an authentication watermark;

using the method of step (3), generating eachThe authentication watermark of the pixel group after data recovery is assumed as a pixel group G_i'(i＝0,1,…,N_g-1) the generated authentication watermark is H_i”＝{h_i,j”|h_i,j”∈{0,1},j＝0,1,…,L–1}；

(6.4) watermark authentication;

according to the group of drawing cells G_i'(i＝0,1,…,N_gWatermark H extracted in-1)_i' and the generated watermark H_i", determine whether the primitive group is tampered, if H_i'＝H_i", the group has not been tampered with; otherwise, the group is tampered; and after the integrity of each primitive group is verified, displaying all tampered primitives.

Suppose P_jComprising u vertices V₁(x₁,y₁),V₂(x₂,y₂),…,V_u(x_u,y_u)，V_m(x_m,y_m) (m-1, 2, …, u) represents P_jM-th vertex of (2), x_mAnd y_mRespectively being vertex V_mThe x-coordinate and the y-coordinate of (c),andare respectively line drawing element P_jThe maximum value and the minimum value of the middle x coordinate, and the judgment vertex V_mX coordinate x of_mThe method for determining whether the watermark vertex coordinates can be embedded comprises the following specific steps:

(1.1) mixingAndis equally divided intoThe length of the section is equal to the length of the section,

wherein,the length of each of the segments is represented,the value of (a) should satisfy the following conditions,

in the formula, tau is the precision error tolerance of the vector map M;

(1.2) according to the length of each segmentCalculating the coordinate x_mThe end points of the boundary of the segment in which the segment is located,

in the formula,denotes the coordinate x_mThe value of the index of the segment in which it is located,andrespectively representing a defined coordinate x_mThe left end point and the right end point of the boundary of the segment range arex_mAndviewed as a space

(1.3) if x_mThe following conditions are satisfied,

scale x_mThe vertex coordinates of the embeddable watermark are obtained;

the method for dividing the graph element group comprises the following specific steps:

(2.1) mixingDivision of line primitives into primitive groups G₀In (1),to satisfy the minimum positive integer of the following relationship,

(2.2) according to the method of step (2.1), dividing the remaining primitives into groups in sequence, i.e. for any primitive G_i(i>0) Selecting from the remaining primitivesThe line-line primitives are taken as its members,to satisfy the minimum positive integer of the following relationship,

delta is a group of picture elements G₀To the group of picture elements G_i-1Number of all primitives in, i.e.

(2.3) since the primitives are divided into groups in sequence, the last group of primitives may not provide enough embedding space, at which point the last group of primitives is divided into the penultimate group.

Generating authentication watermark H_iThe method comprises the following steps:

H_i＝grouphash(hash(I(G_i),k,i,V_i,M_in),L,K)

wherein I (-) denotes a method of acquiring spatial data and attribute data, k denotes a private key generating a hash (-) input parameter, V_iGroup of pictures G_iNumber of vertices, M_inAn index value representing the vector map, hash (·) representing an existing cryptographic hash algorithm, grouhash (H)_i ^aL, K) denotes the slave bit sequence H under the control of the private key K_i ^aA method of selecting L bits; method I (-) obtaining tuple G_iThe group of primitive vertices are scanned as follows: scanning G in sequence according to the storage sequence of the graphics primitives_iLine drawing elements of, i.e. fromScan toIn each line element, scan from the first vertex to the last vertex. Said interval Q_mThe state values of (a) are defined as follows: suppose embeddable watermark vertex coordinate x_mCorresponding to an interval ofWill Q_mIs divided into P (P is more than or equal to 2) sub-intervals, x_mThe index value of the sub-interval is the interval Q_mThe state value of (2).

Suppose that the coordinate x of the vertex of the embeddable watermark_mIn which the embedded watermark is w_i,jThe specific steps of watermark embedding are as follows:

(4.1) calculating the Interval Q_mThe state of (a) is (b),

(4.2) mixing Q_mAverage score of 2^c+1Subinterval, calculating interval Q_mCorresponding watermark-containing spaceS, i.e. x_m' the index value of the sub-interval in which,

s＝2^c×r+w_i,j

(4.3) calculating the coordinate x of the water mark_m'，

Wherein,

suppose a tuple G_i ^wLine drawing elementContains f vertices, denoted asThe t-th vertex of the representation, and respectively vertex V_t ^wX and y coordinates of (a) and the vertex to be inserted is V_g(x_g,y_g)，x_gAnd y_gRespectively being vertex V_gX and y coordinates of (a) and (b), said group of cells G in which it is marked_i ^wThe method comprises the following specific steps:

(5.1) putting the vertex V₁ ^wAnd V₂ ^wIs divided into N on average_t(N_t＝2×N_g) Segments, each segment having a length of l_t，

(5.2) inserting vertex V at the midpoint of the i-th segment_gAnd is marked by thisThe located graphic primitive group G_i ^w，

Wherein,

in thatAfter embedding the mark, the corresponding graphic element containing the mark is obtainedHas the following characteristics:

i) three consecutive vertices at one end are in the sameOn the straight line, the end is the starting end; suppose that the vertex obtained from the start scan is V_t ^mThe t-th vertex represented by (t-1, 2, …, f +1), and the vertex V_t ^mThe x coordinate and the y coordinate of the insertion point are the inserted position vertex;

ii) calculated as followsIndex value i of the located tuple

From set G of watermark-containing patterns_i ^w(i＝0,1,…,N_g-1) embeddable watermark coordinate X_mThe specific steps of extracting the watermark information in' are as follows:

(6.2.1) according to step (4.1), x is calculated_m' corresponding watermark-containing spaceR state of (1);

(6.2.2) spacing Q_m' average division into 2^c+1Sub-intervals, calculating the length l of each sub-interval_s，

(6.2.3) calculating the Interval Q_m' of the state value s of the device,

(6.2.4) extracting the watermark w_i,j'，

w_i,j'＝s-r×2^c

(6.2.5) recovery x_m' of the original data of the above-mentioned publication,

wherein,

the invention has proposed a vector map integrity authentication method based on marking, on the one hand this method divides the primitive of the vector map into different groups adaptively, under the prerequisite of the precision error tolerance of considering the vector map, adopt the hidden method of the reversible information to realize the embedding of the authentication watermark, and on the basis of inserting the method of the vertex, add the marking in each primitive in order to point its affiliated primitive group, guarantee the correct division of the primitive group in the authentication stage of the watermark, while locating and tampering the primitive accurately, have better invisibility, and can tolerate primitive out of order and vertex reverse order attacks; on the other hand, in the watermark authentication stage, after the mark is removed and the authentication information is extracted, the original data of the vector map is restored in a lossless mode, and accurate use of the vector map data can be effectively guaranteed. Compared with other vector map integrity authentication methods, the method has the following advantages:

1. the method adaptively divides the primitive groups, marks the group information for each group, has higher tampering positioning precision, and effectively reduces the data retransmission times caused by the failure of accurately detecting the tampered data;

2. according to the method, the embedding parameters are set according to the precision error tolerance of the vector map, so that the disturbance of the watermark embedding to the vector map data can be effectively controlled, and the quality of the watermark-containing vector map can be ensured;

3. the invention embeds authentication watermarks in each pixel group by using a reversible information hiding method, adds marks in each pixel group based on a vertex inserting method, and not only can realize integrity authentication, but also can recover the original data of the vector map and ensure the accurate use of the vector map after removing the marks and extracting authentication information in an authentication stage.

4. The marking method adopted by the invention can still correctly indicate the group of the primitives and the vertex scanning sequence after being attacked by the operations of keeping the contents, namely the primitive disorder and the vertex reverse order, and is robust to the primitive disorder and the vertex reverse order attack.

Drawings

FIG. 1 is a flowchart of a tag-based vector map integrity authentication method;

fig. 2 is a vector map (gaussian snow block map) before embedding authentication watermark;

fig. 3 is a vector map (gaussian snow block map) with an embedded authentication watermark;

FIG. 4 is a tampered watermark-containing vector map (Gauss mountain snow Block map);

fig. 5 locates a tampered vector map (gaussian snow block map).

Detailed Description

The technical scheme of the invention is further described by combining the drawings and the examples:

as shown in fig. 1, the method for authenticating integrity of a tag-based vector map of the present invention is generally divided into two aspects: A. vector map watermark embedding algorithm; B. and (5) a vector map watermark authentication algorithm.

A. The vector map watermark embedding algorithm comprises the following steps:

B. identifying vertex coordinates of the embeddable watermark;

C. and identifying the coordinates of the vertex of the embeddable watermark according to the precision error tolerance of the vector map. The same method for judging whether the x coordinate and the y coordinate of the primitive vertex are the coordinates of the embeddable watermark vertex is adopted, and the invention takes the x coordinate as an example to explain the method for judging the coordinates of the vertex of the embeddable watermark.

Suppose that the vector map M contains N line primitives, denoted as P₁,P₂,…,P_N，P_jDenotes the j (j ═ 1,2, …, N) th line element, P_jComprising u vertices V₁(x₁,y₁),V₂(x₂,y₂),…,V_u(x_u,y_u)，V_m(x_m,y_m) (m-1, 2, …, u) represents P_jM-th vertex of (2), x_mAnd y_mRespectively being vertex V_mThe x-coordinate and the y-coordinate of (c),andare respectively line drawing element P_jThe maximum and minimum of the medium x coordinate. Determining vertex V_mX coordinate x of_mThe concrete method for determining whether the vertex coordinate of the embeddable watermark is as follows:

a. will be provided withAndis equally divided intoThe length of the section is equal to the length of the section,

wherein,the length of each of the segments is represented,the value of (a) should satisfy the following conditions,

where τ is the accuracy error margin of the vector map M.

b. According to the length of each segmentCalculating the coordinate x_mThe end points of the boundary of the segment in which the segment is located,

in the formula,denotes the coordinate x_mThe value of the index of the segment in which it is located,andrespectively representing a defined coordinate x_mThe left end point of the boundary and the right end point of the boundary of the segment range. Will be provided withx_mAndviewed as a space

c. If x_mThe following conditions are satisfied,

scale x_mAre embeddable watermark vertex coordinates. A line primitive P_jThe number of vertex coordinates in which the watermark can be embedded is recorded as

(2) Adaptively dividing the graph element group;

and adaptively dividing the vector map primitives into non-overlapping groups according to the number of the coordinates of the embedded watermark vertexes in the primitives. In the invention, the authentication watermark length of each group is L bits, and the watermark length embedded by each embeddable watermark vertex coordinate is c (c is 1,2, …). Thus, the number of embeddable watermark vertex coordinates required for each set isAssume that the number of tuples is N_g(1≤N_gN), ith (i ═ 0,1, …, N_g-1) the groups of graph cells are G_i，G_iThe number of vertex coordinates of the embeddable watermark isIf in the group of pixels G_iFully embeds its corresponding L-bit authentication watermark,and N_rIt is necessary to satisfy the following relationship,

the graph tuples are divided using the following method:

a. will be provided withDivision of line primitives into primitive groups G₀In (1),to satisfy the minimum positive integer of the following relationship,

b. sequentially dividing the remaining primitives into groups according to the method of step (a). I.e. for arbitrary tuples G_i(i>0) Selecting from the remaining primitivesThe line-line primitives are taken as its members,

to satisfy the minimum positive integer of the following relationship,

delta is a group of picture elements G₀To the group of picture elements G_i-1Number of all primitives in, i.e.

c. Because the primitives are divided into groups in sequence, the last group of primitives may not provide enough embedding space, at which point the last group of primitives is divided into a penultimate group.

Group of drawing graphs G_iThe included line drawing elements are marked as

(3) Generating an authentication watermark;

and (3) generating the authentication watermark of each image element group in the step (2) by using a hash algorithm. Group of drawing graphs G_i(i＝0,1,…,N_g-1) authentication watermark is denoted as H_i，

H_i＝{h_i,j∈{0,1},j＝0,1,...,L-1}

Wherein L represents H_iNumber of middle bits, h_i,j(j-0, 1, …, L-1) represents H_iThe jth bit of (a).

Generating an authentication watermark H_iThe method comprises the following steps:

H_i＝grouphash(hash(I(G_i),k,i,V_i,M_in),L,K)

wherein I (-) denotes a method of acquiring spatial data and attribute data, k denotes a private key generating a hash (-) input parameter, V_iGroup of pictures G_iNumber of vertices, M_inAn index value representing the vector map, hash (·) representing an existing cryptographic hash algorithm, grouhash (H)_i ^aL, K) denotes the slave bit sequence H under the control of the private key K_i ^aThe method of selecting L bits.

Method I (-) obtaining tuple G_iThe group of primitive vertices are scanned as follows: scanning G in sequence according to the storage sequence of the graphics primitives_iLine drawing elements of, i.e. fromScan toIn each line element, scan from the first vertex to the last vertex.

H is to be_iConversion into a sequence W of watermarks to be embedded_i＝{w_i,j|w_i,j＝0,1,…,2^c–1,j＝0,1,…,N_r–1}，

w_i,j＝h_i,j×c×2^c-1+h_i,j×c+1×2^c-2+…+h_i,(j+1)×c-1×2⁰

(4) Embedding an authentication watermark;

using reversible information hiding method based on interval state value to embed watermark sequence W generated in step (3)_i(i＝0,1,…,N_g-1) embedding into group of primitives G_iFront N of_rEach can be embedded in watermark vertex coordinates. Suppose embeddable watermark vertex coordinate x_mCorresponding to an interval ofInterval Q_mThe state values of (a) are defined as follows:

will Q_mIs divided into P (P is more than or equal to 2) sub-intervals, x_mThe index value of the sub-interval is the interval Q_mThe state value of (2).

Since the invention embeds the watermark by changing the state value of the interval, x_mCorresponding water mark containing vertex coordinate x_m' still located in the intervalIn (1).

Suppose that the coordinate x of the vertex of the embeddable watermark_mIn which the embedded watermark is w_i,jThe method comprises the following specific steps:

a. calculating the interval Q_mThe state of (a) is (b),

b. will Q_mAverage score of 2^c+1Subinterval, calculating interval Q_mCorresponding watermark-containing spaceS, i.e. x_m' the index value of the sub-interval in which,

s＝2^c×r+w_i,j

c. calculating the coordinate x containing the watermark_m'，

Wherein,

in the group of picture elements G_iInto which its corresponding authentication watermark H is embedded_iThen, obtaining the watermark-containing pattern group G_i ^w. G is to be_i ^wThe primitive containing the watermark line is marked as

(5) Marking the graphic primitive;

by means of inserting vertex, embedding mark in each primitive containing watermark to indicate the primitive group. Suppose a tuple G_i ^wLine drawing elementContains f vertices, denoted as The t-th vertex of the representation, and respectively vertex V_t ^wX and y coordinates of (a) and the vertex to be inserted is V_g(x_g,y_g)，x_gAnd y_gRespectively being vertex V_gX-coordinate and y-coordinate. Mark the group G of graph cells in which it is located_i ^wThe method comprises the following specific steps:

a. let the vertex V₁ ^wAndis divided into N on average_t(N_t＝2×N_g) Segments, each segment having a length of l_t，

b. Inserting vertex V at midpoint of ith segment_gAnd is marked by thisThe located graphic primitive group G_i ^w，

Wherein,

the inserted vertex is referred to as a positional vertex. In thatAfter embedding the mark, the corresponding graphic element containing the mark is obtainedHas the following characteristics:

i)three continuous vertexes at one end are on the same straight line, and the other end isThe start of (2). Assuming scanning from the beginningHas a vertex of V_t ^m(t-1, 2, …, f +1) representsThe (t) th vertex of (a),andrespectively being vertex V_t ^mX and y coordinates ofIs the inserted position vertex;

ii) calculated as followsThe index value i of the located tuple of the graph,

according to the characteristics of the marked primitives, the position vertex can be correctly identified, and the primitive group where the position vertex is located can be obtained.

And inserting a mark into each graphic element to obtain a vector map containing the mark. As shown in fig. 2-3, the comparison of the vector map before and after embedding the authentication watermark is shown, where fig. 2 is an original gaussian snow block map, and fig. 3 is the situation after embedding the authentication watermark.

B. Vector map watermark authentication algorithm

(6) Watermark authentication and original data recovery;

according to the primitive marking and reversible information hiding method, vector map data are restored and positioned and tampered, and the specific steps are as follows:

a. identifying an original graph tuple;

and (5) identifying the original primitive of each primitive group according to the characteristics of the marked primitives in the step (5), and deleting the inserted position vertex.

b. Extracting a watermark and recovering original data;

and (3) identifying the watermark-containing embeddable watermark vertex coordinates of the map element group by using the embeddable watermark vertex coordinate determination method in the step (1), extracting the watermark and recovering the original data of the vector map. From set G of watermark-containing patterns_i ^w(i＝0,1,…,N_g-1) embeddable watermark coordinates x_mThe specific steps of extracting the watermark information in' are as follows:

p1. calculating x according to sub-step (a) of step (4)_m' corresponding watermark-containing spaceR state of (1);

p2. will separate the space Q_m' average division into 2^c+1Sub-intervals, calculating the length l of each sub-interval_s，

p3. calculating the interval Q_m' of the state value s of the device,

p4. extraction of watermark w_i,j'，

w_i,j'＝s-r×2^c

p5. recovery x_m' of the original data of the above-mentioned publication,

wherein,

the watermark-containing image group G after data recovery_i ^wIs marked as G_i', from G_i ^wThe watermark sequence extracted from the sequence is recorded as W_i'＝{w_i,j'|w_i,j'＝0,1,…,2^c–1,j＝0,1,…,N_r-1}. Using the following formula, W_i' conversion to binary sequence H_i'＝{h_i,j'|h_i,j'∈{0,1},j＝0,1,…,L–1}，

c. Generating an authentication watermark;

and (4) generating the authentication watermark of each pixel group after the data is recovered by using the method in the step (3). Assumed to be a tuple G_i'(i＝0,1,…,N_g-1) generatingAuthentication watermark of H_i”＝{h_i,j”|h_i,j”∈{0,1},j＝0,1,…,L–1}。

d. Watermark authentication;

according to the group of drawing cells G_i'(i＝0,1,…,N_gWatermark H extracted in-1)_i' and the generated watermark H_i", determine whether the group of primitives is tampered. If H is_i'＝H_i", the group has not been tampered with; otherwise the group is tampered with.

And after the integrity of each primitive group is verified, displaying all tampered primitives. Fig. 4 shows the vector map of fig. 3 after the watermark-containing gaussian snow block map has been tampered with, and the region A, B, C has been tampered with. In fig. 5, after the integrity of each primitive group is detected, the primitives of the tampered primitive group are displayed as dark gray. Therefore, the method can accurately position tampering.

Claims (6)

1. A vector map integrity authentication method based on marks is characterized by comprising the following steps:

(1) identifying embeddable watermark vertex coordinates;

identifying the vertex coordinates of the embeddable watermark according to the precision error tolerance of the vector map; suppose that the vector map M contains N line primitives, denoted as P₁,P₂,…,P_N，P_jRepresents the jth line drawing element, j is 1,2, …, N, P_jThe number of coordinates of the embeddable watermark is

(2) Adaptively dividing the graph element group;

adaptively dividing the vector map primitives into non-overlapping groups according to the number of coordinates of the embedded watermark vertices in the primitives; the length of each group of authentication watermarks is L bits, the length of each watermark embedded into each embeddable watermark vertex coordinate is c bits, c is 1,2 and …, and the number of the embeddable watermark vertex coordinates required by each group is N_r，Assume that the number of tuples is N_g，1≤N_gN is less than or equal to N, the ith figure group is G_i，i＝0,1,…,N_g–1，G_iThe number of vertex coordinates of the embeddable watermark isIf in the group of pixels G_iFully embeds its corresponding L-bit authentication watermark,and N_rIt is necessary to satisfy the following relationship,group of drawing graphs G_iThe included line drawing elements are marked as

(3) Generating an authentication watermark;

generating the authentication watermark of each image element group in the step (2) by using a hash algorithm; group of drawing graphs G_iIs marked as H_i，i＝0,1,…,N_g–1，H_i＝{h_i,jE {0,1}, j 0,1_iNumber of middle bits, h_i,jRepresents H_iJ ═ 0,1, …, L-1; h is to be_iConversion to a watermark to be embeddedSequence W_i＝{w_i,j|w_i,j＝0,1,…,2^c–1,j＝0,1,…,N_r–1}，w_i,j＝h_i,j×c×2^c-1+h_i,j×c+1×2^c-2+Λ+h_i,(j+1)×c-1×2⁰；

(4) Embedding an authentication watermark;

using reversible information hiding method based on interval state value to embed watermark sequence W generated in step (3)_iEmbedding into groups of primitives G_iFront N of_rCan be embedded into the watermark vertex coordinates, i is 0,1, …, N_g-1; in the group of picture elements G_iInto which its corresponding authentication watermark H is embedded_iThen, obtaining the watermark-containing pattern group G_i ^w；

(5) Marking the graphic primitive;

embedding a mark indicating the image group where the watermark-containing primitive is located in each primitive containing the watermark by using a vertex inserting method, wherein the inserted vertex is called as a position vertex, the corresponding primitive containing the mark is obtained after the mark is embedded in the primitive containing the watermark, the position vertex can be correctly identified according to the characteristics of the primitive containing the mark, and the primitive group where the position vertex is located is obtained; inserting a mark into each primitive to obtain a vector map containing the mark;

(6) watermark authentication and original data recovery;

according to the primitive marking and reversible information hiding method, vector map data are restored and positioned and tampered, and the specific steps are as follows:

(6.1) identifying an original graph group;

according to the characteristics of the marked primitives contained in the step (5), identifying the original primitive of each primitive group, and deleting the inserted position vertex;

(6.2) watermark extraction and original data recovery;

identifying the watermark-containing embeddable watermark vertex coordinates of the image group by using the embeddable watermark vertex coordinate judgment method in the step (1), extracting the watermark and recovering the original data of the vector map, and recovering the watermark-containing image group G after the data is recovered_i ^wIs marked as G_i'，i＝0,1,…,N_g-1, from G_i ^wThe watermark sequence extracted from the data is recorded asW_i'＝{w_i,j'|w_i,j'＝0,1,…,2^c–1,j＝0,1,…,N_r-1}, using the following formula, W is expressed_i' conversion to binary sequence H_i'＝{h_i,j'|h_i,j'∈{0,1}，j＝0,1,…,L–1}，

(6.3) generating an authentication watermark;

and (4) generating the authentication watermark of each pixel group after the data is recovered by using the method in the step (3), wherein the authentication watermark is assumed to be a pixel group G_i' authentication watermark generated is H_i”＝{h_i,j”|h_i,j”∈{0,1},j＝0,1,…,L–1}，i＝0,1,…,N_g–1；

(6.4) watermark authentication;

according to the group of drawing cells G_i' the extracted watermark H_i' and the generated watermark H_i”，i＝0,1,…,N_g-1, determining whether the group of primitives has been tampered with, if H_i'＝H_i", the group has not been tampered with; otherwise, the group is tampered; and after the integrity of each primitive group is verified, displaying all tampered primitives.

2. The tag-based vector map integrity authentication method of claim 1, wherein: suppose P_jComprising u vertices V₁(x₁,y₁),V₂(x₂,y₂),…,V_u(x_u,y_u)，V_m(x_m,y_m) And m is 1,2, …, u represents P_jM-th vertex of (2), x_mAnd y_mRespectively being vertex V_mThe x-coordinate and the y-coordinate of (c),andare respectively line drawing element P_jThe maximum value and the minimum value of the middle x coordinate, and the judgment vertex V_mX coordinate x of_mThe method for determining whether the watermark vertex coordinates can be embedded comprises the following specific steps:

(1.1) mixingAndis equally divided intoThe length of the section is equal to the length of the section,

wherein,the length of each of the segments is represented,the value of (a) should satisfy the following conditions,

in the formula, tau is the precision error tolerance of the vector map M;

(1.2) according to the length of each segmentCalculating the boundary end point of the segment where the coordinate xm is positioned,

in the formula,denotes the coordinate x_mThe value of the index of the segment in which it is located,andrespectively representing a defined coordinate x_mThe left end point and the right end point of the boundary of the segment range arex_mAndviewed as a space

(1.3) if x_mThe following conditions are satisfied,

scale x_mAre embeddable watermark vertex coordinates.

3. The tag-based vector map integrity authentication method of claim 1, wherein: the method for dividing the graph element group comprises the following specific steps:

(2.1) mixingDivision of line primitives into primitive groups G₀In (1),to satisfy the minimum positive integer of the following relationship,

(2.2) according to the method of step (2.1), dividing the remaining primitives into groups in sequence, i.e. for any primitive G_i，i>0, select from the remaining primitivesThe line-line primitives are taken as its members,to satisfy the minimum positive integer of the following relationship,

delta is a group of picture elements G₀To the group of picture elements G_i-1Number of all primitives in, i.e.

(2.3) since the primitives are divided into groups in sequence, the last group of primitives may not provide enough embedding space, at which point the last group of primitives is divided into the penultimate group.

4. The tag-based vector map integrity authentication method of claim 1, wherein: generating authentication watermark H_iThe method comprises the following steps:

H_i＝gro uphash(hash(I(G_i),k,i,V_i,M_in),L,K)

where I (-) denotes a method of acquiring spatial data and attribute data, k denotes a private key for generating a hash (-) input parameter, I ═ 0,1, …, N_g–1，V_iGroup of pictures G_iNumber of vertices, M_inAn index value representing the vector map, hash (·) representing an existing cryptographic hash algorithm, grouhash (H)_i ^aL, K) tableFrom bit sequence H under control of private key K_i ^aA method of selecting L bits; method I (-) obtaining tuple G_iThe group of primitive vertices are scanned as follows: scanning G in sequence according to the storage sequence of the graphics primitives_iLine drawing elements of, i.e. from P_Gi,1Scan toIn each line element, scan from the first vertex to the last vertex.

5. The tag-based vector map integrity authentication method of claim 1, wherein: said interval Q_mThe state values of (a) are defined as follows: suppose embeddable watermark vertex coordinate x_mCorresponding to an interval ofWill Q_mEqually divided into P sub-intervals, P is more than or equal to 2, x_mThe index value of the sub-interval is the interval Q_mThe state value of (2).

6. The tag-based vector map integrity authentication method of claim 1, wherein: suppose that the coordinate x of the vertex of the embeddable watermark_mIn which the embedded watermark is w_i,jThe specific steps of watermark embedding are as follows:

(4.1) calculating the Interval Q_mThe state of (a) is (b),

(4.2) mixing Q_mAverage score of 2^c+1Subinterval, calculating interval Q_mCorresponding watermark-containing spaceS, i.e. x_m' the index value of the sub-interval in which,

s＝2^c×r+w_i,j

(4.3) calculating the coordinate x of the water mark_m'，

Wherein,