Objective

2

Raster geographical data are important and sensitive. Once the raster geographic data are destroyed or tampered with

security risks to users occur. In addition

if users maliciously disseminate data

many unauthorized users will use the data beyond their authority

which also poses a threat to the data security. Strengthening the integrity of data inspection is necessary to prevent data from being destroyed and tampered with. Strengthening the copyright protection of data is also necessary to prevent raster geographic data from being maliciously disseminated. With the various requirements of integrity checking and copyright protection for watermarking

achieving the requirements of integrity checking and copyright protection at the same time by embedding only one watermarking information in raster geographic data is difficult. If the two technologies are combined

then the protection of raster geographic data will be comprehensive

and the dual watermarking technology can simultaneously achieve integrity checking and copyright protection.

Method

2

XOR(2

2)-VCS and discrete wavelet transform (DWT) are used to embed double watermarking into digital raster geographic data. Semi-fragile watermarking is used as the first watermarking for integrity test. The watermarking information is embedded according to the size relationship between the horizontal component

$$HL$$

in the high-frequency coefficients after DWT transformation

which can correctly distinguish between accidental and malicious attacks

and accurately locate malicious attacks. Zero watermarking is used as the second watermarking for copyright protection in extracting the eigenvalues of

$$LL$$

sub-bands after DWT transform and singular value decomposition to generate feature copies. XOR-based (2

2)-VCS is used to generate copyright copies according to feature copies and watermarking information. Copyright watermarking is robust and has good visual effect. The algorithm of embedding the double watermark is as follows. First

the raster geographic data is separated into red

green

and blue gray images. Second

the blue gray image is transformed by DWT

and the watermark image

$$\boldsymbol{W}_1$$

is scrambled by Arnold. Third

the scrambled watermark image

$$\boldsymbol{W}'_1$$

is embedded into the

$$HL$$

sub-band. Fourth

the red gray image is scrambled by Arnold

and then the scrambled red gray image is transformed by DWT. Fifth

the eigenvalue is calculated by singular value decomposition (SVD) operation for the

$$LL$$

sub-band

and the copyright share W

$$_2^2$$

is generated according to

$$\boldsymbol{W}_{2}$$

and

$$\boldsymbol{W}_2^1$$

by XOR (2

2)-VCS

which is saved by the copyright party. Sixth

the blue and red gray images of the watermarked image are obtained by inverse discrete wavelet transform (IDWT) transformation of each sub-band

which are synthesized with the green gray images to obtain the watermarked raster geographic data. The algorithm of extracting double watermark is as follows. First

the watermarked raster geographic data is separated into red

green

and blue gray images. Second

the blue gray image is transformed by IDWT

and the scrambled watermark image is extracted from the

$$HL$$

sub-band. Third

the watermark image is extracted by Arnold. Fourth

the red gray image is scrambled by Arnold

and then the scrambled red gray image is transformed by DWT. Fifth

the eigenvalue is calculated by SVD operation for the

$$LL$$

sub-band

and the copyright watermark image is generated according to copyright share and eigenvalue share by XOR (2

2)-VCS.

Result

2

To verify the effectiveness of the algorithm

we analyzed the specific raster geographic data experimentally using the proposed algorithm. The experimental results show that the integrity watermark in this algorithm can correctly distinguish between accidental attack and malicious damage. After JPEG compression with quality factors 90

80

70

60

and 50

the normalized correlation (NC) values of the extracted integrity watermark are 1

0.996

0.987

0.9513

and 0.949

respectively. When locating the tailoring attack

the algorithm can accurately locate the tampered position. When locating the replacement attack

the algorithm can locate the tampered approximate position. Copyright watermarking has good visual effect and strong robustness. As the embedding and extracting of the copyright watermark have no change to the raster geographic data itself

the attacker cannot detect whether the raster geographic data contain a watermark image. Obtaining the feature copies is difficult

and even if the eigenvalue share is obtained

the copyright share cannot be obtained because no copyright watermark information exists. The NC value of the copyright watermark is better than that of other schemes by testing the performance of the watermarked raster geographic data such as filtering attack

JPEG compression

tailoring attack

and scaling attack.

Conclusion

2

According to the requirement of integrity checking and copyright protection of raster geographic data

on the basis of deeply analyzing the characteristics of raster geographic data

integrity checking and copyright protection technology

an algorithm of integrity checking and copyright protection of raster geographic data is proposed based on DWT and VCS. The algorithm uses DWT and XOR (2

2)-VCS to embed double watermarking into raster geographic data. Semi-fragile watermarking is used as the first watermarking for integrity checking and zero watermarking is used as the second watermarking for copyright protection. Experiments show that the integrity watermarking can accurately locate the malicious damage

and the copyright watermarking is robust and has good visual effect.