CN108615216A - A kind of holographic watermark authentication method of notarial - Google Patents

Abstract

The invention discloses a holographic watermark authentication method for a just document. The holographic watermark authentication method for a just document first converts an image containing important information into a hologram, that is, a digital watermark. Then, the notarized document produced by the notary office is used as the carrier image, and the digital watermark is embedded in the carrier image, so as to realize the embedding and hiding of the digital watermark in the notarized document. Afterwards, the notarized documents containing digital watermarks are digitally signed using cryptographic technology, and the keys are distributed to relevant agencies for archiving and document holders for preservation. The notarized documents containing digital watermarks obtained through the network, copying, etc. are extracted and decrypted from the notarized documents through decryption and inverse operations. This method has many advantages such as strong robustness, high degree of freedom, and is difficult to crack. It can realize a variety of functions, including: identifying the authenticity of fair documents, ensuring that their contents have not been tampered with, and hiding and reproducing images containing important information.

Description

A holographic watermark authentication method for notarized documents

technical field

The invention relates to the field of information security, in particular to an authentication method for notarized documents.

Background technique

In many aspects of social life, such as property inheritance, property gift, renunciation of property inheritance, child custody, etc., notarized documents are required. How to ensure that its notarized documents are legal, unquestionable and reliable documents that will not be tampered with in the future has become a key technical problem that notarization agencies must solve. Moreover, the content proved by the fair document, that is, the image containing important information requires secrecy, and only a specific person can reproduce the image containing important information, which can greatly enhance the security of the fair document. However, the existing notarization technology does not have such a function.

The main existing anti-counterfeiting marks include: the steel seal of the notary office, the notary's name seal and the number of the notary certificate. Among them, the steel seal of the notary office and the name stamp of the notary are easy to be forged under the current technical conditions, and cannot reliably identify the authenticity of the notary document, and cannot guarantee that the content of the notarial certificate has not been tampered with. Although the query of the notarial certificate number is highly reliable, it requires a special verification from the notary office that issued the certificate. The actual operation is time-consuming and laborious, and it is inconvenient.

Contents of the invention

In view of this, the purpose of the present invention is to propose a method for authenticating notarized documents, which can identify the authenticity of notarized documents, ensure that their contents have not been tampered with, and hide and reproduce images containing important information.

Based on the above purpose, the present invention provides a holographic watermark authentication method for notarized documents, including:

In the process of generating notarized documents, digital holographic processing is performed on the images to be encrypted in notarized documents to obtain digital watermarks;

Embed digital watermarks into fair documents through embedding algorithms;

Adding a digital signature to the notarized document to obtain a notarized document encrypted and embedded with a digital watermark;

During the authentication process of the fair document, digitally signed authentication is performed on the notarized document encrypted and embedded with the digital watermark, and if the authentication is passed, the digital watermark embedded in the fair document is extracted through the inverse operation of the embedding algorithm; The digital watermark is reconstructed to obtain an image containing important information;

If authentication fails, access to the just document is denied.

As an embodiment, the digital holographic processing of the image to be encrypted in the notarized document to obtain the digital watermark includes the steps of:

Establish the Fresnel diffraction integral, that is, formula (1):

In formula (1): U ₀ (x ₀ , y ₀ ) and U(x, y) are the complex amplitudes of the light waves on the object plane and the observation plane, respectively; z is the distance between the observation plane and the object plane; λ is the light Wavelength; k=2π/λ is the wave number, and j represents a complex number;

Perform Fourier transform on both sides of formula (1) and use the law of spatial convolution to get formula (2):

Let f _x , f _y be the coordinates in the frequency domain, and obtain the formula (3), which is the Fresnel diffraction transfer function:

In formula (3), _HF is the _Fresnel diffraction transfer function, and the spectrum of the light wave field of the observation plane is the product of the spectrum of the light wave field of the object plane and HF;

Obtain the interference field intensity distribution of the coherent superposition of light wave and object light wave at CCD by the spectrum of described light wave field and the spectrum of object plane light wave, described interference field intensity distribution is formula (4):

In formula (4), I is the hologram obtained after each phase shift, R is the object light wave, O is the reference light wave, θ is the angle, is the light phase; the digital watermark is generated for obtaining an object light wave and reference light interference fringe pattern from the intensity distribution of the interference field.

As an embodiment, the embedding algorithm is an intensity modulation algorithm or an LSB algorithm.

As an embodiment, the digital holographic reconstruction of the image to be encrypted in the notarized document is to use the formula (7) to obtain the object light phase of the four holograms generated in the formula (4) reaching the CCD

Afterwards, use formula (4) to calculate the reconstructed object plane light wave field:

That is, digital holographic reconstruction is realized through diffraction and the inverse operation of diffraction.

As an embodiment, the intensity modulation algorithm is to filter the image of the notarized document through a low-pass filter to remove its high-frequency components to obtain an original image; add the digital watermark to the frequency spectrum of the original image, Obtain a notarized document embedded with a digital watermark.

As an embodiment, the LSB algorithm is to replace the LSB of the airspace to replace the LSB sequence, that is, add digital watermark information; convert the obtained decimal pixel value added with digital watermark information into binary data; use binary secret information Each bit of information in replaces the least significant bit of the corresponding carrier data; the obtained binary data embedded in the watermark information is converted into a decimal pixel value, thereby obtaining a notarized document embedded with a digital watermark.

As an embodiment, the algorithm for adding a digital signature includes but is not limited to:

SM2, DES algorithm or DSA.

As an embodiment, the algorithm for adding the digital signature is SM2.

It can be seen from the above that the holographic watermark authentication method for a just document provided by the present invention first converts an image containing important information into a digital hologram, that is, a digital watermark. Then, the notarized document produced by the notary office is used as the carrier image, and the digital watermark is embedded in the carrier image, so as to realize the embedding and hiding of the digital watermark in the notarized document. Afterwards, the notarized documents containing digital watermarks are digitally signed using cryptographic technology, and the keys are distributed to relevant agencies for archiving and document holders for preservation. The notarized documents containing digital watermarks obtained through the network, copying, etc. are extracted and decrypted from the notarized documents through decryption and inverse operations. This method has many advantages such as strong robustness, high degree of freedom, and is difficult to crack. It can realize a variety of functions, including: identifying the authenticity of fair documents, ensuring that their contents have not been tampered with, and hiding and reproducing images containing important information.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a flowchart of a holographic watermark authentication method for a just document according to an embodiment of the present invention;

Fig. 2 is a structural diagram of a virtual module of an authentication system according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

As shown in Figure 1, the flow chart of the holographic watermark authentication method for a just document provided by the embodiment of the present invention includes:

Step S101: Generate a digital hologram, and convert the encrypted image in the notarial certificate, which generally refers to an image containing important information, such as: property inheritance documents, photos, signatures, etc., into a digital hologram to obtain digital water mark. The digital hologram is equivalent to the interference fringe pattern of the object light wave and the reference light recorded by the holographic plate. The hidden information is regarded as the object light source and calculated by Fresnel diffraction integral to obtain the object light distribution, and then calculated with the reference light to form a digital hologram.

The Fresnel diffraction integral is the most widely used formula in diffraction application research, and it can be expressed in two forms: Fourier transform and convolution, that is, there is a fast Fourier transform and a fast convolution algorithm. Choose different forms according to the actual situation in different application environments. Formula (1) is the Fresnel diffraction integral:

In formula (1): U ₀ (x ₀ , y ₀ ) and U(x, y) are the complex amplitudes of the light waves on the object plane and the observation plane, respectively; z is the distance between the observation plane and the object plane; λ is the light Wavelength; k=2π/λ is the wave number, and j represents a complex number. Equation (1) can be used to calculate the diffraction of the diffraction field distribution, that is, Fresnel diffraction.

Perform Fourier transform on both sides of formula (1) and use the law of spatial convolution to get formula (2):

Let f _x , f _y be frequency domain coordinates, and formula (3) can be obtained, which is the Fresnel diffraction transfer function:

It can be seen that the Fresnel diffraction process is equivalent to the process of passing the light wave field of the object plane through a linear space invariant system, and the spectrum of the light wave field of the observation plane is the spectrum of the light wave field of the object plane and a Fresnel diffraction transfer function H _F product of .

The light wave and the object light wave are coherently superimposed on the CCD from the spectrum of the light wave field and the spectrum of the object plane light wave, and the interference field intensity distribution recorded by the CCD is obtained to obtain an interference fringe pattern between the object light wave and the reference light, and generate the digital hologram, That is, the digital watermark is generated.

The intensity distribution of the interference field is formula (4):

In formula (4), I is the hologram obtained after each phase shift, R is the object light wave, O is the reference light wave, θ is the angle, is the light phase, and is the interference fringe pattern between the object light wave and the reference light obtained from the intensity distribution of the interference field, and generates the digital watermark.

Step S102, embed the digital watermark in the just document, and the digital watermark embedded in the just document can also be extracted by reverse operation. The digital watermarking technology is a kind of information hiding technology. The basic principle is to embed secret information in digital products such as digital images, audio and video, so as to protect the copyright of digital products, prove the authenticity of products, track piracy or provide products additional information for .

As an embodiment, an intensity modulation algorithm is used to embed a digital watermark into a fair document. As shown in FIG. 2 , it is a schematic diagram of an intensity modulation algorithm embedding a digital watermark according to an embodiment of the present invention.

The just document is used as a carrier image, and the carrier image is filtered by a low-pass filter to remove its high-frequency components to obtain an original image. The digital watermark is loaded into the frequency spectrum of the original image, the embedding process of the digital watermark is completed, and a notarized document containing the digital watermark is obtained. As shown in formula (5):

In formula (5): a is a scale factor, which is used to control the strength of the digital watermark; is the spectrum of the original image; is a digital watermark; It is a notarized document with a digital watermark.

The digital watermark embedded in the just document can be extracted by inverse operation. Digital watermark extraction algorithm, as shown in formula (6):

The formula (6) is the inverse operation of the formula (5).

As another embodiment, the LSB algorithm is used to embed the digital watermark into the fair document. Use the notarized document as a carrier image. The principle of the LSB algorithm is that LSB embeds secret information into the least significant bit of the pixel value of the carrier image, also called the least significant bit, and changing the least significant bit has the least impact on the quality of the carrier image.

Replace the LSB of the airspace to replace the LSB sequence, that is, add digital watermark information. Since the embedded position of the digital watermark information is the LSB, in order to satisfy the invisibility of the watermark, the strength of the allowed embedded watermark cannot be too high.

Convert the obtained decimal pixel value with watermark information into binary data; replace the least significant bit of the corresponding carrier data with each bit of information in the binary secret information; convert the obtained binary data embedded with watermark information into decimal Pixel value, so as to obtain the image embedded with watermark information, that is, the notarized document embedded with digital watermark.

The digital watermark embedded in the just document can be extracted by inverse operation. Convert the decimal pixel value of the carrier image containing watermark information into binary data; extract the data in the least significant bit of the carrier data, and zero the least significant position of the original carrier data; convert the binary data of the digital watermark into decimal pixels value to extract the digital watermark.

Since the holographic information graph is indestructible, it is possible to extract the complete watermark information by using the fragment information of some notarized documents. Therefore, it can be seen that the notarized documents embedded with digital watermarks have the advantages of high degree of freedom and strong robustness.

Step S103, adding a digital signature to the notarized document to obtain an encrypted notarized document embedded with a digital watermark. The selected digital signature algorithm includes but not limited to: SM2, DES algorithm or DSA.

As an embodiment, the national secret algorithm SM2 is used to manage and distribute digital signature keys, that is, the SM2 algorithm is used to add the digital signature. The encryption security of the SM2 algorithm is high and the management is simple. The SM2 encryption of the notarized document does not affect the overall visual quality of the notarized document. The digital signature is difficult to forge, can realize reliable certification of notarized documents, and strengthens the anti-tampering function of notarized documents.

Step S104, in order to extract the information in the notarized document for authentication and processing, first authenticate the digital signature of the notarized document, judge whether the digital signature can pass the authentication, if the authentication is passed, extract the Digital watermarking is to extract digital holograms containing important information. If the authentication fails, access to fair documents will be denied.

Step S105, reconstructing the extracted digital hologram to obtain an image containing important information. (In formula (4), if four holograms are generated, then the phase of the object light reaching the CCD can be obtained by formula (7)

Moreover, it is easy to obtain by using formula (4)

That is, through the inverse operation of diffraction and diffraction, the light wave field of the object plane is directly reconstructed, and the reconstruction of the digital hologram is realized)

To sum up, the holographic watermark authentication method for a just document provided by the present invention first converts an image containing important information into a digital hologram, that is, a digital watermark. Then, the notarized document produced by the notary office is used as the carrier image, and the digital watermark is embedded in the carrier image, so as to realize the embedding and hiding of the digital watermark in the notarized document. Afterwards, the notarized documents containing digital watermarks are digitally signed using cryptographic technology, and the keys are distributed to relevant agencies for archiving and document holders for preservation. The notarized documents containing digital watermarks obtained through the network, copying, etc. are extracted and decrypted from the notarized documents through decryption and inverse operations. This method has many advantages such as strong robustness, high degree of freedom, and is difficult to crack. It can realize a variety of functions, including: identifying the authenticity of fair documents, ensuring that their contents have not been tampered with, and hiding and reproducing images containing important information.

Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is exemplary only, and is not intended to imply that the scope of the present disclosure (including claims) is limited to these examples; under the idea of the present invention, the above embodiments or Combinations between technical features in different embodiments are also possible, steps may be carried out in any order, and there are many other variations of the different aspects of the invention as described above, which are not presented in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. a kind of holographic watermark authentication method of notarial, which is characterized in that including：

In just document generating process, image to be encrypted in notarial is subjected to digital hologram and handles to obtain digital water Print；

It will be in digital watermark embedding to just document by embedded mobile GIS；

Digital signature is added for the notarial, is encrypted and be embedded in the notarial of digital watermarking；

During just authentication instrument, recognize what the notarial of the encryption and embedded digital watermarking was digitally signed Card, if certification passes through, is extracted the digital watermarking of the just document of insertion by the inverse operation of the embedded mobile GIS； The digital watermarking is rebuild, the image containing important information is obtained；

If certification does not pass through, the just document of denied access.

2. the holographic watermark authentication method of notarial according to claim 1, which is characterized in that described by notarial In image to be encrypted carry out digital hologram and handle to obtain digital watermarking to include step：

Establish fresnel diffraction integration, i.e. formula (1)：

In formula (1)：U₀(x₀,y₀) and U (x, y) be respectively the light wave complex amplitude of object plane and plane of vision；Z be viewing plane with The distance between object plane；λ is the wavelength of light；K=2 π/λ are wave number, and j represents plural number；

Fourier transformation is made to formula (1) both sides and obtains formula (2) using spatial domain convolution law：

Enable f_x,f_yIt is frequency domain coordinates, obtains formula (3), i.e. fresnel diffraction transmission function：

In formula (3), H_FFor fresnel diffraction transmission function, the frequency spectrum of the light wave fields of plane of vision is the frequency spectrum of object plane light wave fields With H_FProduct；

Light wave is obtained with Object light wave in the CCD coherent superpositions carried out by the frequency spectrum of the light wave fields and the frequency spectrum of object plane light wave Interference field intensity distribution, the interference field intensity distribution are formula (4):

In formula (4), I is the hologram of gained after each phase shift, and R is Object light wave, and O is reference light wave, and θ is angle,For light phase Position；To obtain Object light wave by the interference field intensity distribution and referring to optical interferometric fringe pattern sample, the digital watermarking is generated.

3. the holographic watermark authentication method of notarial according to claim 1, which is characterized in that the embedded mobile GIS is Intensity modulated algorithm or LSB algorithms.

4. the holographic watermark authentication method of notarial according to claim 1, which is characterized in that described by notarial In image to be encrypted carry out digital hologram and be redeveloped into the four width holograms found out using formula (7) generated in formula (4) reaching The object light phase of CCD

Later, it is calculated using formula (4) and rebuilds object plane light wave fields：

Digital hologram is realized by the inverse operation of diffraction and diffraction to rebuild.

5. the holographic watermark authentication method of notarial according to claim 3, which is characterized in that the intensity modulated is calculated Method is to be filtered the image of notarial by low-pass filter, removes its radio-frequency component, obtains original image；It will be described Digital watermarking is loaded among the frequency spectrum of the original image, obtains embedded digital watermarking notarial.

6. the holographic watermark authentication method of notarial according to claim 3, which is characterized in that the LSB algorithms are The LSB in spatial domain is replaced, for replacing the sequence of LSB, that is, digital watermark information is added；Obtained addition digital watermarking is believed The decimal system pixel value of breath is converted to binary data；It is replaced in contrast with each bit information in binary system secret information The least significant bit for the carrier data answered；The binary data of obtained insertion watermark information is converted into decimal system pixel value, To obtain the notarial of embedded digital watermarking.

7. the holographic watermark authentication method of notarial according to claim 1, which is characterized in that the addition number label Name algorithm include but not limited to：SM2, DES algorithm or DSA.

8. the holographic watermark authentication method of notarial according to claim 6, which is characterized in that the addition number label The algorithm of name is SM2.