High-precision ghost diffraction encryption method for dynamic target

Abstract

The invention provides a high-precision ghost diffraction encryption method for a dynamic target, and the method comprises the steps: carrying out the observation of the moving number of interference fringes of an object through a Michelson interferometer, carrying out the phase calculation, obtaining a set of observed phase change values, carrying out the conversion of the set of observed phase change values through a conversion function, and carrying out the encryption of the ghost diffraction. And taking the conversion function as a first-level key, establishing a ghost diffraction light path based on the optical element and the first-level ciphertext, and performing ghost diffraction operation on the first-level ciphertext and the four reference quantities respectively to obtain a second-level ciphertext and a second-level key respectively. According to the method, the ghost diffraction technology is introduced into the encryption process, ghost diffraction performs imaging by using the statistical correlation characteristic of the light field, and the image can still be restored through the statistical correlation characteristic under the condition that part of the light path is shielded or is interfered by noise, so that the anti-interference performance of the encryption method provided by the invention is effectively enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical image encryption, and particularly to a high-precision ghost diffraction encryption method for dynamic targets. Background Art

[0002] The phenomenon of ghost diffraction can be traced back to the research on the characteristics of quantum entanglement in the mid-20th century. Due to its non-local characteristics, ghost diffraction technology provides a new way to achieve high-level quantum secure communication. With the in-depth research, researchers found that many classical light sources can also be used to achieve ghost diffraction, which has greatly promoted the application of ghost diffraction technology in secure communication in daily life. In a classical ghost diffraction experiment, a laser beam is irradiated on a rotating ground glass to generate a pseudo-thermal light field with random speckle distribution characteristics. The light beam passes through a non-polarizing beam splitter, generating two light beams with the same distribution characteristics, forming two optical paths. One of them is called the test optical path, where an object is placed. After the light beam irradiates the object, the light intensity is recorded by a point detector. The other optical path is called the reference optical path, where there is no object. After the light beam propagates through free space, it is received by a high-resolution area detector. The image information of the object cannot be obtained separately from either of the above two optical paths. Ghost diffraction technology is to perform a correlation operation on the information collected by the point detector in the test optical path and the information collected by the area detector in the reference optical path, so as to obtain the information of the object. Such an imaging method makes ghost diffraction have the advantages of strong anti-interference and high sensitivity. Therefore, ghost diffraction technology has shown great application potential in the fields of secure communication, biomedicine, precision measurement, military defense, etc.

[0003] In today's digital age, data information security has become the lifeline of all industries. Optical image encryption technology shows significant advantages in the field of information security due to its unique physical characteristics. When encrypting through a traditional optical imaging system, the image is directly obtained by a pixel sensor, so there are problems of relying on precise optical devices and a stable optical path. Slight vibration or temperature fluctuation may cause the optical path to shift, making the encrypted image unable to be correctly decrypted. Applying a ghost diffraction system to optical image encryption can solve this problem. Different from the "what you see is what you get" of traditional imaging methods, it is based on the statistical correlation characteristics of the light field for imaging. Even if part of the optical path is blocked or interfered by noise, the image can still be restored through the statistical correlation characteristics. Therefore, ghost diffraction has a natural image encryption function, and the acquisition and reconstruction of its information have high anti-interference ability.

[0004] Existing ghost diffraction encryption technologies usually encrypt the light field information of static targets, and it is difficult to completely record and encrypt the position change information of dynamic targets. Summary of the Invention

[0005] In view of the above situation, the main purpose of the present invention is to propose a high-precision ghost diffraction encryption method for dynamic targets to solve the above technical problems.

[0006] The present invention proposes a high-precision ghost diffraction encryption method for dynamic targets, and the method includes the following steps: Step 1: Use a Michelson interferometer to observe the number of moving interference fringes of an object and perform phase calculation to obtain a set of observed phase change values. Use a transformation function to transform the set of observed phase change values to obtain a first-level ciphertext, and use the transformation function as the first-level key; Step 2: Construct four reference functions based on the principle of the four-step phase-shifting method, and multiply the four reference functions with the first-level ciphertext respectively to obtain four reference quantities; Step 3: Obtain an optical element and build a ghost diffraction optical path based on the optical element and the first-level ciphertext; Step 4: Based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain a second-level ciphertext and a second-level key; Step 5: Perform a second-order correlation operation on the second-level key and the second-level ciphertext based on the ghost diffraction principle to obtain the ghost diffraction image of the first-level ciphertext and the ghost diffraction images of the four reference quantities respectively. Process the ghost diffraction images of the four reference quantities based on the principle of the four-step phase-shifting method and perform phase calculation to obtain the phase of the restored Fourier image of the first-level ciphertext. Process the ghost diffraction image of the first-level ciphertext and perform an inverse Fourier operation with the phase of the restored Fourier image of the first-level ciphertext to obtain the restored first-level ciphertext; Step 6: Use the first-level key to decrypt the restored first-level ciphertext to obtain the high-precision displacement information of the restored object on the optical axis.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention introduces the ghost diffraction technology into the encryption process. Ghost diffraction uses the statistical correlation characteristics of the light field for imaging. Even when part of the optical path is blocked or interfered by noise, the image can still be restored through the statistical correlation characteristics, effectively enhancing the anti-interference ability of the encryption method proposed by the present invention; 2. The present invention encrypts by converting the object displacement information into phase information. Since a small movement of the object will generate a large phase change, measuring the phase information of a dynamic target using the interference principle can sensitively reflect its small displacement, improving the detection accuracy of the object displacement, thereby effectively improving the accuracy of the encryption method proposed by the present invention and at the same time broadening the application range of the encryption method proposed by the present invention; 3. The present invention encrypts by assigning the phase form of the object position change process to the original object, that is, converting the video content of the object movement into image content. While ensuring the encryption of the moving target and its displacement information, the encryption data volume is significantly reduced, effectively improving the encryption efficiency.

[0008] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the embodiments of the present invention. Description of the Drawings

[0009] Figure 1 It is a flowchart of the steps of a high-precision ghost diffraction encryption method for dynamic targets proposed by the present invention; Figure 2 It is a method framework diagram of a high-precision ghost diffraction encryption method for dynamic targets proposed by the present invention. Detailed Embodiments

[0010] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0011] Referring to the following description and drawings, these and other aspects of the embodiments of the present invention will become clear. In these descriptions and drawings, some specific embodiments of the embodiments of the present invention are specifically disclosed to represent some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0012] Please refer to Figure 1 , this embodiment provides a high-precision ghost diffraction encryption method for dynamic targets, and the method includes the following steps: Step 1: Use a Michelson interferometer to observe the number of moving interference fringes of an object and perform phase calculation to obtain a set of observed phase change values. Use a transformation function to transform the set of observed phase change values to obtain a first-level ciphertext, and use the transformation function as the first-level key.

[0013] Please refer to Figure 2 , in Step 1, use a Michelson interferometer to observe the number of moving interference fringes of an object and perform phase calculation to obtain a set of observed phase change values. Use a transformation function to transform the set of observed phase change values to obtain a first-level ciphertext, and use the transformation function as the first-level key, which specifically includes the following sub-steps: Obtain a transmissive plate, use the transmissive plate as the object to be encrypted, construct a function based on the transmissive plate to obtain an object transmission function, and there are the following relational expressions in the corresponding process: ; Among them, represents the object transmission function, represents the coordinates of the object, Indicates being processed by the rectangular function, represents the length of the transmission plate, and ; Obtain a Michelson interferometer, and use the Michelson interferometer to observe the number of fringe shifts of an object once every second to obtain a set of measured fringe shift numbers ; Among them, represents the set of measured fringe shift numbers, and ; represents the number of observation time points, and ; represents the number of fringe shifts obtained from the th measurement, represents the index of the number of measurements, and ; Calculate the set of measured fringe shift numbers and the wavelength of the light source to obtain the high-precision displacement of the object on the optical axis. There is the following relational expression in the corresponding process: ; Among them, represents the high-precision displacement of the object on the optical axis, represents the difference between the current position and the initial position of the object, represents the current position of the object, represents the wavelength of the light source, and ; Based on the set of measured fringe shift numbers, perform phase calculation on the measured fringe shift numbers to obtain a set of observed phase change values. There is the following relational expression in the corresponding process: ; Among them, represents the phase change value of the th observation, represents pi; Set the phase width based on the set of observed phase change values, and use the conversion function to convert the set of observed phase change values to obtain new phase information. There is the following relational expression in the corresponding process: ; Among them, represents the new phase information, represents the set of observed phase change values, and ; represents the phase width, and ; Assign the new phase information to the object to obtain the first-level ciphertext. Use the transformation function as the first-level key. The following relational expressions exist in the corresponding process: ; Among them, represents the first-level ciphertext, represents the phase information of the first-level ciphertext, represents the exponential function, represents the imaginary unit.

[0014] Step 2: Construct four reference functions based on the principle of the four-step phase-shifting method. Multiply the four reference functions with the first-level ciphertext respectively to obtain four reference quantities.

[0015] In Step 2, construct four reference functions based on the principle of the four-step phase-shifting method. Multiply the four reference functions with the first-level ciphertext respectively to obtain four reference quantities. The specific sub-steps are as follows: Construct four reference functions based on the principle of the four-step phase-shifting method to obtain four reference functions respectively. The following relational expressions exist in the corresponding process: ; Among them, represents the first reference function, represents the second reference function, represents the third reference function, represents the fourth reference function, represents the coordinates of the reference function, represents after being processed by the exponential function, represents the coordinate interval in the frequency domain, and ; represents the resolution of the detector, and ; represents the distance from the object to the detector, and ; Multiply the first-level ciphertext with the four reference functions respectively to obtain four reference quantities. The following relational expressions exist in the corresponding process: ; Among them, represents the first reference quantity, represents the second reference quantity, represents the third reference quantity, represents the fourth reference quantity.

[0016] Step 3: Obtain the optical element and build a ghost diffraction optical path based on the optical element and the first-level ciphertext.

[0017] In Step 3, build a ghost diffraction optical path based on the optical element and the first-level ciphertext. The specific process is as follows: Place a He-Ne laser, a beam expander, a collimating lens, a diaphragm, a polarizer, a spatial light modulator, an analyzer, a diaphragm, a condenser lens, a first-level ciphertext, a converging lens, and a point detector in sequence.

[0018] It should be noted that the He-Ne laser is the light source, the beam expander is used to expand the diameter of the laser beam, the collimating lens is used to make the beam parallel, the diaphragm is used to limit the size of the beam, the polarizer and the analyzer are used to adjust the polarization state of the light, the spatial light modulator is used to modulate the phase or amplitude of the light wave, the condenser lens and the converging lens are used to focus the beam, and the point detector is used to detect the light source intensity.

[0019] Step 4: Based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain the second-level ciphertext and the second-level key respectively.

[0020] In Step 4, based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain the second-level ciphertext, which specifically includes the following sub-steps: Based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain the ghost diffraction image of the first-level ciphertext and the ghost diffraction images of the four reference quantities. The following relational expressions exist in the corresponding process: ; Among them, represents the ghost diffraction image of the first-level ciphertext, represents the intensity fluctuation correlation formula, represents the coordinates of the detector in the test optical path, represents the coordinates of the detector in the reference optical path, represents the light source intensity, represents the distance from the light source to the object, and ; represents the Fourier image of the first-level ciphertext, represents the ghost diffraction image of the first reference quantity, represents the ghost diffraction image of the second reference quantity, represents the ghost diffraction image of the third reference quantity, represents the ghost diffraction image of the fourth reference quantity; Based on the ghost diffraction operation, record the detection value of the point detector in the ghost diffraction optical path and the random speckle used to irradiate the object. Take the detection value of the point detector as the second-level ciphertext and the random speckle as the second-level key. The following relational expressions exist in the corresponding process: ; Among them, represents the detection value of the point detector, represents the coordinates of the random light source, Represents the light field distribution of the light source.

[0021] Step 5: Based on the principle of ghost diffraction, perform a second-order correlation operation on the secondary key and the secondary ciphertext to respectively obtain the ghost diffraction image of the primary ciphertext and the ghost diffraction images of the four reference quantities. Process the ghost diffraction images of the four reference quantities based on the principle of the four-step phase-shifting method and perform phase calculation to obtain the phase of the recovered Fourier image of the primary ciphertext. Process the ghost diffraction image of the primary ciphertext and perform an inverse Fourier operation with the phase of the recovered Fourier image of the primary ciphertext to obtain the recovered primary ciphertext.

[0022] In step 5, based on the principle of ghost diffraction, perform a second-order correlation operation on the secondary key and the secondary ciphertext to respectively obtain the ghost diffraction image of the primary ciphertext and the ghost diffraction images of the four reference quantities. Process the ghost diffraction images of the four reference quantities based on the principle of the four-step phase-shifting method and perform phase calculation to obtain the phase of the recovered Fourier image of the primary ciphertext. Process the ghost diffraction image of the primary ciphertext and perform an inverse Fourier operation with the phase of the recovered Fourier image of the primary ciphertext to obtain the recovered primary ciphertext, which specifically includes the following sub-steps: Based on the principle of ghost diffraction, perform a second-order correlation operation on the secondary key and the secondary ciphertext to respectively obtain the ghost diffraction image of the primary ciphertext and the ghost diffraction images of the four reference quantities. Based on the principle of the four-step phase-shifting method, process the ghost diffraction images of the four reference quantities to obtain an intermediate quantity. The following relational expressions exist in the corresponding process: ; Among them, represents the intermediate quantity, represents the conjugate of the Fourier image of the primary ciphertext; Perform phase calculation on the intermediate quantity to obtain the phase of the recovered Fourier image of the primary ciphertext. The following relational expressions exist in the corresponding process: ; Among them, represents the phase of the recovered Fourier image of the primary ciphertext, and ; represents the th phase of the Fourier image of the primary ciphertext at the th detection point, represents the index of the detection point, and ; represents the th phase of the intermediate quantity at the th detection point, It should be noted that when , let .

[0023] Process the ghost diffraction image of the first-level ciphertext to obtain the amplitude of the Fourier image of the recovered first-level ciphertext. The following relational expressions exist in the corresponding process: ; Among them, represents the amplitude of the Fourier image of the recovered first-level ciphertext; Based on the phase of the Fourier image of the recovered first-level ciphertext and the amplitude of the Fourier image of the recovered first-level ciphertext, perform an inverse Fourier transform to obtain the recovered first-level ciphertext. The following relational expressions exist in the corresponding process: ; Among them, represents the recovered first-level ciphertext, represents the coordinates in the frequency domain, represents positive infinity, represents negative infinity.

[0024] Step 6: Use the first-level key to decrypt the recovered first-level ciphertext to obtain the high-precision displacement information of the recovered object on the optical axis.

[0025] In Step 6, use the first-level key to decrypt the recovered first-level ciphertext to obtain the high-precision displacement information of the recovered object on the optical axis, which specifically includes the following sub-steps: Obtain the phase information based on the recovered first-level ciphertext, and perform an inverse operation on the phase information based on the first-level key to obtain the set of recovered observed phase change values. The following relational expressions exist in the corresponding process: ; Among them, represents the set of recovered observed phase change values; Perform an inverse calculation on the set of recovered observed phase change values and the wavelength of the light source to obtain the high-precision displacement information of the recovered object on the optical axis. The following relational expressions exist in the corresponding process: ; Among them, represents the high-precision displacement information of the recovered object on the optical axis.

[0026] It should be understood that although the steps in the flowcharts of the embodiments of the present invention are shown sequentially in the direction of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise clearly stated in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in each embodiment may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0027] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following technologies well known in the art can be used: discrete logic circuits with logic gate circuits for implementing logical functions on data signals, application specific integrated circuits with appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0028] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0029] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A high-precision ghost diffraction encryption method for dynamic targets, characterized in that, The method includes the following steps: Step 1: Use a Michelson interferometer to observe the number of moving interference fringes of an object and perform phase calculation to obtain a set of observed phase change values. Use a transformation function to transform the set of observed phase change values to obtain a first-level ciphertext, and use the transformation function as the first-level key. Step 2: Construct four reference functions based on the principle of the four-step phase-shifting method. Multiply the four reference functions with the first-level ciphertext respectively to obtain four reference quantities. Step 3: Obtain an optical element and build a ghost diffraction optical path based on the optical element and the first-level ciphertext. Step 4: Based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain a second-level ciphertext and a second-level key. Step 5: Perform a second-order correlation operation on the second-level key and the second-level ciphertext based on the ghost diffraction principle to obtain the ghost diffraction image of the first-level ciphertext and the ghost diffraction images of the four reference quantities respectively. Process the ghost diffraction images of the four reference quantities based on the principle of the four-step phase-shifting method and perform phase calculation to obtain the phase of the restored Fourier image of the first-level ciphertext. Process the ghost diffraction image of the first-level ciphertext and perform an inverse Fourier operation with the phase of the restored Fourier image of the first-level ciphertext to obtain the restored first-level ciphertext. Step 6: Use the first-level key to decrypt the restored first-level ciphertext to obtain the high-precision displacement information of the restored object on the optical axis.

2. The high-precision ghost diffraction encryption method for dynamic targets according to claim 1, wherein, In the said Step 1, using a Michelson interferometer to observe the number of moving interference fringes of an object and perform phase calculation to obtain a set of observed phase change values, using a transformation function to transform the set of observed phase change values to obtain a first-level ciphertext, and using the transformation function as the first-level key, specifically includes the following sub-steps: Obtain a transmission plate, use the transmission plate as the object to be encrypted, and build a function based on the transmission plate to obtain the object transmission function. Obtain a Michelson interferometer, and use the Michelson interferometer to observe the number of moving interference fringes of the object once every second to obtain a set of measured numbers of moving interference fringes. Calculate the set of measured numbers of moving interference fringes with the wavelength of the light source to obtain the high-precision displacement of the object on the optical axis. Based on the set of measured numbers of moving interference fringes, perform phase calculation on the measured numbers of moving interference fringes to obtain a set of observed phase change values. Set a phase width based on the set of observed phase change values, and use a transformation function to transform the set of observed phase change values to obtain new phase information. Assign the new phase information to the object to obtain a first-level ciphertext, and use the transformation function as the first-level key.

3. The high-precision ghost diffraction encryption method for dynamic targets according to claim 2, wherein, Obtain a transmission plate, use the transmission plate as the object to be encrypted, and build a function based on the transmission plate to obtain the object transmission function. There are the following relational expressions in the corresponding process: ； Among them, represents the object transmission function, represents the coordinates of the object, represents being processed by the rectangle function, represents the length of the transmission plate; In the step of calculating the set of measured numbers of moving interference fringes with the wavelength of the light source to obtain the high-precision displacement of the object on the optical axis, there are the following relational expressions in the corresponding process: ； Among them, represents the high-precision displacement of the object on the optical axis, represents the difference between the current position and the initial position of the object, represents the current position of the object, represents the set of the measured number of moving interference fringes, represents the wavelength of the light source; In the step of calculating the phase of the measured interference fringe shift number based on the set of measured interference fringe shift numbers to obtain the set of observed phase change values, the following relational expressions exist in the corresponding process: ； Among them, represents the phase change value of the th observation, represents pi, represents the number of interference fringe shifts obtained from the th measurement, represents the index of the number of measurements; In the step of setting the phase width based on the set of observed phase change values and using a conversion function to convert the set of observed phase change values to obtain new phase information, the following relational expressions exist in the corresponding process: ； Among them, represents the new phase information, represents the set of observed phase change values, represents the phase width; In the step of assigning the new phase information to an object to obtain a first-level ciphertext and using the conversion function as the first-level key, the following relational expressions exist in the corresponding process: ； Among them, represents the first-level ciphertext, represents the phase information of the first-level ciphertext, represents the exponential function, represents the imaginary unit.

4. A high-precision ghost diffraction encryption method for dynamic targets according to claim 3, characterized in that In step 2, four reference functions are constructed based on the four-step phase-shifting method principle, and the four reference functions are respectively multiplied by the first-level ciphertext to obtain four reference quantities. Specifically, it includes the following sub-steps: Construct four reference functions based on the four-step phase-shifting method principle to obtain four reference functions respectively; Multiply the first-level ciphertext by the four reference functions respectively to obtain four reference quantities.

5. A high-precision ghost diffraction encryption method for dynamic targets according to claim 4, characterized in that, Construct four reference functions based on the four-step phase-shifting method principle to obtain four reference functions respectively. The following relational expressions exist in the corresponding process: ； Among them, represents the first reference function, represents the second reference function, represents the third reference function, represents the fourth reference function, represents the coordinates of the reference function, represents being processed by an exponential function, represents the coordinate interval in the frequency domain; In the step of multiplying the first-level ciphertext by the four reference functions respectively to obtain four reference quantities, the following relational expressions exist in the corresponding process: ； Among them, represents the first reference quantity, represents the second reference quantity, represents the third reference quantity, represents the fourth reference quantity.

6. The high-precision ghost diffraction encryption method for dynamic targets according to claim 5, wherein In step 4, based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain a second-level ciphertext and a second-level key. Specifically, it includes the following sub-steps: Based on the ghost diffraction optical path, perform ghost diffraction operations on the first-level ciphertext and the four reference quantities respectively to obtain the ghost diffraction images of the first-level ciphertext and the four reference quantities. The following relational expressions exist in the corresponding process: ； Among them, represents the ghost diffraction image of the first-level ciphertext, represents the intensity fluctuation correlation formula, represents the coordinates of the detector in the test optical path, represents the coordinates of the detector in the reference optical path, represents the distance from the object to the detector, represents the distance from the light source to the object, represents the light source intensity, represents the Fourier image of the first-level ciphertext, represents the ghost diffraction image of the first reference quantity, represents the ghost diffraction image of the second reference quantity, represents the ghost diffraction image of the third reference quantity, represents the ghost diffraction image of the fourth reference quantity; Based on the ghost diffraction operation, record the detection value of the point detector in the ghost diffraction optical path and the random speckle used to irradiate the object. Use the detection value of the point detector as the second-level ciphertext and the random speckle as the second-level key. The following relational expressions exist in the corresponding process: ； Among them, represents the detection value of the point detector, represents the coordinates of the random light source, represents the optical field distribution of the light source.

7. A high-precision ghost diffraction encryption method for dynamic targets according to claim 6, characterized in that, In step 5, perform a second-order correlation operation on the second-level key and the second-level ciphertext based on the ghost diffraction principle to obtain the ghost diffraction images of the first-level ciphertext and the four reference quantities respectively. Process the ghost diffraction images of the four reference quantities based on the four-step phase-shifting method principle and perform phase calculation to obtain the phase of the restored first-level ciphertext Fourier image. Process the ghost diffraction image of the first-level ciphertext and perform an inverse Fourier operation with the phase of the restored first-level ciphertext Fourier image to obtain the restored first-level ciphertext. Specifically, it includes the following sub-steps: Based on the ghost diffraction principle, perform a second-order correlation operation on the second-level key and the second-level ciphertext to obtain the ghost diffraction images of the first-level ciphertext and the four reference quantities respectively. Based on the four-step phase-shifting method principle, process the ghost diffraction images of the four reference quantities to obtain an intermediate quantity; Perform phase calculation on the intermediate quantity to obtain the phase of the restored first-level ciphertext Fourier image; Process the ghost diffraction image of the first-level ciphertext to obtain the amplitude of the Fourier image of the restored first-level ciphertext; Based on the phase of the Fourier image of the restored first-level ciphertext and the amplitude of the Fourier image of the restored first-level ciphertext, perform inverse Fourier transform to obtain the restored first-level ciphertext.

8. A high-precision ghost diffraction encryption method for dynamic targets according to claim 7, characterized in that, Based on the principle of ghost diffraction, perform second-order correlation operation on the second-level key and the second-level ciphertext to obtain the ghost diffraction image of the first-level ciphertext and the ghost diffraction images of four reference quantities respectively. Based on the principle of four-step phase-shifting method, process the ghost diffraction images of the four reference quantities to obtain intermediate quantities. The following relational expressions exist in the corresponding process: ； Among them, represents an intermediate quantity, represents the conjugate of the Fourier image of the first-level ciphertext; In the step of calculating the phase of the intermediate quantity to obtain the phase of the Fourier image of the restored first-level ciphertext, the following relational expressions exist in the corresponding process: ； Among them, represents the phase of the Fourier image of the restored first-level ciphertext, represents the phase of the Fourier image of the first-level ciphertext at the th detection point, represents the index of the detection point, represents the phase of the intermediate quantity at the th detection point, represents the phase of the Fourier image of the first-level ciphertext at the th detection point; In the step of processing the ghost diffraction image of the first-level ciphertext to obtain the amplitude of the Fourier image of the restored first-level ciphertext, the following relational expressions exist in the corresponding process: ； Among them, represents the amplitude of the restored first-level ciphertext Fourier image; In the step of performing inverse Fourier transform based on the phase of the Fourier image of the restored first-level ciphertext and the amplitude of the Fourier image of the restored first-level ciphertext to obtain the restored first-level ciphertext, the following relational expressions exist in the corresponding process: ； Among them, represents the restored first-level ciphertext, represents the coordinates in the frequency domain, represents positive infinity, represents negative infinity.

9. A high-precision ghost diffraction encryption method for dynamic targets according to claim 8, characterized in that In the said step 6, use the first-level key to decrypt the restored first-level ciphertext to obtain the high-precision displacement information of the restored object on the optical axis, which specifically includes the following sub-steps: Obtain phase information based on the restored first-level ciphertext, and perform inverse operation on the phase information based on the first-level key to obtain a set of restored observed phase change values; Perform inverse calculation on the set of restored observed phase change values and the wavelength of the light source to obtain the high-precision displacement information of the restored object on the optical axis.

10. A high-precision ghost diffraction encryption method for dynamic targets according to claim 9, characterized in that Obtain phase information based on the restored first-level ciphertext, and perform inverse operation on the phase information based on the first-level key to obtain a set of restored observed phase change values. The following relational expressions exist in the corresponding process: ； Among them, represents a set of restored observed phase change values; In the step of performing inverse calculation on the set of restored observed phase change values and the wavelength of the light source to obtain the high-precision displacement information of the restored object on the optical axis, the following relational expressions exist in the corresponding process: ； Among them, represents the high-precision displacement information of the restored object on the optical axis.

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