CN111583395B - Multiple complex three-dimensional scene encryption and decryption method - Google Patents
Multiple complex three-dimensional scene encryption and decryption method Download PDFInfo
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Abstract
The invention discloses a multiple complex three-dimensional scene encryption and decryption method, which uses a phase recovery algorithm to generate a kinoform for each color layered image of a three-dimensional scene, and multiplies the kinoform by a random sign function to form a light wave signal with noise interference. Multiplying the noise-interfered kinoform plane light wave signals of different three-dimensional scenes and different color channels to form a composite light wave signal; the composite lightwave signal is decomposed into two phase functions which are multiplied, one of which is used as a common encryption phase template, and the other of which is combined with the interference suppression signal to form a phase function for decryption. The Fresnel inverse diffraction of specific wavelength and distance is calculated by the phase function for decryption to obtain amplitude and phase, a phase recovery algorithm is applied to the amplitude to generate a first decryption phase template, and the phase formed by the first decryption phase template through forward Fresnel diffraction are combined to form a second decryption phase template. And decrypting each color component of the three-dimensional scene by placing the encryption phase template of the cascade structure and the first and second decryption phase templates on the specific plane of the virtual light path, and combining to recover the colored three-dimensional scene. The invention has good safety and robustness.
Description
Technical Field
The invention relates to the technical field of data image processing, in particular to a multiple complex three-dimensional scene encryption and decryption method based on an improved phase recovery algorithm and a cascade structure decryption phase template.
Background
Compared with a common two-dimensional image, the digital carrier containing the object depth information can bring the personally on-the-scene feeling to a viewer in three-dimensional presentation, and has a wide development space in the fields of machine vision, 3D televisions, 3D movies, 3D conversations, 3D maps, 3D games, aerial surveying and mapping, navigation, telemedicine and the like. The binocular stereo image based on the binocular parallax 3D display principle and the digital hologram based on the true 3D display principle are two common recording modes of an object three-dimensional scene and are also important components of multimedia information. The popularization of computers, the internet and mobile intelligent terminals accelerates the spread of digital works, but the security protection problem of the digital works is also caused, and the security problem of multiple digital works is also needed to be solved in the aspects of multi-user authentication, content distribution, encryption information capacity expansion, secret information transmission efficiency improvement and the like.
Disclosure of Invention
The invention aims to provide a multiple complex three-dimensional scene encryption and decryption method which is used for improving the safety of a digital carrier containing a complex three-dimensional scene.
The technical scheme adopted by the invention is as follows:
a multiple complex three-dimensional scene encryption and decryption method comprises an encryption step and a decryption step, and specifically comprises the following steps:
an encryption step:
s11) determining the layering number according to the histogram characteristics of the depth map, taking the average depth value of each layer of objects as a depth value, and converting the depth value into the Fresnel diffraction distance between the object layer and the kinoform plane;
s12) generating kinoforms respectively corresponding to R, G and B color channels by using a one-to-many planar improved phase recovery algorithm, wherein the kinoforms show random signal characteristics;
s13) multiplying the light wave distribution of each kinoform plane by a random sign function to form a kinoform plane light wave distribution signal with noise interference;
s14) multiplying the kinoform plane light wave distribution signals with noise interference from different three-dimensional scenes and different color channels to form a composite light wave signal containing a plurality of three-dimensional scenes;
s15) decomposing the composite lightwave signal into two phase functions for multiplication, taking one of the two phase functions as a common encryption phase template, and combining the other phase function with an interference suppression signal to form a phase function for decryption;
s16) calculating Fresnel inverse diffraction of specific wavelength and distance to a phase function for decryption to obtain amplitude and phase, wherein the amplitude is used for a phase recovery algorithm (GSA) to generate a first decryption phase template, and the phase is combined with a phase signal formed by forward diffraction of parameters in the GSA algorithm by the first decryption phase template to form a second decryption phase template.
And a decryption step:
s21) building a virtual light path, and respectively placing a common encryption phase template in a cascade structure form and a first decryption phase template and a second decryption phase template corresponding to a single color component for decrypting the three-dimensional scene on a specific plane of the virtual light path;
s22) calculating a diffraction image of a specific observation surface in a virtual light path under the irradiation of parallel light, obtaining a single color component reconstructed image of an original three-dimensional scene and storing the reconstructed image;
s23) changing the first and second decryption phase template pairs to obtain R, G and B color component reconstructed images of each three-dimensional scene and storing the R, G and B color component reconstructed images;
s24) combining the R, G and B color component reconstructed images of the three-dimensional scenes to obtain a color three-dimensional scene reconstructed image.
Further, step S11) with [ D 1 ，D 2 ]Indicating the depth interval of the i-th layer object, and taking the depth value of the layer
The Fresnel diffraction distance corresponding to the i-th layer object field information is expressed by formula (1);
wherein d is min Represents the distance from the nearest object plane to the kinoform plane, d max Representing the distance of the farthest object plane to the kinoform plane.
Further, the specific method of step S12) is:
step S12-1) setting the kinoform plane as an initial pure phase function, and respectively calculating the wavelength as lambda and the distance as d i Obtaining diffraction light wave complex signals of the three-dimensional scene layers from 1 to M;
step S12-2) replacing the amplitude in the complex signal with the object field information image of the corresponding layer for the diffraction light wave complex signal of each layer, and reserving the phase to obtain the diffraction light wave signal of each layer after amplitude constraint;
step S12-3) calculating Fresnel diffraction on signals of each layer after amplitude constraint to obtain complex amplitude signals of an kinoform plane;
step S12-4) averaging the complex amplitude signals of the kinoform plane, reserving the phase and modulating the amplitude of the phase to be 1 to obtain a pure phase function;
and S12-5) the pure phase function is used as the next initial object wave function for re-iteration until the algorithm converges or the iteration times are reached.
Further, the composite lightwave signal S (u, v) in step S14) is represented by formula (2).
Wherein s is 1R (u,v)...s NB (u, v) represent the random sign functions used for the three color channels R, G, B of the three-dimensional scene, respectively, exp () represents an exponential function, j represents an imaginary unit
Which represents the sum operation of the N terms,
and representing the phase corresponding to the R color component of the kth three-dimensional scene.
Further, the composite lightwave signal S (u, v) is decomposed into two phase functions P1 (u, v) and P2 (u, v) in step S15), i.e. P (u, v) are multiplied
S(u,v)＝P 1 (u,v) P 2 (u,v) (3)
Wherein
Function angle () represents the phase; p 1 (u, v) as common encryption phase template, i.e. encryption phase template
P 2 (u, v) are used in combination with the interference suppression signal to construct the decrypted phase templates D1 and D2 in the form of a concatenated structure.
Further, the phase function D (u, v) decrypted in step S15) is represented as:
D(u,v)＝P 2 (u,v)I(u,v)
wherein I (u, v) represents an interference suppression signal.
Further, the specific steps of step S16) are as follows:
step S16-1) of calculating the wavelength of the combined signal D (u, v) as lambda and the distance as Z 1 The inverse fresnel diffraction transformation of (a) to obtain the amplitude a and the phase ψ, as shown in equation (6),
wherein the symbol IFrT represents the inverse fresnel diffraction transform;
step S16-2) uses the wavelength of lambda and the distance of Z for the amplitude A 2 The Fresnel domain phase recovery algorithm generates a first decrypted phase template e jθ I.e. the first decryption phase template e jθ And the amplitude A satisfies the formula (7):
wherein the symbol "|" indicates taking amplitude operation, e jθ As a first decryption phase template, i.e. a first decryption phase template D 1 ＝e jθ ；
Step S16-3) for the first decrypted phase template e jθ The parameters are calculated as wavelength λ and distance Z 2 The phase phi is obtained by the fresnel diffraction forward transformation, as shown in formula (8),
step S16-3) combining the phase phi and the phase phi to obtain a second decrypted phase template D2, i.e. D 2 ＝e j(ψ-φ) 。
Further, the reconstructed signal of the mth layer of the three-dimensional scene i in step S24) is represented as:
wherein D is 1 Representing a first decrypted phase template, D 2 Representing a second decrypted phase template, E representing a common encrypted phase template, symbol
Denotes a wavelength of λ and a distance of d m Fresnel diffraction positive transformation, sign
Wavelength λ and distance z 1 Fresnel diffractive positive transformation of (1), sign
Denotes a wavelength of λ and a distance of z 2 The fresnel diffraction forward transform of (1).
By adopting the technical scheme, in order to solve the safety problem of digital works bearing complex three-dimensional scenes, layered images corresponding to R, G and B color components are formed according to the depth aiming at each color complex three-dimensional scene, an improved phase recovery algorithm is used for generating a kinoform for the layered image corresponding to each color component of each three-dimensional scene, and the kinoform shows the characteristic of random signals. And multiplying the light wave distribution corresponding to each kinoform by a random sign function to form a kinoform light wave distribution signal with noise interference. Multiplying kinoform light wave distribution signals with noise interference from different three-dimensional scenes and different color channels to form a composite light wave signal in a noise form containing a plurality of three-dimensional scenes; the composite lightwave signal is decomposed into two phase functions, one of the two phase functions is used as a common encryption phase template, and the other phase function is combined with the interference suppression signal to form a phase function for decryption. And calculating Fresnel inverse diffraction of specific wavelength and distance on the phase function for decryption to obtain amplitude and phase, wherein the amplitude is used for a phase recovery algorithm (GSA) to generate a first decryption phase template, and the phase is combined with a phase signal formed by forward diffraction of the GSA algorithm parameters of the first decryption phase template to form a second decryption phase template. Through the encryption phase template and the first and second decryption phase templates of the cascade structure in the virtual light path, the three-dimensional scene of each color component can be decrypted, and the R, G and B components from the same three-dimensional scene can be combined to restore the colorful three-dimensional scene. Test results show that the proposed method has good safety and robustness. The reconstruction of the three-dimensional scene fails due to mismatching of the decrypted phase template or the reconstruction parameters, and the three-dimensional scene can still be reconstructed under the condition that the encrypted phase template is sheared or superimposed with Gaussian noise with certain intensity.
Drawings
The invention is described in further detail below with reference to the accompanying drawings and the detailed description;
FIG. 1 is a flow chart of the present invention for encrypting multiple complex three-dimensional scenes;
FIG. 2 is a flowchart of the complex three-dimensional scene decryption process of the present invention;
FIG. 3 is a schematic diagram of the improved phase recovery algorithm for generating a kinoform in accordance with the present invention;
FIG. 4 is a schematic diagram of the generation of an encryption and decryption phase template according to the present invention;
FIG. 5 is a diagram of virtual light paths for decrypting three-dimensional scenes in accordance with the present invention;
FIG. 6 is a color image and a depth map corresponding to a complex three-dimensional scene according to the present invention;
FIG. 7 is a layered image of R, G, B channels of a three-dimensional scene and corresponding kinoforms of the same;
FIG. 8 is an encrypted phase template comprising three-dimensional scenes according to the present invention;
FIG. 9 is a reconstructed image of a complex three-dimensional scene according to the present invention;
FIG. 10 is a reconstructed image of a three-dimensional scene 1 when a decryption phase template of the present invention is in error;
FIG. 11 is a reconstructed image of a three-dimensional scene 1 with diffraction distances of 494.1mm,489.6mm and 485.6mm respectively after an encrypted phase template E of the present invention is horizontally sheared by 1/16;
FIG. 12 shows a reconstructed image of a three-dimensional scene 1 with an average value of 0, a variance of 0.01, and diffraction distances of 494.1mm,489.6mm, and 485.6mm respectively for an encrypted phase template E according to the present invention;
FIG. 13 shows the three-dimensional scene 1 reconstructed image at positions with a 2% deviation of the decryption distance parameter Z2, and with diffraction distances of 494.1mm,489.6mm and 485.6mm respectively;
FIG. 14 shows a three-dimensional scene 1 reconstructed image at positions with diffraction distances of 494.1mm,489.6mm and 485.6mm respectively when the decryption distance parameter Z1 of the invention deviates by 2%;
FIG. 15 shows a three-dimensional scene 1 reconstructed image at the diffraction distances of 494.1mm,489.6mm and 485.6mm respectively when the wavelength of the plane wave for irradiation deviates by 2% in the reconstructed virtual optical path.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be described below with reference to the drawings in the embodiments of the present application.
As shown in fig. 1 to fig. 15, the present invention discloses a multiple complex three-dimensional scene encryption and decryption method, which includes an encryption step and a decryption step.
As shown in fig. 1, the multiple complex three-dimensional scene encryption steps are:
s11) determining the number of layers of a complex three-dimensional scene recorded by a color image and a depth map according to the histogram characteristics of the depth map, taking the average value of the depth of each layer of objects as the depth value of the layer, and converting the depth value into the Fresnel diffraction distance between the object layer and a kinoform plane;
s12) generating kinoforms respectively corresponding to R, G and B color channels by using a one-to-many planar improved phase recovery algorithm, wherein the kinoforms show random signal characteristics;
s13) multiplying the light wave distribution of each kinoform plane by a random sign function to form the kinoform plane light wave distribution with noise interference;
s14) multiplying the planar light wave distribution of the kinoform with noise interference from different three-dimensional scenes to form a composite light wave signal containing a plurality of three-dimensional scenes;
s15) decomposing the composite lightwave signal into two phase functions for multiplication, taking one of the phase functions as a common encryption phase template, and combining the other phase function with an interference suppression signal to form a phase function for decryption;
s16) calculating Fresnel inverse diffraction of specific wavelength and distance to a phase function for decryption to obtain amplitude and phase, wherein the amplitude is used for a phase recovery algorithm to generate a first decryption phase template, and the phase is combined with a phase signal formed by forward diffraction of parameters in the phase recovery algorithm for the first decryption phase template to form a second decryption phase template.
As shown in fig. 2, the decrypting step includes:
s21) building a virtual light path, and respectively placing a common encryption phase template of a cascade structure and a first decryption phase template and a second decryption phase template corresponding to a single color component for decrypting the three-dimensional scene on a specific plane of the virtual light path;
s22) calculating a diffraction image of a specific observation surface in a virtual light path under the irradiation of parallel light, obtaining and storing a single color component reconstructed image of the original three-dimensional scene;
s23) changing the first decryption phase template pair and the second decryption phase template pair to obtain R, G and B color component reconstructed images corresponding to the three-dimensional scenes and storing the R, G and B color component reconstructed images;
s24) combining the R, G and B color component reconstructed images of the three-dimensional scene to obtain a color three-dimensional scene reconstructed image.
Fig. 3 shows the generation principle of the kinoform of the complex three-dimensional scene: fig. 3 (a) shows a complex three-dimensional scene calculation kinoform generation method, fig. 3 (b) shows a schematic diagram of a kinoform plane and an object layer position relationship in a three-dimensional scene, and fig. 3 (c) shows an iterative calculation process for generating a complex three-dimensional scene calculation kinoform by an improved phase recovery algorithm.
Referring to fig. 3 (a), the color image and the depth map record information such as gray scale, color, depth, and the like of the complex three-dimensional scene, comprehensively consider the size of the encrypted signal and the three-dimensional reconstruction effect, form layered images corresponding to R, G, and B color components for each complex three-dimensional scene according to the color and depth of the complex three-dimensional scene, and generate a kinoform for the layered image corresponding to each color component of each three-dimensional scene by using an improved phase recovery algorithm. Compared with an amplitude hologram, the kinoform only has a single diffraction image, a complex three-dimensional scene can be reconstructed by using all light intensity, and the diffraction efficiency is high. The generation of kinoform from layered images using a modified phase recovery algorithm is shown in fig. 3 a. In fig. 3a, the number of layers is determined according to the histogram characteristics of the depth map, the average depth of each layer of object is taken as the depth value, and the depth value is converted into the fresnel diffraction distance between the object layer and the kinoform plane; the signals of all layers of the complex 3D scene are integrated into a Fresnel calculated kinoform by an improved phase recovery algorithm, and the position relation between the kinoform plane and the object field information layer of the three-dimensional scene is shown in figure 3 (b).
Let the depth map take the value of [0, 255 ]]Is shown in 8-bit grayscale. From the depth map histogram, f (D) = k may be obtained, where k denotes the number of pixels of object field information for which the depth value is D, and the size of the k value indicates how much object field information the depth gathers. Since object field information of different layers in the depth map shows discontinuous depth values, meaning that the object field information gathered at some depths will be few, the frequency of occurrence of depth values in the depth histogram will present the feature of gathering groups, and the segmentation points between clusters and adjacent clusters can be used as different layers of objectsA segmentation threshold for field information. And determining the number of layers according to the depth threshold, combining the objects of each layer, and taking the average value of the depths of the objects as the depth value of the layer. By [ D ] 1 ，D 2 ]The depth value of the layer is taken as the depth interval of the i-th layer object
The fresnel diffraction distance corresponding to the i-th layer object field information can be expressed by equation (1). Wherein d is min Represents the distance from the nearest object plane to the kinoform plane, d max Representing the distance of the farthest object plane to the kinoform plane.
In FIG. 3c, a Fresnel calculated kinoform is obtained between the kinoform plane and the object field information plane by using an improved phase recovery algorithm, and the kinoform is represented as a random signal characteristic;
in FIG. 3c, the kinoform plane is set as the initial pure phase function, and the wavelength is λ and the distance is d are calculated respectively i Obtaining diffraction light wave complex signals of the three-dimensional scene layers from 1 to M; replacing the amplitude in the complex signal with the object field information image of the corresponding layer for the diffraction light wave complex signal of each layer, and reserving the phase to obtain the diffraction light wave signal of each layer after amplitude constraint; calculating Fresnel diffraction on signals of each layer after amplitude constraint to obtain complex amplitude signals of an kinoform plane; averaging the complex amplitude signals of the kinoform plane, reserving the phase, and modulating the amplitude of the complex amplitude signals to be 1 to obtain a pure phase function; the pure phase function is used as the next initial object wave function for re-iteration until the algorithm converges or the iteration times are reached;
as shown in FIG. 4, a total of N three-dimensional scenes are set, and the kinoform planar lightwave distributions of the three color channels R, G and B of the ith three-dimensional scene are respectively used
Expressed by the random sign function used being s iR (u,v)，s iG (u,v)，s iB (u, v) is shown. The method comprises the steps of multiplying the kinoform plane light wave distribution corresponding to each color channel of each three-dimensional scene by a random sign function to obtain the interference-added kinoform plane light wave distribution, multiplying the interference-added kinoform plane light wave distribution signals from each color channel of each three-dimensional scene to obtain a composite light wave signal containing a plurality of pieces of three-dimensional scene information, wherein the composite light wave signal is represented in a noise form. The composite lightwave signal is decomposed into two phase functions for multiplication, one of the two phase functions is taken as an encryption phase template, and the other phase function is combined with an interference suppression signal and used for constructing two decryption phase templates in a cascade structure form.
The composite lightwave signal S (u, v) in fig. 4 can be represented by equation (2).
Decomposing S (u, v) into two phase functions P1 (u, v) multiplied by P2 (u, v), i.e.
S(u,v)＝P 1 (u,v)P 2 (u,v) (3)
Wherein
The function angle () represents taking the phase.
P 1 (u, v) can be used as a common encryption phase template, i.e. encryption phase template
P 2 (u, v) are used in combination with the interference suppression signal to construct the decrypted phase templates D1 and D2 in the form of a cascaded structure.
Planar lightwave distribution signal of kinoform corresponding to R component of three-dimensional scene i
For example, the interference suppression signal may be expressed as:
will phase function P 2 (u, v) is combined with the interference suppressed signal I (u, v) for constructing a decrypted phase template in the form of a concatenated structure.
The combined signal is represented as: d (u, v) = P 2 (u,v)I(u,v) (5)
Calculating the wavelength of the combined signal D (u, v) as lambda and the distance as Z 1 The amplitude a and the phase ψ are obtained as shown in equation (6), where the notation IFrT denotes the inverse fresnel diffraction transform.
For amplitude A, the wavelength is λ and the distance is Z 2 The Fresnel domain phase recovery algorithm generates a first decrypted phase template e jθ I.e. the first decryption phase template e jθ And the amplitude A satisfies the formula (7).
Wherein the symbol "|" indicates taking amplitude operation, e jθ As a first decryption phase template, i.e. a first decryption phase template D 1 ＝e jθ 。
For the first decrypted phase template e jθ The calculation parameters are lambda wavelength and Z distance 2 The phase phi is obtained by the Fresnel diffraction forward transformation.
Combining the phase psi and the phase phi to obtain a second decrypted phase template D2, i.e.
D 2 ＝e j(ψ-φ) (9)
As shown in fig. 5, a virtual light path is constructed, an encryption phase template E, and a first decryption phase template D1 and a second decryption phase template D2 corresponding to each color component of a scene i are placed on a specific plane of the virtual light path, and a three-dimensional scene i of each color component can be reconstructed by irradiating parallel light. And changing the decryption phase template pair to reconstruct each three-dimensional scene. And combining the R, G and B color channels of the three-dimensional scenes to obtain the colorful three-dimensional scene.
The reconstructed signal of the mth layer of the three-dimensional scene i in fig. 5 can be represented as:
the following is a detailed description of the specific effectiveness test of the present invention:
the quality of reconstructing a three-dimensional scene can be evaluated by the correlation coefficient, which is defined as equation (11).
Wherein O represents the original three-dimensional scene and R represents the reconstructed three-dimensional scene.
As shown in fig. 6, the original color image and depth map of three-dimensional scenes have an image size of 256 × 256 dots. And combining the color layered image of the histogram distribution characteristic of the depth map and the kinoform of the R, G and B color channels generated by the phase recovery algorithm. As shown in fig. 7, the distances between the kinoform plane and the three object field levels in the scene 1 are: 494.1mm,489.6mm and 485.6mm; the distances between the kinoform plane and the three object field levels in scene 2 are: 493.7mm,489.8mm,484.7mm; distances between the kinoform plane and the three object field layer planes in the scene 3 are respectively as follows: 498.4mm;495.8mm;491.1mm; the wavelength λ was 532nm.
As shown in fig. 8, a common encrypted phase template containing the three-dimensional scenes of fig. 6 is 256 × 256 dots in size. The reconstructed signals of each layer of the three-dimensional scenes recovered by the decrypted phase templates corresponding to the three-dimensional scenes are shown in fig. 9, and the focusing layer is clear, the non-focusing layer is fuzzy and conforms to the characteristics of holographic three-dimensional display.
The correlation coefficients between the reconstructed three-dimensional scene and the original three-dimensional scene are calculated as shown in table 1.
TABLE 1 decrypted three-dimensional scene and original three-dimensional scene correlation coefficients
Decrypting phase template D using errors 1 The resulting reconstructed image of the three-dimensional scene 1 is shown in fig. 10.
As shown in fig. 11, a reconstructed image of the three-dimensional scene 1, which is horizontally cut by 1/16, of the phase template E is encrypted.
As shown in fig. 12, the diffraction distances of the encrypted phase template E after superposition of gaussian noise with a mean of 0 and a variance of 0.001 are 494.1mm,489.6mm, and 485.6mm respectively to reconstruct an image of the three-dimensional scene 1.
As shown in fig. 13, the reconstructed image of scene 1 is reconstructed when the reconstruction distance parameter Z2 deviates by 2%.
As shown in fig. 14, scene 1 reconstructs an image when the decrypted reconstruction distance parameter Z1 deviates by 2%.
As shown in fig. 15, when the wavelength of the plane wave for irradiation deviates by 2% in the reconstructed virtual optical path, the reconstructed image of the scene 1 is obtained.
By adopting the technical scheme, in order to solve the safety problem of the digital works bearing the complex three-dimensional scenes, layered images corresponding to R, G and B color components are formed for each complex three-dimensional scene according to the color and the depth of the complex three-dimensional scene, an improved phase recovery algorithm is used for generating a kinoform for the layered images corresponding to each color component of each three-dimensional scene, and the kinoform shows the characteristic of random signals. And multiplying the light wave signal of each kinoform plane by a random sign function to form the light wave signal with noise interference. Multiplying the kinoform plane light wave signals with noise interference from different three-dimensional scenes and different color channels to form a composite light wave signal containing a plurality of three-dimensional scenes; the composite lightwave signal is decomposed into two phase functions, one of the two phase functions is used as a common encryption phase template, and the other phase function is combined with the interference suppression signal to form a phase function for decryption. And calculating Fresnel inverse diffraction of specific wavelength and distance by using a phase function for decryption to obtain amplitude and phase, wherein a phase recovery algorithm is applied to the amplitude to generate a first decryption phase template, and the phase and the first decryption phase template are combined by a phase formed by forward Fresnel diffraction to form a second decryption phase template. By placing the encryption phase template and the first and second decryption phase templates in the form of the cascade structure at the specific position of the virtual light path, each color component of the three-dimensional scene can be decrypted, and the color three-dimensional scene can be restored by combining the R, G and B color components. The test result shows that the method has good safety and robustness, the reconstruction of the three-dimensional scene fails due to mismatching of wrong decryption phase templates or reconstruction parameters, and the three-dimensional scene can still be reconstructed under the condition that the encryption phase templates are sheared and superimposed with Gaussian noise with certain intensity. The method can be widely applied to the field of data confidentiality.
Claims (7)
1. A multiple complex three-dimensional scene encryption and decryption method is characterized in that: the method comprises an encryption step and a decryption step, and specifically comprises the following steps: an encryption step:
s11) determining the number of layers according to the histogram characteristics of the depth map, taking the average depth value of each layer of objects as a depth value, and converting the depth value into a Fresnel diffraction distance between the object layer and the kinoform plane;
s12) generating kinoforms respectively corresponding to R, G and B color channels by using a one-to-many planar improved phase recovery algorithm, wherein the kinoforms show random signal characteristics; the specific method of step S12) is:
step S12-1) setting the kinoform plane as an initial pure phase function, and respectively calculating the wavelength as lambda and the distance as d i Obtaining diffraction light wave complex signals of the three-dimensional scene layers from 1 to M;
step S12-2) replacing the amplitude in the complex signal with the object field information image of the corresponding layer for the diffraction light wave complex signal of each layer, and reserving the phase to obtain the diffraction light wave signal of each layer after amplitude constraint;
step S12-3) calculating Fresnel diffraction on signals of each layer after amplitude constraint to obtain complex amplitude signals of an kinoform plane;
step S12-4) averaging the complex amplitude signals of the kinoform plane, reserving the phase and modulating the amplitude of the phase to be 1 to obtain a pure phase function;
step S12-5) the pure phase function is used as the next initial object wave function for re-iteration until the algorithm converges or the iteration times are reached;
s13) multiplying the light wave distribution of each kinoform plane by a random sign function to form a kinoform plane light wave distribution signal with noise interference;
s14) multiplying the noise-interfered kinoform plane light wave distribution signals from different three-dimensional scenes and different color channels to form a composite light wave signal containing a plurality of three-dimensional scenes;
s15) decomposing the composite lightwave signal into two phase functions for multiplication, taking one of the phase functions as a common encryption phase template, and combining the other phase function with an interference suppression signal to form a phase function for decryption;
s16) calculating Fresnel inverse diffraction of specific wavelength and distance on a phase function for decryption to obtain amplitude and phase, wherein the amplitude is used for a phase recovery algorithm to generate a first decryption phase template, and the phase and a phase signal formed by forward diffraction of parameters in a GSA algorithm of the first decryption phase template are combined to form a second decryption phase template;
and a decryption step:
s21) building a virtual light path, and respectively placing a public encryption phase template in a cascade structure form and a first decryption phase template and a second decryption phase template corresponding to a single color component for decrypting the three-dimensional scene on a specific plane of the virtual light path;
s22) calculating a diffraction image of a specific observation surface in a virtual light path under the irradiation of parallel light, obtaining a single color component reconstructed image of an original three-dimensional scene and storing the reconstructed image;
s23) changing the first and second decryption phase template pairs to obtain R, G and B color component reconstructed images of each three-dimensional scene and storing the R, G and B color component reconstructed images;
s24) combining the R, G and B color component reconstructed images of the three-dimensional scenes to obtain a color three-dimensional scene reconstructed image.
2. The multiple complex three-dimensional scene encryption and decryption method of claim 1, wherein: using [ D ] in step S11) 1 ，D 2 ]Indicating the depth interval of the i-th layer object, and taking the depth value of the layer
The Fresnel diffraction distance corresponding to the ith layer object field information is expressed by formula (1);
wherein d is min Represents the distance from the nearest object plane to the kinoform plane, d max Representing the distance from the farthest object plane to the kinoform plane.
3. The multiple complex three-dimensional scene encryption and decryption method of claim 1, wherein: the composite lightwave signal S (u, v) in step S14) is expressed by equation (2):
wherein s is 1R (u,v)...s NB (u, v) represent the random sign functions used for the three color channels R, G, B of the three-dimensional scene, respectively, exp () represents an exponential function, j represents an imaginary unit
Which represents the sum operation of the N terms,
and representing the phase corresponding to the R color component of the kth three-dimensional scene.
4. The multiple complex three-dimensional scene encryption and decryption method of claim 3, wherein: step S15) the composite lightwave signal S (u, v) is decomposed into two phase functions P 1 (u, v) and P 2 (u, v) multiplication, i.e.
S(u,v)＝P 1 (u,v)P 2 (u,v) (3)
Wherein
Function angle () represents the phase; p 1 (u, v) as common encryption phase template, i.e. encryption phase template
P 2 (u, v) are used in combination with the interference suppression signal to construct the decrypted phase templates D1 and D2 in the form of a concatenated structure.
5. The multiple complex three-dimensional scene encryption and decryption method of claim 4, wherein: the phase function D (u, v) decrypted in step S15) is represented as:
D(u,v)＝P 2 (u,v)I(u,v)
wherein I (u, v) represents an interference suppression signal.
6. The multiple complex three-dimensional scene encryption and decryption method of claim 5, wherein: the specific steps of step S16) are as follows:
step S16-1) of calculating the wavelength of the combined signal D (u, v) as lambda and the distance as Z 1 The inverse fresnel diffraction transformation of (a) to obtain the amplitude a and the phase ψ, as shown in equation (6),
wherein the symbol IFrT represents the inverse fresnel diffraction transform;
step S16-2) uses the wavelength of lambda and the distance of Z for the amplitude A 2 The Fresnel domain phase recovery algorithm generates a first decrypted phase template e jθ I.e. the first decryption phase template e jθ And the amplitude A satisfies the formula (7):
wherein the symbol "|" indicates taking amplitude operation, e jθ As a first decryption phase template, i.e. a first decryption phase template D 1 ＝e jθ ；
Step S16-3) for the first decrypted phase template e jθ The parameters are calculated as wavelength λ and distance Z 2 The phase phi is obtained by the fresnel diffraction forward transformation of (1), as shown in equation (8),
step S16-3) combining the phase psi and the phase phi to obtain a second decrypted phase template D2, i.e. D 2 ＝e j(ψ-φ) 。
7. The multiple complex three-dimensional scene encryption and decryption method of claim 6, wherein: the reconstructed signal of the mth layer of the three-dimensional scene i in the step S24) is represented as:
wherein D is 1 Representing a first decrypted phase template, D 2 Representing a second decrypted phase template, E representing a common encrypted phase template, symbol
Denotes the wavelength λ and the distance d m Fresnel diffraction positive transformation, sign
Denotes the wavelength λ and the distance z 1 Fresnel diffraction positive transformation, sign
Denotes a wavelength of λ and a distance of z 2 The fresnel diffraction forward transform.
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