CN114936375A - Asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition - Google Patents
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Abstract
The invention discloses an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, and belongs to the technical field of optical instruments. The invention comprises a phase truncation Fourier transform encryption module and a two-dimensional empirical mode decomposition module. The phase truncation Fourier transform encryption module is used for carrying out asymmetric encryption processing on the plane wave carrying object information, and extracting phases to be used as two phase private keys. The two-dimensional empirical mode decomposition encryption module performs two-dimensional empirical mode decomposition on a repeated value encrypted image, decomposes the image into a plurality of components, and selects the component with the least information amount as a double encrypted image, so that the dimensionality of a key space is improved. The invention can improve the statistical attack resistance and the iterative attack resistance of the optical encryption system and improve the safety and the robustness of the asymmetric integrated optical encryption system. The invention combines the liquid crystal spatial light modulator to assist control to realize a pure optical asymmetric integrated optical encryption system, and improves the flexibility and accuracy of the encryption system.
Description
Technical Field
The invention relates to an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, which is particularly suitable for the information security fields of optical encryption, optical information hiding, optical authentication and the like and belongs to the technical field of optical instruments.
Background
Optical encryption technology has received increasing attention in the information security and optics fields due to its parallel signal processing and high dimensional wavefront adjustment capabilities. Since the optical encryption system based on dual random phase encoding was proposed in 1995, many optical encryption systems based on dual random phase encoding but employing different transform domains have been developed, such as: fractional fourier transform optical encryption systems, fresnel diffractive optical encryption systems, linear regularized optical encryption systems, and the like. However, due to the inherent linearity and symmetry of these systems, they are easily cracked by specific attack means, and the optical devices corresponding to the transform domain are expensive and have poor practicability, so that they are difficult to be effectively popularized.
The present invention relates to a method for encrypting an asymmetric optical image based on cylindrical diffraction transformation and equivalent mode decomposition, which is similar to the present invention in China, and is called as "an asymmetric optical image encryption method based on cylindrical diffraction transformation and equivalent mode decomposition", and is called as CN201811212721.3, and the method is characterized in that a complex amplitude image encrypted by a cylindrical lens is decomposed into two complex amplitude mask images, the amplitude of the equivalent film decomposition is calculated according to a specific formula as a ciphertext, the phase angle of a first mask is used as a public key, the phase angle of a second mask is used as a private key, but before the module decomposition, the phase of one mask needs to be given to the complex amplitude image, and then the other mask is obtained by the module decomposition rule decomposition, and once an attacker knows the corresponding private key as the public key, the encoding method is complicated and the security is difficult to guarantee. In addition, although the patent adopts the concept of mode decomposition, how to perform equivalent mode decomposition on a complex amplitude image in an actual optical system is not described, the equivalent mode decomposition part is realized in computer processing, namely a virtual optical process, and optical information processing is not performed by using the actual optical system, the speed and the effect of the whole encryption-decryption mainly depend on hardware performance, the real situation of optical spatial transmission and processing is not considered, and the integrated design of the optical-mechanical system cannot be realized.
Disclosure of Invention
The invention mainly aims to provide an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, which utilizes phase truncation Fourier transform and two-dimensional empirical mode decomposition to realize double encryption of plaintext information, improves the statistical attack resistance and iterative attack resistance of the optical encryption system, and further improves the safety and robustness of the asymmetric integrated optical encryption system. On the basis, the pure optical asymmetric integrated optical encryption system is realized by combining with the auxiliary control of the liquid crystal spatial light modulator, and the flexibility and the accuracy of the encryption system are improved.
The purpose of the invention is realized by the following technical scheme:
the invention discloses an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition. The phase truncation Fourier transform encryption module is used for carrying out asymmetric encryption processing on the plane wave carrying object information, extracting phases as two phase private keys and obtaining a repeated value encrypted image. The two-dimensional empirical mode decomposition encryption module is used for carrying out two-dimensional empirical mode decomposition on a repeated real value encrypted image, decomposing the repeated real value encrypted image into a plurality of components, selecting the component with the least information amount as a repeated encrypted image, and using the rest components as keys, thereby improving the dimensionality of a key space.
The phase truncation Fourier transform encryption module is used for carrying out phase truncation Fourier transform on plaintext information, asymmetric encryption processing is carried out on plane waves carrying object information, random phase superposition of [0,2 pi ] is realized on an incident parallel plane light beam in a space domain, then the phase of complex amplitude after Fourier transform is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted. The amplitude of the reserved complex amplitude realizes [0,2 pi ] random phase superposition on a frequency spectrum surface, then the random phase superposition is subjected to inverse Fourier transform to a space domain, the phase of the complex amplitude at the moment is extracted from a parallel plane light beam after the inverse Fourier transform to the space domain to be used as a private key, and the amplitude part of the complex amplitude is reserved to be used as a repeated value encrypted image. And performing two-dimensional empirical mode decomposition on a repeated real value encrypted image output by the phase truncation Fourier transform encryption module through a two-dimensional empirical mode decomposition encryption module, decomposing the repeated real value encrypted image into a plurality of components, selecting the component with the least information amount as a double encrypted image, and using the rest components as keys. By introducing the two-dimensional empirical mode decomposition encryption module, the repeated value encrypted image can be decomposed in a targeted manner, a component key can be generated, the key space dimension of the asymmetric optical encryption system is increased, and the iterative attack resistance of the optical encryption system is improved. The flexibility and the accuracy of the encryption system are improved by decomposing the liquid crystal spatial light modulator in the encryption module by using a two-dimensional empirical mode. The secret keys comprise random phase secret keys generated by a phase truncation Fourier transform encryption module and component secret keys generated by two-dimensional empirical mode decomposition, and the two secret keys are respectively used as a private key and a public key of the asymmetric optical encryption system. Plaintext information is subjected to double encryption by a phase truncation Fourier transform encryption module and a two-dimensional empirical mode decomposition encryption module to obtain a stable double-encrypted image which accords with the statistical characteristic of white noise, the statistical attack resistance and the iterative attack resistance of the optical encryption system are improved, and the safety and the robustness of the asymmetric integrated optical encryption system are further improved.
An optical encryption system that decomposes complex amplitude encrypted images by a computer through a virtual optical process cannot be realized based on a pure optical path. The two-dimensional empirical mode decomposition encryption module can decompose a double-real-value encrypted image and load each component obtained by decomposition of a computer into the liquid crystal spatial light modulator, corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, and the output plane light waves only carry component information with the minimum information content, so that double encryption is realized. The phase truncation Fourier transform encryption module and the two-dimensional empirical mode decomposition encryption module can be realized on the basis of a pure optical path and virtual optics, and preferably, the phase truncation Fourier transform encryption module and the two-dimensional empirical mode decomposition encryption module are realized on the basis of a pure optical path.
The phase truncation Fourier transform encryption module comprises a laser light source, a light beam expander, a first random phase plate, a first Fourier lens, a second random phase plate and a second Fourier lens, wherein narrow beams of laser light emitted by the laser light source are expanded and collimated by the light source expander to form parallel plane light beams with a larger caliber, the output parallel plane light beams enter the phase truncation Fourier transform encryption module to be subjected to asymmetric encryption processing, the first Fourier lens and the second Fourier lens form a conventional 4f optical information processing system, the two independent first random phase plate and the second random phase plate which accord with white noise distribution perform phase modulation on a space domain and a frequency domain of information, are respectively arranged on a front focal plane and a spectrum transformation plane of the first Fourier lens to serve as important components of the truncation phase Fourier transform encryption module, and the phases of the first random phase plate and the second random phase plate are extracted to serve as private keys of the asymmetric optical encryption system, its amplitude is retained as a re-encrypted image output.
The two-dimensional empirical mode decomposition encryption module comprises a first liquid crystal spatial light modulator, a second liquid crystal spatial light modulator, a third liquid crystal spatial light modulator and a CCD detector, wherein a re-encrypted image passing through the phase truncation Fourier transform encryption module is regarded as a two-dimensional signal, the two-dimensional empirical mode decomposition is carried out on the two-dimensional signal to obtain a plurality of components, the component image with the minimum information content is selected as a final ciphertext, the rest components are used as public keys in an asymmetric optical encryption system and are respectively loaded into the first liquid crystal spatial light modulator, the second liquid crystal spatial light modulator and the third liquid crystal spatial light modulator, the corresponding components are reduced when parallel plane light beams pass through the liquid crystal spatial light modulators, and finally output plane light waves only carry the component with the weakest information and are received by the CCD detector to obtain a double-encrypted image.
The invention discloses a working method of an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, which comprises the following steps: the laser light source is used as a coherent light source of the optical encryption system to emit a thin laser beam with a smaller caliber; the light source beam expander consists of a collimation and beam expansion lens group with positive focal power, and narrow-beam laser forms parallel plane light beams with larger caliber after being expanded and collimated by the light source beam expander and enters the phase truncation Fourier transform encryption module; the phase truncation Fourier transform encryption module is a 4f optical information processing system mainly composed of a first random phase plate, a first Fourier lens, a second random phase plate and a second Fourier lens, wherein the first random phase plate is located on a front focal plane of the first Fourier lens, the second random phase plate is located on a frequency spectrum plane of the first Fourier lens, the two random phase plates are mutually independent and accord with random white noise distribution, incident parallel plane light beams pass through the first random phase plate, so that [0,2 pi ] random phase superposition is realized on a space domain, then Fourier transform is carried out on the space domain through the first Fourier lens to the frequency domain, then the phase of complex amplitude after Fourier transform is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted. The amplitude of the reserved complex amplitude passes through a second random phase plate on a frequency spectrum surface to realize [0,2 pi ] random phase superposition on a frequency domain, then a second Fourier lens performs inverse Fourier transform from the frequency domain to a space domain, the phase of the complex amplitude at the moment is extracted from a parallel plane beam after the inverse Fourier transform is performed on the parallel plane beam to the space domain to serve as a private key, and the amplitude part of the complex amplitude is reserved as a repeated value encrypted image, so that the condition of two-dimensional empirical mode decomposition can be met; the two-dimensional empirical mode decomposition encryption module mainly comprises a first liquid crystal spatial light modulator, a second liquid crystal spatial light modulator, a third liquid crystal spatial light modulator and a CCD detector, a re-encrypted image is regarded as a two-dimensional signal, the signal can be decomposed by using the two-dimensional empirical mode, various frequency components in data can be effectively separated in a self-adaptive mode, the mean value envelope of the two-dimensional signal is calculated in a computer, the original signal is subtracted from the mean value envelope to obtain a residual quantity, if the residual quantity meets a preset screening criterion, a first-order component of the original signal is obtained, and the process is repeated until the residual quantity is a monotonic function or a constant. Performing two-dimensional empirical mode decomposition on the re-encrypted image by a two-dimensional empirical mode decomposition module to obtain a plurality of component images, taking the component image with the minimum information content as the final output, the other components are used as public keys in an asymmetric optical encryption system and are respectively loaded into a first liquid crystal spatial light modulator, a second liquid crystal spatial light modulator and a third liquid crystal spatial light modulator through a computer, the corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, the finally output plane light waves only carry the components with the minimum information content, double encryption is realized, a double encrypted image is received by a CCD detector, and a stable double encrypted image which accords with the statistical characteristics of white noise is finally obtained, therefore, the statistical attack resistance and the iterative attack resistance of the optical encryption system are improved, and the safety and the robustness of the asymmetric integrated optical encryption system are further improved.
Preferably, the phase-truncated fourier transform encryption module performs phase-truncated fourier transform on plaintext information, and the implementation method is as follows:
the plane wave carrying object plaintext information is subjected to asymmetric encryption processing, random phase superposition of [0,2 pi ] is realized on a space domain by incident parallel plane light beams, then the phase of complex amplitude after Fourier transform is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted, namely:
g(u,v)＝PT{FT[I(x,y)R(x,y)]}
P(u,v)＝PR{FT[I(x,y)R(x,y)]}
wherein: i (x, y) is a parallel plane beam carrying plaintext information, R (x, y) is a random phase in the spatial domain with values in the range [0,2 π ], FT [. cndot. ] represents a Fourier transform operation, PT {. cndot.. cndot. ] represents a phase truncation operation, g (u, v) represents an amplitude component of the output complex amplitude, PR {. cndot. ] represents a phase preservation operation, and P (u, v) represents a phase component of the output complex amplitude, i.e., a first phase key.
The amplitude of the reserved complex amplitude realizes random phase superposition of [0,2 pi ] on a frequency spectrum plane, then is transformed to a space domain through inverse Fourier transform, the phase of the complex amplitude at the moment is extracted from a parallel plane light beam transformed to the space domain through inverse Fourier transform and is used as a private key, and the amplitude part of the complex amplitude is reserved as a repeated value encrypted image, namely:
g(x,y)＝PT{IFT[g(u,v)R'(u,v)]}
P'(x,y)＝PR{IFT[g(u,v)R'(u,v)]}
wherein: r '(u, v) is a random phase in the frequency domain and takes values in the range of [0,2 π ], IFT [. cndot. ] represents an inverse Fourier transform operation, g (x, y) represents the amplitude portion of the output complex amplitude, i.e., a reconstructed value encrypted image, and P' (x, y) represents the phase portion of the output complex amplitude, i.e., a second phase key.
Preferably, the two-dimensional empirical mode decomposition encryption module performs two-dimensional empirical mode decomposition on a truthful value encrypted image, and the implementation method is as follows:
a two-dimensional empirical mode can be utilized to decompose signals by considering a repeated real value encrypted image as a two-dimensional signal, various frequency components in data can be effectively separated in a self-adaptive manner, and the maximum value and the minimum value of a two-dimensional signal envelope surface are calculated in a computer and are respectively recorded as g MAX (x) And g MIN (x) Taking the mean value of them as the mean envelope of a double-real-valued encrypted image, namely:
subtracting the average envelope from the original signal to obtain a residual amount, and if the residual amount meets a preset screening criterion, obtaining a first-order component of the original signal, namely:
D 1 (x,y)＝g(x,y)-g 1 (x,y)
wherein: d i (x, y) is the residual amount, D 1 (x, y) is the first-stage residue, SD is the screening criterion, SD is generally less than or equal to 0.3, if D is 1 (x, y) satisfying the sieving criteria, then defining
The first order component image is encrypted as a recomputed value.
Then C is added 1 (x, y) separating the remainder R from a reconstructed value encrypted image 1 (x, y), namely:
R 1 (x,y)＝g(x,y)-C 1 (x,y)
then, the remainder is used as a new signal, the above process is repeated until the remainder is a monotonic function or constant, and finally a recomputed encrypted image is decomposed into:
and performing two-dimensional empirical mode decomposition on the one-repeated-value encrypted image through a two-dimensional empirical mode decomposition module to obtain a plurality of component images, taking the component image with the minimum information content as final output, and taking the rest components as public keys in the asymmetric optical encryption system, thereby realizing double encryption.
Has the advantages that:
1. the invention discloses an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, which adopts a method of combining phase truncation Fourier transform and two-dimensional empirical mode decomposition to carry out double encryption on plaintext information, tightly combines optical encryption and two-dimensional signal processing, increases the key space dimension of the asymmetric optical encryption system, improves the statistical attack resistance and iterative attack resistance of the optical encryption system, further improves the safety and robustness of the asymmetric integrated optical encryption system, and can improve the operability of the optical encryption system.
2. In the prior art, an optical encryption system for decomposing a complex amplitude encrypted image through a virtual optical process by using a computer cannot be realized based on a pure optical path. The invention discloses an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, wherein a re-encrypted image output by a phase truncation Fourier transform encryption module is a real-valued image, the two-dimensional empirical mode decomposition encryption module can decompose the re-real-valued encrypted image and load each component obtained by decomposition by a computer into a liquid crystal spatial light modulator, corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, and the output plane light waves only carry component information with the minimum information quantity, so that double encryption is realized. The asymmetric integrated optical encryption system can be realized based on a pure optical path by reasonably matching optical elements such as the transmission type liquid crystal spatial light modulator, the Fourier lens, the random phase plate and the like, and has the advantages of easy realization of integrated design and strong popularization.
3. The asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition disclosed by the invention utilizes the characteristic that a transmission type liquid crystal spatial light modulator is flexible and controllable to ensure that each component image can be accurately loaded in a two-dimensional empirical mode decomposition encryption module, and the quantity of the component images can be changed according to specific requirements, so that the flexibility and the accuracy of the encryption system are improved, and the system is simple in structure and strong in expansibility.
Drawings
Fig. 1 is an optical structural diagram of an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition according to the present invention.
Fig. 2a is a plaintext image to be encrypted in an experiment.
Fig. 2b is a random phase plate 1.
Fig. 2c is a random phase plate 2.
Fig. 2d is a re-encrypted image that has been subjected to a phase truncated fourier transform encryption module.
Fig. 3 is a two-dimensional empirical mode decomposed double encrypted image.
Fig. 4 is a statistical distribution characteristic of a double encrypted image.
Figure 5a is private key 1.
Figure 5b is private key 2.
Fig. 5c is public key 1.
Figure 5d is public key 2.
Fig. 5e is public key 3.
Fig. 6 is a correctly decrypted image.
Fig. 7 is an error-decrypted image that passes directly through a phase-truncated fourier transform decryption module without passing through a two-dimensional empirical mode decomposition decryption module.
Fig. 8a is a cracked image of a classical two-step phase iterative cracking method for cracking an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition.
Fig. 8b is a first step iteration process for breaking the asymmetric integrated optical encryption system based on the two-dimensional empirical mode decomposition by the classical two-step phase iterative cracking method.
FIG. 8c is a second iteration process for a classical two-step phase iterative cracking method to crack an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition
Wherein: the system comprises a laser light source 1, a light source beam expander 2, a first random phase plate 3, a first Fourier lens 4, a second random phase plate 5, a second Fourier lens 6, a first liquid crystal spatial light modulator 7, a second liquid crystal spatial light modulator 8, a third liquid crystal spatial light modulator 9, a CCD detector 10 and a computer 11.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1:
the embodiment is as follows: as shown in fig. 1, in the asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition disclosed in this embodiment, a laser light source 1 is used as a coherent light source of the optical encryption system to emit a thin laser beam with a small aperture; the light source beam expander 2 consists of a collimation beam expanding lens group with positive focal power, narrow-beam laser forms a parallel plane light beam with a larger caliber after being expanded and collimated by the light source beam expander 2, and the light beam enters a phase truncation Fourier transform encryption module after passing through a plaintext image to be encrypted, wherein the plaintext image is shown in figure 2 a; the phase truncation Fourier transform encryption module is a 4f optical information processing system mainly composed of a first random phase plate 3, a first Fourier lens 4, a second random phase plate 5 and a second Fourier lens 6, the two random phase plates are respectively shown in FIG. 2b and FIG. 2c, wherein the first random phase plate 3 is positioned on the front focal plane of the first Fourier lens 4, the second random phase plate 5 is positioned on the frequency spectrum plane of the first Fourier lens 4, the two random phase plates are mutually independent and accord with random white noise distribution, the incident parallel plane light beam passes through the first random phase plate 3, therefore, random phase superposition of [0,2 pi ] is realized in a space domain, then Fourier transformation is carried out from the space domain to the frequency domain through the first Fourier lens 4, then the phase of complex amplitude after Fourier transformation is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted. The amplitude of the reserved complex amplitude passes through a second random phase plate 5 on a frequency spectrum surface to realize random phase superposition of [0,2 pi ] on a frequency domain, then a second Fourier lens 6 carries out inverse Fourier transform from the frequency domain to a space domain, the phase of the complex amplitude at the moment is extracted from a parallel plane beam after the inverse Fourier transform is carried out on the parallel plane beam to the space domain to be used as a private key, the amplitude part of the complex amplitude is reserved to be used as a repeated value encrypted image, one repeated encrypted image is shown as figure 2d, two phase private keys are shown as figures 5a and 5b, and the obtained repeated encrypted image can meet the condition of two-dimensional empirical mode decomposition; the two-dimensional empirical mode decomposition encryption module mainly comprises a first liquid crystal spatial light modulator 7, a second liquid crystal spatial light modulator 8, a third liquid crystal spatial light modulator 9 and a CCD detector 10, a two-dimensional signal can be decomposed by using a two-dimensional empirical mode by regarding a re-encrypted image as the two-dimensional signal, various frequency components in data can be effectively separated in a self-adaptive mode, the mean value envelope of the two-dimensional signal is calculated in a computer, the mean value envelope is subtracted from the original signal to obtain a residual quantity, if the residual quantity meets a preset screening criterion, a first-order component of the original signal is obtained, and the process is repeated until the residual quantity is a monotonic function or a constant. The method comprises the steps of carrying out two-dimensional empirical mode decomposition on a re-encrypted image through a two-dimensional empirical mode decomposition module to obtain four component images, taking the component image with the minimum information content as final output, taking the other three components as public keys in an asymmetric optical encryption system, respectively loading the public keys into a first liquid crystal spatial light modulator 7, a second liquid crystal spatial light modulator 8 and a third liquid crystal spatial light modulator 9 through a computer, reducing corresponding components when parallel plane light beams pass through the liquid crystal spatial light modulators, enabling the finally output plane light waves to only carry the component with the minimum information content, achieving double encryption, receiving the double encrypted image through a CCD detector 10, and displaying the double encrypted image in a mode shown in FIG. 3, wherein three public keys obtained through the two-dimensional empirical mode decomposition are shown in FIGS. 5c, 5d and 5 e. As shown in fig. 4, the statistical properties of the finally obtained double encrypted image are in accordance with white noise distribution, so that the statistical attack resistance and iterative attack resistance of the optical encryption system are improved, and the security and robustness of the asymmetric integrated optical encryption system are further improved.
Fig. 6 shows a correct decrypted image of an asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition, where the decryption process is the inverse process of the encryption process, and a CC (Correlation Coefficient) between an original image and the decrypted image is used to indicate the correct degree of the decrypted image, and a CC closer to 1 indicates that the information loss of the encryption and decryption system is less, and the CC of the decrypted image and the original image finally obtained in this embodiment reaches 1, that is, complete decryption is implemented without losing any information.
Fig. 7 shows an error decryption image obtained by directly passing through a phase truncation fourier transform decryption module without passing through a two-dimensional empirical mode decomposition decryption module, where the CC value of the error decryption image with an original image is 0.5292, which indicates that only a double encryption image with the least information amount cannot obtain valid information through the phase truncation fourier decryption module, and the introduction of the two-dimensional empirical mode decomposition encryption module enhances the security of the asymmetric encryption system.
Fig. 8a shows an error decryption image cracked by a classical two-step phase iterative cracking method in the asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition disclosed in this embodiment. The classical phase iterative decryption method has obvious decryption effect on the traditional optical encryption system based on phase truncation Fourier transform, but the decrypted image of the method in the embodiment cannot obtain effective information, namely the method has strong capacity of resisting iterative attack. As shown in fig. 8b and 8c, the first and second iterative processes of the asymmetric integrated optical encryption system for breaking the two-dimensional empirical mode decomposition by the classical two-step phase iterative solution are respectively the first and second iterative processes, and although the iterative processes can converge, the final iteration result is the iterative recovery result of the component image with the least amount of information, so that effective information cannot be obtained.
The above detailed description is further intended to illustrate the objects, technical solutions and advantages of the present invention, and it should be understood that the above detailed description is only an example of the present invention and should not be used to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. An asymmetric integrated optical encryption system based on two-dimensional Empirical Mode Decomposition (EMD), comprising: the device comprises a phase truncation Fourier transform encryption module and a two-dimensional empirical mode decomposition module; the phase truncation Fourier transform encryption module is used for carrying out asymmetric encryption processing on the plane wave carrying object information, extracting phases as two phase private keys and obtaining a repeated value encrypted image; the two-dimensional empirical mode decomposition encryption module is used for carrying out two-dimensional empirical mode decomposition on a repeated real value encrypted image, decomposing the repeated real value encrypted image into a plurality of components, selecting the component with the least information amount as a repeated encrypted image, and using the rest components as keys, thereby improving the dimensionality of a key space.
2. An asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition (emp) as claimed in claim 1 wherein: the phase truncation Fourier transform encryption module is used for carrying out phase truncation Fourier transform on plaintext information, asymmetric encryption processing is carried out on plane waves carrying object information, random phase superposition of [0,2 pi ] is realized on an incident parallel plane light beam in a space domain, then the phase of complex amplitude after Fourier transform is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted; the amplitude of the reserved complex amplitude realizes [0,2 pi ] random phase superposition on a frequency spectrum plane, then is transformed to a space domain through inverse Fourier transform, the phase of the complex amplitude at the moment is extracted from a parallel plane light beam transformed to the space domain through inverse Fourier transform and is used as a private key, and the amplitude part of the complex amplitude is reserved as a repeated value encrypted image; performing two-dimensional empirical mode decomposition on a repeated real value encrypted image output by the phase truncation Fourier transform encryption module through a two-dimensional empirical mode decomposition encryption module, decomposing the repeated real value encrypted image into a plurality of components, selecting the component with the least information amount as a double encrypted image, and using the rest components as keys; by introducing the two-dimensional empirical mode decomposition encryption module, the repeated real value encrypted image can be decomposed in a targeted manner, a component key can be generated, the key space dimension of the asymmetric optical encryption system is increased, and the iterative attack resistance of the optical encryption system is improved; the flexibility and the accuracy of an encryption system are improved by utilizing a liquid crystal spatial light modulator in a two-dimensional empirical mode decomposition encryption module; the secret key comprises a random phase secret key generated by a phase truncation Fourier transform encryption module and each component secret key generated by two-dimensional empirical mode decomposition, and the two secret keys are respectively used as a private key and a public key of the asymmetric optical encryption system; plaintext information is subjected to double encryption by a phase truncation Fourier transform encryption module and a two-dimensional empirical mode decomposition encryption module to obtain a stable double-encrypted image which accords with the statistical characteristic of white noise, so that the statistical attack resistance and iterative attack resistance of the optical encryption system are improved, and the safety and the robustness of the asymmetric integrated optical encryption system are further improved;
an optical encryption system which decomposes complex amplitude encrypted images through a virtual optical process by using a computer cannot be realized based on a pure optical path; the two-dimensional empirical mode decomposition encryption module can decompose a double-real-value encrypted image and load each component obtained by decomposition of a computer into the liquid crystal spatial light modulator, corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, and the output plane light waves only carry component information with the minimum information content, so that double encryption is realized.
3. An asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition (emp) as claimed in claim 2, wherein: the phase truncation Fourier transform encryption module and the two-dimensional empirical mode decomposition encryption module are realized on the basis of a pure optical path.
4. An asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition according to claim 2 or 3, characterized in that: the phase truncation Fourier transform encryption module comprises a laser light source (1), a light beam expander (2), a first random phase plate (3), a first Fourier lens (4), a second random phase plate (5) and a second Fourier lens (6), wherein narrow-beam laser emitted by the laser light source (1) is expanded by the light source expander (2) and collimated to form a parallel plane light beam with a larger caliber, the output parallel plane light beam enters the phase truncation Fourier transform encryption module to be subjected to asymmetric encryption, the first Fourier lens (4) and the second Fourier lens (6) form a conventional 4f optical information processing system, the two independent first random phase plate (3) and the second random phase plate (5) which accord with white noise distribution perform phase modulation on a space domain and a frequency domain of information, and the two independent first random phase plate (3) and the second random phase plate (5) are respectively arranged on a front focal plane and a spectrum transform plane of the first Fourier lens (4) to serve as a heavy phase truncation transform encryption module The component is required, the phase of the component is extracted to be used as a private key of the asymmetric optical encryption system, and the amplitude of the component is reserved to be used as a re-encrypted image to be output;
the two-dimensional empirical mode decomposition encryption module comprises a first liquid crystal spatial light modulator (7), a second liquid crystal spatial light modulator (8), a third liquid crystal spatial light modulator (9) and a CCD detector (10), wherein a double-encrypted image passing through the phase truncation Fourier transform encryption module is regarded as a two-dimensional signal, the two-dimensional empirical mode decomposition is carried out on the double-encrypted image to obtain a plurality of components, the component image with the minimum information content is selected as a final ciphertext, the rest components are used as public keys in an asymmetric optical encryption system and are respectively loaded into the first liquid crystal spatial light modulator (7), the second liquid crystal spatial light modulator (8) and the third liquid crystal spatial light modulator (9), the corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, and finally output plane light waves only carry the component with the weakest information and are received by the CCD detector (10), a double encrypted image is obtained.
5. An asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition (emp) as claimed in claim 4 wherein: the laser light source (1) is used as a coherent light source of an optical encryption system to emit a thin laser beam with a smaller caliber; the light source beam expander (2) consists of a collimation beam expanding lens group with positive focal power, and narrow-beam laser forms parallel plane light beams with larger apertures after being expanded and collimated by the light source beam expander (2) and enters the phase truncation Fourier transform encryption module; the phase truncation Fourier transform encryption module is a 4f optical information processing system mainly composed of a first random phase plate (3), a first Fourier lens (4), a second random phase plate (5) and a second Fourier lens (6), wherein the first random phase plate (3) is positioned on the front focal plane of the first Fourier lens (4), the second random phase plate (5) is positioned on the frequency spectrum plane of the first Fourier lens (4), the two random phase plates are mutually independent and accord with random white noise distribution, the incident parallel plane light beam passes through the first random phase plate (3), therefore, random phase superposition of [0,2 pi ] is realized in a space domain, then Fourier transformation is carried out from the space domain to the frequency domain through a first Fourier lens (4), then the phase of complex amplitude after Fourier transformation is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted; the amplitude of the reserved complex amplitude passes through a second random phase plate (5) on a frequency spectrum surface to realize random phase superposition of [0,2 pi ] on a frequency domain, then a second Fourier lens (6) carries out inverse Fourier transform from the frequency domain to a space domain, the phase of the complex amplitude at the moment is extracted from a parallel plane beam subjected to inverse Fourier transform to the space domain to be used as a private key, and the amplitude part of the complex amplitude is reserved to be used as a repeated value encrypted image, so that the condition of two-dimensional empirical mode decomposition can be met; the two-dimensional empirical mode decomposition encryption module mainly comprises a first liquid crystal spatial light modulator (7), a second liquid crystal spatial light modulator (8), a third liquid crystal spatial light modulator (9) and a CCD detector (10), a two-dimensional signal can be decomposed by using a two-dimensional empirical mode by regarding a re-encrypted image as the two-dimensional signal, various frequency components in data can be effectively separated in a self-adaptive mode, the mean value envelope of the two-dimensional signal is calculated in a computer, the original signal is subtracted by the mean value envelope to obtain a residual quantity, if the residual quantity meets a preset screening criterion, a first-order component of the original signal is obtained, and the process is repeated until the residual quantity is a monotonic function or a constant; the two-dimensional empirical mode decomposition module is used for carrying out two-dimensional empirical mode decomposition on the re-encrypted image to obtain a plurality of component images, the component image with the minimum information content is taken as the final output, the other components are used as public keys in an asymmetric optical encryption system and are respectively loaded into a first liquid crystal spatial light modulator (7), a second liquid crystal spatial light modulator (8) and a third liquid crystal spatial light modulator (9) through a computer, the corresponding components are reduced when parallel plane light beams pass through each liquid crystal spatial light modulator, finally the output plane light waves only carry the components with the minimum information quantity, double encryption is realized, a double encrypted image is received by a CCD detector (10), and finally a stable double encrypted image which accords with the statistical property of white noise is obtained, therefore, the statistical attack resistance and the iterative attack resistance of the optical encryption system are improved, and the safety and the robustness of the asymmetric integrated optical encryption system are further improved.
6. An asymmetric integrated optical encryption system based on two-dimensional Empirical Mode Decomposition (EMD) as claimed in claim 5 wherein: the phase truncation Fourier transform encryption module carries out phase truncation Fourier transform on plaintext information and has the following realization method,
the plane wave carrying object plaintext information is subjected to asymmetric encryption processing, random phase superposition of [0,2 pi ] is realized on a space domain by incident parallel plane light beams, then the phase of complex amplitude after Fourier transform is extracted as a private key, and the amplitude of the complex amplitude is kept to be continuously transmitted, namely:
g(u,v)＝PT{FT[I(x,y)R(x,y)]}
P(u,v)＝PR{FT[I(x,y)R(x,y)]}
wherein: i (x, y) is a parallel plane light beam carrying plaintext information, R (x, y) is a random phase in a space domain and has a value range of [0,2 pi ], FT [. cndot ] represents Fourier transform operation, PT {. cndot } represents phase truncation operation, g (u, v) represents an amplitude part of output complex amplitude, PR {. cndot } represents phase retention operation, and P (u, v) represents a phase part of the output complex amplitude, namely a first phase key;
the amplitude of the reserved complex amplitude realizes random phase superposition of [0,2 pi ] on a frequency spectrum surface, then the random phase superposition is subjected to inverse Fourier transform to a space domain, the phase of the complex amplitude at the moment is extracted from a parallel plane light beam after the inverse Fourier transform to the space domain to be used as a private key, and the amplitude part of the complex amplitude is reserved to be used as a repeated value encrypted image, namely:
g(x,y)＝PT{IFT[g(u,v)R'(u,v)]}
P'(x,y)＝PR{IFT[g(u,v)R'(u,v)]}
wherein: r '(u, v) is a random phase in the frequency domain and takes values in the range of [0,2 π ], IFT [. cndot. ] represents an inverse Fourier transform operation, g (x, y) represents the amplitude portion of the output complex amplitude, i.e., a reconstructed value encrypted image, and P' (x, y) represents the phase portion of the output complex amplitude, i.e., a second phase key.
7. An asymmetric integrated optical encryption system based on two-dimensional empirical mode decomposition (emp) as claimed in claim 6 wherein: the two-dimensional empirical mode decomposition encryption module carries out two-dimensional empirical mode decomposition on a repeated real value encrypted image, and the realization method is as follows,
a two-dimensional empirical mode can be utilized to decompose signals by considering a repeated real value encrypted image as a two-dimensional signal, various frequency components in data can be effectively separated in a self-adaptive manner, and the maximum value and the minimum value of a two-dimensional signal envelope surface are calculated in a computer and are respectively recorded as g MAX (x) And g MIN (x) Taking the mean value of them as the mean envelope of a double-real-valued encrypted image, namely:
subtracting the average value envelope from the original signal to obtain a residual amount, and if the residual amount meets a preset screening criterion, obtaining a first-order component of the original signal, namely:
D 1 (x,y)＝g(x,y)-g 1 (x,y)
wherein: d i (x, y) is the residual amount, D 1 (x, y) is the first-stage residue, SD is the screening criterion, SD is generally less than or equal to 0.3, if D is 1 (x, y) satisfying the sieving criteria, then defining
A first order component image as a recomputed encrypted image;
then C is added 1 (x, y) separating the remainder R from a reconstructed value encrypted image 1 (x, y), namely:
R 1 (x,y)＝g(x,y)-C 1 (x,y)
then using the remainder as a new signal, repeating the above process until the remainder is a monotonic function or constant, and finally decomposing a recomputed encrypted image into:
and performing two-dimensional empirical mode decomposition on the one-repeated-value encrypted image through a two-dimensional empirical mode decomposition module to obtain a plurality of component images, taking the component image with the minimum information content as final output, and taking the rest components as public keys in the asymmetric optical encryption system, thereby realizing double encryption.
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