Metasurface unit based on electromagnetic physical dimension joint encryption, metasurface and holographic encryption method

Abstract

The invention discloses a metasurface unit based on electromagnetic physical dimension joint encryption, a metasurface and a holographic encryption method, and relates to the technical field of metasurface encryption. The invention aims to solve the problem that the existing secret sharing encryption strategy limits the information capacity and endangers the security of secret information. The metasurface unit comprises a substrate, a split ring resonator and an open slot resonator, wherein the split ring resonator and the open slot resonator are located on the substrate. A plurality of metasurface units which are closely arranged in a rectangular array form a metasurface. Encrypting the to-be-encrypted image by using a chaos algorithm to generate a chaos sequence; performing XOR operation on a to-be-encrypted image and the chaos sequence to generate a ciphertext image; an incident polarization key, a system security key and a ciphertext image are simultaneously coded to different physical dimensions of a metasurface through amplitudes and phases, so that the password image and the key are embedded into four amplitude and phase channels of electromagnetic waves at different spatial positions at two different working frequencies when different polarization incidence is carried out, and encryption is completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metasurface encryption, and particularly relates to electromagnetic structure design. Background Art

[0002] With the rapid development of wireless communication technologies, especially in the fields of the Internet of Things, 6G networks, and intelligent healthcare, the demand for information security has been continuously increasing. In recent years, protecting information by leveraging the multi-dimensional attributes of electromagnetic wavefronts (such as amplitude, phase, wavelength, and polarization) has become one of the key methods. Due to its excellent electromagnetic wavefront manipulation ability, the metasurface has become a promising encryption platform in the field of information security. The metasurface can encode multiple secret images into different channels, ensuring that each image can only be accessed through a decoding channel with specific electromagnetic parameters. However, existing multi-channel encryption schemes suffer from the problem of limited information multiplexing freedom and are vulnerable to brute-force attacks by potential eavesdroppers. To this end, additional encryption algorithms are introduced into the metasurface hardware platform to further enhance the security of metasurface-based cryptographic encryption methods.

[0003] Recently, researchers have proposed an innovative phase encoding scheme, a metasurface-assisted visual secret sharing method that combines one-time key storage and information authentication, enhancing the security of the system. However, existing secret sharing encryption strategies rely on the superposition of ciphertext images, and channel information is only encoded in the amplitude or phase channels. At least two ciphertext images are required during the decryption process, limiting the information capacity. Meanwhile, unauthorized users may obtain ciphertext images through systematic attacks, endangering the security of secret information. Therefore, there is an urgent need for an encryption method that can simultaneously utilize the amplitude channel and the phase channel to improve the encryption channel capacity and system security. Summary of the Invention

[0004] The present invention aims to solve the problems that existing secret sharing encryption strategies rely on the superposition of ciphertext images, and channel information is only encoded in the amplitude or phase channels. At least two ciphertext images are required during the decryption process, limiting the information capacity. Meanwhile, unauthorized users may obtain ciphertext images through systematic attacks, endangering the security of secret information. Now, a metasurface unit, a metasurface, and a holographic encryption method based on joint encryption of electromagnetic physical dimensions are provided.

[0005] The metasurface unit based on joint encryption of electromagnetic physical dimensions includes: a substrate and two metal layers located on both sides of the substrate respectively;

[0006] Each metal layer includes split-ring resonators and split-slot resonators;

[0007] The split-ring resonator is a ring-shaped metal sheet, and an opening is provided on the ring-shaped metal sheet;

[0008] The open slot resonator is a circular metal sheet, and an open annular slot is formed on the circular metal sheet;

[0009] The split ring resonator is concentrically nested outside the open slot resonator.

[0010] Furthermore, the dielectric constant of the above substrate is 2.2, the tangent of the loss angle is 0.001, the dielectric thickness is 2 mm, the material is F4B, and the unit period is 8 mm.

[0011] Furthermore, the thickness of the above metal layer is 0.035 mm;

[0012] The radius of the annular metal sheet is 3.7 mm, the ring width is 0.4 mm, and the opening width is 0.5 mm;

[0013] The radius of the circular metal sheet is 3 mm;

[0014] The outer diameter of the annular slot is 2.7 mm, the slot width is 0.3 mm, and the opening width is 0.5 mm.

[0015] The metasurface based on the above metasurface unit includes: a plurality of metasurface units densely arranged in a rectangular array.

[0016] The holographic encryption method of the above metasurface includes:

[0017] Using a chaotic algorithm to encrypt the image to be encrypted to generate a chaotic sequence, the chaotic sequence includes a system security key;

[0018] Performing an exclusive OR operation on the image to be encrypted and the chaotic sequence to generate a ciphertext image;

[0019] Encoding the incident polarization key, the system security key, and the ciphertext image into different physical dimensions of the metasurface through amplitude and phase simultaneously, so that the cipher image and the key are embedded into the four amplitude and phase channels of the electromagnetic wave at two different operating frequencies at different spatial positions when incident with different polarizations, completing the encryption.

[0020] Furthermore, the above uses the GS algorithm to independently encode the incident polarization key, the system security key, and the ciphertext image into multiple electromagnetic physical dimensions of the metasurface through amplitude modulation and phase modulation methods.

[0021] Furthermore, the above holographic encryption method further includes:

[0022] Irradiating the left circularly polarized wave to the metasurface to make the ciphertext image, the incident polarization key, and the system security key appear;

[0023] Generating a chaotic sequence using the system security key;

[0024] Perform an exclusive OR operation on the chaotic sequence and the encrypted image, so that the encrypted image is restored.

[0025] Furthermore, at 10.4 GHz, the encrypted image and the incident polarization key appear in the amplitude channel and the phase channel of the transmission space respectively, and the imaging planes are located at 8 mm and 120 mm from the metasurface respectively;

[0026] At 15.6 GHz, the chaotic keys "0.1" and "4" appear in the amplitude channel and the phase channel of the reflection space respectively, and the imaging planes are located at 10 mm and 140 mm from the metasurface respectively.

[0027] The present invention precisely controls electromagnetic waves in multiple electromagnetic dimensions (including amplitude, phase, frequency, and polarization), and combines a chaotic encryption algorithm and a metasurface hardware platform to solve the deficiencies of traditional wireless communication systems in terms of information encryption security and channel capacity. Compared with the prior art, the present invention embeds the encrypted image and the security key into independent amplitude channels and phase channels, and encodes them at different frequencies, polarization states, and spatial distances, effectively improving the encryption security and anti-attack ability of the wireless communication system. In addition, by combining the unpredictability of the chaotic algorithm with the encryption of metasurface electromagnetic physical parameters, the present invention not only enhances the security of information encryption, but also significantly improves the information encryption capacity of the system. The novel encryption method proposed by the present invention meets the requirements of high-security and high-capacity wireless communication systems, and opens up a new development direction for future efficient information encryption, data protection, and the application of large-scale storage devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a metasurface unit, where (a) represents the top layer, (b) represents the bottom layer, and (c) represents the three-dimensional view;

[0029] Figure 2 It is a characteristic curve diagram of a metasurface unit, where (a) and (d) respectively represent the influence of changing the orientation angle difference (denoted as a1 and a2) between the top and bottom metal layers of the split ring resonator (SRR) and the split slot resonator (SSR) on the amplitude response at 10.4 GHz and 15.6 GHz, (b) and (c) respectively represent the influence of changing the rotation angle θ1 on the transmission amplitude and phase shift at 10.4 GHz, and (e) and (f) respectively represent the influence of changing the rotation angle θ2 on the reflection amplitude and phase shift at 15.6 GHz.

[0030] Figure 3 It is an encryption flowchart of a metasurface-assisted high-security wireless communication system based on a chaotic algorithm;

[0031] Figure 4It is a decryption flow chart of a metasurface-assisted high-security wireless communication system based on a chaotic algorithm. Specific embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0033] Specific embodiment 1: Refer to Figure 1 and Figure 2 Specifically describe this embodiment. The metasurface unit based on electromagnetic physical dimension joint encryption described in this embodiment includes: a substrate, and two metal layers with a thickness t = 0.035 mm and a material of copper located on both sides of the substrate respectively. Each metal layer includes SRRs and SSRs, and the split-ring resonators are concentrically nested outside the split-slot resonators.

[0034] The dielectric constant ε of the substrate r = 2.2, the loss tangent tanδ = 0.001, the dielectric thickness h = 2 mm, the material is F4B, and the unit period p = 8 mm.

[0035] The split-ring resonator is an annular metal sheet with a ring width w1 = 0.4 mm and a radius r1 = 3.7 mm, and an opening with a width g1 = 0.5 mm is provided on the annular metal sheet.

[0036] The split-slot resonator is a circular metal sheet with a radius d = 3 mm, and a concentrically arranged opening annular groove is opened on the circular metal sheet. The outer diameter of the annular groove r2 = 2.7 mm, the groove width w2 = 0.3 mm, and the opening g2 = 0.5 mm.

[0037] Taking the two midlines of the substrate as the x-axis and the y-axis, the orientation angles of the SRRs and SSRs of the top metal layer with respect to the x-axis are respectively represented as θ1 and θ2, and the orientation angles of the SRRs and SSRs of the bottom metal layer with respect to the top SRRs and SSRs are respectively represented as a1 and a2.

[0038] In order to achieve wavefront control and obtain a 1-bit amplitude change and a 2π phase change, the metasurface unit structure described in this embodiment controls the amplitude and phase of the circularly polarized wave based on the transmission phase principle and the geometric phase principle. By changing the relative direction angles a1 and a2 of the SRRs and SSRs, this embodiment can control the amplitude to change between "0" and "1", and at the same time the phase is hardly affected, as shown in the appendix Figure 2(as shown in (a) and (d)). According to the geometric phase theory, rotating the two resonators of the metasurface unit relative to the x-axis at an interval of π / 8 from 0 to π can generate a 2π phase change in two frequency channels, while the amplitude always remains at a high level, thereby realizing 3-bit phase encoding, as shown in the appendix Figure 2 (as shown in (b), (c), (e), and (f)).

[0039] Specific Embodiment 2: The metasurface based on the metasurface unit described in Specific Embodiment 1 includes: a plurality of metasurface units closely arranged in a rectangular array.

[0040] Specific Embodiment 3: Refer to Figure 3 and Figure 4 Specifically describe this embodiment. This embodiment is a holographic encryption method based on the metasurface described in Specific Embodiment 2, including: chaotic sequence generation, ciphertext image creation, amplitude and phase modulation, and metasurface encoding.

[0041] Chaotic sequence generation: Use a chaotic algorithm to encrypt the image "V" to be encrypted, generate a chaotic sequence, and use the initial value and control parameters as the system security keys "0.1" and "4"

[0042] Ciphertext image creation: Perform an exclusive OR operation on the image "V" to be encrypted and the chaotic sequence to generate a ciphertext image.

[0043] Amplitude and phase modulation: Use the Gerchberg-Saxton (GS) algorithm to simultaneously encode the incident polarization key "L", the system security keys "0.1" and "4", and the ciphertext image into different physical dimensions of the metasurface through amplitude and phase modulation.

[0044] Metasurface encoding: When the generated cipher image and security key are incident with different polarizations, they are embedded in the four amplitude and phase channels of the electromagnetic wave at two different operating frequencies at different spatial positions.

[0045] This embodiment combines a chaotic algorithm based on cryptographic encryption with the encryption of the electromagnetic physical parameters of the metasurface, and proposes a high-security wireless communication encryption method based on the metasurface hardware platform. This method uses a four-channel metasurface with independent amplitude and phase control capabilities as a cryptographic encryption platform, encodes different images in the amplitude channel and the phase channel respectively, and doubles the number of available communication / encryption channels.

[0046] This embodiment integrates the cryptographic chaos encryption algorithm with electromagnetic parameter regulation to achieve collaborative encryption of the physical layer and the algorithm layer. By introducing the nonlinearity and unpredictability of the chaos algorithm, the defense ability of the system against complex attacks is significantly enhanced. At the same time, in this embodiment, the chaos key and the ciphertext image are respectively encoded into different channels, enabling each encryption channel to independently decrypt the corresponding secret information, avoiding the limitation of the traditional double-layer encryption scheme that relies on multi-channel superposition for decryption, thereby effectively improving the encryption capacity and security of the system.

[0047] Furthermore, this embodiment also includes a decryption process. When the metasurface is irradiated by a left-circularly polarized wave, at 10.4 GHz, the ciphertext image and the polarization key "L" appear in the amplitude channel and the phase channel of the transmission space respectively, and the imaging planes are located at 8 mm and 120 mm from the metasurface respectively; while at 15.6 GHz, the chaos keys "0.1" and "4" appear in the amplitude channel and the phase channel of the reflection space respectively, and the imaging planes are located at 10 mm and 140 mm from the metasurface respectively. The cipher image and the security keys (i.e., the two chaos keys) are reconstructed at the preset positions at the receiving end. After obtaining the reconstructed cipher image and security keys, the corresponding chaos sequences are generated using the security keys (i.e., the two chaos keys), and then the chaos sequences are XOR-operated with the ciphertext image to restore the original secret information.

[0048] Although during the experiment, the ciphertext image and the keys may experience a certain degree of quality degradation due to noise or error effects, the secret image obtained after decryption remains clear and is highly consistent with the full-wave simulation results. This result fully verifies the effectiveness and reliability of the proposed scheme.

[0049] This embodiment realizes multi-dimensional collaborative encryption of information by encoding the ciphertext image and the security key into the amplitude and phase channels respectively and combining multiple electromagnetic degrees of freedom such as frequency, polarization state, and spatial propagation distance. The decryptor must obtain the parameters of all electromagnetic dimensions simultaneously to successfully decrypt, thereby significantly improving the encryption capacity and anti-attack ability of the system.

[0050] This embodiment can effectively obtain the ciphertext image and the security key under different frequency, polarization, and distance conditions and achieve reliable decryption. Only two chaos keys are required to encrypt and decrypt multiple secret information simultaneously. Moreover, the combination of physical layer electromagnetic physical parameter encryption and the chaos algorithm further improves the security of the system.

[0051] In summary, based on the principles of chaotic cryptography, holographic imaging, and digital coding metasurface technology, the present invention proposes a metasurface holographic encryption method based on the joint encryption of chaotic algorithms and electromagnetic physical dimensions. By utilizing three electromagnetic physical parameters, namely frequency, polarization, and spatial distance, and combining with chaotic encryption algorithms, the security and encryption capacity of wireless communication are significantly improved. During the encryption process, the sender uses a chaotic algorithm to encrypt the secret information, generating a ciphertext image and a security key. At the same time, the polarization state of the incident wave is used as an electromagnetic parameter key and encoded onto the metasurface together with the ciphertext image and the chaotic key, thus constructing an encryption system based on a four-channel metasurface hardware platform. The ciphertext image and the security key are respectively embedded into the four amplitude and phase channels of two different operating frequencies of the electromagnetic wave, and combined with the encoding of the polarization state and spatial position to achieve electromagnetic parameter encryption at the physical layer. During the decryption process, when the metasurface is irradiated by a left-handed circularly polarized wave, the ciphertext image and the security key (including two chaotic keys and a polarization key) will be reconstructed on a predetermined plane at the receiving end. After the receiver obtains this reconstructed information, the original secret information is successfully decrypted through the corresponding decryption algorithm. If the irradiation condition or the polarization state is selected incorrectly, it will lead to decryption failure or the generation of an incorrect image, thus effectively preventing unauthorized access. Even if an attacker obtains the ciphertext image and the security key, without knowing the encryption algorithm, they are still unable to crack the original information. By combining unpredictable chaotic encryption algorithms with electromagnetic physical parameter encryption, the method proposed in the present invention improves the encryption security and anti-attack ability of the communication system, overcomes the security and encryption capacity bottlenecks of the existing technologies, and provides a new technical solution and development direction for future high-security wireless communication and large-scale data storage applications.

[0052] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. The metasurface unit based on electromagnetic physical dimension joint encryption includes: A substrate and two metal layers respectively located on both sides of the substrate, characterized in that, Each metal layer includes split-ring resonators and split-slot resonators. The split-ring resonator is an annular metal sheet, and an opening is provided on the annular metal sheet. The split-slot resonator is a circular metal sheet, and an annular slot with an opening is formed on the circular metal sheet. The split-ring resonator is concentrically nested outside the split-slot resonator.

2. The metasurface unit based on electromagnetic physical dimension joint encryption according to claim 1, characterized in that The dielectric constant of the substrate is 2.2, the tangent of the loss angle is 0.001, the dielectric thickness is 2 mm, the material is F4B, and the unit period is 8 mm.

3. The metasurface unit based on joint encryption of electromagnetic physical dimensions according to claim 1 or 2, characterized in that The thickness of the metal layer is 0.035 mm; The radius of the annular metal sheet is 3.7 mm, the ring width is 0.4 mm, and the opening width is 0.5 mm; The radius of the circular metal sheet is 3 mm; The outer diameter of the annular slot is 2.7 mm, the slot width is 0.3 mm, and the opening width is 0.5 mm.

4. The metasurface based on the metasurface unit according to any one of claims 1 to 3, characterized in that Comprising: A plurality of metasurface units closely arranged in a rectangular array.

5. The holographic encryption method based on the metasurface according to claim 4, characterized in that, Comprising: Using a chaotic algorithm to encrypt the image to be encrypted to generate a chaotic sequence, the chaotic sequence includes a system security key; Performing an exclusive OR operation on the image to be encrypted and the chaotic sequence to generate a ciphertext image; Encoding the incident polarization key, the system security key, and the ciphertext image into different physical dimensions of the metasurface through amplitude and phase simultaneously, so that when the encrypted image and the key are incident with different polarizations, they are embedded into the four amplitude and phase channels of the electromagnetic wave at two different operating frequencies at different spatial positions, completing the encryption.

6. The holographic encryption method according to claim 5, characterized in that Using the GS algorithm, the incident polarization key, the system security key, and the ciphertext image are independently encoded into multiple electromagnetic physical dimensions of the metasurface through amplitude modulation and phase modulation methods.

7. The holographic encryption method according to claim 5 or 6, characterized in that, Further comprising: Irradiating a left circularly polarized wave onto the metasurface to make the ciphertext image, the incident polarization key, and the system security key appear; Generating a chaotic sequence using the system security key; Performing an exclusive OR operation on the chaotic sequence and the ciphertext image to restore the encrypted image.

8. The holographic encryption method according to claim 7, characterized in that At 10.4 GHz, the ciphertext image and the incident polarization key appear in the amplitude channel and the phase channel of the transmission space respectively, and the imaging planes are located at 8 mm and 120 mm from the metasurface respectively; At 15.6 GHz, the chaotic keys "0.1" and "4" appear in the amplitude channel and the phase channel of the reflection space respectively, and the imaging planes are located at 10 mm and 140 mm from the metasurface respectively.

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