Differential Chaos Interleaving Secure Communication System and Method Based on Reconfigurable Intelligent Surface

Abstract

Differential chaotic interleaving secure communication system and method based on reconfigurable intelligent surface, which relates to secure communication in wireless communication systems. The system transmitter includes a chaotic signal generator, a signal block interleaver, an interleaving mode selector, a multi - element DCSK modulator, a bit separator, a bit / symbol converter, an on - off keying controller, a RIS and a RIS controller; the system receiver includes a delay device, a signal block de - interleaver, a joint detection algorithm module, and a bit combiner. The system interleaves the multi - element information - bearing signal blocks using two block interleaving modes to improve the confidentiality of wireless communication. Deploying the RIS in the transmitter not only significantly improves the signal quality of the legitimate user's receiving antenna and improves its bit error rate performance, but also reduces the risk of illegal users eavesdropping on data information when they successfully obtain the block interleaving mode. This secure communication system and method have broad application prospects in future wireless communication.

Description

Technical Field

[0001] The present invention belongs to the field of secure communication in wireless communication systems, and in particular, relates to a differential chaos interleaving secure communication system and method based on a reconfigurable intelligent surface. Background Art

[0002] As a broadband noise-like signal, a chaotic signal is extremely sensitive to initial conditions and has the characteristic of long-term unpredictability. Even if the chaotic iterative map has two very close initial conditions, the two chaotic sequences obtained after several iterations exhibit low cross-correlation. Therefore, chaotic secure communication using a chaotic signal as a carrier hides the data information to be transmitted in a noise-like chaotic waveform, greatly reducing the risk of the useful data information being eavesdropped by malicious users, thereby realizing chaotic secure communication.

[0003] Differential Chaos Shift Keying (DCSK) system is a typical non-coherent chaotic communication system (G. Kolumban, G. K. Vizvari, W. Schwarz, and A. Abel, “Differential chaos shift keying: A robust coding for chaos communication,” in Proc. Nonlinear Dyn. Electron. Syst., Seville, Spain, 1996, pp. 92-97). This system exhibits good Bit Error Rate (BER) performance in fading channels. However, the squared amplitude spectrum of the DCSK signal waveform has zero spectral value points, which seriously threatens the secure communication performance of the DCSK system. Therefore, some scholars have proposed a Permutation-based DCSK (P-DCSK) system (F. C. M. Lau, K. Y. Cheong, and C. K. Tse, “Permutation-based DCSK and multiple-access DCSK systems,” IEEE Trans. Circuits Syst. I, Fundam. Theory Appl., vol. 50, no. 6, pp. 733-742, Jun. 2003). This system performs chip permutation on the transmitted information-bearing signal. The permutation operation makes the amplitude spectrum of the transmitted signal similar to the noise spectrum, effectively improving the confidentiality of the communication system. Some scholars have proposed a Permutation Index DCSK (PI-DCSK) system (M. Herceg, G. Kaddoum, D. Vranjes, and E. Soujeri, “Permutation index DCSK modulation technique for secure multiuser high-data-rate communication systems,” IEEE Trans. Veh. Technol., vol. 67, no. 4, pp. 2997-3011, Apr. 2018). This system uses the indices of different permutation operations to transmit additional information bits, improving the data rate of the system while ensuring the secure communication performance of the system.To improve the bit error rate performance of the PI-DCSK system in a large-delay multipath Rayleigh fading channel, some scholars have proposed a DCSK (Differential PI-DCSK, DPI-DCSK) system with a differential permutation index structure (S. Liu, P. Chen, and G. Chen, “Differential permutation index DCSK modulation for chaotic communication system,” IEEE Commun. Lett., vol. 25, no. 6, pp. 2029-2033, Jun. 2021). This system also has high secure communication performance. In addition, two adjacent information-bearing signals in the signal frame structure of the DPI-DCSK system adopt a differential transmission mode. Therefore, this system has higher energy efficiency than the PI-DCSK system.

[0004] By reusing the reference signal, a reference-modulated PI-DCSK (RM-PI-DCSK) system has been proposed in the literature (H. Chen, P. Chen, S. Wang, S. Lai and R. Chen, “Referencemodulated PI-DCSK: A new efficient chaotic permutation indexmodulation scheme,” IEEE Trans. Veh. Technol., vol. 71, no. 9, pp. 9663-9673, Sept. 2022). This system can simultaneously meet the requirements of high data rate transmission and high security transmission in wireless communication. A scholar has proposed an overlapped chaotic chip position shift keying (OCCPSK) system (L. Zhang, Z. Chen, W. Rao, and Z. Wu, “Efficient and secure noncoherentOFDM-based overlapped chaotic chip position shift keying system: Design andperformance analysis,” IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 67, no. 1, pp. 309-321, Jan. 2020), which uses overlapping and shuffling operations to smooth the waveform of the transmitted signal. Since the eavesdropping device does not have the overlapping and shuffling parameters of the OCCPSK system, it is very difficult for illegal users to obtain the useful data information transmitted by this system even if they use brute-force detection methods.Some scholars have proposed a Parallel-Transmitted Code Index Modulation aided DCSK (PT-CIM-DCSK) system (H. Chen, P. Chen, Y. Fang, F. Chen and L. Kong, “Parallel differential chaotic shift keying with code index modulation for wireless communication,” IEEE Trans. Commun., vol. 70, no. 8, pp. 5113-5127, Aug. 2022). This system uses a permutation operation to superimpose and transmit multiple information-bearing signals while ensuring orthogonality, achieving high-data-rate secure communication.

[0005] As a highly competitive and promising technology, reconfigurable intelligent surface (RIS) assisted communication can make the wireless channel intelligently controllable, thus improving the quality of the transmitted signal and enhancing the performance of the communication system. However, the open and broadcast nature of the wireless channel makes wireless communication systems vulnerable to interference and eavesdropping by malicious users. However, most of the existing RIS-assisted wireless communication systems are in the coherent communication mode. For example, the RIS aided Spatial Modulation (RIS-SM) system (E. Basar, “Reconfigurable intelligent surface-based index modulation: A new beyond MIMO paradigm for 6G,” IEEE Trans. Commun., vol. 68, no. 5, pp. 3187-3196, May 2020). This system has poor communication secrecy and its bit error rate performance severely depends on the quality of the channel state information. Summary of the Invention

[0006] An object of the present invention is to provide a differential chaotic interleaved secure communication system RIS-MDCSK-BI based on a reconfigurable intelligent surface, which uses two block interleaving modes to perform block interleaving operations on multi-ary information-bearing signals, thereby improving the secrecy of wireless communication, aiming at problems such as poor secure communication performance of existing differential chaotic communication systems.

[0007] Another object of the present invention is to provide a differential chaotic interleaving secure communication method based on a reconfigurable intelligent surface, which can not only significantly improve the signal quality of the legitimate user's receiving antenna and improve its bit error rate performance, but also reduce the risk of eavesdropping on data information by illegal users in the case of successfully obtaining the block interleaving mode.

[0008] The differential chaotic interleaving secure communication system based on a reconfigurable intelligent surface includes a transmitter and a receiver;

[0009] The transmitter includes: a chaotic signal generator, a signal block interleaver, an interleaving mode selector, a multi - element DCSK modulator, a bit separator, a bit / symbol converter, an on - off keying controller, a RIS, and a RIS controller;

[0010] The chaotic signal generator is used to generate a chaotic signal c with a length of β R as a reference signal;

[0011] The signal block interleaver is used to input the reference signal to generate U quasi - orthogonal chaotic signals;

[0012] The interleaving mode selector is used to select two signals from the U quasi - orthogonal chaotic signals generated by the signal interleaver by using m I interleaving bits;

[0013] The multi - element DCSK modulator is used to modulate the multi - element constellation symbol s onto the two quasi - orthogonal chaotic signals selected by the interleaving mode selector to construct a multi - element information - bearing signal c I ;

[0014] The bit separator is used to divide the Ω information bits to be transmitted into m R RIS bits, m I interleaving bits, and n modulation bits;

[0015] The bit / symbol converter is used to convert the n modulation bits into a multi - element constellation symbol s;

[0016] The on - off keying controller is used to transmit the reference signal c R and the multi - element information - bearing signal c I in two adjacent time slots to form a signal t l ;

[0017] The RIS is used to transmit the signal t l to the wireless channel;

[0018] The RIS controller is used to control the RIS by using m R RIS bits to make a certain receiving antenna in the receiver obtain the maximum signal - to - noise ratio SNR;

[0019] The receiver includes: a delay unit, a signal block de - interleaver, a joint detection algorithm module, and a bit combiner;

[0020] The delay unit is used to delay the received signal r i.p and take the real part to obtain a reference signal

[0021] The signal block de - interleaver is used to perform signal block de - interleaving operations on the real and imaginary parts of the received information - bearing signal;

[0022] The joint detection algorithm module is used to recover m R RIS bits, m I interleaved bits, and n modulated bits through a joint detection algorithm.

[0023] The bit combiner is used to combine m R RIS bits, m I interleaved bits, and n modulated bits to obtain Ω information bits to be received.

[0024] A differential chaos interleaving secure communication method based on a reconfigurable intelligent surface includes the following steps:

[0025] 1) The bit separator of the transmitter divides the Ω information bits to be transmitted into m R RIS bits, m I interleaved bits, and n modulated bits;

[0026] 2) The chaos signal generator of the transmitter generates a chaos signal as a reference signal, and inputs the reference signal into the signal block interleaver to obtain U different quasi - orthogonal chaos signals; the interleaving indices at corresponding positions in U block interleaving patterns are different from each other to ensure the secrecy and bit - error rate performance of the system;

[0027] 3) The bit / symbol converter converts n modulated bits into a multi - ary constellation symbol s, and the multi - ary DCSK modulator constructs a multi - ary information - bearing signal by using the signals after two different block interleaving operations and the multi - ary constellation symbol s;

[0028] 4) The on - off keying controller transmits the reference signal c R and the multi - ary information - bearing signal c I in two adjacent time slots to construct the transmitted signal t l ;

[0029] 5) Deploy N R receiving antennas at the receiving end of the system, and use a joint detection algorithm to recover m R RIS bits, m I interleaved bits, and n modulated bits;

[0030] 6) The system receiver uses a bit combiner to combine the m R RIS bits, m I interleaved bits, and n modulation bits obtained by the joint detection algorithm to recover the Ω information bits transmitted by the system.

[0031] In step 1), the m R RIS bits are used to control the RIS to maximize the SNR of a certain receiving antenna in the system receiver, and the m I interleaved bits are used to select two patterns from U block interleaving patterns to construct a multi - carrier information - bearing signal, and the n modulation bits are transmitted using the multi - carrier information - bearing signal.

[0032] In step 2), the chaotic signal generator generates a chaotic signal c R = [c R,1 , c R,2 , …, c R,β of length β as a reference signal. The reference signal is input into the signal block interleaver to obtain U different quasi - orthogonal chaotic signals; the U block interleaving patterns can be represented as {w1, w2, …, w U}, and the u - th interleaving pattern contains V interleaving indices w u = [w u,1 , w u,2 , …, w u,V ; two patterns are selected from the U block interleaving patterns for the block interleaving operation of the reference signal, and there are selection cases, where represents the permutation number; the total number of interleaved bits can be calculated as m I = log2K, where K is an integer power of 2 and satisfies

[0033] In step 3), the multi - carrier constellation symbol is The constructed multi - carrier information - bearing signal is expressed as: where, represents the imaginary unit, and a and b represent the real part and the imaginary part of the multi - carrier constellation symbol respectively; and represent two different signal block interleaving patterns.

[0034] In step 4), the transmitted signal t l of the system can be expressed as:

[0035]

[0036] where, represents the phase of the l - th RIS unit; the spreading factor β of the system is defined as the length of the reference chaotic signal c R .

[0037] In step 5), the N R receiving antennas, where the received signal of the i-th receiving antenna is expressed as:

[0038]

[0039] where r i,p represents the p-th chip of the received signal in the i-th receiving antenna, and t l,p represents the p-th chip of the signal transmitted from the l-th RIS unit. N represents the number of units on the RIS, and n i,p is complex additive white Gaussian noise with zero mean and variance N0; represents the wireless channel between the l-th RIS unit and the i-th receiving antenna, where α i,l and ψ i,l represent the channel coefficient and the corresponding channel phase, respectively.

[0040] The joint detection algorithm includes the following steps:

[0041] (1) Input and are initialized, where represents the real part of the received reference signal, and represent the real part and the imaginary part of the received multi-information-bearing signal, respectively, and represent the signal block inverse interleaving operations for receiving the real part and the imaginary part of the multi-information-bearing signal, respectively;

[0042] (2) The real part of the reference signal in the i-th receiving antenna is respectively correlated with the real part and the imaginary part of the information-bearing signal after the k-th signal block inverse interleaving, and a complex decision variable G i,k is constructed using the two obtained decision variables. The construction method is

[0043] (3) Find a maximum value from the absolute value |G i,k | of G i,k and record the row index and column index of this maximum value as and

[0044] (4) Convert the row index obtained in (3) into m R RIS bits, and convert the column index into m I interleaved bits;

[0045] (5) Using the minimum distance decision criterion, demodulate the decision variable to recover n modulated bits.

[0046] The present invention performs block interleaving operations on multi - ary information - bearing signals using two block interleaving patterns, thereby improving the confidentiality of communication systems. In addition, the present invention deploys RIS in the transmitter, which can not only improve the signal quality of the legitimate user's receiving antenna and improve its bit - error rate performance, but also reduce the risk of illegal users eavesdropping on data information when successfully obtaining the block interleaving pattern. Compared with the existing permutation - based differential chaos secure communication system, the present invention can significantly improve the bit - error rate performance of legitimate users and significantly reduce the risk of illegal users eavesdropping on data information. Such a secure communication system and method have broad application prospects in future wireless communications. Description of the Drawings

[0047] Figure 1 is the block diagram of the reconfigurable intelligent surface - based differential chaos interleaving secure communication (RIS - MDCSK - BI) system;

[0048] Figure 2 is the bit - error rate performance of RIS - MDCSK - BI and RIS - SM systems in the Rayleigh fading channel;

[0049] Figure 3 is the bit - error rate performance of RIS - MDCSK - BI, PI - DCSK, DPI - DCSK, PT - CIM - DCSK, and RM - PI - DCSK systems in the Rayleigh fading channel;

[0050] Figure 4 is the information leakage rate performance of RIS - MDCSK - BI, PI - DCSK, DPI - DCSK, PT - CIM - DCSK, and RM - PI - DCSK systems in the Rayleigh fading channel;

[0051] Figure 5 is the correlation peak amplitude spectrum of the DCSK system;

[0052] Figure 6 is the correlation peak amplitude spectrum of the PI - DCSK system;

[0053] Figure 7 is the correlation peak amplitude spectrum of the PT - CIM - DCSK system;

[0054] Figure 8 is the correlation peak amplitude spectrum of the RM - PI - DCSK system;

[0055] Figure 9 is the correlation peak amplitude spectrum of the RIS - MDCSK - BI system. Detailed implementation manners

[0056] To make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following embodiments will further elaborate on the present invention in conjunction with the accompanying drawings.

[0057] Figure 1 A block diagram of the RIS-MDCSK-BI system is given. The system described in the present invention includes a transmitter and a receiver. The transmitter includes a chaotic signal generator, a signal block interleaver, an interleaving mode selector, a multi - element DCSK modulator, a bit separator, a bit / symbol converter, a RIS, and a RIS controller. The receiver includes a delay element, a signal block de - interleaver, a joint detection algorithm, a bit combiner, etc.

[0058] The specific working process of the RIS-MDCSK-BI system is as follows:

[0059] The system transmitter divides the Ω information bits to be transmitted into m R RIS bits, m I interleaving bits, and n modulation bits. Among them, m R RIS bits are used to control the RIS to make a certain receiving antenna in the system receiver obtain the maximum SNR, m I interleaving bits are used to select two patterns from U block interleaving patterns to construct a multi - element information - bearing signal, and n modulation bits are used to transmit using the multi - element information - bearing signal.

[0060] The chaotic signal generator of the transmitter first generates a chaotic signal c R = [c R,1 , c R,2 , …, c R,β of length β as a reference signal. Subsequently, the obtained reference signal is input into the signal block interleaver to obtain U different quasi - orthogonal chaotic signals. The U block interleaving patterns can be expressed as {w1, w2, …, w U}, where the u - th interleaving pattern contains V interleaving indices w u = [w u,1 , w u,2 , …, w u,V . To ensure the confidentiality and bit - error rate performance of the system, the interleaving indices at the corresponding positions in these U block interleaving patterns are different from each other. Subsequently, two patterns are selected from the U block interleaving patterns for the block interleaving operation of the reference signal. Therefore, there are a total of selection cases, where represents the permutation number. At this time, the total number of interleaving bits can be calculated as m I = log2K, where K is an integer power of 2 and satisfies

[0061] The bit / symbol converter converts n modulated bits into a multi - ary constellation symbol where represents the imaginary unit, and a and b represent the real and imaginary parts of the multi - ary constellation symbol respectively. The multi - ary DCSK modulator constructs a multi - ary information - bearing signal using two block - interleaved signals and the multi - ary constellation symbol s, expressed as where and represent two different signal block - interleaving patterns. Subsequently, the on - off keying modulator transmits the reference signal c R and the multi - ary information - bearing signal c I in two adjacent time slots, thus constructing the transmitted signal t of the RIS - MDCSK - BI system l . Therefore, the transmitted signal of the RIS - MDCSK - BI system can be expressed as:

[0062]

[0063] where represents the phase of the l - th RIS element. The spreading factor β of the system is defined as the length of the reference chaotic signal c R .

[0064] At the receiver of the RIS - MDCSK - BI system, N R receiving antennas are deployed, and the received signal of the i - th receiving antenna is expressed as:

[0065]

[0066] where r i,p represents the p - th chip of the received signal in the i - th receiving antenna, t l,p represents the p - th chip of the signal transmitted from the l - th RIS element, N represents the number of elements on the RIS, and n i,p is complex additive white Gaussian noise with zero mean and variance N0. represents the wireless channel between the l - th RIS element and the i - th receiving antenna, where α i,l and ψ i,l represent the channel coefficient and the corresponding channel phase respectively.

[0067] In the legitimate receiver, one of the N R receiving antennas can obtain the maximum SNR because the phase of the RIS element is tuned to cancel the phase of the channel between the RIS and this receiving antenna. Therefore, in order to recover all the transmitted information bits, the legitimate receiver first needs to find the index of the position of the receiving antenna that can make the received signal obtain the maximum SNR, so as to recover m RA RIS bit. Secondly, perform a signal block de - interleaving operation on the received multi - information - bearing signal, and perform a correlation operation on the de - interleaved signal and the real part of the received reference signal. Immediately afterwards, find the position where the correlation maximum value is located, and convert the position index information into m I interleaved bits. Finally, use the minimum - distance decision criterion to recover n modulated bits. For this purpose, design a joint detection algorithm to recover m R RIS bits, m I interleaved bits, and n modulated bits.

[0068] The joint detection algorithm includes the following steps:

[0069] (1) Input and for initialization, where represents the real part of the received reference signal, and respectively represent the real part and the imaginary part of the received multi - information - bearing signal, and respectively represent the signal block de - interleaving operations for receiving the real part and the imaginary part of the multi - information - bearing signal.

[0070] (2) The real part of the reference signal in the i - th receiving antenna is respectively correlated with the real part and the imaginary part of the information - bearing signal after the k - th signal block de - interleaving, and a complex decision variable G i,k is constructed using the two obtained decision variables. The construction method is

[0071] (3) Find a maximum value from the absolute value |G i,k | of G i,k and record the row index and column index of this maximum value as and

[0072] (4) Convert the row index obtained in step (3) into m R RIS bits, and convert the column index into m I interleaved bits.

[0073] (5) Use the minimum - distance decision criterion to demodulate the decision variable to recover n modulated bits.

[0074] Finally, the system receiver uses a bit combiner to combine the m R RIS bits, mI The interleaved bits and the n modulated bits are combined to recover the Ω information bits transmitted by the system.

[0075] The present invention provides a differential chaotic interleaved secure communication system and method based on a reconfigurable intelligent surface. To better illustrate its effectiveness, some computer simulation results are given.

[0076] Figure 2 Compare the bit error rate performance of legitimate users in the RIS-MDCSK-BI and RIS-SM systems over a Rayleigh fading channel. RIS-SM-ML and RIS-SM-GD in the figure respectively represent that the RIS-SM system uses the maximum likelihood detection and greedy detection algorithms. The number of modulated bits n of the RIS-MDCSK-BI and RIS-SM systems is the same. In addition, the simulation parameters of the RIS-MDCSK-BI system are N = 100, N R = 8, K = 8, and β = 128. The simulation parameters of the RIS-SM system are N = 100 and N R = 8. It can be seen from the figure that when n = 2 and BER = 10 -5 , the RIS-MDCSK-BI system can obtain performance gains of 1 dB and 2 dB compared with the RIS-SM-ML and RIS-SM-GD systems respectively. When n = 2 and BER = 10 -5 , the RIS-MDCSK-BI system can obtain performance gains of 3 dB and 4 dB better than the RIS-SM-ML and RIS-SM-GD systems.

[0077] Figure 3 Compare the bit error rate performance of legitimate users in the RIS-MDCSK-BI, PI-DCSK, DPI-DCSK, RM-PI-DCSK, and PT-CIM-DCSK systems over a Rayleigh fading channel. The spreading factor of all systems is set to β = 560 and the number of bits carried in one transmission symbol of all systems is the same, i.e., Ω = 3 or Ω = 6. When Ω = 3 and Ω = 6, the number of modulated bits of the RIS-MDCSK-BI system is n = 1 and n = 2 respectively. The other simulation parameters of the RIS-MDCSK-BI system are N R = 2 and K = 2. In addition, the number of parallel transmission branches of the PT-CIM-DCSK system is set to 2. It can be seen from the figure that legitimate users can obtain better bit error rate performance compared with other systems if they use the RIS-MDCSK-BI system for communication.

[0078] Suppose the illegal user successfully obtains the block interleaving pattern of the RIS-MDCSK-BI system and also successfully obtains the permutation patterns of PI-DCSK, DPI-DCSK, RM-PI-DCSK, and PT-CIM-DCSK.Figure 4 The information leakage rates of these systems are compared. Generally, the mutual information between the transmitted data information d and the received data information of illegal users can be used to evaluate the information leakage rate of the communication system. Therefore, the information leakage rate of the communication system can be expressed as:

[0079]

[0080] where H(·) represents the entropy function, and P Eve represents the bit error probability of illegal users. The simulation parameters of the RIS-MDCSK-BI system are N = 20, N R = 16, K = 2, and n = 1. For the sake of fairness in comparison, the total number of bits transmitted by one symbol for all systems in the figure is Ω = 6, and the spreading factor of all systems is set to β = 128. The information leakage rate of the RIS-MDCSK-BI system is lower than 0.1 in all SNR ranges. When the SNR is large, the information leakage rate of the RIS-MDCSK-BI system is much smaller than that of other systems in the figure.

[0081] Figures 5 to 9 The relevant peak amplitude spectra of DCSK, PI-DCSK, PT-CIM-DCSK, RM-PI-DCSK, and RIS-MDCSK-BI systems are shown, where the relevant peak is obtained by calculating the correlation value between the reference signal and the cyclic shift information-bearing signal. It can be seen from the figure that the relevant peak of the DCSK signal always appears at the cyclic shift index "0", which indicates that the secure communication performance of the DCSK system is extremely poor. In addition, it can be seen from the figure that according to the position of the maximum value of the relevant peak of the PI-DCSK, PT-CIM-DCSK, and RIM-PI-DCSK systems, the cyclic shift characteristics of the information-bearing signal can be obtained, which enables malicious illegal users to easily eavesdrop on the data information transmitted in these systems. Therefore, the secure communication performance of these systems is still very poor. In contrast, the maximum value of the relevant peak of the RIS-MDCSK-BI system shows an irregular characteristic, so this system exhibits excellent secure communication performance.

[0082] The present invention uses two block interleaving modes to perform block interleaving operations on the multi-source information-bearing signal, thereby improving the confidentiality of the communication system. In addition, the present invention deploys the RIS in the transmitter, which can not only improve the signal quality of the legitimate user's receiving antenna and improve its bit error rate performance, but also reduce the risk of illegal users eavesdropping on data information when they successfully obtain the block interleaving mode. Compared with the existing permutation-based differential chaos secure communication system, the present invention can reduce the risk of illegal users eavesdropping on data information on the basis of significantly improving the bit error rate performance of legitimate users, and has broad application prospects in future secure communication.

Claims

1. A differential chaos interleaving secure communication system based on a reconfigurable intelligent surface, characterized in that It includes a transmitter and a receiver; The transmitter includes: a chaotic signal generator, a signal block interleaver, an interleaving pattern selector, a multi - ary DCSK modulator, a bit separator, a bit / symbol converter, an on - off keying controller, a RIS, and a RIS controller; The chaotic signal generator generates a chaotic signal c with a length of β R = [c R,1 , c R,2 , …, c R,β as a reference signal. The reference signal is input into the signal block interleaver to obtain U different quasi - orthogonal chaotic signals; The U block interleaving patterns are denoted as {w1, w2, …, w U}, and the u - th interleaving pattern contains V interleaving indices w u = [w u,1 , w u,2 , …, w u,V ; Two patterns are selected from the U block interleaving patterns for the block interleaving operation of the reference signal, and there are selection cases in total, where represents the permutation number; The total number of interleaved bits is calculated as m I = log2K, where K is an integer power of 2 and satisfies The signal block interleaver is used to input a reference signal to generate U quasi - orthogonal chaotic signals; The interleaving mode selector is used to select two signals from the U quasi-orthogonal chaotic signals generated by the signal interleaver using m I interleaving bits; The multi - ary DCSK modulator is used to modulate the multi - ary constellation symbol s onto two quasi - orthogonal chaotic signals selected by the interleaving pattern selector, thereby constructing a multi - ary information - carrying signal c I ; The bit separator is used to divide the Ω information bits to be transmitted into m R RIS bits, m I interleaved bits and n modulation bits; The bit / symbol converter is used to convert n modulated bits into a multi - constellation symbol s; the multi - constellation symbol is Construct a multi - information - bearing signal expressed as: where represents the imaginary unit, and a and b respectively represent the real part and the imaginary part of the multi - constellation symbol; and represent two different signal block interleaving patterns; The on-off keying controller is used to transmit a reference signal c R and a multi-information bearing signal c I in two adjacent time slots to form a signal t l ; The RIS is used to transmit the signal t l to the wireless channel; The RIS controller is used to control the RIS by using m R RIS bits to enable a certain receiving antenna in the receiver to obtain the maximum signal-to-noise ratio (SNR). The receiver includes: a delay element, a signal block de - interleaver, a joint detection algorithm module, and a bit combiner; The delay device is used to delay the received signal r i.p and take the real part to obtain a reference signal The signal block de - interleaver is used to perform a signal block de - interleaving operation on the real part and the imaginary part of the received information - bearing signal; The joint detection algorithm module is used to recover m R RIS bits, m I interleaved bits and n modulated bits through the joint detection algorithm; The bit combiner is used to combine m R RIS bits, m I interleaved bits, and n modulated bits to obtain Ω information bits to be received.

2. Differential chaotic interleaving secure communication method based on reconfigurable intelligent surface, characterized in that Using the differential chaotic interleaving secure communication system based on a reconfigurable intelligent surface as claimed in claim 1, the specific method includes the following steps: 1) The bit separator of the transmitter divides the Ω information bits to be transmitted into m R RIS bits, m I interleaved bits, and n modulation bits; 2) The chaotic signal generator of the transmitter generates a chaotic signal as a reference signal, and inputs the reference signal into the signal block interleaver to obtain U different quasi - orthogonal chaotic signals; the interleaving indices at corresponding positions in U block interleaving patterns are different from each other to ensure the confidentiality and bit - error rate performance of the system; 3) The bit / symbol converter converts n modulation bits into a multi - ary constellation symbol s, and the multi - ary DCSK modulator constructs a multi - ary information - bearing signal by using the signals after two different block interleaving operations and the multi - ary constellation symbol s; 4) The on-off controller transmits the reference signal c R and the multi-information bearing signal c I in two adjacent time slots to construct the transmitted signal t l ; 5) Deploy N receiving antennas at the receiving end of the system, and use the joint detection algorithm to recover m RIS bits, m interleaved bits, and n modulated bits; R R I ​​​ 6) The system receiver uses a bit combiner to combine the m R RIS bits obtained by the joint detection algorithm, the m I interleaved bits, and the n modulation bits to recover the Ω information bits transmitted by the system.

3. The differential chaos interleaving secure communication method based on a reconfigurable intelligent surface according to claim 2, wherein In step 1), the m R RIS bits are used to control the RIS to enable a certain receiving antenna in the system receiver to obtain the maximum SNR, and the m I interleaving bits are used to select two patterns from U block interleaving patterns for constructing a multi - element information - bearing signal, and n modulation bits are transmitted using the multi - element information - bearing signal.

4. The differential chaos interleaving secure communication method based on a reconfigurable intelligent surface according to claim 2, wherein In step 2), the chaotic signal generator generates a chaotic signal c of length β R =[c R,1 , c R,2 , …, c R,β as a reference signal, and the reference signal is input into the signal block interleaver to obtain U different quasi-orthogonal chaotic signals; the U block interleaving patterns are denoted as {w1, w2, …, w U}, and the u-th interleaving pattern contains V interleaving indices w u =[w u,1 , w u,2 , …, w u,V ; two patterns are selected from the U block interleaving patterns for the block interleaving operation of the reference signal, and there are selection cases in total, where represents the permutation number; the total number of interleaved bits is calculated as m I = log2K, where K is an integer power of 2 and satisfies 5. The differential chaos interleaving secure communication method based on a reconfigurable intelligent surface according to claim 2, characterized in that In step 3), the multi - constellation symbol is Construct the multi - information - carrying signal expressed as: where represents the imaginary unit, and a and b respectively represent the real part and the imaginary part of the multi - constellation symbol; and represent two different signal block interleaving patterns.

6. The differential chaos interleaving secure communication method based on a reconfigurable intelligent surface according to claim 2, wherein In step 4), the transmitted signal t of the system l is expressed as: Among them, represents the phase of the l-th RIS unit; the spreading factor β of the system is defined as the length of the reference chaotic signal c R .

7. The differential chaotic interleaving secure communication method based on a reconfigurable intelligent surface according to claim 2, characterized in that In step 5), the N R receiving antennas, and the received signal of the i-th receiving antenna is expressed as: where r i,p represents the p-th chip of the received signal in the i-th receive antenna, and t l,p represents the p-th chip of the signal transmitted from the l-th RIS element, N represents the number of elements on the RIS, and n i,p is complex additive white Gaussian noise with zero mean and variance N0; represents the wireless channel between the l-th RIS element and the i-th receive antenna, where α i,l and ψ i,l represent the channel coefficient and the corresponding channel phase, respectively.

8. The differential chaos interleaving secure communication method based on reconfigurable intelligent surface according to claim 2, characterized in that In step 5), the joint detection algorithm includes the following steps: (1) Input and are initialized, where represents the real part of the received reference signal, and represent the real part and the imaginary part of the received multi-information-bearing signal respectively, and represent the signal block inverse interleaving operations for receiving the real part and the imaginary part of the multi-information-bearing signal respectively; (2) The real part of the reference signal in the i-th receiving antenna is respectively correlated with the real part of the information-bearing signal after inverse-interleaving of the k-th signal block and the imaginary part to perform a correlation operation, and a complex decision variable G is constructed using the two obtained decision variables i,k , and its construction method is (3) From G i,k Find the absolute value of |G i,k |, find a maximum value, and record that the row index and column index of this maximum value are respectively and (4) Convert the row index obtained in step (3) into m R RIS bits, and convert the column index into m I interleaved bits; (5) Using the minimum distance decision criterion, demodulate the decision variable to recover n modulated bits.

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