A minimalist optical chaos secure communication system for enhanced security

Abstract

The present invention provides a minimalist optical chaos secure communication system for enhancing security, which relates to the field of chaotic secure communication, and includes: a transmitting end and a receiving end; at the transmitting end, by directly injecting binary random plaintext into a time-delay optical chaos source as a dynamic variable of the system to participate in the nonlinear evolution process of the system, a ciphertext signal is output through a chaotic signal generating device; a part of the ciphertext signal is fed back to the system to form a delayed closed loop, and the remaining part is injected into a communication channel for secure communication transmission. After the channel transmission, at the receiving end, the communicator divides the received interfered ciphertext signal into two paths, one of which is processed by a delay module to obtain a delayed signal, and the delayed signal and the other interfered ciphertext signal are injected into a demodulation module for demodulation, thereby demodulating the final plaintext signal. The beneficial effects of the present invention are: while effectively improving the security of the communication system, it also simplifies the system structure of the two communicating parties.

Description

Technical Field

[0001] The invention relates to the field of chaotic secure communication, and in particular to a minimalist optical chaotic secure communication system for enhancing security. Background Art

[0002] Chaotic secure communication is a physical layer encryption technology based on nonlinear dynamic transformation. At the transmitting end, the simulated nonlinear carrier output by the chaotic system is used to conceal the plaintext signal. The high randomness and long-term unpredictability of the noise-like carrier are the basis for ensuring the security of chaotic secure communication. At the receiving end, the receiver has a symmetrical physical transformation device and physical parameters that match the transmitting end (often used as an encryption key). Based on chaotic synchronization control, the chaotic carrier of the transmitting end is reproduced, thereby demodulating the transmitted plaintext information from the ciphertext signal.

[0003] As an effective means of secure communication at the physical layer, chaotic secure communication has developed from early circuit chaos to the unprecedentedly active optical chaos in recent years, and has been significantly improved in transmission rate, transmission distance, and security. However, the further large-scale application of chaotic secure optical communication still faces the following bottlenecks:

[0004] 1. There is a fundamental contradiction between the high security of the communication system and the complexity of its implementation. Improving the security of the system will inevitably complicate the physical structure of the system.

[0005] 2. The existing chaos masking confidentiality system has inherent defects. The information signal and the carrier are superimposed to form a ciphertext signal. The power of the information signal cannot be too large or too small, making it impossible for the communication system to take into account both security and noise immunity. Summary of the invention

[0006] In order to solve the contradiction between the high security of the system and the complexity of implementation, and the problem that security and noise immunity cannot be taken into account at the same time, the present invention provides a minimalist optical chaos secure communication system for enhancing security, which effectively improves the security of the communication system and simplifies the system structure of both communicating parties. The system mainly includes: a transmitting end and a receiving end;

[0007] At the transmitting end, the plaintext signal m(t) is directly injected into the time-delay optical chaotic source as the system's dynamic variable to participate in the nonlinear evolution of the system. A chaotic signal generator is built according to the plaintext self-injection perturbation system. The signal output by the plaintext signal m(t) after passing through the chaotic signal generator will be transmitted as a ciphertext signal.

[0008] Part of the ciphertext signal is fed back to the system to form a delay closed loop, and the remaining part is injected into the communication channel for confidential communication transmission. After transmission through the channel, the interfered ciphertext signal is obtained. At the receiving end, the communicator divides the received interfered ciphertext signal into two paths. One path is processed by the delay module to obtain the delayed signal s(t-τ). The delayed signal and the other interfered ciphertext signal are injected into the demodulation module for demodulation, thereby obtaining the demodulated signal m′(t).

[0009] The technical solution provided by the present invention has the following beneficial effects: compared with the method of superimposing a plaintext signal and a chaotic carrier signal to generate a ciphertext signal in a traditional optical chaotic secure communication system, the present invention directly injects plaintext information into an optical chaotic transmitter, and the plaintext signal is regarded as a dynamic variable, participating in the nonlinear evolution process of the system, thereby outputting the corresponding ciphertext. Accordingly, the system designs a non-synchronous demodulator based on variable inversion using a deep neural network. The proposed scheme not only effectively improves the security of the communication system, but also reduces the physical complexity of the system structure of both communicating parties. Compared with the prior art, the present invention adopts a simpler encryption and demodulation device structure to reduce the difficulty of hardware implementation. The performance analysis of the bit error rate of the present invention under different signal-to-noise ratios shows that reliable communication can still be provided under various signal-to-noise ratio environments, and the bit error rate can be kept within an acceptable range even under a lower signal-to-noise ratio. The present invention has significant security enhancement advantages in protecting confidential information and resisting various attack methods, and has considerable noise resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0011] Figure 1 It is a structural diagram of a minimalist optical chaos secure communication system for enhancing security in an embodiment of the present invention.

[0012] Figure 2 Schematic diagram of model training in an embodiment of the present invention.

[0013] Figure 3 It is a structural diagram of a chaotic signal generating device built based on a plaintext self-injection disturbance system in an embodiment of the present invention.

[0014] Figure 4 It is a rendering obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0016] Please refer to Figure 1 , Figure 1This is a flow chart of a minimalist optical chaos secure communication system for enhancing security in an embodiment of the present invention, which specifically includes:

[0017] At the transmitting end, the binary random plaintext signal m(t) is directly injected into the time-delay optical chaotic source. As the dynamic variable of the system, it participates in the nonlinear evolution process of the system. The plaintext self-injection disturbance system is: Among them, x(t) represents the system variable, x(tτ) is the system time-delay variable, τ represents the delay parameter, p is the system parameter, and the plaintext signal m(t) is regarded as the dynamic variable of the system, which is the external disturbance signal. According to the plaintext self-injection disturbance system, a chaotic signal generator is built. After the plaintext signal m(t) passes through the chaotic signal generator, the output signal x(t) will be transmitted as a ciphertext signal, which contains the plaintext information. A part of it is fed back to the system to form a delayed closed loop, and the other part is injected into the communication channel for confidential communication transmission. It is disturbed by noise N in the communication channel, and the disturbed ciphertext signal s(t) is obtained.

[0018] After transmission through the channel, at the receiving end, the communicator divides the interfered ciphertext signal s(t) into two paths, one of which is directly input into the demodulation module for demodulation, and the other is first processed by the delay module to obtain the delayed signal s(t-τ), and then input into the demodulation module for demodulation, thereby outputting the demodulated signal m′(t). The signal s(t) is the signal after the ciphertext signal x(t) is affected by the noise in the channel. The demodulation module is constructed based on a deep neural network, and does not require a dynamic variable inversion model of a synchronous demodulator. The traditional parameter modulation technology demodulator is very complex. Based on the adaptive synchronous control technology, it is necessary to design corresponding parameter estimators according to different systems. The demodulation module proposed in the present invention is not limited to a certain system and does not require the design of a special decoder. It is a new demodulation mechanism. The receiving end is a design of a non-synchronous demodulator based on variable inversion, and the decrypted ciphertext signal is directly inverted from the neural network.

[0019] refer to Figure 2 In the pre-training process of the demodulation model based on the neural network, any binary random sequence n(t) is input into the time-delay optical chaotic source to obtain the ciphertext signal x(t). The received x(t) is divided into two paths, one of which is processed by the delay module to obtain the delayed signal x(t-τ). The delayed signal and the other signal are used as the input of the model, and the final plaintext signal n(t) is the target output of the model.

[0020] The error signal u(t) = n'(t) - n(t) is used as the loss function of the training model. The mapping function f obtained by training satisfies the following mapping relationship:

[0021] n(t)=f(x(t),x(t-τ))

[0022]

[0023] Among them, τ=L*Δt, L represents the delay time after discretization, Δt represents the step size, x j represents the j-th sampling point signal of the signal sequence, j represents the j-th sampling point, n and m represent the start and end sampling points corresponding to an arbitrarily selected time series segment, n(t) represents the plaintext signal used for training the neural network model, and n′(t) is the output result of the neural network model.

[0024] The chaotic signal generator based on the plaintext self-disturbance system is located at the sending end of the minimalist optical chaotic secure communication system. Figure 3 As shown, the generating device includes a laser diode (LD), a polarization controller (PC), a Mach-Zehnder modulator (MZM), a photodetector (PD) and a radio frequency amplifier (RF), wherein the PD includes a first photodetector (PD1), a second photodetector (PD2), and a third photodetector (PD3), and the RF includes a first radio frequency amplifier (RF1), a second radio frequency amplifier (RF2), and a third radio frequency amplifier (RF3). The PC input end is connected to the LD, and the output end is connected to the first input end of the MZM. The MZM output end is connected to the input end of the first optical coupler (OC1). The first output end of OC1 is connected to the input end of PD1 through the first delay line (DL1). The output end of PD1 is connected to the input end of RF1. The output end of RF1 is connected to the second input end of MZM. The second output end of OC1 is connected to the input end of the second optical coupler (OC2). The first output end of OC2 is connected to the input end of PD2. The output end of PD2 is connected to the input end of RF2. The output end of RF2 is connected to the first input end of the demodulation module. The second output end of OC2 is connected to the input end of PD3 through the second delay line (DL2). The output end of PD3 is connected to the input end of RF3. The output end of RF3 is connected to the demodulation module (by Figure 3 The second input terminal is composed of a trained neural network in the demodulation module, and the output terminal of the demodulation module outputs the final ciphertext signal. Among them, the transmitting end includes LD, PC, MZM, OC1, DL1, PD1, RF1, and the receiving end includes OC2, DL2, PD2, RF2, PD3, RF3 and a demodulation module. The transmitting end and the receiving end are connected through a communication channel. In this embodiment, the communication channel refers to an optical fiber channel.

[0025] At the transmitting end, the output light of the LD passes through the PC and is injected into the MZM. The output light of the MZM is divided into two parts through the first optical coupler (OC1). One part is used to form a photoelectric feedback loop, that is, the optical signal after transmission through the first delay line (DL1) is converted into an electrical signal by the first photodetector (PD1). Then, the electrical signal is amplified by the first radio frequency amplifier (RF1), mixed with the plaintext signal m(t), and fed back to the MZM to generate chaos. The other part is securely transmitted through the optical fiber channel. The system at the transmitting end can be described as:

[0026]

[0027] At the receiving end, the input light is divided into two parts by OC2. One beam of light is input to PD2 and then amplified by RF2 to obtain the first electrical signal. The other beam of light is input to the second delay line and then enters PD3 and RF s Then the first electrical signal and the second electrical signal are input into a demodulation module based on a deep neural network to output a demodulated signal m'(t).

[0028] In this embodiment, the system parameters are set as follows: feedback strength β = 5, bias phase Φ = π / 4, feedback loop response time ε = 5×10 -6 , delay parameter τ = 30ns. Reservoir computing is used as the demodulation module based on neural network. The parameters of the demodulation module are as follows: the number of neurons in the reservoir N = 300, the leakage rate α = 0.5, the spectrum radius ρ = 0.9, and the regularization parameter λ of ridge regression = 1 × 10. After the above settings, we get Figure 4 The effect diagram is shown in the figure. The plaintext waveform of the original message m(t) is as follows Figure 4 As shown in (a) of Figure 1, the data transmission rate is set to 1 Gbps. The ciphertext signal is the chaotic signal output by the MZM, as shown in Figure 4 The correlation coefficient between the plaintext signal and the ciphertext signal is about 10 -3 orders of magnitude, i.e., the ciphertext does not reveal information about the plaintext. Figure 4 (c) in the figure shows the corresponding spectrum of the ciphertext signal. It can be seen that the attacker cannot extract any useful information to recover the message in either the time domain or the frequency domain. Subsequently, the encrypted signal is transmitted through an additive white Gaussian noise channel with a signal-to-noise ratio of 7 dB, and the final signal is demodulated as follows: Figure 4 The solid line in (e) shows the original plaintext signal, and the dotted line shows the original plaintext signal. The bit error rate (BER) is about 10 -4 order of magnitude. Figure 4 (f) in FIG. 1 shows the eye diagram of the decrypted signal after low-pass filtering. It can be seen that the eye diagram is clear and open, indicating that the solution disclosed in the present invention has achieved an excellent decryption effect.

[0029] In addition, the present invention also studies the time delay signature (TDS) suppression by using delay mutual information (DMI). Figure 4 As shown in (d) in the figure, the time domain features are greatly suppressed. No obvious peak can be detected for delay feature extraction. Finally, the bit error rate (BER) performance of the proposed system is analyzed. The bit error rate performance under different signal-to-noise ratios (SNR) is shown in Figure 4 As shown in (g) in the figure. When the signal-to-noise ratio is greater than 8dB, error-free transmission can be maintained. Even when the signal-to-noise ratio drops to 5dB, the bit error rate is 1.2×10, which is still lower than the forward error correction (FEC) limit of 3.8×10. In other words, reliable communication can still be provided in a harsh channel transmission environment.

[0030] The transmitting end of the present invention adopts the method of self-injecting disturbance of plain text to encrypt information. The plain text information can be regarded as an external disturbance signal, participating in the nonlinear evolution process of the system, enhancing the encryption capability, and improving the security of information transmission. The receiving end adopts the design of a demodulator based on variable inversion and does not require synchronization. The neural network can directly inverse the plain text information, simplifying the hardware facilities.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A minimalist optical chaos secure communication system for enhancing security, characterized in that: include: Transmitter and receiver; At the transmitting end, the binary random plaintext signal m(t) is directly injected into the time-delay optical chaotic source as the system's dynamic variable to participate in the nonlinear evolution of the system. A chaotic signal generator is built according to the plaintext self-injection perturbation system. The signal output by the plaintext signal m(t) after passing through the chaotic signal generator will be transmitted as a ciphertext signal. Part of the ciphertext signal is fed back to the system to form a delay closed loop, and the remaining part is injected into the communication channel for confidential communication transmission. After transmission through the channel, the interfered ciphertext signal is obtained. At the receiving end, the communicator divides the received interfered ciphertext signal into two paths. One path is processed by the delay module to obtain the delayed signal s(t-τ). The delayed signal and the other interfered ciphertext signal are injected into the demodulation module for demodulation, thereby obtaining the demodulated signal m′(t).

2. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, characterized in that: The source of delayed optical chaos is x(t) is the system variable, x(t-τ) is the system time-delay variable, p is the system parameter, f() represents the mapping function, τ represents the delay parameter, and t represents time.

3. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, characterized in that: The plaintext self-injection perturbation system is: x(t) is the system variable, x(t-τ) is the system time-delay variable, p is the system parameter, the plaintext signal m(t) is the dynamic variable of the system, f() represents the mapping function, τ represents the delay parameter, and t represents time.

4. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, characterized in that: The loss function of the demodulation model is: u(t)=n′(t)-n(t) Among them, u(t) represents the error signal, n(t) represents the plaintext signal used for demodulation model training, and n′(t) represents the output result of the demodulation model.

5. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, characterized in that: The mapping function f() satisfies: n(t)=f(x(t),x(t-τ)) Among them, τ=L*Δt, L represents the delay time after discretization, Δt represents the step size, x j represents the j-th sampling point signal of the signal sequence, j represents the j-th sampling point, n and m represent the start and end sampling points corresponding to an arbitrarily selected time series segment, and n(t) represents the plaintext signal used for demodulation model training.

6. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, characterized in that: The chaotic signal generating device includes a laser diode, a polarization controller, a Mach-Zehnder modulator, a photodetector and a radio frequency amplifier; the photodetector includes a first photodetector, a second photodetector and a second photodetector; the radio frequency amplifier includes a first radio frequency amplifier, a second radio frequency amplifier and a third radio frequency amplifier; the input end of the polarization controller is connected to the laser diode, the output end is connected to the first input end of the Mach-Zehnder modulator, the output end of the Mach-Zehnder modulator is connected to the input end of the first optical coupler, the first output end of the first optical coupler is connected to the input end of the first photodetector through a first delay line, and the output end of the first photodetector is connected to the first radio frequency amplifier The first RF amplifier output end is connected to the Mach-Zehnder modulator connected to the second input end, the first optical coupler second output end is connected to the second optical coupler input end, the second optical coupler first output end is connected to the second photodetector input end, the second photodetector output end is connected to the second RF amplifier input end, the second RF amplifier output end is connected to the first input end of the demodulation module, the second optical coupler second output end is connected to the third photodetector input end through the second delay line, the third photodetector output end is connected to the third RF amplifier input end, the third RF amplifier output end is connected to the second input end of the demodulation module, and the demodulation module output end outputs the ciphertext signal that is finally decrypted.

7. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 6, characterized in that: The system works as follows: At the transmitting end, the output light of the laser diode is injected into the Mach-Zehnder modulator through the polarization controller. The output light of the Mach-Zehnder modulator is divided into two parts through the first optical coupler. One part is used to form a photoelectric feedback loop, that is, the optical signal after being transmitted through the first delay line is converted into an electrical signal by the first photodetector; then, the electrical signal is amplified by the first radio frequency amplifier, mixed with the plaintext signal, and fed back to the Mach-Zehnder modulator to generate chaos; The other part is securely transmitted through the optical fiber channel. At the receiving end, the input light is divided into two parts by the second optical coupler. One beam of light is input into the second photodetector and then amplified by the second radio frequency amplifier to obtain the first electrical signal; the other beam of light is input into the second delay line and then enters the third photodetector and the third radio frequency amplifier to obtain the second electrical signal; then the first electrical signal and the second electrical signal are input into the demodulation module to output the final decrypted ciphertext message.

8. A minimalist optical chaos secure communication system for enhancing security as claimed in claim 1, 6 or 7, characterized in that: The demodulation module is constructed based on a deep neural network.

Images