A covert underwater acoustic communication method based on steganography algorithm encryption

Abstract

The application discloses a kind of based on steganography algorithm encryption concealed underwater acoustic communication method, comprising: real-time collection to marine environment background noise;Marine environment noise is filtered, and band-limited noise signal is obtained;The band-limited noise signal is divided in time domain, then time domain is reversed, and the rotating phase is selected as steganography parameter, and information bearing signal is obtained;Concealed communication signal is obtained;According to Doppler sampling factor sequence, the received signal is resampled, and the received signal after Doppler compensation is obtained;According to the steganography parameter of transmitting end, the received signal after resampling is steganography demodulation processing by receiving end, and different intermediate signals are obtained, and the intermediate signal is correlated with the signal after resampling, and according to correlation value, information demodulation is completed.The present application not only has the characteristics of difficult to detect, but also has strong encryption function, and can work under low signal-to-noise ratio, can guarantee platform security and information security simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic communication, and relates to underwater covert communication technology, specifically to a covert underwater acoustic communication method based on steganography encryption. Background Technology

[0002] The stealth of underwater platforms is crucial to their survival. Underwater platforms primarily communicate via sound waves, a technology known as underwater acoustic communication. When their communication activities are detected, their stealth is significantly reduced, thus diminishing their deterrent effect. In particular, if the transmitted information is intercepted, information security is severely threatened. Therefore, covert underwater acoustic communication technology is essential for information transmission between underwater platforms.

[0003] Depending on the communication carrier, covert underwater acoustic communication technologies mainly include spread spectrum technology using traditional communication signals as carriers, biomimetic covert underwater acoustic communication technology using biological sounds as carriers, and covert communication technology using environmental noise as carriers. Compared to the former two, environmental noise has natural concealment, and its corresponding covert communication signals can be well hidden in the environment and are not limited by geographical conditions. Spread spectrum communication technology mainly aims to reduce the power spectrum by spreading the signal spectrum, making it difficult for non-cooperative parties to detect or decipher communication activities through conventional detection methods. However, spread spectrum communication signals can be accurately estimated for the symbol period and carrier frequency using advanced detection methods, such as cyclic spectrum, cepstral spectrum, and higher-order statistics, thereby detecting the existence of communication activities and even intercepting communication information. Biomimetic covert underwater acoustic communication technology using biological sounds as carriers mainly modulates information into the calls of dolphins, whales, etc., disguising underwater platforms as marine life to achieve a concealment effect. However, the concealment effect of biomimetic covert underwater acoustic communication technology depends on non-cooperative parties mistaking the communication signal for biological sounds and not detecting it. However, when transmitting the same information, the waveforms of the emitted underwater acoustic communication signals are consistent. For non-cooperative parties, the frequent transmission of the same signals will significantly increase the risk of exposure of communication activities. Furthermore, biomimetic covert underwater acoustic communication technology must also consider the distribution and migration characteristics of organisms in different sea areas; otherwise, the risk of exposure will also increase. To avoid detection of the communication by non-cooperative parties and to protect the covert information, marine environmental noise is more covert than traditional modulated signals and biological calls, and is not limited by sea area. At the same time, to avoid repetitive characteristics, novel modulation methods need to be studied to avoid directly modulating the signal waveform with the modulated information.

[0004] Marine environmental noise is widespread in the marine environment, covering almost all frequency bands and possessing natural concealment. To avoid repetitive waveforms in communication signals when transmitting the same information, covert communication using the marine environment as a carrier requires special modulation and demodulation techniques. This ensures that although the same information is transmitted, the transmitted communication signal waveforms are completely different, thus eliminating repetition. Furthermore, the modulation method must guarantee information security, making it difficult for non-cooperative parties to decipher even if they know the modulation method. Based on marine environmental noise and special modulation techniques, a highly secure and covert underwater acoustic communication method can be developed. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing covert underwater acoustic communication technologies in terms of concealment, this invention provides a covert underwater acoustic communication method based on steganography encryption, which features undetectable characteristics and strong encryption capabilities.

[0006] Technical Solution: To achieve the above objectives, this invention provides a covert underwater acoustic communication method based on steganography encryption, comprising the following steps:

[0007] S1: The underwater platform collects background noise of the marine environment in real time according to communication requirements;

[0008] S2: Based on the communication frequency band of the underwater platform, a broadband filter is used to filter the marine environmental noise to obtain a band-limited noise signal. ;

[0009] S3: Based on the partitioning mode, the band-limited noise signal Perform time-domain partitioning, randomly dividing into The segment signal is then time-reversed, and the rotation phase is chosen as the steganography parameter to modulate the information into the signal, thus obtaining the information-carrying signal. ;

[0010] S4: Carry information signals The covert communication signal is obtained by adding it to the original band-limited noise signal. And transmit communication signals into the seawater environment through a transducer;

[0011] S5: The receiver acquires the received signal in real time via a hydrophone. According to the Doppler sampling factor sequence The received signal is resampled to obtain the Doppler-compensated received signal;

[0012] S6: Based on the steganographic parameters of the transmitter, the receiver performs steganographic demodulation processing on the resampled received signal to obtain different intermediate signals. The intermediate signals are then correlated with the resampled signal, and a decision is made based on the correlation value to complete the demodulation of the information.

[0013] Furthermore, in step S3 The expression of a joke signal is as follows: The time range for each segment is ; Perform time-domain inversion on each sub-signal to obtain ,in This is the midpoint of the sub-signal. = .

[0014] Furthermore, step S3 employs steganographic parameters, namely, rotational phase combinations. Phase modulation is performed on the time-reversed signal to obtain the information-carrying signal. :

[0015]

[0016] in, It is the nth segment of the information-carrying signal. This refers to the steganography algorithm operation; j is the imaginary unit; for Integer multiples of.

[0017] Furthermore, in step S4, the communication signal is concealed. The expression is as follows:

[0018]

[0019] in, For the transmitted BPSK information, take -1 or 1, with the corresponding information bits being 0 and 1.

[0020] Furthermore, in step S5, the Doppler sampling factor sequence Then we get The signal after Doppler compensation .

[0021] Furthermore, in step S6, for each compensated signal Processing is performed to obtain the corresponding intermediate signals. :

[0022]

[0023] Furthermore, in step S6, the compensation signal With intermediate signal Perform correlation to obtain the correlation value vector. The relevant steps are as follows:

[0024]

[0025] in, Represents conjugate operations.

[0026] Furthermore, the process of making a decision based on the relevant value and completing the demodulation of the information in step S6 includes:

[0027] A1: Find relevant vectors The relevant value corresponding to the maximum absolute value ;

[0028] A2: Regarding the relevant values The actual part makes a hard judgment and obtains information for mediation. .

[0029] Furthermore, the relevant values ​​in step A1 The expression is as follows:

[0030]

[0031] Further, the information in step A2 The expression is as follows:

[0032]

[0033] in, Represents the real part of the relevant value Take the symbol, when When it is greater than or equal to 0, it is 1; when... When the value is less than 0, take -1.

[0034] Beneficial Effects: Compared with existing technologies, this invention maps covert information to steganographic parameters (such as rotation phase and partitioning method) using steganography, thereby ensuring that the transmitted covert information is independent of the specific carrier signal. Even if the same information is repeatedly transmitted, the transmitted communication signal will not repeat, eliminating the characteristics of the communication signal. Furthermore, the steganographic parameters are diverse and difficult for non-cooperative parties to estimate. Therefore, this invention not only has the characteristics of being difficult to detect but also has strong encryption capabilities and can operate at a low signal-to-noise ratio. It can simultaneously ensure platform security and information security, making it a highly covert communication method that can provide secure information transmission support for underwater platforms. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method of the present invention;

[0036] Figure 2This is a simulation performance demonstration diagram;

[0037] Figure 3 The correlation peak diagram between the compensated communication signal and the intermediate signal;

[0038] Figure 4 To generate a statistical distribution map of the amplitude of covert communication signals;

[0039] Figure 5 A comparison of the power spectrum of covert communication signals and marine environmental noise;

[0040] Figure 6 This is a cepstral feature map of a covert communication signal.

[0041] Figure 7 The cepstral cyclic spectrum feature map of the concealed communication signal;

[0042] Figure 8 For BER with The trend chart. Detailed Implementation

[0043] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0044] Example 1:

[0045] like Figure 1 As shown, this embodiment provides a covert underwater acoustic communication method based on steganography encryption, including the following steps:

[0046] S1: The underwater platform collects background noise of the marine environment in real time according to communication requirements;

[0047] S2: Based on the communication frequency band of the underwater platform, a broadband filter is used to filter the marine environmental noise to obtain a band-limited noise signal. ;

[0048] S3: Steganographic modulation: Based on the partitioning pattern, the band-limited noise signal is... Perform time-domain partitioning, randomly dividing into The segment signal is then time-reversed, and the rotation phase is chosen as the steganography parameter to modulate the information into the signal, thus obtaining the information-carrying signal. ;

[0049] The expression of a joke signal is as follows: The time range for each segment is ; Perform time-domain inversion on each sub-signal to obtain ,in This is the midpoint of the sub-signal. = ;

[0050] Using steganographic parameters, i.e., rotational phase combination Phase modulation is performed on the time-reversed signal to obtain the information-carrying signal. :

[0051]

[0052] in, It is the nth segment of the information-carrying signal. This refers to the steganography algorithm operation; j is the imaginary unit; for Integer multiples of;

[0053] S4: Carry information signals The covert communication signal is obtained by adding it to the original band-limited noise signal. The covert communication signal is transmitted through a process of filtering, amplification, and power amplification before being sent to the transmitting transducer, which then transmits the communication signal into the seawater environment.

[0054] Covert communication signals The expression is as follows:

[0055]

[0056] in, For the transmitted BPSK information, take -1 or 1, with the corresponding information bits being 0 and 1.

[0057] S5: Receiver-side two-dimensional Doppler search: The receiver acquires the received signal in real time via a receiving hydrophone. According to the Doppler sampling factor sequence The received signal is resampled to obtain the Doppler-compensated received signal;

[0058] Doppler sampling factor sequence Then we get The signal after Doppler compensation .

[0059] S6: Receiver Steganography Demodulation: Based on the steganography parameters of the transmitter, the receiver performs steganography demodulation on the resampled received signal to obtain different intermediate signals. The intermediate signals are then correlated with the resampled signal, and a decision is made based on the correlation value to complete the demodulation of the information.

[0060] For each compensated signal Processing is performed to obtain the corresponding intermediate signals. :

[0061]

[0062] Compensation signal With intermediate signal Perform correlation to obtain the correlation value vector. The relevant steps are as follows:

[0063]

[0064] in, Represents conjugate operations.

[0065] The process of demodulating information by making a judgment based on relevant values ​​includes:

[0066] A1: Find relevant vectors The relevant value corresponding to the maximum absolute value :

[0067]

[0068] A2: Regarding the relevant values The actual part makes a hard judgment and obtains information for mediation. :

[0069]

[0070] in, Represents the real part of the relevant value Take the symbol, when When it is greater than or equal to 0, it is 1; when... When the value is less than 0, take -1.

[0071] Example 2:

[0072] To verify the effectiveness and efficacy of the method of the present invention, a corresponding performance simulation experiment was conducted in this embodiment. The specific simulation parameters were set as follows:

[0073] 1. The original band-limited noise signal is obtained by broadband filtering of real randomly collected marine environmental noise and is used as a carrier. Its duration is 1 second and the number of segments is 4. It is used to generate the covert communication signal to be transmitted; the interference noise is real collected marine environmental noise.

[0074] 2. The signal bandwidth is 4-8kHz, and a total of 1 bit of information, i.e. 1 BPSK symbol, is transmitted. The overall communication rate is 1 bit / s, and the sampling rate is 64kHz. When transmitting the signal, each frame of the signal contains 4 covert communication signals, i.e. 4 bits of information.

[0075] 3. The received covert communication signals are measured data from the South China Sea. By adding different levels of interference noise to the measured covert communication signals, the signal-to-noise ratio (SNR) is reduced to different levels. This method uses the bit error rate (BER) curve, i.e., the relationship between the BER and SNR, as a performance evaluation method, which is defined as follows:

[0076]

[0077] in, The number of bits erroneously demodulated at the receiving end. This represents the total number of bits transmitted. The power of the received signal. The power of the interference noise.

[0078] During the simulation, the SNR was set to {-12, -9, -8, -7, -6, -5, -4}, with the unit being decibels (dB). 2000 Monte Carlo simulations were performed for each SNR.

[0079] This embodiment obtains Figure 2 The simulation performance results shown indicate that, under the condition of SNR of -5dB, BER is close to 3×10⁻⁶. -4 This addresses the low-power transmission requirements for instructions and other information that can be used for long-term underwater operating platforms.

[0080] Figure 3 The correlation peak values ​​between the compensated communication signal and the intermediate signal are given, and it can be seen that the correlation peak is obvious, which proves the effectiveness of the method of the present invention.

[0081] To demonstrate that the method of this invention is difficult to detect, statistical features, power spectrum, cycle spectrum, cepstral spectrum, and other detection methods are used to detect and analyze different features of the method. Figure 4 The statistical distribution of the amplitude of the covert communication signal generated by the method of the present invention shows that it is very similar to the amplitude distribution of marine environmental noise, and can be well concealed in the marine environment. Figure 5 A comparison of the power spectra of the covert communication signal and marine environmental noise showed that they were very similar, proving that the covert communication signal of the present invention has strong concealment. Figure 6 and Figure 7 The cepstral and cyclic spectral features of the covert communication signal are shown respectively. It can be seen that high-order detection methods cannot detect these features, which verifies that the present invention has a low detection rate.

[0082] To verify the strong encryption capability of the method of this invention, the original signal is uniformly divided into two segments, and then a communication signal is generated using ORP phase rotation, where the rotation phases of the two segments are 0 and π, respectively. Assuming the interceptor already knows the steganography parameters, i.e., the rotation phase, but still needs to adjust the duration of the two signal segments to attempt to decipher the steganography algorithm's segmentation pattern. The ratio of the first segment to the total duration is denoted as... When the partitioning pattern matches a symmetric partition, It should be equal to 0.5. Figure 8 For BER with The changing trend. When Within the range of 0.5 ± 0.0002, the BER is 0. Since the signal duration is 0.75 s, communication performance rapidly degrades when the mismatch in the partitioning pattern exceeds 0.15 ms. Therefore, interceptors can only decipher the secret information when the partitioning pattern is strictly matched. It is evident that the partitioning pattern possesses strong encryption capabilities and is crucial for protecting information security.

[0083] In this embodiment, by adding noise of different magnitudes to the measured signal, the bit error rate curves were simulated, verifying the performance of the proposed method. Furthermore, covert communication signals were detected and analyzed using statistical features, power spectrum features, cyclic spectrum, and cepstral spectra, but none of these methods were detected, verifying the method's low detection rate. Simultaneously, even with non-cooperative guidance on steganography parameters and without knowing the partitioning method, simulation results show that the information still cannot be detected, proving the method's encryption functionality.

[0084] In summary, the covert communication signal generated by the method of this invention is not only difficult to detect, but also has strong encryption capabilities and can operate at a low signal-to-noise ratio. It can simultaneously ensure platform security and information security, making it a highly covert communication method that can provide secure information transmission support for underwater platforms.

Claims

1. A covert underwater acoustic communication method based on steganography encryption, characterized in that, Includes the following steps: S1: The underwater platform collects background noise of the marine environment in real time according to communication requirements; S2: Based on the communication frequency band of the underwater platform, a broadband filter is used to filter the marine environmental noise to obtain a band-limited noise signal. ; S3: Based on the partitioning mode, the band-limited noise signal Perform time-domain partitioning, randomly dividing into The segment signal is then time-reversed, and the rotation phase is chosen as the steganography parameter to modulate the information into the signal, thus obtaining the information-carrying signal. ; S4: Carry information signals The covert communication signal is obtained by adding it to the original band-limited noise signal. And transmit communication signals into the seawater environment through a transducer; S5: The receiver acquires the received signal in real time via a receiving hydrophone. According to the Doppler sampling factor sequence The received signal is resampled to obtain the Doppler-compensated received signal; S6: Based on the steganographic parameters of the transmitter, the receiver performs steganographic demodulation processing on the resampled received signal to obtain different intermediate signals. The intermediate signals are then correlated with the resampled signal, and a decision is made based on the correlation value to complete the demodulation of the information.

2. The covert underwater acoustic communication method based on steganography encryption according to claim 1, characterized in that, In step S3 The expression of a joke signal is as follows: The time range for each segment is ; By inverting the time domain of each sub-signal, we obtain ,in This represents the midpoint of the sub-signal. = .

3. The covert underwater acoustic communication method based on steganography encryption according to claim 2, characterized in that, The step S3 uses steganographic parameters, namely, rotation phase combination. Phase modulation is performed on the time-reversed signal to obtain the information-carrying signal. : ； in, It is the nth segment of the information-carrying signal. This refers to the steganography algorithm operation; j is the imaginary unit; for Integer multiples of.

4. The covert underwater acoustic communication method based on steganography encryption according to claim 3, characterized in that, The concealed communication signal in step S4 The expression is as follows: ； in, This is the BPSK information for transmission.

5. The covert underwater acoustic communication method based on steganography encryption according to claim 4, characterized in that, The Doppler sampling factor sequence in step S5 Then we get The signal after Doppler compensation .

6. The covert underwater acoustic communication method based on steganography encryption according to claim 5, characterized in that, In step S6, each compensated signal... Processing is performed to obtain the corresponding intermediate signals. : 。 7. A covert underwater acoustic communication method based on steganography encryption according to claim 6, characterized in that, The compensation signal in step S6 With intermediate signal Perform correlation to obtain the correlation value vector. The relevant steps are as follows: ； in, Represents conjugate operations.

8. The covert underwater acoustic communication method based on steganography encryption according to claim 7, characterized in that, The process of making a decision based on the relevant value and completing the information demodulation in step S6 includes: A1: Find relevant vectors The relevant value corresponding to the maximum absolute value ; A2: Regarding the relevant values The actual part makes a hard judgment and obtains information for mediation. .

9. A covert underwater acoustic communication method based on steganography encryption according to claim 8, characterized in that, The relevant values ​​in step A1 The expression is as follows: 。 10. A covert underwater acoustic communication method based on steganography encryption according to claim 8, characterized in that, Information in step A2 The expression is as follows: ； in, Represents the real part of the relevant value Take the symbol.

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