A method and device for generating a key

Abstract

The present invention belongs to the technical field of underwater acoustic physical layer, and particularly relates to a key generation method and device, which is used to realize channel detection and key generation under the condition of frequency selective fading and impaired channel reciprocity. The transmitting end and the receiving end of the legal communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain the channel observation sequence by carrying data in the detection sequence for information exchange, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legal communication parties respectively; the legal communication parties use a single-bit quantization method to extract the underwater acoustic physical layer key in the channel observation sequence, and use error correction codes to negotiate keys, and use hash functions to amplify privacy. The present invention can solve the problems of impaired channel reciprocity caused by large propagation delays in the presence of frequency selective fading, and can obtain a lower key mismatch rate in an underwater acoustic environment, which is convenient for application in actual scenarios; and further through experimental simulation, a lower key mismatch rate is still maintained under the condition of underwater acoustic frequency selective fading and impaired channel reciprocity.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater acoustic physical layer, and particularly relates to a key generation method and device for realizing channel detection and key generation under the condition of frequency selective fading and impaired channel reciprocity. Background Art

[0002] Physical layer key generation technology is a security technology that directly uses channel characteristics as a random source to generate keys. This technology uses the reciprocity of wireless channels to generate random keys, uses the decorrelation characteristics of the channel to ensure the security of the keys, and uses the time-varying nature of the channel to ensure the rapid update of the keys. It has the advantages of no need for key distribution, high security, and fast key update speed. Physical layer key generation usually includes channel detection, feature extraction, quantization, key negotiation, and privacy amplification. It can effectively solve the problems of difficult key distribution and easy loss of cryptographic equipment in underwater acoustic confidential communication. It has received widespread attention from the academic community and has broad prospects. The physical layer key generation technology for radio communications has developed rapidly. Since underwater acoustic channels also have reciprocity, spatial independence, and time-varying characteristics, people have extended the idea of ​​physical layer key generation to underwater acoustic communications in recent years. In 2016, Luo proposed to use the receiving intensity of underwater acoustic signals as a random source to extract physical layer keys, systematically studied the feasibility of applying physical layer key generation technology to underwater acoustic environments, and proposed to use orthogonal frequency division multiplexing (OFDM) to increase the key generation rate and use smoothing filters to improve the reciprocity of detection sequences. However, he only introduced the traditional radio physical layer key generation technology into the underwater field, and did not optimize the characteristics of the underwater acoustic channel; then Petroni et al. built an underwater acoustic physical layer key generation system and verified the feasibility of the system through field experiments. However, he mainly discussed the characteristics of the underwater acoustic channel suitable for key generation, and did not discuss the problem of reciprocity loss caused by the large delay of the underwater acoustic channel in the time division half-duplex system; while Liu Junkai et al. used the generated underwater acoustic physical layer key to complete covert communication for the first time, but they did not fully consider the characteristics of the underwater acoustic channel and the communication distance was only 60 meters, which was difficult to meet actual needs.

[0003] The first step in generating physical layer keys for underwater acoustic communication is underwater acoustic channel detection. Through channel detection, both communicating parties can obtain the observation sequence of the random source, and use the observation sequence to extract the channel characteristics, and then generate the physical layer key. Most underwater acoustic communications are half-duplex communications, and the reciprocity of half-duplex communication channels will be affected by transmission delay, system delay, hardware device fingerprint characteristics and noise. Due to the slow propagation rate of underwater acoustics, the impact of transmission delay on the detection of channel reciprocity is more obvious. Assuming that the speed of sound is 1500m / s and the communication distance is 1km, it takes about 1.3 seconds to complete the two-way transmission of half-duplex communication. Furthermore, due to the relative motion of the communicating parties, changes in the hydrological environment and other factors, the channel characteristics will also change in time, which will also cause the channel detection reciprocity to be damaged. When the communicating parties use the channel characteristics as a random source to extract the observation sequence, the time-varying characteristics of the random source will reduce the correlation of the observation sequence, affecting the subsequent feature extraction, quantization and other links. In response to the above problems, Liu Jingmei et al. proposed a local pilot auxiliary wait protocol (LPAWP) method, which provides a new idea for solving the problem of impaired channel reciprocity in time-division half-duplex systems. However, the premise for the application of this method is that the channel is flat fading. In fact, the coherent bandwidth of the underwater acoustic channel is relatively narrow, which often causes frequency selective fading of the signal, making it difficult for this method to obtain a low key mismatch rate. Summary of the invention

[0004] To this end, the present invention provides a key generation method and device, which can solve the problems of channel reciprocity impairment caused by large propagation delay in the presence of frequency selective fading, and can obtain a lower key mismatch rate in an underwater acoustic environment, which is convenient for application in actual scenarios.

[0005] According to the design scheme provided by the present invention, a key generation method is provided, which includes the following contents:

[0006] The transmitting end and the receiving end of the legitimate communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain a channel observation sequence by exchanging information through the data carried in the detection sequence, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legitimate communication parties respectively;

[0007] The two parties in legal communication use the single-bit quantization method to extract the underwater acoustic physical layer key from the channel observation sequence;

[0008] The two parties in legitimate communication use Hamming error correction codes to negotiate keys and use the MD5 function to amplify privacy.

[0009] As a key generation method of the present invention, further, the two legal communicating parties use OFDM sequence to perform underwater acoustic channel detection and information exchange, and when sending the detection sequence to perform underwater acoustic channel detection, the common pilot sequence used to constitute the detection sequence is pre-stored at the transmitting end and the receiving end.

[0010] As the key generation method of the present invention, further, the OFDM random pilot sequence adopts a uniformly distributed pseudo-random sequence and adopts PSK mapping.

[0011] As the key generation method of the present invention, further, underwater acoustic channel detection includes the following two stages:

[0012] In the sender-led phase, the sender sends its detection sequence for channel detection; the receiver receives the first sender detection sequence and sends a sequence containing forward channel impulse response information in response; the sender receives the first receiver detection sequence, and the communicating parties use the received first sender detection sequence and the first receiver detection sequence to obtain the observation sequence of the forward channel random source respectively;

[0013] In the receiving-end-dominated phase, the receiving end sends its detection sequence for channel detection; the transmitting end receives the second receiving-end detection sequence and sends a sequence containing reverse channel impulse response information in response; the receiving end receives the second sending-end detection sequence, and the communicating parties respectively use the received second receiving-end detection sequence and the received second sending-end detection sequence to obtain the observation sequence of the reverse channel random source.

[0014] As the key generation method of the present invention, before each round of underwater acoustic channel detection, the transmitting end and the receiving end randomly generate a local random pilot sequence X on the kth subcarrier. R (k), V A (k) and V B (k), and obtain the common pilot sequence X by pre-distribution P , the detection sequence X generated by the transmitter and the receiver TA , Respectively expressed as:

[0015] N is the number of subcarriers.

[0016] As a physical layer key detection method for underwater acoustic communication based on OFDM pilot sequence of the present invention, further, in the dominant stage of the transmitter, the transmitter and the receiver send pilot sequences in sequence to perform channel detection, wherein the detection sequence sent by the transmitter includes a local random pilot sequence and a common pilot sequence, and the detection sequence sent by the receiver includes a first sender detection sequence, a local random pilot sequence and a common pilot sequence; and in the entire underwater acoustic channel detection process, the communicating parties obtain an observation sequence for the channel amplitude-frequency response based on the frequency domain processing of the pilot sequence for the received detection sequence.

[0017] As the key generation method of the present invention, further, in the channel detection using OFDM symbols as the pilot detection sequence, a cyclic prefix is ​​inserted between OFDM symbols as a protection interval, and the cyclic prefix length is set to be greater than the maximum delay extension of the channel, so that the multipath interference of the previous OFDM symbol on the next OFDM symbol is limited within the protection interval.

[0018] As the key generation method of the present invention, further, Hamming error correction code is used for key negotiation, and the communicating parties finally generate a consistent underwater acoustic physical layer key through multiple error correction negotiations.

[0019] As the key generation method of the present invention, further, the negotiated consistent key is enhanced using the MD5 function.

[0020] Furthermore, the present invention also provides a key generation device, comprising: a channel observation module, a key extraction module, and a key negotiation and key enhancement module, wherein:

[0021] Channel observation module: the transmitter and receiver of the legitimate communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain the channel observation sequence by exchanging information with data carried in the detection sequence, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legitimate communication parties respectively;

[0022] In the key extraction module, the two parties in legitimate communication use the single-bit quantization method to extract the underwater acoustic physical layer key from the channel observation sequence.

[0023] In the key negotiation and key enhancement module, the two parties in legitimate communication use the Hamming error correction code to negotiate the generated underwater acoustic physical layer key. The negotiated key is enhanced using the MD5 function to finally obtain the underwater acoustic physical layer key.

[0024] Beneficial effects of the present invention:

[0025] The present invention uses a detection sequence composed of local pilots and common pilots to detect underwater acoustic channels, and uses the detection sequence to carry channel information for information interaction. Compared with other channel detection methods, it can solve the problems of underwater acoustic frequency selective fading and channel reciprocity impairment; it uses single-bit quantization, error correction code, and hash function for quantization, key negotiation, and key enhancement, and finally extracts a consistent underwater acoustic physical layer key. The algorithm is simple and easy to implement. Further experimental simulation shows that a low key mismatch rate is maintained under the conditions of underwater acoustic frequency selective fading and channel reciprocity impairment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the underwater acoustic communication physical layer key detection process in the embodiment;

[0027] Figure 2 This is a schematic diagram of a typical physical layer key generation scenario in the embodiment;

[0028] Figure 3 It is a schematic diagram of the principle of legal double-sent physical layer key detection in a typical scenario in the embodiment;

[0029] Figure 4 This is a schematic diagram of the OFDM pilot structure in the embodiment;

[0030] Figure 5 Schematic diagram of the OFDM pilot structure with a cyclic prefix in the embodiment;

[0031] Figure 6 It is a schematic diagram of the simulation environment in the embodiment;

[0032] Figure 7 It is a schematic diagram of the sound velocity profile in the embodiment;

[0033] Figure 8 Schematic diagram of the influence of Doppler on the mean square error of the method in the embodiment;

[0034] Fig. 9 Schematic diagram of the influence of Doppler on the key mismatch rate of the method in the embodiment;

[0035] Fig.10 Schematic diagram of the change of the key mismatch rate with the key negotiation rounds in the embodiment. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and technical solutions.

[0037] Traditional physical layer key generation technology uses channel time-varying, reciprocity, and spatial decorrelation to achieve key distribution and rapid update. However, the underwater acoustic channel environment is complex, highly time-varying, and has large delays. The channel environment often changes during channel detection, resulting in the loss of channel reciprocity measured by both communicating parties. Figure 1 As shown, a key generation method is provided, including the following contents:

[0038] The transmitting end and the receiving end of the legitimate communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain a channel observation sequence by exchanging information through the data carried in the detection sequence, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legitimate communication parties respectively;

[0039] The two parties in legal communication use the single-bit quantization method to extract the underwater acoustic physical layer key from the channel observation sequence;

[0040] The two parties in legitimate communication use Hamming error correction codes to negotiate keys and use the MD5 function to amplify privacy.

[0041] For the time division half-duplex communication system, the local random pilot sequence and the common pilot sequence generated by the communicating parties can be used to form a detection sequence through the OFDM pilot structure; the communicating parties respectively send the detection sequence to complete the underwater acoustic channel detection and use the information carried by the pilot sequence to realize information exchange; the communicating parties use the obtained observation sequence to use the single-bit quantization method, error correction code negotiation, and hash key enhancement to extract the underwater acoustic physical layer key, which can effectively solve the problem of channel reciprocity damage during the underwater acoustic physical layer key detection process and can obtain a lower key inconsistency rate.

[0042] See also Figure 2 As shown in Figure 1, Alice and Bob are legitimate communication parties, and Eve is an eavesdropper. Alice and Bob send a detection signal X TA and X TB , and use the received signal Y RA and Y RB Generate an observation sequence to characterize the channel impulse response H AB and H BA Eve does not send any signal, but only uses the received signal Y RE-Alice and Y RE-Bob Generate an observation sequence to characterize the channel impulse response H AE and H BE The randomness of .

[0043] When the channel reciprocity between Alice and Bob is impaired, that is, H AB and H BAWhen the consistency is low, in the embodiment of this case, OFDM sequence can be used to carry channel information, and both parties can extract keys from two random sources of the forward and reverse channels at the same time through information interaction. The two parties in legal communication use OFDM sequence for underwater acoustic channel detection and information interaction, and when sending the detection sequence for underwater acoustic channel detection, the common pilot sequence used to form the detection sequence is pre-stored at the transmitting end and the receiving end.

[0044] Furthermore, in the present embodiment, underwater acoustic channel detection includes the following two stages:

[0045] In the sender-led phase, the sender sends its detection sequence for channel detection; the receiver receives the first sender detection sequence and sends a sequence containing forward channel impulse response information in response; the sender receives the first receiver detection sequence, and the communicating parties use the received first sender detection sequence and the first receiver detection sequence to obtain the observation sequence of the forward channel random source respectively;

[0046] In the receiving-end-dominated phase, the receiving end sends its detection sequence for channel detection; the transmitting end receives the second receiving-end detection sequence and sends a sequence containing reverse channel impulse response information in response; the receiving end receives the second sending-end detection sequence, and the communicating parties respectively use the received second receiving-end detection sequence and the received second sending-end detection sequence to obtain the observation sequence of the reverse channel random source.

[0047] See also Figure 3 As shown, Alice generates a random sequence V A ,X R , Bob generates a random sequence V B . Common pilot sequence X P In the first phase of channel detection, Alice sends a detection sequence Perform channel detection. Bob receives the detection sequence After that, send the H AB Information detection sequence Alice receives the probe sequence Alice and Bob then use the received sequence and Get the random source H AB The observation sequence The first phase of channel detection is over. In the second phase, Bob sends a detection sequence Alice receives the probe sequence After that, send the H BA Information detection sequence Bob receives the probe sequence Alice and Bob then use the received sequence and Get the random source H BA The observation sequence The second phase of channel detection ends. At this point, the observation sequences generated in the two phases simultaneously utilize the forward channel H AB and reverse channel H BA , so a consistent key can be generated.

[0048] Furthermore, in the transmitter-dominated stage, the transmitter and the receiver send pilot sequences in turn to perform channel detection, wherein the detection sequence sent by the transmitter includes a local random pilot sequence and a common pilot sequence, and the detection sequence sent by the receiver includes a first-sender detection sequence, a local random pilot sequence and a common pilot sequence; and in the entire underwater acoustic channel detection process, the communicating parties obtain an observation sequence for the channel amplitude-frequency response based on the frequency domain processing of the pilot sequence for the received detection sequence.

[0049] During the channel detection process, OFDM sequence is used to complete channel detection and information exchange. OFDM uses mutually orthogonal subcarriers to carry different data to complete information transmission. It has the advantages of strong resistance to frequency selective fading, high spectrum utilization, simple system implementation, and simple channel estimation. When used for physical layer key generation, the OFDM channel frequency response has rich characteristic information and is easy to estimate, and the key generation rate is high. Since all OFDM subcarriers are orthogonal, an OFDM symbol containing N subcarriers can be expressed in matrix form:

[0050]

[0051] In the present invention, X is an OFDM symbol, where X(k) represents the complex data k=1, 2, ... N carried by the kth subcarrier. Assuming that the channel frequency response of the kth subcarrier is H(k) and the noise is W(k), the received OFDM symbol Y can be expressed as:

[0052]

[0053] Where H is the channel vector, H = [H(1), H(2), …, H(N)] T ; W is the Gaussian noise vector, W=[W(1),W(2),…,W(N)] T The received symbol Y(k) on the kth subcarrier can be expressed as:

[0054] Y(k)=X(k)H(k)+W(k),k=1,2,…,N (3)

[0055] In this embodiment, the detection sequence uses n OFDM symbols to achieve information exchange. Assuming that there is no inter-symbol interference between OFDM blocks, formula (3) can be expanded to:

[0056]

[0057] Where, for the i-th OFDM symbol on the k-th subcarrier, Y(k,i) represents the received symbol, X(k,i) represents the transmitted symbol, H(k,i) represents the channel frequency response, W(k,i) represents the local noise, and i = 1, 2, ..., n. Transmit OFDM pilot sequence and The pilot structure is shown in Figure 4 shown.

[0058] Still taking the first stage of channel detection as an example, on the kth subcarrier, channel detection can be specifically divided into four steps:

[0059] Step 1: Alice generates a local pilot symbol X R (k) and V A (k), Bob generates local pilot symbol V B (k). Common pilot symbol X P (k) is pre-stored on Alice and Bob. R (k),V A (k),V B (k),X P (k) is the OFDM pilot symbol on the kth subcarrier. Before each round of channel detection, Alice and Bob randomly generate local pilot symbols, so the local pilot symbols cannot be obtained in advance by a third party.

[0060] Step 2: Alice sends a pilot sequence consisting of 2 OFDM symbols It is expressed as:

[0061]

[0062] Step 3: Bob receives the OFDM sounding sequence It is expressed as:

[0063]

[0064] Among them, W B (k,i) is the local noise at Bob’s end. Using the received symbol and the common pilot symbol X P (k) Availability of:

[0065]

[0066] Under high signal-to-noise ratio, it can be approximately expressed as:

[0067]

[0068] Bob then uses the received symbol and local random pilot symbol V B (k) Generate OFDM sounding sequence It is expressed as:

[0069]

[0070] Step 4: Alice receives the probe sequence It is expressed as:

[0071]

[0072] Among them, W A (k,i) is the local noise at Alice. Using Alice's local pilot symbol V A (k),X R (k) and the common pilot symbol X P (k) Observable values It is expressed as:

[0073]

[0074] Under high signal-to-noise ratio, it can be approximately expressed as:

[0075]

[0076] In a slowly time-varying channel, the impulse responses of adjacent OFDM symbols are consistent or approximately consistent, so

[0077] H AB (k,1)=H AB (k,2),k=1,2,…,N (13)

[0078] H BA (k,1)=H BA (k,2),k=1,2,…,N (14)

[0079] From formula (12) and formula (14), we can get:

[0080]

[0081] From formula (8), formula (13) and formula (15), we can get:

[0082]

[0083] At this point, the first phase of channel detection is completed, and Alice and Bob obtain observation values ​​respectively. and

[0084] In order to complete channel detection, two OFDM symbols can be used as pilot sequences for channel detection in the embodiment. In actual underwater acoustic OFDM communication, there is often inter-symbol interference caused by the underwater acoustic multipath delay characteristics, which affects the reliability of communication. In order to eliminate the inter-symbol interference caused by the multipath channel to the greatest extent, a cyclic prefix (CP) is often inserted between OFDM symbols as a guard interval, and the length of the cyclic prefix CP is set to T G Greater than the maximum channel delay spread T L At this time, the multipath interference of the previous OFDM symbol to the next OFDM symbol will be limited within the protection interval, and will no longer affect the demodulation of the next OFDM symbol, thus avoiding inter-symbol interference. Figure 5 shown.

[0085] In step 4, formula (13) and formula (14) are based on the premise that the channel is slowly time-varying. In the embodiment, the channel coherence time can be used to quantitatively describe the channel time-varying property. S Less than the channel coherence time T 相干 When , the channel can be considered as a slowly time-varying channel, in which case the impulse responses of adjacent OFDM symbol channels are approximately consistent.

[0086] In summary, under the condition of slowly time-varying multipath channel, by sending OFDM pilot sequence containing CP, both communicating parties can use the same random source to generate observation sequence and complete channel detection when channel reciprocity is impaired.

[0087] After completing the channel detection, using formula (17), the communicating parties use the single-bit quantization method to generate the initial physical layer key K for the observation sequence A and K B The single-bit quantization process is expressed as:

[0088]

[0089] For the quantized key, the (7,4) Hamming error correction code is used for key negotiation. The specific steps are as follows:

[0090] Step 1: Alice initiates a negotiation process, randomly selects a string of error correction codewords c, and then performs error correction encoding on it to obtain an error correction code C = code(c).

[0091] Step 2: Alice obtains the quantized sequence K A XOR with the error correction code C to get the negotiation information Then send it to Bob.

[0092] Step 3: Bob receives the negotiation information and then compares the received negotiation information s with the local quantized sequence K B The XOR recovery error correction code is

[0093] Step 4: Correct C′ and obtain c′=decode(C′). A With K B If the inconsistency length is within the error correction code capability, then the decoded codeword satisfies c′=c.

[0094] Step 5: Error correction encode the code word c′ to obtain C″=code(c′).

[0095] Step 6: XOR the error correction code C″ with the negotiation information to obtain the key bit sequence after error correction.

[0096] Step 7: Alice and Bob calculate K respectively A With K B2 The CRC sequence is used to exchange key information through the channel. If the CRC check is consistent, the key negotiation is successful. If not, proceed to step 1 again.

[0097] After key negotiation is completed, the MD5 function is used to amplify privacy and ultimately generate a consistent underwater acoustic physical layer key.

[0098] Furthermore, based on the above method, an embodiment of the present invention also provides a key generation device, comprising: a channel observation module, a key extraction module, and a key negotiation and key enhancement module, wherein:

[0099] Channel observation module: the transmitter and receiver of the legitimate communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain the channel observation sequence by exchanging information with data carried in the detection sequence, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legitimate communication parties respectively;

[0100] In the key extraction module, the two parties in legitimate communication use the single-bit quantization method to extract the underwater acoustic physical layer key from the channel observation sequence.

[0101] In the key negotiation and key enhancement module, the two parties in legitimate communication use the Hamming error correction code to negotiate the generated underwater acoustic physical layer key. The negotiated key is enhanced using the MD5 function to finally obtain the underwater acoustic physical layer key.

[0102] In order to verify the effectiveness of this solution, the following is a further explanation based on the test data:

[0103] Figure 6In the figure, Alice and Bob are transceivers deployed 200m underwater and 5000m apart. Alice remains stationary, and Bob moves in the opposite direction of Alice at a speed of 2 knots. The underwater acoustic channel simulation software bellhop is used to generate the channel impulse responses of Alice-Bob and Bob-Alice respectively. The longitude and latitude coordinates of the two communicating parties are set to (115.5°N, 19.5°N), and the Argo database is used to obtain the sound velocity profile information and ocean depth information of the corresponding area. The sound velocity profile is shown in the figure below. Figure 7 Other simulation parameters are shown in Table 1. When the relative speed of the two communicating parties is 2 knots (about 1m / s), the pilot signal carrier frequency f c When the channel frequency is 10kHz, the channel coherence time is approximately:

[0104]

[0105] Among them, f d is the maximum Doppler frequency deviation, Δ is the Doppler factor, v is the relative speed of the two communicating parties, c is the speed of sound and according to the speed of sound profile, c=1517m / s.

[0106] When the two communicating parties are in relative motion, it is necessary not only to consider Doppler interference, but also to consider different communication distances when simulating Alice-Bob and Bob-Alice channels. Taking the first phase of detection as an example, the distance between the two communicating parties is set to 3000 meters at the beginning of the detection. At this time, it takes about 2 seconds from Alice sending the pilot sequence to Bob receiving the pilot sequence, that is, to complete a one-way channel detection. Due to the back-to-back motion, when Bob sends the pilot sequence, the distance between the two communicating parties becomes 3002 meters, and the channel parameters change.

[0107] Table 1 Simulation parameter information

[0108]

[0109] In order to verify the improvement effect of this scheme on underwater acoustic physical layer key detection, the experiment simulated and verified the mean square error of the channel observation sequence of both parties and the initial key mismatch rate after quantization. The detection signal adopts OFDM modulation, and the specific parameters are shown in Table 2.

[0110] Table 2 OFDM modulation parameters

[0111] project illustrate Signal sampling rate 64kHz Carrier frequency 10kHz Subcarrier spacing 25Hz Number of OFDM subcarriers 128 OFDM cyclic prefix 1 / 2 One detection signal length 120ms

[0112] The relative motion of the two communicating parties will cause Doppler interference, and the change in the positions of the two parties will further cause changes in the channel environment. Figure 8 and Fig. 9The mean square error and initial key mismatch rate of the observation values ​​of the two communicating parties are compared when the maximum Doppler frequency deviation of the received pilot sequence is 0Hz, 6Hz, and 10Hz. The simulation results show that when the Doppler frequency deviation is low, the correlation of the observation sequences generated by the two communicating parties is better. And in the absence of frequency deviation, the initial key mismatch rate obtained by single-bit quantization is less than 0.1.

[0113] When the signal-to-noise ratio is 20 dB, the initial key is obtained using the parameters in Table 2, and then multiple rounds of key negotiation are performed using error correction codes. Fig.10 The figure shows the change of key mismatch rate with the number of key negotiation rounds. It can be seen that after 4 rounds of negotiation, both parties can obtain the same underwater acoustic physical layer key.

[0114] Unless otherwise specifically stated, the relative steps, numerical expressions and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0115] Based on the above method and / or system, an embodiment of the present invention also provides a server, including: one or more processors; a storage device for storing one or more programs, when the one or more programs are executed by the one or more processors, the one or more processors implement the above method.

[0116] Based on the above method and / or system, an embodiment of the present invention further provides a computer-readable medium having a computer program stored thereon, wherein the above method is implemented when the program is executed by a processor.

[0117] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limiting, and thus other examples of the exemplary embodiments may have different values.

[0118] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0119] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A key generation method, characterized in that: Contains the following: Before each round of underwater acoustic channel detection, the transmitter and receiver randomly generate a local random pilot sequence X on the kth subcarrier. R (k), V A (k) and V B (k), and obtain the common pilot sequence X by pre-distribution P , the transmitter and receiver of the legal communication parties respectively send a detection sequence to perform underwater acoustic channel detection, and obtain a channel observation sequence by carrying data in the detection sequence for information exchange, wherein before each round of channel detection, the legal communication parties randomly generate a local random pilot sequence, and the detection sequence uses n OFDM symbols as pilots to realize information exchange, and the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legal communication parties respectively; in the channel detection using the OFDM symbol as the pilot detection sequence, a cyclic prefix is ​​inserted between the OFDM symbols as a protection interval, and the cyclic prefix length is set to be greater than the maximum delay extension of the channel, so that the multipath interference of the previous OFDM symbol on the next OFDM symbol is limited within the protection interval; underwater acoustic channel detection includes the following two stages: the transmitter-dominated stage, the transmitter sends its detection sequence consisting of 2 OFDM symbols Perform channel detection. The receiving end receives the first sender's detection sequence And send the forward channel impulse response information H AB The detection sequence To respond, k=1,2,…,N, N is the number of subcarriers, W B (k,i) is the local noise at the receiving end; the sending end receives the first receiving end detection sequence, and the communicating parties use the received first sending end detection sequence and the first receiving end detection sequence to obtain the observation sequence of the random source of the forward channel and The receiver leads the phase, and the receiver sends its detection sequence Perform channel detection; the transmitting end receives the second receiving detection sequence and sends a reverse channel impulse response information H BA The detection sequence The receiving end receives the second sender detection sequence, and the communicating parties use the received second receiving detection sequence and the second sender detection sequence to obtain the reverse channel random source H BA The observation sequence Based on the observation sequence generated by the two stages of the transmitter-dominated stage and the receiver-dominated stage in underwater acoustic channel detection, the forward channel impulse response information H is used to generate the observation sequence. AB and the reverse channel random source H BA ,The legal communication parties use the single-bit quantization method to generate the initial physical layer key; For the initial physical layer key generated by quantization, the legitimate communicating parties use the (7,4) Hamming error correction code for key negotiation and use the MD5 function for privacy amplification, and finally generate a consistent underwater acoustic physical layer key. The key negotiation process includes: the sender initiates the negotiation process, randomly selects a string of error correction codewords c and performs error correction coding to obtain the error correction code C = code(c), and converts the quantized initial physical layer key sequence K A XOR with the error correction code C to get the negotiation information s, Send s to the receiving end; the receiving end compares the received negotiation information s with the initial physical layer key sequence K obtained after local quantization B XOR is performed and the recovered error correction code C′ is obtained. Correct C′ and get c′=decode(C′). A With K B If the length of inconsistency is within the error correction code capability, the decoded codeword satisfies c′=c, and the codeword c′ is error-corrected to obtain C″=code(c′). The error correction code C″ is XORed with the negotiation information to obtain the key bit sequence K after error correction. B2 , The sender and receiver calculate K respectively A With K B2 The CRC sequence is sent and the key negotiation is successful if the CRC check is consistent. If not, the sender initiates the negotiation process again to negotiate the key.

2. The key generation method according to claim 1, characterized in that: The two parties in legal communication use OFDM sequences for underwater acoustic channel detection and information exchange, and when sending the detection sequence for underwater acoustic channel detection, the common pilot sequence used to form the detection sequence is pre-stored at the transmitting end and the receiving end.

3. The key generation method according to claim 2, characterized in that: The OFDM random pilot sequence uses a uniformly distributed pseudo-random sequence and adopts PSK mapping.

4. The key generation method according to claim 1, characterized in that: In the transmitter-dominated stage, the transmitter and the receiver send pilot sequences in turn to perform channel detection, wherein the detection sequence sent by the transmitter includes a local random pilot sequence and a common pilot sequence, and the detection sequence sent by the receiver includes a first-sender detection sequence, a local random pilot sequence and a common pilot sequence; and in the entire underwater acoustic channel detection process, the communicating parties obtain an observation sequence for the channel amplitude-frequency response based on the frequency domain processing of the pilot sequence for the received detection sequence.

5. The key generation method according to claim 1, characterized in that: The negotiated consistent key is enhanced using the MD5 function.

6. A key generation device, characterized in that: The method according to claim 1 is implemented, comprising: a channel observation module, a key extraction module, a key negotiation and key enhancement module, wherein: Channel observation module: the transmitter and receiver of the legitimate communication parties respectively send a detection sequence to detect the underwater acoustic channel, and obtain the channel observation sequence by exchanging information with data carried in the detection sequence, wherein the detection sequence is composed of a local random pilot sequence and a common pilot sequence generated by the legitimate communication parties respectively; The key extraction module uses the single-bit quantization method to extract the underwater acoustic physical layer key from the channel observation sequence by the legal communicating parties; In the key negotiation and key enhancement module, the two legal communicating parties use Hamming error correction code to negotiate the generated underwater acoustic physical layer key. The negotiated consistent key is enhanced using the MD5 function to finally obtain the underwater acoustic physical layer key.

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