Storage-assisted time-sensitive information covert communication method and system

Abstract

The invention discloses a storage-assisted time-sensitive information covert communication method and system. The storage-assisted time-sensitive information covert communication method comprises the following steps: S1, sensing and storing information; the source node continuously perceives a private time-sensitive data packet by using an information perception module and stores the data packet in a storage queue; s2, key exchange and codebook sharing are carried out; a secret key is generated between the source node and the destination node by using a wireless channel, and a private data packet coding codebook encrypted by using the secret key is periodically shared; s3, information coding and transmission; when the data packet to be sent exists in the storage queue, the source node encodes the information and transmits the data packet at the transmission power capable of keeping hidden; s4, information decoding; and the destination node decodes by using the codebook shared by the destination node and the source node in each transmission period. And when no data packet exists in the storage queue, the source node is kept silent, so that the communication concealment is improved. Compared with a traditional hidden wireless communication method without a storage queue, the method provided by the invention can ensure better information timeliness.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless network information transmission, and in particular to a storage-assisted time-sensitive information covert communication method and system. Background Art

[0002] With the development of wireless communication technology, wireless sensor networks have greatly facilitated daily production and life by extending human senses, and have played an irreplaceable role in emerging applications such as remote monitoring, smart home, and autonomous driving. Timely and reliable wireless information transmission is the key to supporting these emerging applications. Therefore, taking into account both the reliability and timeliness of information has received widespread attention in the key application scenarios of next-generation mobile communications. However, in the network design for real-time status update applications, traditional performance metrics such as throughput and latency will not be able to effectively describe the freshness of information in the system. Therefore, Kaul et al. proposed the concept of age of information (AoI) in the paper "Real-time status: How often should one update?, 2012 Proceedings IEEE INFOCOM, 2012, pp. 2731--2735." Subsequently, information age has received widespread attention from academia and industry as a metric for evaluating information timeliness.

[0003] At the same time, due to the open nature of wireless channels, the security of information transmission has gradually attracted people's attention. Traditional communication security mechanisms mainly rely on the computational complexity of encryption and decryption algorithms to ensure the secure transmission of information. However, communication security mechanisms based on computational complexity are difficult to ensure the absolute security of information. As a supplement to traditional security mechanisms, physical layer security technology uses the fading characteristics of wireless channels to ensure the security of information transmission and achieves absolute security in the sense of Shannon's information theory. It is worth pointing out that traditional information security transmission mechanisms based on encryption and physical layer security only protect the content of information from being deciphered by illegal eavesdropping nodes, focusing more on the security of the transmitted information itself, but ignoring the undetectability of the information transmission process. In fact, the basis for eavesdropping nodes to decipher information is the correct detection of information transmission behavior. Therefore, stronger security performance can be achieved by hiding wireless transmission behavior. In addition, in military application scenarios such as battlefield situation monitoring and drone reconnaissance, monitors may not care about the specific content of the information, but are more concerned about the existence of the sender and the receiver. Once the information transmission process is detected, it may take measures such as full-band high-power interference or even physical attacks to destroy the information transmission process. At this time, ensuring that information transmission behavior is undetectable is of great significance for protecting user privacy and information transmission security.

[0004] Covert wireless communication technology has attracted the attention of researchers by using the randomness of the wireless communication environment to hide the wireless transmission behavior and ensure that the information transmission is undetectable. Specifically, the source node sends the private message at a lower power after adopting appropriate signal processing technology. Since the source node does not send messages continuously, it is difficult for the monitoring node to accurately infer whether the observed signal contains the private message. The paper "Delay-intolerant covert communications with either fixed or random transmit power, IEEE Trans. Inf.Forensics Secur., vol. 14, no. 1, pp. 129--140, Jan. 2019" first studied the covert communication problem in delay-constrained wireless networks. The study showed that finite block length coding can meet the transmission delay constraint and enhance the concealment of information transmission. However, the above paper considers that the source node sends the private message with a prior probability of 0.5 in each transmission cycle. This limitation makes the proposed covert transmission scheme not universal and cannot be directly applied to the scenario where the private data packet is randomly generated over time. The paper “Fundamental limits of covert packet insertion, IEEE Trans. Commun., vol. 68, no. 6, pp. 3401--3414, Jun. 2020” models the generation of private data packets as a Poisson process, achieves covert transmission by embedding private messages into the public channel, and derives the covert transmission performance bound of Poisson data streams under a specific arrival rate. In the above research on Poisson data packet covert transmission, data packets are sent as soon as they are generated, and the prior probability of data packet sending depends entirely on the data packet arrival rate, which is the key to ensuring communication covertness. Data packet storage can effectively adjust the prior probability of data packet transmission, but the storage of data packets and the selection of transmission opportunities will bring additional storage waiting delays to time-sensitive information. Therefore, how to design a covert wireless communication scheme that meets the optimal information age based on the data packet arrival rate, and how to strike a compromise between information timeliness and transmission covertness, still face challenges. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a storage-assisted time-sensitive information covert communication method and system. The random information transmission behavior provided by the storage system is more covert, and the priori transmission probability of covert communication is changed by storing data packets, achieving a compromise between information timeliness and transmission concealment.

[0006] To achieve the above object, the method of the present invention comprises the following steps: Step S1: Information perception and storage: The source node is equipped with independent information perception, storage and sending modules, and uses the information perception module to perceive the privacy data packet. The module can adjust the Poisson distribution generation parameters of the perception data in real time. The latest sensed data packets are stored in the queue, and the data in the queue is waiting for transmission in a first-in, first-out order. If the current queue contains data packets, the data at the head of the queue will be sent in the upcoming transmission cycle. If there is no data packet in the queue within the current transmission duration, the source node remains silent.

[0007] Step S2: key exchange and codebook sharing: before data packet transmission, the source node and the destination node generate a key by using the wireless channel, and encrypt the shared codebook encoded with the private data packet using the key.

[0008] Step S3: Information encoding and transmission: The source node uses the codebook shared with the destination node to encode the privacy data packet to be transmitted. The encoding length is , and then the power Send the data packet to be transmitted. In order to meet the communication concealment constraint, the encoding length and transmit power Should meet: in, represents the prior sending probability of the source node in each transmission cycle; represents the noise power of the monitoring node; is an arbitrarily small real number, representing the tolerance value of covert communication; Represents the average channel gain from the source node to the monitoring node.

[0009] Step S4: Information decoding; the destination node uses the codebook shared with the source node for decoding in each transmission cycle; the parameters generated for the data packets in the queue are as follows according to the Poisson distribution: Poisson distribution arrives and arrives at a fixed time To complete the service, the expected peak information age of the data packet that successfully reaches the receiving end is expressed as: Among them, the packet error rate , is the channel power gain of the destination node, The transmission rate is set.

[0010] For time-sensitive information, when the peak information age of the data successfully received by the destination node exceeds the peak information age threshold, the information becomes invalid. , then the probability of information age interruption It can be expressed as: .

[0011] A storage-assisted time-sensitive information covert communication system, the system is used to implement any of the storage-assisted time-sensitive information covert communication methods described above.

[0012] Compared with the existing transmission methods, the present invention has the following advantages and significant effects: In the specific operation of the storage-assisted time-sensitive information covert communication method and system described in the present invention, the source node can adjust the parameters by storing in the queue The privacy data packets are generated by Poisson distribution and are sent at fixed time The destination node decodes the fixed-rate data packets to ensure the reliability of transmission. At the same time, when there is no data packet in the queue, the source node remains silent and adjusts the parameters. The priori transmission probability of the source node can be changed to achieve the purpose of improving the concealment of wireless transmission behavior. Compared with the traditional queue-free covert wireless communication method, the present invention can obtain higher information timeliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the architecture of the storage-assisted time-sensitive information covert communication method and system of the present invention; Figure 2 is a flow chart of covertly transmitting information in an embodiment of the present invention; Figure 3 is a graph showing the change of peak information age with transmission rate; Figure 4 Updated graph for peak information age status. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0016] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] The following combination Figure 1-Figure 4 The specific embodiments of the present invention are described in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0018] The present invention provides a storage-assisted time-sensitive information covert communication method and system, which can be applied to application scenarios such as remote monitoring, smart home, and autonomous driving to improve the reliability of private data transmission. Figure 1 As shown in Figure 1, the system includes a source node, a destination node, and an illegal monitoring party. All nodes are equipped with a single antenna and work in half-duplex mode. The source node senses the privacy data packet at an adjustable frequency, and the arrival of the data packet satisfies the parameter The Poisson distribution is used to store the latest data packets in the queue. When the queue contains data, it is sent to the destination node in a first-in-first-out order through finite block length coding; the illegal monitoring party continuously observes the wireless transmission environment to determine whether the source node has sent a privacy data packet to the destination node. Considering that the privacy data packet generation rate that satisfies the Poisson arrival determines the system's prior transmission probability, and the finite block length coding makes it inevitable for the destination node to make decoding errors, by adjusting the parameters The system's prior sending probability can be adjusted, while improving the reliability of privacy data packet transmission. In specific application scenarios, the source node may be a mobile device equipped with sensors, such as a data collection drone, or a fixed data collection device with wireless transmission function, such as various traffic monitors. This type of data generally requires high timeliness and high security. The destination node is generally some small data collection terminal, which sends the collected data to the data platform via wired transmission for further data analysis. The illegal monitoring party may exist at any location in this scenario, equipped with a receiving antenna, with the purpose of determining whether there is communication behavior on the legal link, and further monitoring and cracking down on the equipment.

[0019] Specifically, the method of the present invention comprises the following steps: Step S1: Information perception and storage; the source node is equipped with independent information perception modules, storage modules and sending modules, wherein the information perception module is generally a sensor. Depending on the task type, you can choose to install sensor devices such as cameras or infrared detectors. These sensors do not generate data continuously. Their feature is that a control unit is installed, which can adjust the frequency of sensor data generation. The data generation parameters satisfy the Poisson distribution, and the adjustment method is to input different Poisson distribution generation parameters. , specifically, due to the generation parameters In this system, the a priori emission probability is affected and is empirically set to , then it is considered that the prior probability of emission of the system is the same as the prior probability of non-emission, which is 0.5. However, this is often not optimal. If you want to find the optimal generation parameter λ of this system, you can optimize the variable in step S4. About The storage module is a data storage device that stores the latest data packets sensed by the sensor in a queue. The data in the queue is waiting for transmission in a first-in-first-out order. The sending module contains an antenna, which first checks whether there are data packets in the queue. If the current queue contains data packets, the data at the head of the queue will be transmitted in the upcoming transmission cycle. The destination node has an antenna, which receives and decodes the signal if it detects it.

[0020] The parameters for generating And store the Poisson data packets in the queue. At the same time, since this system directly sends the data packets when there are data packets in the queue, according to the conclusion of the M / D / 1 queue model, the probability that the queue contains data is the same as the prior sending probability of the system, which is expressed as: in, is a fixed transmission time.

[0021] Step S2: key exchange and codebook sharing: before data packet transmission, the source node and the destination node generate a key by using the wireless channel, and encrypt the shared codebook encoded with the private data packet using the key.

[0022] Step S3: Information encoding and transmission: The source node uses the codebook shared with the destination node to encode the privacy data packet to be transmitted. The encoding length is , and then the power Send the data packet to be transmitted. In order to meet the communication concealment constraint, according to the principle of covert communication technology, the encoding length and transmit power Should meet: in, represents the prior sending probability of the source node in each transmission cycle; represents the noise power of the monitoring node; Indicates the covert communication tolerance value, which represents the security level of the system and is determined by different application scenarios. If it is set to 0.01, it means that the system is safe with a probability of 99%; Represents the average channel gain from the source node to the monitoring node.

[0023] Step S4: Information decoding: The destination node uses the codebook shared with the source node for decoding in each transmission cycle. Poisson distribution arrives and arrives at a fixed time To complete the service, the expected peak information age of the data packet that successfully reaches the receiving end is expressed as: Among them, the packet error rate ,in , is the set transmission rate, is the channel power gain of the destination node. The expected peak information age can characterize the timeliness of the data packet in the worst case during this transmission process. This indicator can help us evaluate whether the transmission meets the timeliness requirements or improve the timeliness of information in a targeted manner.

[0024] For time-sensitive information, different tasks generally have different timeliness requirements. For example, if a certain information requires that the sensor collection, generation, transmission and reception be completed within 2 seconds, then the information that exceeds 2 seconds is invalid. If this requirement is used as the threshold of information age, then when the peak information age of the data successfully received by the destination node exceeds the peak information age threshold, the information is invalid. If the peak information age threshold is defined as , according to Markov inequality, the probability of information age interruption It can be expressed as: By calculating the interruption probability of information age, we can obtain the probability that the current transmission is valid information in a certain transmission process and the proportion of valid information to the total transmitted information.

[0025] The effective covert transmission rate of the system can be expressed as: in, The effective concealed transmission rate is defined as , which represents the real rate that satisfies both concealment and timeliness in the proposed system. It can be used to evaluate the real throughput of the system that can meet all transmission tasks in the current scenario. It is composed of the product of the set rate and the non-interruption probability of the information age. st is the concealment constraint in step S4. In order to ensure concealment, the transmission power of the source node is required to satisfy this formula. The specific meaning of the parameters is explained in detail in step S4. Here, an optimization problem can also be constructed to obtain the effective concealment rate Maximize the optimal generation parameters and transmit power allocation scheme.

[0026] The peak information age in the transmission method of the present invention is simulated as follows: Figure 3 As shown, the encoding length in each privacy data packet is , hidden tolerance , the source node is far from the destination node , the source node is far from the detection node , the noise power is , the system bandwidth is , the duration of a transmission cycle seconds, the transmission power is the maximum transmission power that satisfies the concealment constraint. Figure 3 As can be seen in the figure, by using the arrival parameter found by maximizing the effective concealment rate There is an optimal transmission rate that minimizes the system peak information age, and compared with the covert communication system without queues, the information peak information age, i.e., information timeliness, of the proposed method is better.

[0027] Specifically, the expected calculation method of the peak information age in step S4 is as follows: Considering the collection information is subject to the parameter Poisson distribution is generated, and at the same time, the fixed transmission rate Make the same packet length The data can be stored at a fixed time When the packet at the front of the queue is being served, other packets are waiting in the queue, and packets leave at a fixed time interval of t. Such a system can be described by the M / D / 1 model in queuing theory. According to the conclusion of the M / D / 1 model, its steady-state distribution satisfies ,in represents the probability that there is no data packet in the queue. When there is no data in the queue, the transmission is silent, and the prior probability of not sending the system under consideration is , that is, the prior emission probability satisfies: like Figure 4 The peak information age state update diagram is shown. If the information collected by the sensor enters the queue and The current information packet is sent at the moment. At the moment when it is successfully received by the destination node, according to the research related to information age, the peak information age of the entire system is Next, in A data packet is sent at time , and The peak information age is However, in The data packet sent at time has a probability of The receiving end has not received any data until The data sent at any time When it is successfully received, the peak information age is Any time the information age reaches its peak value, it means that the current receiving end has successfully received a packet, and its peak information age is the waiting and transmission time of the currently successfully received data packet. and the time interval between the generation of one or more packets and the previous one This part of time is related to whether the previous data packet is successfully received, that is, the packet error rate For The peak value of the information age generated by a data packet that successfully reaches the receiving end can be expressed as follows: in, It indicates the probability that the current information can be successfully received, that is, the probability that no packet error occurs. It follows a geometric distribution. Before The data packets are sent incorrectly until the In addition, at the transmission rate Under certain circumstances, the packet error rate is related to the signal-to-noise ratio. For short packet communication, the packet error rate is expressed as: in, Represents the right tail function of the normal distribution, also called Function. Further expansion of the above formula yields: Its expectations are:

[0028] From the above discussion, For the The time it takes for a data packet to be successfully received from being generated to waiting in queue. According to the conclusion of M / D / 1 queue model, the sum of the average waiting time and transmission time of the data packet in the queue can be obtained, that is, At the same time, since the packet generation time follows a Poisson distribution with parameter , we can get , so there are the following transformations:

[0029] In summary, the expected peak information age of a data packet that successfully reaches the receiving end can be expressed as: Compared with the traditional queue-free covert wireless communication method, the present invention can obtain higher information timeliness.

[0030] Any process or method described in the flowchart of the present invention or in other ways herein can be understood as a module, fragment or part of a code including one or more executable instructions for implementing the steps of a specific logical function or process, which can be implemented in any computer-readable medium for use by an instruction execution system, device or equipment, and the computer-readable medium can be any medium containing storage, communication, propagation or transmission programs for use by execution systems, devices or equipment, including read-only memories, magnetic disks or optical disks, etc.

[0031] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art can combine or combine different embodiments or examples described in this specification and the features therein without causing any contradiction.

[0032] Although the above content has shown and described the embodiments of the present invention, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace, modify and other update operations on the above embodiments within the scope of the present invention.

Claims

1. A storage-assisted time-sensitive information covert communication method, characterized in that: The method comprises the following steps: Step S1: Information perception and storage; the source node is equipped with an independent information perception module, a storage module and a sending module; the information perception module continuously perceives the privacy-sensitive time-sensitive data packets and stores the data packets in the storage queue; the information perception module adjusts the frequency of perceived data in real time, and its regulation method is: information perception and generation obey Poisson distribution, and the Poisson distribution generation parameter Real-time adjustments; Step S2: key exchange and codebook sharing: the source node and the destination node generate a key by using the wireless channel, and periodically share the privacy data packet encoding codebook encrypted by the key; Step S3: Information encoding and transmission; when there is a data packet to be sent in the storage queue, the source node encodes the information and transmits the data packet at a transmission power that can maintain concealment; the encoding length is , indicating that the source node passes through The secondary channel is used to send the data packet completely, and the transmission power is ; Step S4: Information decoding; the destination node uses the codebook shared with the source node for decoding in each transmission cycle; when there is no data packet in the storage queue, the source node remains silent, thereby improving the concealment of communication.

2. A storage-assisted time-sensitive information covert communication method according to claim 1, characterized in that: In step S1, the latest sensed data packet is stored in a queue, and the data in the queue waits for transmission in a first-in-first-out order.

3. A storage-assisted time-sensitive information covert communication method according to claim 2, characterized in that: If the current queue contains data packets, the data at the head of the queue will be in the upcoming transmission cycle. Sent by the source node.

4. A storage-assisted time-sensitive information covert communication method according to claim 2, characterized in that: If the queue has no data packets within the current transmission duration, the source node remains silent.

5. A storage-assisted time-sensitive information covert communication method according to claim 2, characterized in that: For a Poisson distribution with parameters And store the Poisson data packets in the queue. At the same time, since this system directly sends the data packets when there are data packets in the queue.

6. A storage-assisted time-sensitive information covert communication method according to claim 2, characterized in that: The probability that a queue contains data is the same as the system's a priori send probability.

7. A storage-assisted time-sensitive information covert communication method according to claim 1, characterized in that: In step S3, in order to meet the communication concealment constraint, the transmission power Should meet: in, represents the prior sending probability of the source node in each transmission cycle; represents the noise power of the monitoring node; represents the covert communication tolerance value; Represents the average channel gain from the source node to the monitoring node.

8. A storage-assisted time-sensitive information covert communication method according to claim 1, characterized in that: In step S4, the parameters generated for the packets in the queue according to the Poisson distribution are: Poisson distribution arrives at a fixed time To complete the service, the expected peak information age of the data packet that successfully reaches the receiving end is expressed as: Among them, the packet error rate , is the channel power gain of the destination node.

9. A storage-assisted time-sensitive information covert communication method according to claim 8, characterized in that: Define a peak information age threshold , when the peak information age of the data successfully received by the destination node exceeds the peak information age threshold, the information is considered invalid, and the information age interruption probability is expressed as: 。 10. A storage-assisted time-sensitive information covert communication system, characterized in that: The system is used to implement the storage-assisted time-sensitive information covert communication method according to any one of claims 1-9.

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