A Secure Time Synchronization Method for Wireless Sensor Networks Oriented to Industrial Applications

Abstract

The present invention discloses a secure time synchronization method for wireless sensor networks for industrial applications, belonging to the field of industrial wireless communication networks. Aiming at the active industrial network environment, by making full use of the network topology structure and clock status information, a mesh plus star network topology structure is built, and then a time synchronization link between the leaf nodes and the clock source gateway nodes is constructed; secondly, based on the common neighbor broadcast forwarding mechanism and the message sequence number, the time difference between the local node and the reference node when receiving the common neighbor broadcast message is obtained, effectively shielding the attack information of information manipulators and masqueraders; then, the linear regression technology is used to estimate the relative clock compensation parameter between the local node and the reference node, and the local clock is adjusted to achieve time synchronization with the reference node. The present invention solves the problems of high complexity of traditional secure time synchronization algorithms and inability to effectively resist intelligent masquerade attacks, and realizes secure time synchronization in the industrial wireless sensor network environment.

Description

Technical Field

[0001] The present invention relates to the field of industrial wireless communication networks, and particularly to a secure time synchronization method for wireless sensor networks for industrial applications. Background Art

[0002] Wireless sensor networks have advantages such as low cost and convenient and flexible networking methods, and can achieve real-time acquisition of the temperature, pressure, environmental humidity, etc. of industrial field devices, obtaining production process parameters that are difficult for traditional wired networks to obtain in industrial production processes. They are suitable for information perception and production control in areas with harsh environments where workers cannot enter, and can meet the requirements of large-scale ubiquitous perception of production processes in new industrial production models of intelligence and personalization.

[0003] Time synchronization is the basis for many industrial application scenarios. Typical application scenarios include distributed real-time control such as motion control, high-definition machine vision, and robot collaborative operation; data fusion perception in process industries such as biological fermentation and petrochemical industry; communication protocols such as time-division multiple access transmission scheduling and time-sensitive data transmission. Existing time synchronization research mostly focuses on industrial networks in steady-state environments, emphasizing single time synchronization requirements such as high precision and low energy consumption, lacking a security defense mechanism, and ignoring the security requirements of industrial network time synchronization for new manufacturing models. Industrial networks that are often in an unattended environment are vulnerable to physical attacks against node identities and delay attacks against communication links, and the types and means of attacks are diverse. Using information encryption and authentication technologies to prevent time information from being tampered with or insecure information inserted by attackers during transmission has high security, but the additional communication, computing, and storage overheads are not suitable for resource-constrained industrial networks.

[0004] Time synchronization design involves two basic elements: clock timing and time information interaction. During the clock timing process, the relative clock rates between nodes are stably unique. Moreover, at present, the perception control networks in industrial environments are mostly centralized structures, and the actions of lower-layer nodes depend on the commands of the master node. Therefore, the lower-layer nodes need to synchronize with the master node, that is, active time synchronization. The network topology structure is closely related to time synchronization performance. Therefore, the present invention integrates time synchronization information transmission and network topology structure construction, and designs a secure, reliable, and low-overhead industrial active network time synchronization method based on the correlation of clock information. Summary of the Invention

[0005] Aiming at the above deficiencies existing in the prior art, the technical problem to be solved by the present invention is to provide a secure time synchronization method for wireless sensor networks for industrial applications, which integrates the network topology structure and clock state information, reduces the complexity of the encryption and decryption security key algorithms, and improves the security of time synchronization technology.

[0006] The technical solution adopted by the wireless sensor network security time synchronization method for industrial applications described in the present invention is as follows:

[0007] Build the network nodes in the industrial field into a hybrid hierarchical network topology structure of mesh and star;

[0008] Construct a time synchronization link between the leaf nodes and the clock source gateway nodes;

[0009] The local node uses the two-hop neighbor as the clock reference node and the one-hop common neighbor as the broadcast node to design a time synchronization security defense communication mechanism;

[0010] The local node records the information related to the clock state and calculates the relative clock compensation information between the local node and the clock reference node by using the linear regression technology;

[0011] The local node adjusts the local clock to synchronize with the clock reference node.

[0012] The hybrid network topology structure refers to: the upper-layer network topology structure is a mesh, which is composed of gateways, routers, and edge access devices; the lower-layer network topology structure is a star, which is composed of industrial field sensing network devices and is connected to the upper-layer network through edge access devices.

[0013] The time synchronization link refers to: using the gateway node as the clock source and the industrial field sensing network device as the leaf node; the leaf node communicates with the clock source node through a multi-hop link, and the router and edge device are intermediate forwarding nodes; there is at least one triangular loop link in the communication link between the leaf node and the clock source node.

[0014] The time synchronization security defense communication mechanism includes:

[0015] The one-hop neighbor broadcast node R of the local node broadcasts the time information τ r (i) periodically at a preset time interval;

[0016] The local node S and the two-hop neighbor clock reference node M respectively record the time τ r (i) when receiving the time information τ s (i), τ m (i) based on their respective clocks;

[0017] The node S and the reference node M respectively calculate the time difference from the broadcast node R: Δ sr (i) = τ s (i) - τ r (i), Δ mr (i) = τ m (i) - τ r (i);

[0018] Reference node M unicasts the time difference Δ to node R mr (i);

[0019] Broadcast node R forwards the received time difference Δ to node S mr (i);

[0020] Local node S stores the latest N groups of time information pairs (τ s (i), Δ sm (i)), where i is the index value of the information pair, and Δ sm (i) = Δ mr (i) - Δ sr (i) = τ m (i) - τ s (i).

[0021] The use of linear regression technology to calculate the relative clock compensation information between the local node and the clock reference node is specifically as follows:

[0022] Local node S uses the time information pair (τ s (i), Δ sm (i)) and, based on the linear regression of the least squares method, calculates the relative clock slope between local node S and reference node M:

[0023]

[0024] Among them, The time offset between local node S and reference node M is:

[0025]

[0026] The adjustment of the local clock of the local node to be synchronized with the clock reference node means that local node S adjusts the local time based on the calculated relative clock slope and time offset to adjust the local time:

[0027]

[0028] Finally, the time synchronization with the reference node is achieved.

[0029] The advantages of the present invention adopting the above technical solutions are as follows:

[0030] 1. The secure time synchronization method for wireless sensor networks for industrial applications of the present invention fully considers the characteristics and application requirements of industrial control networks, designs a secure time synchronization defense mechanism based on an active hierarchical network topology, and solves the problems of high complexity of traditional secure time synchronization algorithms and inability to effectively resist intelligent camouflage attacks.

[0031] 2. Based on the mesh and star hybrid topology, the present invention utilizes the common neighbor broadcast node and the message sequence number consistency detection mechanism to obtain the time difference between the local node and the reference node when receiving the broadcast message of the common neighbor node, shielding the attack information of information manipulators and pretenders and improving the security of time synchronization.

[0032] 3. The time synchronization security defense communication mechanism provided by the present invention does not require verifying the identity of nodes and collecting a large number of data packets for information filtering. Only through simple arithmetic operations can it obtain reliable time information, and uses linear regression technology to estimate the relative clock compensation parameter between the local node and the reference node, with small algorithm complexity and high reliability.

[0033] 4. The mesh plus star hierarchical network topology adopted by the present invention is applicable to large-scale industrial network scenarios. A large number of star network nodes are synchronized with the gateway node through the time synchronization link, improving the propagation speed of the gateway clock source and effectively reducing the accumulation of synchronization errors caused by long communication links in the traditional tree network topology environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the mesh and star hybrid topology of the industrial control network provided by the embodiment of the present invention;

[0035] Figure 2 is the time synchronization link provided by the embodiment of the present invention;

[0036] Figure 3 is the time synchronization security defense communication mechanism provided by the embodiment of the present invention;

[0037] Figure 4 is the time synchronization process provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following further describes the present invention in detail with reference to the drawings and embodiments, but the present invention is not limited to these embodiments.

[0039] The present invention includes the following contents: building a mesh and star hybrid topology of the industrial control network, constructing a time synchronization link, designing a time synchronization security defense communication mechanism, calculating relative clock compensation information using linear regression technology, and adjusting the local clock of the local node to synchronize with the clock reference node.

[0040] As Figure 1As shown in the figure, the industrial control network with a hybrid mesh and star topology includes a mesh backhaul network responsible for wide-area data transmission and a field star network for industrial field data acquisition and control. The mesh backhaul network consists of a gateway responsible for accessing the backbone network, a router responsible for data forwarding, and an edge access point responsible for accessing the star network. The field star network mostly consists of low-power wireless sensor network nodes, which are used to collect industrial field data such as temperature, pressure, humidity, and pH value, and execute certain control commands.

[0041] All devices in the industrial control network maintain a linear clock based on the local clock: τ(k) = α k t + β k , where τ(k) is the current time of node k, α k is the clock rate, β k is the initial clock offset, and t is the ideal absolute time. The gateway node is the clock source of the industrial control network. Other nodes use the time synchronization security defense communication mechanism to obtain relevant time information and execute the linear regression algorithm to estimate the clock compensation information, and finally adjust the clock to synchronize with the reference node.

[0042] In the network initialization stage, the network clock source node, that is, the gateway, has its own layer number of 0. The time source node periodically broadcasts the communication link topology construction information including the layer number. The nodes that receive the message sent by the time source node set their own layer numbers according to the layering information, and then continue to broadcast the message including their own layering information to other nodes until a layered network structure is formed, that is, a chain-like communication link is established between the clock source node and the leaf nodes.

[0043] As Figure 2 shown in the figure, in the time synchronization link schematic diagram between the leaf node and the clock source node, node 1 is the gateway node, node 8 is the leaf node in the star network, node 7 is the edge access point in the mesh backhaul network, nodes 2, 3, 4, 5, and 6 are router nodes, and node C is the common node of at least one triangular loop link in the mesh backhaul network. Its existence is to ensure the formation of the time synchronization link. Figure 2 The time synchronization link shown is: where means that node 7 synchronizes with its reference node 5 by broadcasting node 6 through a single-hop neighbor.

[0044] During the whole-network time synchronization process, each leaf node establishes a communication link with the gateway node as Figure 2 shown in the figure, and adopts the designed time synchronization mechanism, then the whole-network time synchronization can be achieved.

[0045] As Figure 3As shown in the figure, a time synchronization security defense communication mechanism is described in detail with four network nodes as an example. Node S is the local node, node R is the single-hop neighbor broadcast node, node M is the two-hop neighbor clock reference node, and nodes A1, A2, and A3 are attackers who can disguise themselves as node R at different positions. Among them, the information broadcast by A1 can be received by both node S and node M, the information broadcast by A2 can only be received by node M, and the information broadcast by A3 can only be received by node S.

[0046] As Figure 4 shown, node R broadcasts time information τ r (i) at a preset time interval periodically;

[0047] The local node S and the two-hop neighbor clock reference node M respectively record the time τ r (i) when receiving the time information τ s (i) based on their respective clocks; m (i), τ

[0048] Nodes S and reference node M respectively calculate the time difference from the broadcast node R: Δ sr (i) = τ s (i) - τ r (i), Δ mr (i) = τ m (i) - τ r (i);

[0049] The reference node M unicasts the time difference Δ mr (i) to node R;

[0050] The broadcast node R forwards the received time difference Δ mr (i) to node S;

[0051] The local node S stores the latest N groups of time information pairs (τ s (i), Δ sm (i)), where i is the index value of the information pair, and Δ sm (i) = Δ mr (i) - Δ sr (i) = τ m (i) - τ s (i).

[0052] The local node S uses the time information pair (τ s (i), Δ sm (i)) and calculates the relative clock slope between the local node S and the reference node M based on linear regression of the least squares method:

[0053]

[0054] Among them, The time offset between the local node S and the reference node M is:

[0055]

[0056] The local node S adjusts the local time to synchronize with the reference node based on the calculated relative clock slope and the time offset :

[0057]

[0058] Analysis of the attack on the security defense mechanism:

[0059] When the attacking node A1 disguises itself as the node R and sends the wrong time information τ a1 (i), both the node M and the node S can receive this information. In the line-of-sight environment, the propagation delay of the time information in the space link can be ignored, that is, the time difference Δ’ sr (i) and Δ’ mr (i) calculated by the node M and the node S are actually:

[0060] Δ’ sr (i) = τ s (i) - τ a1 (i), Δ’ mr (i) = τ m (i) - τ a1 (i).

[0061] When the node S receives the time difference Δ’ mr (i), it calculates

[0062] Δ’ mr (i) - Δ’ sr (i) = (τ m (i) - τ a1 (i)) - (τ s (i) - τ a1 (i)) = τ m (i) - τ r (i).

[0063] When the attacking node A2 disguises itself as the node R and sends the wrong time information, only the node M receives this information, and the node R cannot receive it. Based on the received packet sequence number, when the node M calculates Δ’ mr based on the wrong information and forwards this value to the node S via the node R, the node S directly discards this value.

[0064] Similarly, when the attacking node A3 disguises itself as the node R and sends the wrong time information, only the node S receives this information, and the node M cannot receive it. Due to the inconsistent packet sequence numbers, the node S directly discards this value.

[0065] As described above, these are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the relevant art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content above is equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A wireless sensor network security time synchronization method for industrial applications, characterized in that, Including the following steps: Build a hybrid hierarchical network topology of mesh and star for network nodes in the industrial field; Construct a time synchronization link between leaf nodes and clock source gateway nodes based on the hybrid hierarchical network topology; Design a time synchronization security defense communication mechanism; Adopt linear regression technology to calculate the relative clock compensation information between local nodes and clock reference nodes; The local node adjusts its local clock to synchronize with the clock reference node; Design a time synchronization security defense communication mechanism, specifically including: Use two-hop neighbors as clock reference nodes and single-hop common neighbors as broadcast nodes; The single-hop neighbor broadcast node R of the local node broadcasts the time information τ periodically at a preset time interval r (i); The local node S and the two-hop neighbor clock reference node M respectively record the received time information τ based on their respective clocks. r The time τ of (i) s (i), τ m (i); The node S and the reference node M respectively calculate the time difference from the broadcast node R: Δ sr (i) = τ s (i) - τ r (i), Δ mr (i) = τ m (i) - τ r (i); Reference node M unicasts time difference Δ to node R mr (i); The broadcast node R forwards the received time difference Δ to the node S mr (i); The local node S stores the latest N pairs of time information (τ s (i), Δ sm (i)), where i is the index value of the information pair, and Δ sm (i) = Δ mr (i) - Δ sr (i) = τ m (i) - τ s (i); Adopt linear regression technology to calculate the relative clock compensation information between local nodes and clock reference nodes, specifically including: The local node S uses the time information pair (τ s (i), Δ sm (i)) and, based on the linear regression of the least squares method, calculates the relative clock slope between the local node S and the reference node M: Among them, , the time offset between the local node S and the reference node M is:

2. The method according to claim 1, wherein Build a hybrid hierarchical network topology of mesh and star for network nodes in the industrial field, specifically including: The upper-layer network topology is a mesh, composed of gateways, routers, and edge access devices; The lower-layer network topology is a star, composed of industrial field sensing network devices, and is connected to the upper-layer network through edge access devices.

3. The method according to claim 1, wherein Construct a time synchronization link between leaf nodes and clock source gateway nodes, specifically including: Use the gateway node as the clock source and the industrial field sensing network device as the leaf node; The leaf node communicates with the clock source node through a multi-hop link, and the router and edge device are intermediate forwarding nodes; There is at least one triangular loop link in the communication link between the leaf node and the clock source node.

4. The method according to claim 1, wherein The local node adjusts its local clock to synchronize with the clock reference node, specifically including: The local node S adjusts the local time based on the calculated relative clock slope and the time offset : Finally, achieve time synchronization with the reference node.

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