A safety communication method of a measurement and control device field bus

Abstract

The application belongs to the field of industrial communication, and particularly relates to a safety communication method of a measurement and control device field bus, which comprises the following steps: a preparation stage: based on the attributes of the bus device, a hash table with different security levels as the key is constructed, and the gateway performs identity authentication on the bus device; a communication stage: the gateway calculates the attribute set sent by the bus device, and obtains the security coefficient of the attribute set in combination with the hash table, different algorithms are selected based on the security coefficient, and the algorithm information and the key are sent to the bus device, the bus device decrypts the same, and direct communication between the gateway and the bus device is completed. The method of the application has stronger compatibility for the measurement and control field device, can ensure the safety communication of the measurement and control device field bus while ensuring real-time performance and high efficiency, improve the resource utilization rate of the control system, reduce the production cost, and has great application and promotion space.

Description

Technical Field

[0001] This invention belongs to the field of industrial communication, specifically a secure communication method for fieldbus of measurement and control equipment. Background Technology

[0002] With the rapid development of intelligent manufacturing and the Industrial Internet, traditional closed industrial production systems are gradually becoming more open. The closed nature of upstream and downstream enterprises and different production lines is being broken. Industrial control system networks are divided into enterprise office networks, process and monitoring networks, and fieldbus control networks. Currently, the development of information security protocols for industrial networks only exists in enterprise office networks and process and monitoring networks, while the development of information security for fieldbus control networks is still in its infancy. Furthermore, the computing resources of different field devices in fieldbus control networks vary greatly, with some devices exhibiting low bandwidth and limited computing resources. Moreover, bus protocols are often not designed with security requirements in mind, resulting in lax licensing, authorization, and access control. Inappropriate authentication, lack of data integrity verification, and insufficient encryption of transmitted data make bus protocols highly vulnerable to unauthorized control and attacks. How to accurately meet the security requirements of each field device while achieving secure bus communication without affecting the real-time performance of bus communication is a pressing issue in this field. Secure communication methods for fieldbuses in measurement and control equipment can meet the different security level requirements of field devices by implementing authentication, encrypted data transmission, and key updates and integrity checks. Summary of the Invention

[0003] The purpose of this invention is to provide a secure communication method for the fieldbus of measurement and control equipment, which solves the security problem of communication between different devices on the fieldbus of measurement and control equipment.

[0004] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0005] A secure communication method for fieldbus in measurement and control equipment includes the following steps:

[0006] Preparation phase: Based on the attributes of the bus devices, a hash table is constructed with different security levels as keys, and the gateway authenticates the bus devices;

[0007] Communication phase: The gateway calculates the attribute set sent by the bus device and obtains the security coefficient of the attribute set by combining it with the hash table. Based on the security coefficient, it selects different algorithms and sends the algorithm information and key to the bus device. The bus device decrypts the algorithm and completes the communication between the gateway and the bus device.

[0008] The attributes of the bus device include: access permissions, computing resources, value, and maintenance costs.

[0009] The preparation phase includes the following steps:

[0010] Different weights are assigned to different attributes of bus devices. Based on the evaluation model of the superior-inferior solution distance method, the security level of different attribute combinations is divided into score ranges, and different score ranges correspond to different keywords.

[0011] Establish hash tables with different security levels as keys, and different keys map to different security coefficients;

[0012] Bus devices and gateways exchange digital certificates and verify identities.

[0013] The security level is specifically as follows:

[0014] 1) Orient all attribute weights to obtain a oriented matrix about the attribute set, and then standardize the oriented matrix:

[0015] Suppose there are n devices, each with m attributes, and the corresponding matrix is:

[0016]

[0017] Assume x ij Let j be the j-th attribute of the i-th device in the positive matrix. Then the corresponding element after normalization is:

[0018] 2) Use the Analytic Hierarchy Process (AHP) to determine the new weights w for each attribute. i ;

[0019] 3) Calculate the score and normalize it to determine the security level:

[0020] Let the maximum value of each column in the standardized matrix be y. j + =max{y 1j y 2j , ..., y nj The minimum value is Y. j - =min{y 1j y 2j , ..., y nj} Calculate the score for each evaluation object, i.e., each device's set of attributes. in All are coefficients, thus according to S i Obtain the security level corresponding to the bus device.

[0021] The communication phase includes the following steps:

[0022] After successful authentication, the gateway uses an evaluation model to calculate the weights of the attribute set sent by the bus device, determines the security level of the attribute set, and obtains the corresponding security coefficient based on the security level of the attribute set as the key of the hash table.

[0023] Using a security factor, attribute set, and timestamp, an initial key is negotiated, and a key chain based on a one-way hash chain is generated using a one-way hash function for periodically updating the key;

[0024] The gateway selects the corresponding encryption / decryption algorithm and the corresponding HMAC algorithm according to the security level, encrypts the algorithm information and key using the device public key, and sends them to the bus device.

[0025] The bus device obtains the algorithm information and key sent by the gateway by decrypting with the private key, and uses the session key and HMAC key to perform encryption, decryption and message integrity verification.

[0026] The process of negotiating an initial key using security factors, attribute sets, and timestamps involves the gateway calculating weights and determining security levels using the received attribute sets of bus devices. It then uses the security level of the attribute set as the hash table key to obtain the corresponding security factor. The gateway takes a string concatenated from the device's attribute set, security factor, and timestamp as input, processes the input using a one-way hash function, and outputs a fixed-length key.

[0027] The gateway selects the corresponding encryption / decryption algorithm and HMAC algorithm according to the security factor. Specifically, it sorts the different combinations of encryption / decryption algorithms and HMAC algorithms according to the complexity of the algorithms, assigns different security factors to different complexity algorithm combinations, and selects the corresponding algorithm combination according to the security factor.

[0028] A secure communication system for a fieldbus of a measurement and control device includes a memory and a processor; the memory is used to store a computer program; the processor is used to implement the secure communication method for a fieldbus of a measurement and control device when the computer program is executed.

[0029] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements a secure communication method for a fieldbus of a measurement and control device.

[0030] The present invention has the following beneficial effects and advantages:

[0031] 1. Prevent unauthorized devices from accessing the bus. Using digital certificate-based authentication, exchange certificates and mutually authenticate each other before devices begin communicating, effectively preventing unauthorized devices from accessing the bus.

[0032] 2. High flexibility: This invention uses attribute sets and evaluation models to set different security levels for different types of field devices, and uses different security levels to determine encryption and decryption algorithms and HMAC algorithms with different complexities, so as to meet the diverse security needs of different devices.

[0033] 3. High confidentiality. This invention uses a symmetric encryption algorithm and a key update mechanism based on a one-way hash chain during the communication phase, ensuring key freshness and improving data confidentiality.

[0034] 4. Good real-time performance. This invention provides encryption and decryption algorithms of varying complexity and HMAC algorithms of varying complexity for different devices based on their attribute sets. This allows devices with limited computing resources to use algorithms of lower complexity as much as possible while meeting their security requirements, thereby ensuring the real-time performance of bus device communication.

[0035] 5. Strong compatibility. This invention allocates device security levels based on attribute sets. Compared with the method of statically preset device security levels, it does not require pre-storing device security levels and device information in the gateway. The allocation of security levels can be completed simply by the device connecting and sending its device attributes. Attached Figure Description

[0036] Figure 1 This is a functional diagram of the method of the present invention;

[0037] Figure 2 This is a functional diagram of the security level allocation of the present invention;

[0038] Figure 3 This is a flowchart of the information security protection method of the present invention;

[0039] Figure 4 This is a key update function diagram of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0041] like Figures 1-4 As shown, a secure communication method for a fieldbus of measurement and control equipment is used to authenticate device entities based on a set of device attributes and classify the security level of device communication during the communication process of bus devices, perform encryption and decryption processing of data in transmission according to the security level, and apply the HMAC algorithm. The communication method includes:

[0042] The security level is determined by taking different sets of device attributes as input, assigning different weights to different attributes, using an evaluation model to calculate the scores of different sets of device attributes based on the different attribute weights, and determining the security level of the attribute set based on the score range.

[0043] The security level is specifically as follows:

[0044] First, all attribute weight indicators are positiveized to obtain a positiveized matrix about the attribute set. That is, the attributes of the device are used as indicators, and these indicators are transformed into extremely large indicators (the larger the value of the indicator, the higher the score). Then, the positiveized matrix is ​​standardized.

[0045] Suppose there are n devices, each with m attributes, and the corresponding matrix is:

[0046]

[0047] Assume x ij Let j be the j-th attribute of the i-th device in the positive matrix. Then the corresponding element after normalization is: The new weights w of each attribute are determined using the analytic hierarchy process (AHP). i Then, the score is calculated and normalized. Let the maximum value of each column in the normalized matrix be y. j + =max{y 1j y 2j , ..., y nj The minimum value is defined as Y. j - =min{y 1j y 2j , ..., y nj Finally, the score for each evaluation object, i.e., each device's set of attributes, is calculated. in All are coefficients, thus according to S i Obtain the security level corresponding to the bus device.

[0048] A hash table is established in the gateway according to the security level, with different security levels corresponding to different security coefficients;

[0049] The gateway negotiates a key sequence based on a one-way hash chain using a key negotiation algorithm, taking the gateway's security coefficient, the device's attribute set, and the timestamp as inputs, according to different security coefficients.

[0050] The session key is updated periodically based on the input timestamp information. The timestamp determines the existence time of the key. The gateway and device will update the key in the reverse order of key chain generation based on the timestamp information.

[0051] The gateway assigns different types or different bit lengths of encryption and decryption algorithms and different bit lengths of HMAC algorithms based on different security levels and different negotiated key chains.

[0052] The security level takes the attribute set as input, calculates the score of the attribute set using the superior-inferiority distance method, and divides the security level range according to the set score;

[0053] The multiple security levels are keywords, and each security level maps to a different security coefficient.

[0054] Using the security factor, key negotiation factor, device attribute set, and timestamp as input, a key negotiation algorithm is used to negotiate a key chain. In subsequent communication stages, different devices' encryption and decryption algorithms and HMAC algorithms provide keys.

[0055] The key sequence based on the one-way hash chain is characterized in that a generated random number is used as the initial key, and a one-way hash function is used to generate a one-way key sequence, the key update order of which is the reverse of the key chain generation order.

[0056] Different security levels correspond to different security coefficients, which in turn correspond to encryption and decryption algorithms and HMAC algorithms of varying complexity, thereby meeting the security requirements of devices with different attribute sets.

[0057] The present invention uses the Foundation Fieldbus as an example to design the following technical solution:

[0058] A secure communication method for a fieldbus of a measurement and control equipment, used to realize bus security level classification, identity authentication, key update and integrity verification functions during bus communication, characterized by including the following steps:

[0059] Different weights are assigned to the different attributes, and the evaluation model of the superior-inferior solution distance method is used to divide the security level into score ranges according to different attribute combinations. Different score ranges correspond to different keywords.

[0060] Establish hash tables with different security levels as keys, and different keys map to different security coefficients.

[0061] Before the devices begin communicating, the bus devices and the gateway exchange digital certificates and verify each other's identities.

[0062] After successful authentication, the gateway uses an evaluation model to calculate and determine the security level of the attribute set sent by the device. Based on the security level of the attribute set, it obtains the corresponding security coefficient as the hash table key. Using the security coefficient, attribute set, and timestamp as input, it negotiates an initial key and uses a one-way hash function to generate a key chain based on a one-way hash chain for subsequent key updates.

[0063] The gateway selects the corresponding encryption / decryption algorithm and HMAC algorithm based on the security parameters, encrypts the algorithm information to be used and the key using the device's public key, and sends it to the corresponding device.

[0064] The device obtains the algorithm information and key sent by the gateway by decrypting with the private key, and uses the session key and HMAC key to implement encryption, decryption and message integrity verification functions.

[0065] This invention relates to the following key technologies:

[0066] (1) In the secure communication method of the fieldbus of the measurement and control equipment, a hash table is established in the gateway with the security level as the key. The key is mapped to the corresponding security coefficient in the table. The security coefficient is used to generate the key and determine the relevant security algorithm.

[0067] (2) The security communication method of the fieldbus of the measurement and control equipment uses the superior and inferior solution distance method to evaluate the model based on the attribute set sent by the equipment. First, all attribute weight indicators are positiveized, then the positiveized matrix about the attribute set is obtained, and the positiveized matrix is ​​standardized. The analytic hierarchy process is used to determine the new weight of each indicator. Finally, the score of each evaluation object is calculated to obtain the appropriate security level of the equipment.

[0068] (3) Obtain the corresponding security coefficient according to the security level, and obtain the key for the communication stage through the key negotiation algorithm with the security coefficient, timestamp and attribute set as input.

[0069] (4) The underlying layer of the secure communication method of the fieldbus of the measurement and control equipment is the H1 low-speed bus of the Foundation Fieldbus. The bus protocol is divided into physical layer, data link layer, fieldbus access sub-layer, fieldbus message specification sub-layer and user layer. This invention adds an information security layer protocol on the standard protocol of the Foundation Fieldbus to protect the Foundation Fieldbus protocol for information security without changing the original protocol communication.

[0070] (5) The secure communication method of the fieldbus of the measurement and control equipment uses the exchange of digital certificates to realize the identity verification function. The digital certificates are based on digital signature technology, issued by a trusted institution and updated regularly.

[0071] (6) Data encryption and decryption: After the device completes the authentication, it starts normal communication. During normal communication, all transmitted data needs to be encrypted at the sending end using symmetric encryption technology and transmitted on the channel in ciphertext to prevent the communication data from being eavesdropped. At the receiving end, the ciphertext is decrypted.

[0072] (7) Key update: During normal communication, the gateway stores the keys required for the communication phase in the form of a one-way hash chain. During the communication process, the key is updated according to the preset time period and the reverse order generated by the one-way hash chain. The key in the Foundation Fieldbus device is updated according to the input timestamp.

[0073] (8) The key update order is the reverse order generated by the one-way hash chain. When the key used in the current communication is attacked, the attacker cannot deduce the key to be used next based on the one-way nature of the one-way hash chain algorithm.

[0074] (9) In the key update order, the HMAC key is always one step ahead of the session key in the update order, so as to verify whether the session key and the HMAC key belong to the same adjacent position in the key chain after the key is updated.

[0075] The secure communication method described in this invention allocates different security levels and session keys based on different attribute sets of different devices, and assigns different security policies based on the security levels of different devices and different session keys. This method offers stronger compatibility with field measurement and control equipment, ensuring secure communication of the fieldbus of measurement and control equipment while maintaining real-time performance and high efficiency. It improves the resource utilization of the control system, reduces production costs, and has significant potential for application and promotion.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A secure communication method for fieldbus in measurement and control equipment, characterized in that, Includes the following steps: Preparation phase: Different weights are assigned to different attributes of bus devices, the score of the attribute set of each bus device is calculated, the security level corresponding to the bus device is obtained based on the score, the security level of different attribute combinations is divided into score ranges according to the evaluation model of superior-inferior solution distance method, different score ranges correspond to different keywords, a hash table is constructed with different security levels as keywords, and the gateway authenticates the bus devices. Communication phase: The gateway calculates the attribute set sent by the bus device and obtains the security coefficient of the attribute set by combining it with the hash table. Based on the security coefficient, it selects different algorithms and sends the algorithm information and key to the bus device. The bus device decrypts the algorithm and completes the communication between the gateway and the bus device.

2. The secure communication method for a fieldbus of a measurement and control equipment according to claim 1, characterized in that, The attributes of the bus device include: access permissions, computing resources, value, and maintenance costs.

3. The secure communication method for fieldbus of measurement and control equipment according to claim 1, characterized in that, The preparation phase includes the following steps: Different weights are assigned to different attributes of bus devices. Based on the evaluation model of the superior-inferior solution distance method, the security level of different attribute combinations is divided into score ranges, and different score ranges correspond to different keywords. Establish hash tables with different security levels as keys, and different keys map to different security coefficients; Bus devices and gateways exchange digital certificates and verify identities.

4. The secure communication method for fieldbus of measurement and control equipment according to claim 3, characterized in that, The security level is specifically as follows: 1) Orient all attribute weights to obtain a oriented matrix about the attribute set, and then standardize the oriented matrix: Suppose there are n devices, each with m attributes, and the corresponding matrix is: Assumption Let j be the j-th attribute of the i-th device in the positive matrix. Then the corresponding element after normalization is: ; 2) Use the Analytic Hierarchy Process (AHP) to determine the new weights of each attribute. ; 3) Calculate the score and normalize it to determine the security level: Let the maximum value of each column in the standardized matrix be... The minimum value is Calculate the score for each evaluation object, i.e., each device's set of attributes. ,in , , , All are coefficients, therefore according to Obtain the security level corresponding to the bus device.

5. A secure communication method for a fieldbus in a measurement and control equipment according to claim 1, characterized in that, The communication phase includes the following steps: After successful authentication, the gateway uses an evaluation model to calculate the weights of the attribute set sent by the bus device, determines the security level of the attribute set, and obtains the corresponding security coefficient based on the security level of the attribute set as the key of the hash table. Using a security factor, attribute set, and timestamp, an initial key is negotiated, and a key chain based on a one-way hash chain is generated using a one-way hash function for periodically updating the key; The gateway selects the corresponding encryption / decryption algorithm and the corresponding HMAC algorithm according to the security level, encrypts the algorithm information and key using the device public key, and sends them to the bus device. The bus device obtains the algorithm information and key sent by the gateway by decrypting with the private key, and uses the session key and HMAC key to perform encryption, decryption and message integrity verification.

6. A secure communication method for a fieldbus in a measurement and control equipment according to claim 5, characterized in that, The process of negotiating an initial key using security factors, attribute sets, and timestamps involves the gateway calculating weights and determining security levels using the received attribute sets of bus devices. It then uses the security level of the attribute set as the hash table key to obtain the corresponding security factor. The gateway takes a string concatenated from the device's attribute set, security factor, and timestamp as input, processes the input using a one-way hash function, and outputs a fixed-length key.

7. A secure communication method for a fieldbus of a measurement and control equipment according to claim 5, characterized in that, The gateway selects the corresponding encryption / decryption algorithm and HMAC algorithm according to the security factor. Specifically, it sorts the different combinations of encryption / decryption algorithms and HMAC algorithms according to the complexity of the algorithms, assigns different security factors to different complexity algorithm combinations, and selects the corresponding algorithm combination according to the security factor.

8. A secure communication system for a fieldbus of measurement and control equipment, characterized in that, It includes a memory and a processor; the memory is used to store a computer program; the processor is used to implement, when executing the computer program, a secure communication method for a fieldbus of a measurement and control device as described in any one of claims 1-7.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements a secure communication method for a fieldbus of a measurement and control device as described in any one of claims 1-7.

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