TWI472189B - Network monitoring system and method for managing key - Google Patents

Description

Network monitoring system and method for managing keys

The present invention relates to a network monitoring mechanism, and more particularly to a method for a network monitoring system and a management key for a client program to be installed in an untrusted environment.

The supervisory control and data acquisition (SCADA) system is a network monitoring system with monitoring programs and data collection capabilities. At present, SCADA systems have been widely used in the monitoring of infrastructure such as electricity, gas and water. The early SCADA system was a closed system, and only a set of accounts and passwords were used for authentication. There is no need for key management technology and enhanced authentication agreement between the client program and the console. To this end, there are already many options for providing enhanced authentication protocols and Secure Sockets Layer (SSL) connections. However, there are still problems with the management of the current key, and most of the implementations statically place the key on the client program, thus creating a security hole.

For example, similar to the SCADA system's APP market, Digital Rights Management (DRM) system and Advanced Metering Infrastructure (AMI) system, the client program of these systems. It is installed in an open system and is equipped with a key belonging to the network service provider to prevent illegal use by legitimate users.

For example, in the application of the AMI system, in the case of a smart meter, a general smart meter is a device installed outdoors, and a smart meter has a client program installed therein, and a key is stored in the client program to prevent the user from tampering with the transfer. content. In addition, the software market and DRM keys are also stored in the client program of the user host to prevent users from illegally using software and content.

However, the above practices make the protection of the keys more difficult. Because the software market and DRM system put the key in the client program of the user host, it can not resist attacks such as reverse engineering. In the AMI system, the smart meter and the relay device are set outdoors, so that even if equipped with a smart card, effective access control cannot be performed because no password can be typed by the access control password, if executed by the remote end. You will also encounter the problem of how to protect the key.

Since the key is the basis of the security agreement, especially if the client program is installed in an untrusted environment, it is quite insecure if the key is placed directly on the client program. Therefore, how to manage the key is one of the important keys to the security of the overall system.

The invention provides a network monitoring system and a method for managing the key thereof, and the key protection mechanism based on the dynamic module and the agreement is proposed to solve the problem that the client program is installed in an untrusted environment and the key protection is caused. Resist static analysis and mitigate dynamic attacks.

The invention provides a method for managing a key, which is suitable for a network monitoring system, and the network monitoring system comprises a master control system and a client device. The method for managing the key includes: the client device executes the client program to register with the master control system, so that the master control system generates the dynamic module; the master control system transmits the dynamic module to the client device; and the client device verifies through the client program. The dynamic module; the client device verifies the client program through the dynamic module; after the client program is verified, the client device performs a key exchange process with the master control system through the dynamic module to generate the client device and the master control system. The shared key between.

The invention provides a network monitoring system, which comprises a client device and a master control system. The client device is set in a private network, wherein the private network is on a public network, and the client device is installed with a client program. The master control system is connected to the private network through a public network to connect with the client device. The main control system includes an integrity verifier, a dynamic module generator and an authentication server.

● There are two integrity verifier functions. First, the integrity verifier generates verification information, which is put into the dynamic module, so that the dynamic module can perform near-end integrity verification on the client program (such near-end integrity verification can be called near-end Identification). Furthermore, the integrity verifier performs remote integrity verification through the dynamic module (such remote integrity verification can be referred to as remote authentication), and this remote verification only occurs in the near-end integrity verification. After success.

● The dynamic module generator generates a dynamic module. In addition to the above verification information, the dynamic module also includes a dynamic authentication program. After the near-end and far-end verification is successful, the dynamic authentication program will perform authentication and key exchange with the authentication server.

● The authentication server will perform the authentication process with the above dynamic module and jointly generate the key for the client program to use.

In an embodiment of the invention, the dynamic module includes a digital signature, a temporary key, a memory arrangement information, a verification preset result, and a temporary identification code. A digital signature is a signature made by a private key to the content of the dynamic module (except the digital signature), and the private key and the public key in the client program (public key) ) is a key pair. Wherein, when the dynamic module is generated, the dynamic module generator transmits the temporary key, the memory arrangement information, and the verification preset result to the integrity verifier in addition to the above information. And the temporary identification code information is transmitted to the authentication server.

In an embodiment of the invention, the client program verifies the digital signature in the dynamic module according to the public key.

In an embodiment of the present invention, after the dynamic module is verified, the dynamic module obtains the client identification code from the client program, and randomly generates the memory location, and transmits the memory location and the memory layout information to the client. The end program causes the client program to calculate a verification code based on the memory location and the memory layout information, and transmit the verification code to the dynamic module. The dynamic module generates a client key according to the temporary key and the client identification code, and generates a verification result according to the verification code and the client key, so as to compare the verification result with the verification preset result.

In an embodiment of the present invention, the integrity verifier randomly generates a memory location, and transmits the memory location and the memory layout information to the client program, so that the client program arranges information according to the memory location and the memory. A verification code is calculated and the verification code is transmitted to the integrity verifier; and the integrity verifier calculates the verification result according to the verification code and the temporary key to compare the verification result with the verification preset result.

In an embodiment of the present invention, after the client program is verified to be correct, the dynamic module transmits the temporary identification code and the first value to the authentication server, and the authentication server transmits the second value to the dynamic module; and the dynamic module Generating a third value and encrypting the third value through the public key to obtain a secret value to transmit the secret value to the authentication server; and the authentication server decrypts the secret value according to the private key to obtain the third value, so that the authentication servo The dynamic module generates a shared key according to the first value, the second value, and the third value.

Based on the above, the present invention can avoid storing the key directly on the client program, and when the client program wants to communicate with the host control system, the master control system obtains a dynamic module. Moreover, after the client program and the dynamic module are mutually verified, the key exchange program can be performed with the master control system through the dynamic module. As a result, static analysis can be resisted and dynamic attacks can be mitigated.

The above described features and advantages of the present invention will be more apparent from the following description.

Key protection technology is biased towards system security, and there are different practices and security in different host systems. In the current common network monitoring system, since the user of the client device usually has the authority of the system administrator, various analysis can be performed on the client program, so the security provided by the host terminal is very limited. To this end, the present invention proposes a method of managing a key to avoid storing the shared key directly in the client program. In order to clarify the content of the present invention, the following specific examples are given as examples in which the present invention can be implemented.

First embodiment

1 is a schematic diagram of a management key process of a network monitoring system in accordance with a first embodiment of the present invention. Referring to FIG. 1, the network monitoring system includes a main control system 110 and a client device 120. Here, a client program is installed in the client device 120.

Taking the network monitoring system as an example of the SCADA system, the main control system 110 includes a master station and a human machine interface of the SCADA system, and the client device 120 is a remote terminal unit (RTU) of the SCADA system. ). The remote terminal unit of the SCADA system is generally equipped with a sensor to retrieve data, and uses various network technologies to transmit the data back to the main console, and finally displays it to the management personnel through the human-machine interface display.

In this embodiment, the key information is not directly stored in the client program, but is replaced by a key initial procedure (including two functions of authentication and key exchange), and the initial procedure of the key is also It is not stored directly in the client program, but is placed in a dynamic module. When the client device 120 wants to communicate with the main control system 110, the client program acquires the dynamic module by the main control system 110.

In detail, in step S131, when the client device 120 wants to communicate with the main control system 110, the client program registers with the main control system 110, so that the main control system 110 generates a dynamic module. Next, in step S133, the main control system 110 transmits the dynamic module to the client device 120.

Thereafter, in step S135, the client program verifies the dynamic module to ensure that the dynamic module is transmitted by the master system 110. Then, in the dynamic module verification, step S137 is executed, and the dynamic module verifies the client program to ensure the integrity of the client program. For example, such verification can be divided into two categories, and for the AMI system, the memory of the entire client device 120 can be checked for checksum. In addition, for the DRM system or the software marketplace system, since the client device 120 belongs to the user, the integrity verification can only be performed for the client program. In addition, you can set a time limit in the dynamic module, as long as the time spent verifying the calculation exceeds the time limit, it is considered a failure.

In addition, after the dynamic module is deployed to the client device 120, a local attestation is performed on the client device 120, and the client program is verified by the dynamic module. If successful, remote attestation may be further performed by the host system 110 to verify the client program again by the host system 110.

When the client program is verified, step S139 is executed to execute the key exchange program through the dynamic module and the main control system 110, thereby generating a shared key between the main control system 110 and the client device 120. The key exchange program is similar to the key exchange program of the Secure Sockets Layer (SSL) protocol. The difference is that the program of the present invention uses a temporary identification code, a temporary key and a cryptographic algorithm, which are dynamic. The module generator is randomly generated to prevent the attacker from accumulating relevant knowledge by intercepting the packet.

After the shared key is obtained, the different keys can be derived through the shared key. For example, a Message Authentication Code (MAC) key, an encryption key, and a key required for each connection. These keys will not be continuously stored in the client device 120 in any form, but will be dynamically generated each time the client program is executed, thereby reducing the chance of being attacked.

Second embodiment

2A-2F are schematic diagrams showing a flow of a method for managing a key in accordance with a second embodiment of the present invention. In this embodiment, the network monitoring system 200 includes a master control system 210 and at least one client device, and the client devices 220, 230, 240 are listed here as an example. This is for illustrative purposes only and does not limit the number of client devices.

Here, the client devices 220, 230, 240 are architected in a private network 250, while the private network 250 is architected on a public network 260. The public network 260 is, for example, the Internet. Private network 250 is a communication method commonly used to connect private networks between medium and large enterprises or between groups and groups. The private network 250 is connected to the public network 260 via an Internet Service Provider (ISP) 280. For example, a virtual private network 250 is constructed on the public network 260 by using security technologies such as tunneling technology, encryption and decryption, etc., to achieve the security and convenience of the private network 250. In addition, a gateway 270 is used to connect two networks, namely a private network 250 and a public network 260. In other embodiments, the main control system 210 and the client device 120 can communicate with each other through any other network system, and is not limited thereto.

The main control system 210 includes a dynamic module generator 211, an integrity verifier 213, and an authentication server 215. The dynamic module generator 211 is used to generate a dynamic module, the integrity verifier 213 is used to verify the integrity of the client program 221, and the authentication server 215 is used to execute a key exchange program. Here, the dynamic module generator 211, the integrity verifier 213, and the authentication server 215 may be disposed in the same device; or may be respectively disposed in three devices; or, the dynamic module generator 211 is disposed in On one device, the integrity verifier 213 and the authentication server 215 are placed on another device.

For convenience of description, the present embodiment uses the client device 220 as an example to describe the steps of the method for managing the key. Since the operations of the client devices 230 and 240 are the same as those of the client device 220, they are not described in detail.

Referring to FIG. 2A, the client program 221 is executed in the client device 220 to register with the dynamic module generator 211. As shown in step A, the dynamic module generator 211 generates a dynamic module. For example, when the client device 220 launches the client program 221, the client program 221 can issue a registration request to the master control system 210, and the registration request includes a client identification code for the master control system 210 to identify. Where is this registration request sent?

Next, referring to FIG. 2B, when the dynamic module generator 211 receives the registration request, a dynamic module 223 is dynamically generated, and the dynamic module 223 is transmitted to the client device 220, as shown in step B. Here, the dynamic module 223 is, for example, a dynamic library, which includes two functions of authentication and key exchange.

For example, the dynamic module generator 211 dynamically generates an attestation program and a key exchange protocol program, and places the attestation program and the key exchange protocol program into the dynamic module 223 for transmission to the client device 220. The forensic program contains information that can verify the integrity of the client program 221, and this information is dynamically generated in order to avoid prior calculations and resend attacks. For example, the attestation program can be implemented by a checksum function, which is randomly established by basic arithmetic operations instructions, and the checksum function can also contain a time limit. When the checksum and the function calculate the checksum time exceeds the time limit, Will be considered a failure. The key exchange protocol program is used to generate a shared key between the client program 221 and the authentication server 215.

In addition, when the dynamic module generator 211 generates the dynamic module 223, information such as a temporary key, a memory arrangement information, a verification preset result, and a temporary identification code are generated, and the information is placed in the dynamic module 223. in. Moreover, when the dynamic module 223 is generated, the dynamic module generator 221 also transmits the temporary key, the memory arrangement information, and the verification preset result to the integrity verifier 213, and transmits the temporary identification code information. To the authentication server 215.

For example, the forensic program contains information such as temporary keys, memory placement information, and verification preset results, and the key exchange protocol program contains temporary identification codes. After the dynamic module 223 is generated, the dynamic module generator 221 copies the forensic program and the key exchange protocol program, respectively, to transmit the forensic program to the integrity verifier 213, and transmits the key exchange protocol program to the authentication server. 215, for later use.

After the client device 220 receives the dynamic module 223, referring to FIG. 2C, the client program 221 will verify the dynamic module 223, as shown in step C. For example, the client program 221 verifies the digital signature in the dynamic module 223 based on its own public key. For example, assume that the encryption mode between the client program 221 and the main control system 210 is asymmetric encryption, and it is assumed that the client program 221 has a public key, and the main control system 210 has a private key ( Private key), that is, the above public key and private key are key pairs. When the master system 210 generates the dynamic module 223, it will use its private key to implement a digital signature. Accordingly, when the client device 220 receives the dynamic module 223, the client program 221 can use the public key to verify the digital signature, thereby verifying the identity of the dynamic module 223.

After the dynamic module 223 is verified, the client program 221 and the dynamic module 223 are combined. For example, the client program 221 and the dynamic module 223 are combined in a dynamic linking manner or a code injection manner. The way of combining will vary depending on the target platform. In addition, if the verification of the dynamic module 223 does not pass, the subsequent other actions are stopped.

Then, referring to FIG. 2D, the dynamic module 223 will verify the client device 221 as shown in step D. For example, the integrity of the client program 221 is verified using the attestation program in the dynamic module 223. Further, the dynamic module 223 randomly generates a memory location and transmits the memory location and the memory layout information to the client program 221. The client program 221 can calculate a verification code according to the memory location and the memory arrangement information, and transmit the verification code to the dynamic module 223. Thereafter, the dynamic module 223 calculates a verification result according to the verification code and the temporary key to compare the verification result with the verification preset result in the dynamic module 223. If the calculated verification result is the same as the verification preset result, the verification is correct. If the verification result is different from the verification preset result, it indicates a verification error. At this point, the subsequent actions are stopped.

The dynamic module 223 and the client device 221 are taken as an example to illustrate the following. FIG. 3 is a schematic diagram of the process of verifying the client program through the dynamic module according to the second embodiment of the present invention. In this embodiment, the verification information carried by the dynamic module 223 is provided by the dynamic module generator 211. Here, the verification information carried by the dynamic module 223 includes a temporary key K, a memory arrangement information (eg, a memory location function Address), and a verification preset result PRE_RESULT.

Referring to FIG. 3, in step S301, the dynamic module 223 requests the client identifier SN to the client program 221 to retrieve the corresponding information through the client identifier SN. Moreover, the client key KEY is generated according to the temporary key K and the client identifier SN for later use. Here, the client identification code SN is, for example, a serial number that is previously placed in the client program 221.

Next, in step S303, the dynamic module 223 randomly generates m random parameters r ₁ to r _m . In addition, in step S305, the memory address block M _i =Address(r _i ) of the client device 220 is calculated according to the memory location function Address and the random parameters r ₁ to r _m , where i=1~m . Thereby, the client program 231 causes the corresponding memory address block to be retrieved according to M _i .

Then, in step S307, the client program 231 uses the checksum of the client program 231 and the function checksum to calculate the checksum of each memory address block and V _i =checksum(M) according to the extracted memory address block M _i . _i , Size). Wherein, the variable Size is a fixed constant, such as a memory sampling size. Then, in step S309, the verification code Q = V ₁ ⊕ V ₂ ... ⊕ V _{m of} each memory address block is calculated.

Then, in step S311, the client program 221 transmits the verification code Q to the dynamic module 223. Here, a time limit T1 can be set. When the dynamic module 223 does not receive the verification code Q within the time limit T1, it is determined that the verification fails. Thereafter, in step S313, the dynamic module 223 calculates the verification result RESULT according to the temporary key K and the verification code Q, and uses a hash function H to compare the verification result RESULT and verify the preset result. PRE_RESULT. Among them, RESULT=H(H(Q), KEY), KEY=SN⊕K.

The client identifier SN is a serial number that is previously placed in the client program, and the temporary key K is dynamically generated and placed in the dynamic module 223. When the dynamic module generator 211 prepares these parameters, the temporary key K, the hash function H and other related functions are placed in the dynamic module 223, and after the time limit T1 is estimated, the time limit T1 is also placed in the dynamic mode. Group 223.

After the client program 221 verifies that the dynamic module 223 is successful, the dynamic module 223 is also connected to the integrity verifier 213 of the main control system 210 to verify the client program 221. Returning to Figure 2E, the client program 221 is verified by the integrity verifier 213 of the host system 210, as shown in step E. Specifically, the integrity verifier 213 randomly generates a memory location, and transmits the memory location and the memory layout information to the client program 221, so that the client program 221 calculates a memory location and memory layout information. The verification code is transmitted and the verification code is transmitted to the integrity verifier 213. Moreover, the integrity verifier 213 calculates the verification result according to the verification code and the temporary key to compare the verification result with the verification preset result.

For example, FIG. 4 is a schematic diagram of verifying a client program flow by a transparency integrity verifier according to a second embodiment of the present invention. In this embodiment, steps S401 to S413 are the same as or similar to steps S301 to S313, respectively, and therefore will not be described in detail herein.

Referring to FIG. 4, in step S401, the integrity verifier 213 requests the client identifier SN to the client program 221 to generate the client key KEY based on the temporary key K and the client identifier SN. Next, in step S403, the integrity verifier 213 generates m random parameters r ₁ to r _{m in} a random number. And, in step S405, the memory address block M _i = Address(r _i ) is calculated, where i=1~m. Thereafter, in step S407, the client program 231 calculates the collation of each memory address block and V _i =checksum(M _i , Size) according to the extracted memory address block. Wherein, the variable Size is a fixed constant. Then, in step S409, the verification code Q = V ₁ ⊕ V ₂ ... ⊕ V _{m of} each memory address block is calculated.

Then, in step S411, the client program 221 transmits the verification code Q to the integrity verifier 213. Here, a time limit T2 can be set. When the integrity verifier 213 does not receive the verification code Q within the time limit T2, it is determined that the verification fails. Thereafter, in step S413, the integrity verifier 213 calculates the verification result RESULT based on the temporary key K and the verification code Q, and uses a hash function H to compare the verification result RESULT and the verification preset result PRE_RESULT.

That is to say, after the dynamic module 223 is deployed, the integrity of the client program 231 is verified according to the above steps S301 to S309, and it is checked whether the calculation time is within the time limit T1, which is the near-end authentication. If successful, remote authentication will be performed, such as steps S401~S413. After the near-end authentication and the remote authentication are successful, the key exchange program is executed. Such a decentralized structure can reduce the burden on the communication and backend master control system 210.

Returning to FIG. 2F, after the client program 221 is verified to be correct, the client device 221 performs a key exchange process with the authentication server 215 of the master control system 210 via the dynamic module 223, as shown in step F, to generate the client device 220. A shared key with the master system 210.

For example, FIG. 5 is a schematic diagram of an execution key exchange procedure in accordance with a second embodiment of the present invention. Referring to FIG. 5, in step S501, the dynamic module 223 transmits the temporary identification code and the first value to the authentication server 215. Here, the first value may be a value generated by the random number of the dynamic module 223. When the authentication server 215 receives the temporary identification code, the identity of the dynamic module 223 is identified according to the temporary identification code generated by the dynamic module generator 211 when the dynamic module 223 is generated.

And, in step S503, the authentication server 215 transmits the second value to the dynamic module 223. Similarly, the second value can also be generated by the authentication server 215. In addition, in step S505, the dynamic module 223 generates a third value and encrypts the third value through the public key to obtain a secret value. Thereafter, in step S507, the secret value is transmitted to the authentication server 215. After receiving the secret value, the authentication server 215 can decrypt the secret value according to the private key corresponding to the public key to obtain the third value.

Accordingly, the dynamic module 223 and the authentication server 215 respectively have a first value, a second value, and a third value. In step S509 and step S511, the dynamic module 223 and the authentication server 215 can generate the shared key according to the first value, the second value, and the third value. After that, you can export other different keys through the shared key.

It is worth noting that in order to avoid the key exchange process being analyzed, the key exchange protocol program carried by the dynamic module 223 also has a time limit, as long as the time for receiving the response exceeds the time limit, the temporary identification code and the randomly generated value are Will be cancelled.

In summary, in the above embodiment, the key information is not directly stored in the client program, but is instead replaced by a key initial procedure (including two functions of authentication and key exchange), and The initial program of the key is not stored directly in the client program, but is placed in a dynamic module. When the client program wants to communicate with the host system, the client program obtains the dynamic mode by the master control system. group. Since both the authentication and key exchange functions are dynamically generated by the master control system, the attacker can not be accumulated by avoiding the attacker analyzing the dynamic module code or collecting the request/response result in advance. Knowledge of dynamic modules. In addition, the dynamic module includes functions such as near-end authentication, remote authentication, and key exchange. After the near-end authentication is successful, remote authentication and key exchange are performed. This decentralized structure can be reduced. The burden of communication and master control systems. In addition, the analysis of the time limit can also avoid the analysis of the attacker.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

110, 210. . . Master control system

120, 220, 230, 240. . . Client device

211. . . Dynamic module generator

213. . . Integrity verifier

215. . . Authentication server

221. . . Client program

223. . . Dynamic module

250. . . Private network

260. . . Public network

270. . . Gateway

280. . . Network service provider

S131~S139. . . Each step of the management key process of the network monitoring system of the first embodiment

A~F. . . Method for managing a key in the second embodiment

S301~S313. . . The steps of verifying the client program flow through the dynamic module in the second embodiment

S401~S413. . . The pass integrity verifier of the second embodiment is used to verify the steps of the client program flow

S501~S511. . . Steps of executing the key exchange program of the second embodiment

1 is a schematic diagram of a management key process of a network monitoring system in accordance with a first embodiment of the present invention.

2A-2F are schematic diagrams showing a flow of a method for managing a key in accordance with a second embodiment of the present invention.

3 is a schematic diagram of a process of verifying a client program through a dynamic module according to a second embodiment of the present invention.

4 is a schematic diagram of verifying a client program flow by a transparency integrity verifier according to a second embodiment of the present invention.

Figure 5 is a schematic diagram of an execution key exchange procedure in accordance with a second embodiment of the present invention.

S131~S139. . . Each step of the management key process of the network monitoring system of the first embodiment

Claims (17)

A method for managing a key is adapted to a network monitoring system, the network monitoring system comprising a master control system and a client device, and the method comprises: the client device executing a client program to the master The system is registered to enable the master control system to generate a dynamic module; the master control system transmits the dynamic module to the client device; the client device verifies the dynamic module through the client program; the client device transmits the dynamic module The dynamic module verifies the client program; after the client program is verified, the client device performs a key exchange process with the master control system through the dynamic module to generate the client device and the master control system. A shared key between. The method of managing a key according to claim 1, wherein the client device is disposed in a private network, and the private network is configured on a public network, so that the client device transmits the private network. The road is connected to the public network to connect to the main control system. The method for managing a key according to claim 1, wherein the master control system comprises a dynamic module generator, an integrity verifier, and an authentication server, wherein the dynamic module generator is configured to generate the key A dynamic module, the integrity verifier is used to verify the client program, and the authentication server is configured to execute the key exchange program. The method for managing a key according to claim 1, wherein before the step of transmitting the dynamic module to the client device, the method further includes: generating a digital signature of the dynamic module, The digital signature is implemented by a private key that is a key pair with a public key in the client program. The method for managing a key as described in claim 4, wherein the step of the client device verifying the dynamic module through the client program comprises: the client program verifying the dynamic mode according to the public key The digital signature in the group. The method for managing a key as described in claim 1, wherein the dynamic module includes a temporary key, a memory arrangement information, and a verification preset result, and the client device transmits the dynamic mode The step of verifying the client program includes: the dynamic module randomly generates a memory location, and transmits the memory location and the memory arrangement information to the client program; the client program is based on the memory location and the The memory arrangement information, calculating a verification code, and transmitting the verification code to the dynamic module; and the dynamic module calculates a verification result according to the verification code and the temporary key, to compare the verification result with the Verify the preset results. The method for managing a key according to claim 6 , wherein before the step of calculating the verification result by the dynamic module according to the verification code and the temporary key, the method further comprises: the dynamic module from the client A client identifier is obtained in the terminal program; a client key is generated according to the temporary key and the client identifier, so that the dynamic module generates the check result according to the verification code and the client key. The method for managing a key according to claim 1, wherein before the step of executing the key exchange procedure, the method further comprises: when the client device verifies that the client program succeeds through the dynamic module, The master control system verifies the client program, and the step includes: the master control system randomly generates a memory location, and transmits the memory location and a memory arrangement information to the client program; the client program is configured according to the a memory location and the memory arrangement information, calculating a verification code, and transmitting the verification code to the main control system; and the main control system calculates a verification result according to the verification code and a temporary key to compare The verification result is combined with a verification preset result. The method for managing a key according to claim 1, wherein after the step of transmitting the verification code to the main control system, the method further comprises: when the main control system does not receive the verification code within a time limit , to determine that the client program verification failed. The method for managing a key according to claim 1, wherein the client device performs the key exchange procedure with the main control system through the dynamic module to generate a relationship between the terminal unit and the main control system. The step of sharing the key includes: transmitting, by the dynamic module, a temporary identification code and a first value to the main control system; the main control system transmitting a second value to the dynamic module; the dynamic module generates a a third value, and encrypting the third value by a public key to obtain a secret value, and transmitting the secret value to the master control system; the master control system decrypts according to a private key corresponding to the public key Obtaining the third value by the secret value; and the master control system and the dynamic module generate the shared key according to the first value, the second value, and the third value. The method for managing a key according to claim 1, wherein after the step of verifying the dynamic module by the client device, the method further comprises: using a dynamic link or a code injection method. , combining the client program with the dynamic module. A network monitoring system includes: a client device disposed in a private network, wherein the private network is on a public network, and the client device is installed with a client program; and a host system Connecting to the private network through the public network to connect with the client device, the master control system includes: a dynamic module generator for generating a dynamic module; and an integrity validator for Verifying the client program; and an authentication server for executing a key exchange program to generate a shared key with the client program; wherein the client device executes the client program to the dynamic module generator Registering to receive the dynamic module from the dynamic module generator, and verifying the dynamic module through the client program; and after the dynamic module is verified, the client device verifies the dynamic module through the dynamic module a client program, and the master system verifies the client program through the integrity verifier; and after the client program is verified to be correct, the client device transmits the Module to the authentication server executes the key exchange procedure to generate the shared key. The network monitoring system of claim 12, wherein the dynamic module comprises a digital signature, a temporary key, a memory arrangement information, a verification preset result, and a temporary identification code, and The digital signature is implemented by a private key, and the private key is a key pair with a public key in the client program; wherein, when the dynamic module is generated, the dynamic module generates The temporary key, the memory arrangement information, and the verification preset result are transmitted to the integrity verifier, and the temporary identification code information is transmitted to the authentication server. The network monitoring system of claim 13, wherein the client program verifies the digital signature in the dynamic module according to the public key. The network monitoring system of claim 13, wherein after the dynamic module is verified, the dynamic module obtains a client identification code from the client program, and randomly generates a memory location. And transmitting the memory location and the memory arrangement information to the client program, so that the client program calculates a verification code according to the memory location and the memory arrangement information, and transmits the verification code to the dynamic module. And generating, by the dynamic module, a client key according to the temporary key and the client identifier, and generating the verification result according to the verification code and the client key, to compare the verification result with the Verify the preset results. The network monitoring system of claim 13, wherein the integrity verifier randomly generates a memory location, and transmits the memory location and the memory arrangement information to the client program, so that the client The terminal program calculates a verification code according to the memory location and the memory arrangement information, and transmits the verification code to the integrity verifier; and the integrity verifier calculates a school according to the verification code and the temporary key. The result is compared with the check result and the check preset result. The network monitoring system of claim 13, wherein the dynamic module transmits the temporary identification code and a first value to the authentication server after the client program is verified, and the authentication server Transmitting a second value to the dynamic module; and the dynamic module generates a third value, and encrypting the third value through the public key to obtain a secret value, and transmitting the secret value to the authentication server And the authentication server decrypts the secret value according to the private key to obtain the third value, so that the authentication server and the dynamic module generate the first value, the second value, and the third value according to the first value, the second value, and the third value. The shared key.