A security encryption method for network transmission applicable to urban rail transit systems

Abstract

The present disclosure belongs to the field of security encryption technologies, and more particularly relates to a security encryption method applicable to network transmission in an urban rail transit system, including: a key generation center selects system parameters and generates a public-private key pair; on-vehicle communication devices generate part of the public-private key pair; the key generation center of the on-vehicle communication devices generates another part of the public-private key pair of the on-vehicle communication devices to form a complete public-private key pair, and the on-vehicle communication devices verify the complete public key and the complete private key; a message signature is generated based on the message to be transmitted by the device; the message sender device encrypts the message to be transmitted using the message receiver's key to form encrypted data and transmits it; the message receiver decrypts the encrypted data using the device's private key. Through the above settings, the real-time performance is improved.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of security encryption, and particularly relates to a security encryption method for network transmission applicable to urban rail transit systems. Background Art

[0002] As an important national industrial infrastructure, with the trend of informatization, urban rail transit brings risks and challenges of security hazards while developing in an open, interconnected and standardized manner. It is urgent to provide security protection for the information transmission of urban rail transit to ensure that data transmission is not tampered with. Especially for the vehicle-ground wireless communication of the urban rail transit signal system, the physical medium of its transmission exists in an open space range, and the transmission content is important information related to train operation control. Once an illegal device invades, it will lead to the leakage, interception and even tampering of the transmitted data, and in serious cases, it will threaten the operation safety of the rail transit system.

[0003] Existing rail transit systems usually adopt international standard encryption algorithms. With the improvement of computer operation level, some international algorithms have been successfully deciphered, such as MD5, SHA-1, etc. As a key infrastructure in China, it is urgent to implement a communication encryption method for urban rail transit systems that is independently controllable. Domestic encryption technology conforms to the trend of adopting domestic cryptographic algorithms in key industries in China, which is beneficial to protecting the data security of rail transit. Especially in the driverless rail transit system, it can achieve high security and high reliability of vehicle-ground wireless communication.

[0004] Among them, some on-vehicle signal systems of rail transit have added domestic cryptographic protection technology, and realize secure encryption of data communication through four stages: the chip injection stage, the stage of updating the certificate revocation list, the stage of identity authentication and session key negotiation, and the application data communication. The public key infrastructure (PKI) / certificate authority (CA) server is used to authenticate communication devices. However, due to the high running speed of urban rail trains, the traditional authentication method based on the PKI certificate system has a long query time for the CRL certificate revocation list and poor real-time performance. Summary of the Invention

[0005] The present disclosure is precisely proposed based on the above-mentioned needs of the prior art. The technical problem to be solved by the present disclosure is to provide a security encryption method for network transmission applicable to urban rail transit systems to improve real-time performance.

[0006] To solve the above problems, the technical solutions provided by the present disclosure include:

[0007] A network transmission security encryption method applicable to urban rail transit systems is provided, including: the key generation center selects system parameters and generates a public-private key pair; the ground-vehicle communication device generates a partial public-private key pair; the key generation center of the ground-vehicle communication device generates another partial public-private key pair of the ground-vehicle communication device, forms a complete public key based on the partial public key generated by the ground-vehicle communication device and another partial public key generated by the key generation center, and transmits the complete public key to the key generation center; the ground-vehicle communication device forms a complete private key based on the partial private key generated by itself and another partial private key generated by the key generation center, the key generation center transmits the complete public key to the ground-vehicle communication device through a secure channel, and the ground-vehicle communication device verifies the complete public key and the complete private key; generates a message signature based on the message to be transmitted by the device; the message sender device encrypts the message to be transmitted using the message receiver key, forms encrypted data and transmits it; the message receiver decrypts the encrypted data using the device private key; the train communication device batch-verifies the received message and determines the authenticity and integrity of the message.

[0008] Preferably, the key generation center selects system parameters and generates a public-private key pair, including: the system parameters include M pt , denoted as M pt = {a, b, q, G, P KGC}; the elliptic curve equation is Y 2 = X 3 + aX + b, where a and b are parameters of the elliptic curve equation, q is a prime number and is the order of the selected elliptic curve point group, P KGC = sG, the base point G = (x G , y g ), where x G is the abscissa of the base point G, and y G is the ordinate of the base point G; the public-private key pair is (P KGC , M st ), where M st = s, s ∈ [0, q - 1].

[0009] Preferably, the ground-vehicle communication device generates a partial public-private key pair, including: the ground-vehicle communication device selects a random number as the partial private key x, x ∈ [0, q - 1], forms the corresponding partial public key X A , denoted as X A = xG, outputs the partial public-private key pair, denoted as (X A , x), and stores it in the tamper-proof device.

[0010] Preferably, the key generation center of the ground-vehicle communication device generates another partial public-private key pair of the ground-vehicle communication device, including: the ground-vehicle communication device sends the device identifier and the partial public key X ASecurely transmit to the key generation center KGC and calculate by KGC where ID L is the length of the device identifier, and ID A is the device identifier, is the x-axis coordinate quantity of P KGC ; the y-axis coordinate quantity of P is the y-axis coordinate quantity of P KGC ; the key generation center KGC of the communication device generates another part of the public key W A = wG, where w is a randomly selected number and w ∈ [0, q - 1], and H1 is the SM3 national cryptographic algorithm; form a complete public key based on the partial public key generated by the ground-vehicle communication device and the other part of the public key generated by the key generation center, including: during the device registration process, transmit the public key information to the key generation center KGC, that is, KGC can obtain the complete public key information of the device, expressed as: P A = X A + W A , where P A is the complete public key.

[0011] Preferably, the ground-vehicle communication device forms a complete private key based on the partial private key generated by itself and the other part of the private key generated by the key generation center, including: the key generation center generates another part of the private key of the device, expressed as: d A = (w + λs) mod q, where H2() is a hash function, is the x coordinate of the complete public key, is the y coordinate of the complete public key, and mod is the remainder function. The formation method of the complete private key is expressed as: S A = d A + x = (w + λs + x) mod q; the ground-vehicle communication device verifies the complete public key and the complete private key, including: perform the following calculations according to the device identifier and the system initialization parameters: P A ' = S A G - λP KGC , if P A ' = P A holds, it means the key is valid; if not, return to re-register the device identity.

[0012] Preferably, generating a message signature based on the message to be transmitted by the device includes: the message to be transmitted by the ground-vehicle communication device is m, set T as the timestamp of the message to be sent, and at the same time calculate e = H1(m*); select a random number k ∈ [0, q - 1], calculate the elliptic curve point (x1, y1) = R = kG; calculate r = (e + x1) mod q, if r = 0 or r + k = q, then a new random number k needs to be selected for iteration; calculate The signature method is (R, v) to support the scenario of batch message verification.

[0013] Preferably, the message sender device encrypts the message to be transmitted using the message receiver's key, including: The key of the message receiver is represented as: Q B = P B + λ′P KGC , where Q B is the message receiver's key, P B is the message receiver's public key. The message sender device uses the message receiver's key to encrypt the data m and also needs to obtain the receiver's public key P B and the receiver's identifier ID B , and calculate: is the x - coordinate of the message receiver's public key P B , is the y - coordinate of the message receiver's public key P B ; randomly select ρ ∈ [0, q - 1], C1 = ρG, H = ρO B , f = KDF(x H ||y H ), C3 = H1(x H ||m||y H ), where H is an intermediate quantity, O B represents the identity, KDF() represents the key derivation function, x H represents the x - coordinate of H, y H represents the y - coordinate of H, and the ciphertext is C = (C1, C3, C2). The ciphertext is transmitted to the message receiver.

[0014] Preferably, the message receiver decrypts the encrypted data using the device's private key, including: The message receiver decrypts the ciphertext using its private key, and its private key is S B , and the decryption method is represented as: H′ = S B C1, f = KDF(x H′ ||y H′ ), C3′ = H1(x H′ ||m||y H′ ), where x H′ is the x - coordinate of H′, y H′ is the y - coordinate of H′; if C3′ = C3 holds, then the message m is output; if not, the message is rejected.

[0015] Preferably, the train communication device batch - verifies the received messages, including: When n train control messages {(IDA , P A , m1, T, R1, v1), (ID A , P A , m2, T, R2, v2), …, (ID A , P A , m n , T, R n , v n )}, where m i is the i-th message, R i is the elliptic curve point generated when the i-th device signs the message, and v i is the integer part generated when the i-th device signs the message. The batch verification is expressed as: where ε i is the introduced random number, Judge whether X1 = X1' holds. If it holds, the batch message is valid. If it does not hold, the error message is located by the binary method.

[0016] The train communication device performs batch verification on the received messages, including: when n train control messages sent by different communication devices {(ID1, P1, m1, T, R1, v1), (ID2, P2, m2, T, R2, v2), …, (ID n , P n , m n , T, R n , v n )}, where ID i is the i-th communication device, P i is the public key of the i-th communication device, m i is the message sent by the i-th communication device, R i is the elliptic curve point generated when the i-th device signs the message, and v i is the integer part generated when the i-th device signs the message. The batch verification is expressed as: Q i = P i + λ i P KGC , and after sorting, we get:

[0017] Judge whether X1 = X1' holds. If it holds, the batch message is valid; if it does not hold, the error message needs to be located by the binary method.

[0018] Compared with the prior art, the present disclosure provides a network transmission security encryption method applicable to urban rail transit systems, which is used to solve the problem of large communication delay in the existing domestic encryption method based on traditional PKI. By using a certificate-free signature algorithm and combining the domestic commercial cryptography algorithm SM2 to generate a digital signature, the signature is improved to meet the message batch authentication in the case of synchronous transmission of multiple train control instructions, reduce the verification delay, and further form the security encryption of the ground-to-train communication data in rail transit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the embodiments of the present specification. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a flowchart of the steps of the network transmission security encryption method applicable to urban rail transit systems in the embodiments of the present invention;

[0021] Figure 2 It is a flowchart of the network transmission security encryption method applicable to urban rail transit systems in the embodiments of the present invention;

[0022] Figure 3 It is a schematic diagram of ground-to-train communication in urban rail transit systems in the embodiments of the present invention;

[0023] Figure 4 It is a schematic diagram of information transmission between the key generation center and ground-to-train communication devices in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0025] In the description of the embodiments of the present disclosure, it should be noted that unless otherwise clearly specified and limited, the term "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meaning of the above terms in the present disclosure can be understood according to specific circumstances.

[0026] The terms "top", "bottom", "above", "under", and "on" used throughout the description are relative positions with respect to the components of the device, such as the relative positions of the top and bottom substrates inside the device. It is understood that the devices are multifunctional and independent of their orientation in space.

[0027] For ease of understanding the embodiments of the present application, the following will further explain with specific embodiments in conjunction with the accompanying drawings. The embodiments do not limit the embodiments of the present application.

[0028] This embodiment provides a network transmission security encryption method applicable to urban rail transit systems, as Figures 1 - 4 shown.

[0029] The network transmission security encryption method applicable to urban rail transit systems includes:

[0030] Generate system initialization data, including the key generation center KGC selecting system parameters and generating a public-private key pair. The system parameters include M pt , denoted as M pt = {a, b, q, G, P KGC} with the elliptic curve equation Y 2 = X 3 + aX + b, where a and b are parameters of the elliptic curve equation, q is a prime number and is the order of the selected elliptic curve point group, P KGC = sG, the base point G = (x G , y G ), where x G is the abscissa of the base point G and y G is the ordinate of the base point G. The public-private key pair is (P KGC , M st ), where M st = s, s ∈ [0, q - 1].

[0031] The on-vehicle communication device generates a partial public-private key pair. The on-vehicle communication device selects a random number as the partial private key x, x ∈ [0, q - 1]. According to the partial private key, the corresponding partial public key X A is formed, denoted as X A = xG. Output the partial public-private key pair, denoted as (X A , x), and store it in the tamper-proof device.

[0032] Register the on-vehicle communication device. The key generation center of the on-vehicle communication device generates another part of the public-private key pair of the on-vehicle communication device and stores the complete public key of the device.

[0033] The on-vehicle communication device sends the device identifier and the partial public key X ASecurely transmit to the key generation center KGC and calculate by KGC Among them, ID L is the length of the device identifier, ID A is the device identifier, is the x-axis coordinate quantity of P KGC and is the y-axis coordinate quantity of P KGC . The key generation center KGC of the communication device generates another part of the public key W A = wG, where w is a randomly selected number and w ∈ [0, q - 1], and H1 is the SM3 national cryptographic algorithm.

[0034] Based on the partial public key generated by the train-ground communication device and another part of the public key generated by the key generation center, form a complete public key, and transmit the public key information to the key generation center KGC during the device registration process, that is, KGC can obtain the complete public key information of the device, expressed as: P A = X A + W A , where P A is the complete public key.

[0035] The key generation center generates another part of the private key of the device, expressed as: d A = (w + λs) mod q, where H2() is a hash function, is the x coordinate of the complete public key, is the y coordinate of the complete public key, and mod is the remainder function.

[0036] KGC transmits the above-formed complete public key and another part of the private key to the train-ground communication device through a secure channel, and the transmission content is (P A , d A ).

[0037] The train-ground communication device forms a complete private key based on the partial private key generated by itself and another part of the private key generated by the key generation center, and verifies the complete public key and the complete private key.

[0038] The formation method of the complete private key is expressed as: S A = d A + x = (w + λs + x) mod q.

[0039] Verifying the validity of the complete public key P A and the complete private key S A includes performing the following calculations based on the device identifier and the system initialization parameters:

[0040] P A ′ = S A G - λP KGC

[0041] If P A ' = P A holds, it indicates that the secret key is valid; if not, return to re - register the device identity.

[0042] The on - vehicle communication device stores its verified complete public - private key pair (P A , S A ). Since the KGC cannot obtain the complete private key of the device, the key escrow security problem can be avoided.

[0043] The message sender device generates a message signature for the message to be transmitted. Improve the SM2 national cryptography algorithm to generate the message signature. The message to be transmitted by the on - vehicle communication device is m, and set T as the timestamp of the sent message. At the same time, calculate e = H1(m*).

[0044] Select a random number k ∈ [0, q - 1], calculate the elliptic curve point (x1, y1) = R = kG, calculate r = (e + x1) mod q. If r = 0 or r + k = q, a new random number k needs to be selected for iteration.

[0045] Calculate The signature method of the SM2 algorithm for the message m is (r, v). To support the message batch verification scenario, in this embodiment, the signature method is updated to (R, v).

[0046] The message sender device encrypts the message to be transmitted using the message receiver's key, forms encrypted data and transmits it.

[0047] The key of the message receiver is expressed as: Q B = P B + λ'P KGC , where Q B is the message receiver's key, P B is the message receiver's public key. The message sender device uses the message receiver's key to encrypt the data m and also needs to obtain the receiver's public key P B and the receiver's identifier ID B .

[0048] Specifically, calculate:

[0049]

[0050]

[0051] is the x - coordinate of the message receiver's public key P B , is the y - coordinate of the message receiver's public key P B .

[0052] Randomly select ρ ∈ [0, q - 1], C1 = ρG, H = ρO B , f = KDF(x H ||y H ), C3 = H1(x H ||m||y H ), and return the SM2 ciphertext as C = (C1, C3, C2), then transmit the ciphertext to the message recipient. Among them, H is an intermediate quantity, and O B represents the identity, KDF() represents the key derivation function, x H represents the x - coordinate of H, and y H represents the y - coordinate of H.

[0053] The message recipient device decrypts the transmitted message data.

[0054] The message recipient decrypts the ciphertext using its private key, and its private key is S B , and the decryption method is expressed as:

[0055] H′ = S B C1

[0056] f = KDF(x H′ ||y H′ )

[0057]

[0058] C3′ = H1(x H′ ||m||y H′ )

[0059] Among them, x H′ is the x - coordinate of H′, and y H′ is the y - coordinate of H′.

[0060] If C3′ = C3 holds, then output the message m; if not, then reject the message.

[0061] The train communication device batch - verifies the received message and judges the authenticity and integrity of the message.

[0062] When the message received by the train communication device is {ID A , P A , m, T, R, v}, perform the following calculations:

[0063]

[0064] Q A = P A +λP KGC

[0065] Calculate according to signature R:

[0066] r = (e* + x R ) mod q

[0067] t = (r + v) mod q

[0068] (X1, Y1) = vG + tQ A

[0069] where x R is the abscissa of R. Determine whether X1 = R holds. If it holds, the message is valid.

[0070] When n train control messages sent by the same on-vehicle communication device are {(ID A , P A , m1, T, R1, v1), (ID A , P A , m2, T, R2, v2), …, (ID A , P A , m n , T, R n , v n )}, where m i is the i-th message, R i is the elliptic curve point generated when the i-th device signs the message, and v i is the integer part generated when the i-th device signs the message.

[0071] Based on the above situation, the implementation method for batch verification is:

[0072]

[0073] where ε i is the introduced random number, which eliminates the linear relationship to avoid forgery attacks.

[0074]

[0075] Determine whether X1 = X1′ holds. If it holds, the batch message is valid. If it does not hold, locate the error message by the binary method.

[0076] When n train control messages sent by different communication devices are {(ID1, P1, m1, T, R1, v1), (ID2, P2, m2, T, R2, v2), …, (ID n , P n , m n , T, R n , v n )}, where ID iis the i-th communication device, P i is the public key of the i-th communication device, m i is the message sent by the i-th communication device, R i is the elliptic curve point generated when the i-th device signs the message, v i is the integer part generated when the i-th device signs the message.

[0077] Based on the above situation, the implementation method of batch verification is as follows:

[0078]

[0079] Q i = P i + λ i P KGC

[0080] Through arrangement, we get:

[0081]

[0082]

[0083]

[0084] Judge whether X1 = X1' holds. If it holds, the batch message is valid; if not, the error message needs to be located by the bisection method.

[0085] This embodiment is used to solve the problem of large communication delay in the existing domestic encryption method based on traditional PKI. Through the certificate-free signature algorithm, combined with the domestic commercial cryptography algorithm SM2 to generate digital signatures, and improving its signature, it meets the batch authentication of messages in the case of synchronous transmission of multiple train control instructions, reduces the verification delay, and further forms the security encryption of rail transit ground-to-train communication data.

[0086] The above specific implementation manners further elaborate on the purpose, technical solution, and beneficial effects of the present application. It should be understood that the above is only the specific implementation manner of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A security encryption method for network transmission applicable to urban rail transit systems, characterized in that, Including: The key generation center selects system parameters and generates a public-private key pair; The ground-train communication device generates a partial public-private key pair; The key generation center of the ground-train communication device generates another part of the public-private key pair of the ground-train communication device. A complete public key is formed based on the partial public key generated by the ground-train communication device and the other part of the public key generated by the key generation center, and the complete public key is transmitted to the key generation center; The ground-train communication device forms a complete private key based on the partial private key it generates and the other part of the private key generated by the key generation center. The key generation center transmits the complete public key to the ground-train communication device through a secure channel, and the ground-train communication device verifies the complete public key and the complete private key; Generate a message signature based on the message to be transmitted by the device; The message sender device encrypts the message to be transmitted using the message receiver's key, forms encrypted data and transmits it; The message receiver decrypts the encrypted data using the device's private key; The train communication device performs batch verification on the received messages and judges the authenticity and integrity of the messages.

2. The network transmission security encryption method applicable to the urban rail transit system according to claim 1, wherein The key generation center selects system parameters and generates a public-private key pair, including: The system parameters include M pt , denoted as M pt = {a, b, q, G, P KGC}, the elliptic curve equation is Y 2 = X 3 + aX + b, where a and b are parameters of the elliptic curve equation, q is a prime number and is the order of the selected elliptic curve point group, P KGC = sG, the base point G = (x G , y G ), where x G is the abscissa of the base point G, and y G is the ordinate of the base point G. The public-private key pair is (P KGC , M st ), where M st = s, s ∈ [0, q - 1].

3. The network transmission security encryption method applicable to an urban rail transit system according to claim 2, characterized in that, The ground-vehicle communication device generating part of the public-private key pair includes that the ground-vehicle communication device selects a random number as the partial private key \(x\), where \(x\in[0,q - 1]\), and forms the corresponding partial public key \(X\) according to the partial private key A , denoted as \(X\) A = \(xG\), outputs the partial public-private key pair, denoted as \((X A ,x)\), and stores it in the tamper-proof device.

4. The network transmission security encryption method applicable to an urban rail transit system according to claim 3, wherein The key generation center of the ground-train communication device generates another part of the public-private key pair of the ground-train communication device, including: The on-vehicle communication device securely transmits the device identifier and a part of the public key X generated by itself to the key generation center KGC, and KGC calculates A where, ID is the length of the device identifier, ID L is the device identifier, A is the x-axis coordinate quantity of P and KGC is the y-axis coordinate quantity of P ; the key generation center KGC of the communication device generates another part of the public key W KGC = wG of the on-vehicle communication device, where w is a randomly selected number and w ∈ [0, q - 1], and H1 is the SM3 national cryptographic algorithm; A ​ A complete public key is formed by a partial public key generated by the on-vehicle communication device and another partial public key generated by the key generation center, including: transmitting the public key information to the key generation center KGC during the device registration process, that is, KGC can obtain the complete public key information of the device, expressed as: P A = X A + W A , where P A is the complete public key.

5. The network transmission security encryption method applicable to urban rail transit systems according to claim 4, characterized in that The ground vehicle communication device forms a complete private key based on a partial private key generated by itself and another partial private key generated by the key generation center, including: another partial private key of the key generation center generating device, expressed as: d A =(w + λ s ) mod q, where H2() is a hash function, is the x coordinate of the complete public key, is the y coordinate of the complete public key, mod is the modulo function, and the formation method of the complete private key is expressed as: S A =d A +x = (w + λs + x) mod q; Verifying the ground vehicle communication device and the complete public key and the complete private key includes: performing the following calculations according to the device identifier and the system initialization parameters: P A ′ = S A G-λ P KGC , if P A ′ = P A holds, it indicates that the key is valid; if not, return to re-register the device identity.

6. The network transmission security encryption method applicable to an urban rail transit system according to claim 5, wherein The generating a message signature based on the message to be transmitted by the device includes: The message to be transmitted by the vehicle-ground communication device is m, and set T as the timestamp of the sent message, and at the same time calculate e = H1(m*); select a random number k ∈ [0, q - 1], calculate the elliptic curve point (x1, y1) = R = kG; calculate r = (e + x1) mod q, if r = 0 or r + k = q, then a new random number k needs to be selected for iteration; calculate The signature method is (R, v) to support the message batch verification scenario.

7. The network transmission security encryption method applicable to an urban rail transit system according to claim 6, characterized in that, The message sender device encrypts the message to be transmitted using the message recipient key, including: The key of the message recipient is expressed as: Q B = P B + λ′P KGC , where Q B is the message recipient key, P H is the message recipient public key. The message sender device uses the message recipient key to encrypt the data m and also needs to obtain the recipient public key P B and the recipient identifier ID B in advance and calculate: is the x - coordinate of the public key P of the message recipient B , is the y - coordinate of the public key P of the message recipient; B ​ Randomly select ρ ∈ [0, q - 1], C1 = ρG, H = ρO B , f = KDF(x H ||y H ), m, C3 = H1(x H ||m||yH), where H is an intermediate quantity, O H represents an identity, KDF() represents a key derivation function, x H represents the x - coordinate of H, y H represents the y - coordinate of H, the ciphertext is C = (C1, C3, C2), and the ciphertext is transmitted to the message recipient.

8. The network transmission security encryption method applicable to an urban rail transit system according to claim 7, wherein The message recipient decrypts the encrypted data using the device private key, which includes: the message recipient decrypts the ciphertext using its private key, and its private key is S B , and the decryption method is expressed as: H' = S B C1 f = KDF(x H′ || y H′ ) C3'=H l (x H′ ||m||y H′ ) where x H′ is the x - coordinate of H′, and y H′ is the y - coordinate of H′; If C3′ = C3 holds, then output message m; if not, then reject the message.

9. The network transmission security encryption method applicable to an urban rail transit system according to claim 8, wherein The train communication device performing batch verification on the received messages includes: When n train control messages sent by the same on-vehicle communication device {(ID A , P A , m1, T, R1, v1), (ID A , P A , m2, T, R2, v2), …, (ID A , P A , m n , T, R n , v n )}, where m i is the i-th message, R i is the elliptic curve point generated when the i-th device signs the message, and v i is a component of the i-th message signature. The batch verification is expressed as: where ε i is the introduced random number, Judge whether X1 = X1′ holds. If it holds, then the batch message is valid; if not, then locate the error message through the binary search method.

10. The network transmission security encryption method applicable to an urban rail transit system according to claim 8, wherein The train communication device performing batch verification on the received messages includes: When n train control messages {(ID1, P1, m1, T, R1, v1), (ID2, P2, m2, T, R2, v2), …, (ID n , P n , m n , T, R n , v n )} are sent by different communication devices, where ID i is the i-th communication device, P i is the public key of the i-th communication device, m i is the message sent by the i-th communication device, R i is the elliptic curve point generated when the i-th device signs the message, v i is the integer part generated when the i-th device signs the message. The batch verification is expressed as: Q i = P i + λ i P KGC Through arrangement, we get: Judge whether X1 = X1′ holds. If it holds, then the batch message is valid; if not, then it is necessary to locate the error message through the binary search method.

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