A method and system for secure decoding of transponder messages

Abstract

A method for secure decoding of a transponder message comprises the following steps: S1, receiving a message code stream sent by a transponder antenna and adding a timestamp; S2, searching for a complete first scrambled message from the received message code stream; S3, recording data of a specific code position in the first scrambled message; S4, decoding the first scrambled message to obtain a user message; S5, generating a corresponding first code for the data of each code position in the user message; S6, reverse decoding the user message based on the data of the specific code position to generate a second scrambled message; S7, generating a corresponding second code for the data of each code position in the user message based on the first check code in the first scrambled message and the second check code in the second scrambled message and providing it to a vehicle-mounted train control system for use. The present invention also provides a system for secure decoding of transponder messages. The present invention can ensure the security and timeliness of transponder message decoding.

Description

Technical Field

[0001] The present invention relates to the technical field of train control system communication, and in particular to a method and system for securely decoding a transponder message. Background Art

[0002] The transponder message contains important information such as route information, turnout reverse position status, signal status, etc. This information is the basis for the on-board train control system to achieve safe train operation. During the train operation, when the transponder antenna installed on the train passes over the transponder, the transponder receives the electromagnetic energy sent by the antenna, converts the electromagnetic energy into the working power of the transponder, and sends out the 1023-bit transponder transmission message stored in advance or transmitted by the LEU (Lineside Electronic UnitUnit) in a loop until the power is gone.

[0003] Due to the performance differences of various physical components (transponders, transponder antennas, etc.) and the electromagnetic interference of the environment, the transponder messages received by the antenna have a certain bit error rate. In order to improve the bit error recognition rate and the accuracy of message decoding, the mainstream on-board train control in the industry uses a 2-out-of-2 or 3-out-of-2 architecture to compare the decoding consistency through multiple CPUs. However, this method has weak protection against common mode failure problems and plaintext failure problems after decoding. Therefore, how to further improve the security of transponder message decoding is a problem that technical personnel in this field need to solve.

[0004] In addition, from the transponder antenna of the on-board train control system to the on-board train control software processing, it is processed by multiple hardware devices in the middle. When the train is running at high speed, if the message is processed or cached for too long in a certain link in the entire transmission link, it will cause the train position and trackside environment to have changed when the message is used. Therefore, how the on-board train control software can correctly identify the timeliness of the message is also a problem that people in this field need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for secure decoding of transponder messages, firstly, adding a timestamp to the message code stream sent by the received transponder antenna and searching for a first scrambled code message; then, the first scrambled code message is decoded to obtain a user message, and a corresponding first code is generated for each bit of data in the user message; finally, the user message is decoded to obtain a second scrambled code message, and based on the first check code in the first scrambled code message and the second check code in the second scrambled code message, a corresponding second code is generated for each bit of data in the user message and provided to the vehicle-mounted train control system for use. The present invention can prevent user messages from randomly failing, and improve the security of data used by the vehicle-mounted train control system. The present invention also ensures the timeliness of data used by the vehicle-mounted train control system by adding a timestamp to the message code stream and using a valid timestamp to de-timestamp the first scrambled code message.

[0006] In order to achieve the above object, the present invention provides a method for securely decoding a transponder message, wherein the method is independently executed by a plurality of decoding units, and the method comprises the steps of:

[0007] S1, receiving the message code stream sent by the transponder antenna and adding a timestamp;

[0008] S2. Searching for a complete first scrambled message from the received message code stream;

[0009] S3, recording data of a specific code position in the first scrambled code message;

[0010] S4. Decode the first scrambled message to obtain a user message;

[0011] S5. Generate a corresponding first code for each code position of data in the user message;

[0012] S6. Decode the user message based on the data of the specific code position to generate a second scrambled message;

[0013] S7. Generate a corresponding second code for each code position of data in the user message based on the first check code in the first scrambling message and the second check code in the second scrambling message; and provide the second code to the on-board train control system for use.

[0014] Optionally, the decoding unit generates a new timestamp in each working cycle; the message code stream includes multiple message fields, and the data length of the message field is the same as that of the timestamp; the method of timestamping the message code stream in step S1 includes: performing an XOR operation on each message field and the timestamp.

[0015] Optionally, step S2 includes:

[0016] S21, setting a data window for the message code stream, wherein the length of the data window is L bits; setting the count value i=1;

[0017] S22, put the i-th to i+L-1-th data bits of the message code stream into the data window in sequence; set the count value j=1;

[0018] S23, calculating the true check value of the data from the jth bit to the j+l-1th bit in the data window; l is the number of bits contained in the first scrambled message; obtaining a first check value based on the data from the j+lth bit to the j+l+d-1th bit in the data window; wherein d is the number of bits contained in the true check value;

[0019] If the true check value is equal to the first check value, the data from the jth bit to the j+l-1th bit in the data window is a first scrambled code message found, i is updated to i+j+l+d-1, and the process goes to step S22; if the true check value is not equal to the first check value, and j+l+d-1<L, j is updated to j+1, and step S23 is repeated; if j+l+d-1=L, i is updated to i+L, and the process goes to step S22.

[0020] Optionally, the first scrambling code message includes: formalized data, a control code, a scrambling code, a trimming code, and a first check code; in step S3, the specific code position includes the control code, the trimming code, and the scrambling code.

[0021] Optionally, the decoding of the first scrambled message to obtain a user message in step S4 comprises the following steps:

[0022] S41, the formal data in the first scrambled message includes a plurality of formal fields, and the data length of the formal fields is the same as that of the timestamp; each formal field is XORed with the timestamp to implement a timestamp removal operation on the formal data;

[0023] S42: Decode the formalized data after the timestamp removal operation using a set algorithm to obtain a user message.

[0024] Optionally, in step S42, the set algorithm is a decoding algorithm in the Subset-036 protocol specification.

[0025] Optionally, step S5 includes:

[0026] Let x be any bit of data in the user message, [X H ,X L ] is the first code corresponding to x, X H The high bit of the first code, X L The low bit of the first code;

[0027] X H = x;

[0028]

[0029] r kx B is the left shift operation of x by k bits; x is the signature pre-assigned to x; D T is the timestamp, and OrgCheck is the first verification code.

[0030] Optionally, in step S6, based on the control code, the scrambling code, and the trimming code, the user message is encoded by a coding algorithm in the Subset-036 protocol specification to obtain a second scrambled message.

[0031] Optionally, the second code corresponding to the data x is [X′ H ,X′ L ],X′ H is the high bit of the second code, X′ L The low bit of the second code;

[0032] X′ H = x;

[0033]

[0034] CalCheck is the second check code.

[0035] Optionally, in step S23, a CRC verification method is adopted to calculate the true verification value.

[0036] Optionally, in step S41, the formalized data is de-timestamped using a valid timestamp; the valid timestamp includes: a timestamp of the current working cycle, a timestamp of the previous working cycle, and a timestamp of the previous two working cycles.

[0037] Optionally, in step S1, at least one decoding unit performs an inversion operation on each code bit in the message code stream before timestamping the message code stream.

[0038] The present invention also provides a transponder message security decoding system for executing the security decoding method according to the present invention, the system comprising: a plurality of independent decoding units, the decoding units comprising a pre-processing board and a main processing board;

[0039] The first decoding unit is used to receive a message code stream from the transponder antenna and add a time stamp; the first decoding unit also searches for a first scrambled code message from the message code stream with the time stamp;

[0040] The second decoding unit decodes the first scrambled message to obtain a corresponding user message, and generates a corresponding first code for each bit of data in the user message; the second decoding unit also reverse-decodes the user message to generate a corresponding second scrambled message; the second decoding unit also generates a corresponding second code for each code bit of data in the user message based on a first check code in the first scrambled message and a second check code in the second scrambled message, and provides the code to the on-board train control system for use.

[0041] Optionally, the first decoding unit is an FPGA arranged on the pre-processing board, and the second decoding unit is a CPU arranged on the main processing board.

[0042] Compared with the prior art, the method and system for secure decoding of transponder messages of the present invention have the following beneficial effects:

[0043] 1) The present invention obtains a user message by positively decoding the first scrambled message, and obtains a second scrambled message by reverse decoding the user message, and judges whether the user message provided to the vehicle-mounted train control system is correct based on the first check code of the first scrambled message and the second check code of the second scrambled message, thereby improving the security of transponder message decoding and the security of message use;

[0044] 2) The present invention adds a timestamp to the message code stream and removes the timestamp from the first scrambled message through a valid timestamp, thereby ensuring the timeliness of the data used by the on-board train control system and avoiding safety hazards caused by using expired messages.

[0045] 3) The received message code stream is first inverted through one of the series pre-processing boards, thereby reducing the risk of common mode failure of the 2-out-of-2 architecture system and further improving the security of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are an embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0047] Figure 1 A schematic diagram of a security decoding system for transponder messages in an embodiment of the present invention;

[0048] Figure 2 Flow chart of a method for securely decoding a transponder message in an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of the format of a first scrambling code message in an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of searching a first scrambled code message in a message code stream in an embodiment of the present invention;

[0051] Figure 5 A schematic diagram of the format of a user message in an embodiment of the present invention;

[0052] Figure 6 The figure is a schematic diagram of the format of the second scrambling code message in an embodiment of the present invention.

[0053] In the figure:

[0054] 10. Transponder antenna; 20. Pre-processing board; 30. Main processing board. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0057] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0058] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0059] As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0060] In addition, in the description of the present application, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0061] The present invention provides a method for secure decoding of a transponder message, which can be used for interconnection between China High Speed ​​Railway Control System (CTCS) and Urban Rail Transit Train Control System (CBTC) (this is only an example and not a limitation of the present invention). The secure decoding method of the present invention complies with FFFIS for Eurobalise (form fit functional interface specification for Eurobalise transponder), that is, Subset-036 specification.

[0062] The present invention independently executes the security decoding method through multiple decoding units, and the decoding units include a first decoding unit and a second decoding unit. In this embodiment, the first decoding unit is an FPGA set on the pre-processing board 20, and the second decoding unit is a CPU set on the main processing board 30. In this embodiment, Figure 1 As shown, two parallel decoding units are included (the number of decoding units is only used as an example and is not a limitation of the present invention). The main processing board 30 and the pre-processing board 20 transmit data through the cPCI bus, and the pre-processing board 20 and the transponder antenna transmit level signals through the radio frequency cable to realize the cyclic transmission of the transponder message code stream.

[0063] like Figure 1 As shown, a security coding program is stored in the CPU. The data pre-stored inside the security coding program (generated by an offline coding tool and run online) usually adopts the coding form of [H, L] (H represents the high bit of the data, and L represents the low bit of the data). In the present invention, it is necessary to provide the user message obtained from the transponder message (sent by the transponder antenna 10) to the security coding program. Therefore, it is also necessary to encode each bit of data obtained in the user message in the same form for use in the calculation inside the security coding program. Since the encoding of the user message is online encoding, there is no security protection in the calculation process, and there is a risk of random failure in the security principle. For example, the actual value of a certain bit (the bit described in the present invention refers to the bit position) of data in the user message is 1, but when calculating the encoding value of the data, the data randomly fails to a value of 2. The security coding program can only determine whether the code generated based on the value 2 meets the coding principle, but cannot detect random failures when the user message is encoded online.

[0064] In some cases, the transponder message is processed or cached for too long in a certain link of the entire transmission link, resulting in poor timeliness of the transponder message provided to the security encoding program. The above are all technical problems that need to be solved urgently in the industry.

[0065] like Figure 2 As shown, the method for securely decoding a transponder message of the present invention comprises the steps of:

[0066] S1, the pre-processing board 20 receives the message code stream sent by the transponder antenna 10 and adds a time stamp D T .

[0067] In this embodiment, the preprocessing board 20 generates a new timestamp in each working cycle. The message code stream includes multiple message fields Dataflow (in this embodiment, the length of Dataflow is 32 bits, which is only used as an example and not as a limitation of the present invention), and the message field Dataflow has the same data length as the timestamp; the method of adding a timestamp to the message code stream in step S1 includes: adding each message field Dataflow to the timestamp D T Perform an XOR operation:

[0068]

[0069] like Figure 1 As shown, in another embodiment, the FGPA of at least one decoding unit performs an inversion operation on each code bit in the message code stream before timestamping the message code stream.

[0070] S2. Searching for a complete first scrambled code message from the received message code stream.

[0071] Figure 3 The data format of the first scrambling code message is shown. In this embodiment, the first scrambling code message contains 1023 bits of data, which are: Shaped Data, Control Code cb, Scrambling Code sb, Trimming Code esb, and First Check Code OrgCheck.

[0072] Step S2 comprises:

[0073] S21, setting a data window for the message code stream, wherein the length of the data window is L bits (in this embodiment, L is 1100); setting the count value i=1;

[0074] S22, put the i-th to i+L-1-th data bits of the message code stream into the data window in sequence; set the count value j=1;

[0075] S23. Calculate the true check value of the data from the jth bit to the j+l-1th bit in the data window (in this embodiment, the true check value is calculated by the CRC check method, which is only used as an example and is not a limitation of the present invention); l is the number of bits included in the first scrambling code message, and in this embodiment, l=1023; obtain a first check value based on the data from the j+lth bit to the j+l+d-1th bit in the data window; wherein d is the number of bits included in the true check value, and in this embodiment, d=32.

[0076] If the true check value is equal to the first check value, the data from the jth bit to the j+l-1th bit in the data window is a first scrambled code message found, i is updated to i+j+l+d-1, and the process goes to step S22; if the true check value is not equal to the first check value, and j+l+d-1<L, j is updated to j+1, and step S23 is repeated; if j+l+d-1=L, i is updated to i+L, and the process goes to step S22.

[0077] like Figure 4 As shown, starting from the leftmost start bit of the data window, 1023 bits of data are sequentially intercepted in the data window for CRC check, and it is determined whether the obtained true check value (32 bits) is equal to the first check value corresponding to the 32 bits of data after the 1023 bits of data. If they are equal, the 1023 bits of data are a first scrambled code message, and the data in the data window is updated. If they are not equal, shift right one bit in the data window, intercept new 1023 bits of data for CRC check. If the first scrambled code message is not found in the current data window, the data in the data window is updated.

[0078] S3. Record data of specific code positions in the first scrambled code message; the specific code positions include a control code cb, a trimming code esb, a scrambling code sb and a first check code OrgCheck.

[0079] S4, decoding the first scrambled message to obtain a user message, Figure 5 The data format of the user message is shown, including the frame data Frame Header, user data User Data and end byte Ending Chars. Step S4 includes:

[0080] S41: The formal data in the first scrambled message includes a plurality of formal fields, wherein the formal fields and the timestamp D T The same length as the data; each formal field and the timestamp D T Performing an XOR operation to remove the timestamp from the formalized data;

[0081] S42: Decode the formalized data after the timestamp removal operation by using a set algorithm to obtain a user message. In this embodiment, the set algorithm is a decoding algorithm in the Subset-036 protocol specification (this is a prior art and will not be described in detail here).

[0082] S5. Generate a corresponding first code for each code position of the user message:

[0083] Let x be any bit of data in the user message, [X H ,X L ] is the first code corresponding to x, X HThe high bit of the first code, X L The low bit of the first code;

[0084] X H = x;

[0085]

[0086] e kx B is the left shift operation of x by k bits; x is the signature pre-assigned to x; D T is the timestamp, and OrgCheck is the first verification code.

[0087] S6. Based on the control code cb, scrambling code sb, and trimming code esb in the first scrambling message, the user message is encoded by the encoding algorithm in the Subset-036 protocol specification to obtain a second scrambling message (this is a prior art and will not be described in detail here). Figure 6 As shown, the data format of the second scrambled message is the same as that of the first scrambled message, including formalized data NewshapedData, control code New cb, scrambled code New sb, trimming code New esb, and second check code CalCheck

[0088] S7. Generate a corresponding second code for each code position in the user message based on the first check code in the first scrambled message and the second check code in the second scrambled message; and provide the second code to the on-board train control system (security coding program) for use.

[0089] x is any bit of data in the user message, and the second code corresponding to data x is [X′ H ,X′ L ],X′ H is the high bit of the second code, X′ L The low bit of the second code;

[0090] X′ H = x;

[0091]

[0092] CalCheck is the second check code.

[0093] It is easy to understand that if the data x does not fail randomly, OrgCheck is equal to CalCheck, and the second code received by the security coding program is equal to [x, X L The secure coding program can calculate X based on the high bit x in the second code through an internal program. L , which is equal to the low bit in the corresponding second code, thus determining the security of the transponder message.

[0094] If data x fails randomly, the first check code and the second check code are different. The security coding program calculates X based on the high bit x in the second code through an internal program. L , X L Not equal to the low bit X' in the second code L , so it is possible to identify message data that has undergone random failures.

[0095] In another embodiment, if the second code corresponding to the data x is not equal to the first code, the process returns to step S41, and the first scrambled message is de-timed by using the timestamp of the previous working cycle or the timestamp of the previous two working cycles, and then the subsequent steps (S4 to S7) are performed. The timestamp of the current working cycle, the timestamp of the previous working cycle, and the timestamp of the previous two working cycles are all valid timestamps. If the second code obtained after decoding the first scrambled message by using the timestamps of the previous two working cycles is still not equal to the first code, the first scrambled message is considered to have lost its timeliness and is discarded.

[0096] The present invention also provides a transponder message security decoding system for executing the security decoding method of the present invention, such as Figure 1 As shown, the system includes: a plurality of independent decoding units, the decoding units include a first decoding unit and a second decoding unit. The first decoding unit in the present invention is an FPGA arranged on the pre-processing board 20, and the second decoding unit is a CPU arranged on the main processing board 30.

[0097] The first decoding unit is used to receive a message code stream from the transponder antenna 10 and add a time stamp, and search for a first scrambled message from the message code stream with the time stamp;

[0098] The second decoding unit decodes the first scrambled message to obtain a corresponding user message, and generates a corresponding first code for each bit of data in the user message; the second decoding unit also reversely decodes the user message to generate a corresponding second scrambled message; the second decoding unit also generates a corresponding second code for each code bit of data in the user message based on the first check code in the first scrambled message and the second check code in the second scrambled message, and provides it to the on-board train control system for use.

[0099] The present invention obtains a user message by positively decoding a first scrambled message, obtains a second scrambled message by reversely decoding the user message, and judges whether the user message provided to the vehicle-mounted train control system is correct based on a first check code of the first scrambled message and a second check code of the second scrambled message, thereby improving the security of transponder message decoding and the security during message use.

[0100] The present invention adds a timestamp to the message code stream and removes the timestamp from the first scrambled message through the effective timestamp, thereby ensuring the timeliness of the data used by the on-board train control system and avoiding the safety hazards caused by using expired messages.

[0101] In the present invention, at least one first decoding unit first performs an inversion operation on the received message code stream and then performs a timestamp, thereby reducing the risk of common mode failure of the 2-out-of-2 architecture system and further improving the security of the system.

[0102] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0103] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for securely decoding a transponder message, characterized in that: The decoding method is independently executed by multiple decoding units, and the decoding method includes the steps: S1. Receive the message code stream sent by the transponder antenna and timestamp it; S2. Search for a complete first scrambled message in the received message code stream; the first scrambled message includes: formalized data, control code, scrambler code, trimming code, first check code; S3. Record the data of specific code bits in the first scrambled message; the specific code bits include the control code, trimming code, and scrambler code; S4. Decode the first scrambled message to obtain a user message; S5. Generate corresponding first encodings for the data of each code bit in the user message; Step S5 includes: Let x be any bit of data in the user message, [X H , X L ] is the first code corresponding to x, X H The high bit of the first code, X L The low bit of the first code; X H =x; r kx B is the left shift operation of x by k bits; x is the signature pre-assigned to x; D T is the timestamp, and OrgCheck is the first verification code; S6. Based on the data of the specific code bits, perform inverse decoding on the user message to generate a second scrambled message; S7. Based on the first check code in the first scrambled message and the second check code in the second scrambled message, generate corresponding second encodings for the data of each code bit in the user message and provide them to the on-vehicle train control system; The second code corresponding to the data x is [X′ H , X′ L ],X′ H is the high bit of the second code, X′ L The low bit of the second code; X′ H =x; CalCheck is the second check code.

2. The method for securely decoding a transponder message according to claim 1, characterized in that: The decoding unit generates a new timestamp in each working cycle; the message code stream includes multiple message fields, and the data lengths of the message fields are the same as that of the timestamp; the method of timestamping the message code stream in step S1 includes: performing an exclusive OR operation on each message field and the timestamp.

3. The method for securely decoding a transponder message according to claim 1, characterized in that: Step S2 includes: S21. Set a data window for the message code stream, and the length of the data window is L bits; let the count value i = 1; S22. Sequentially put the data from the i-th to the (i + L - 1)-th bits of the message code stream into the data window; Let the count value j = 1; S23. Calculate the true check value of the data from the j-th to the (j + l - 1)-th bits in the data window; l is the number of bits included in the first scrambled message; obtain the first check value based on the data from the (j + l)-th to the (j + l + d - 1)-th bits in the data window; where d is the number of bits included in the true check value; If the true check value is equal to the first check value, the data from the j-th to the (j + l - 1)-th bits in the data window is a found first scrambled message, update i to i + j + l + d - 1, and enter step S22; if the true check value is not equal to the first check value and j + l + d - 1 < L, update j to j + 1 and repeat step S23; if j + l + d - 1 = L, update i to i + L and enter step S22.

4. The method for securely decoding a transponder message according to claim 1, wherein: The step of decoding the first scrambled message to obtain a user message in step S4 includes the steps: S41. The formalized data in the first scrambled message includes multiple formalized fields, and the data lengths of the formalized fields are the same as that of the timestamp; perform an exclusive OR operation on each formalized field and the timestamp to implement the de-timestamping operation on the formalized data; S42. Decode the formalized data after the de-timestamping operation through a set algorithm to obtain a user message.

5. The method for securely decoding a transponder message according to claim 4, characterized in that: In step S42, the set algorithm is the decoding algorithm in the Subset-036 protocol specification.

6. The method for securely decoding a transponder message according to claim 1, characterized in that: In step S6, based on the control code, scrambler code, and trimming code, encode the user message through the encoding algorithm in the Subset-036 protocol specification to obtain a second scrambled message.

7. The method for securely decoding a transponder message according to claim 3, characterized in that: In step S23, the CRC verification method is used to calculate the true verification value.

8. The method for securely decoding a transponder message according to claim 4, characterized in that: In step S41, the formalized data is de-time-stamped by using a valid timestamp; the valid timestamp includes: a timestamp of the current working cycle, a timestamp of the previous working cycle, and a timestamp of the previous two working cycles.

9. The method for securely decoding a transponder message according to claim 1, characterized in that: In step S1, at least one decoding unit performs an inversion operation on each code bit in the message code stream before timestamping the message code stream.

10. A security decoding system for transponder messages, used to execute the security decoding method according to any one of claims 1 to 9, characterized in that: It comprises: a plurality of independent decoding units, wherein the decoding units comprise a first decoding unit and a second decoding unit; The first decoding unit is used to receive a message code stream from the transponder antenna and add a time stamp; the first decoding unit also searches for a first scrambled code message from the message code stream with the time stamp; The second decoding unit decodes the first scrambled message to obtain a corresponding user message, and generates a corresponding first code for each bit of data in the user message; The second decoding unit also reverse decodes the user message to generate a corresponding second scrambled message; the second decoding unit also generates a corresponding second code for the data of each code position in the user message based on the first check code in the first scrambled message and the second check code in the second scrambled message, and provides it to the on-board train control system for use.

11. The system for secure decoding of transponder messages according to claim 10, characterized in that: The first decoding unit is an FPGA arranged on the pre-processing board, and the second decoding unit is a CPU arranged on the main processing board.

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