Lightweight message authentication and integrity protection method based on fc-ae-asm security information field

Abstract

This invention provides a lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field. The method includes: establishing several ASM channels and assigning a channel key to each ASM channel; the sending end selecting the ASM frame header, message payload, and SEQ_ID as authentication data, generating a truncated message authentication code, and embedding it into the security information field of the FC-AE-ASM frame header; the receiving end comparing the received truncated message authentication code with the locally calculated one, and implementing anti-replay protection based on a sliding window; if the verification fails, the message is discarded and a security alarm is triggered; periodic key rotation is supported, and when the number of consecutive authentication failures of a channel exceeds a preset threshold, channel isolation is performed and an emergency alarm is sent. This invention solves the problem that the FC-AE-ASM protocol security information field in existing technologies is only used for encryption key management or simple data verification, without achieving cryptographically strong message authentication and integrity protection.

Description

Technical Field

[0001] This invention relates to the technical field of avionics network communication security, and more specifically, to a lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field. Background Technology

[0002] Fibre Channel (FC) possesses inherent technological advantages such as gigabit-level transmission rates, strong anti-interference capabilities, light weight, and suitability for high-speed, long-distance transmission, making it the preferred solution for the backbone communication network of next-generation fighter jets. The Fibre Channel - Avionics Environment - Anonymous Subscriber Messaging (FC-AE-ASM) protocol is the core upper-layer protocol in the FC-AE protocol family, used to support deterministic, low-latency communication between various processors, sensors, and displays in avionics environments.

[0003] The FC-AE-ASM protocol employs an anonymous subscription messaging model. Each ASM channel consists of three elements: the Message ID in the FC-AE-ASM frame header, and the source FCID (SID) and destination FCID (DID) in the FC frame header, representing a unidirectional data flow. The ASM protocol uses Class 3 connectionless service and does not provide a delivery acknowledgment mechanism. In the standard-defined FC-AE-ASM frame header format, bytes 4-7 are defined as the "Vendor Specific - Security" field. The standard specifies that this field is an "implementation-dependent" security field and should be set to hex'00 00 00 00' when not used. However, in practical engineering applications, this security field is almost entirely filled with zeros, failing to provide any security functionality.

[0004] Due to limitations inherent in the protocol's mechanisms, FC-AE-ASM networks exhibit significant security vulnerabilities: Because of the anonymous subscription nature of the ASM protocol, receivers cannot verify the true origin of messages; because Class 3 services do not provide delivery confirmation, attackers can easily inject unauthorized ASM messages into the network; and because security fields are left unused, message integrity cannot be protected. These security flaws expose FC-AE-ASM networks to security threats such as message injection, tampering, and replay attacks.

[0005] Existing related technical solutions have obvious limitations:

[0006] Application number CN117499146A, entitled "Encrypted Communication Method, Apparatus, and System for FC to Ethernet Protocol Conversion," utilizes the 4th-7th bytes of the FC-AE-ASM protocol's Optional Pitch (OPT) secure reserved field. The 4th byte is defined as follows: the first 6 bits are the key identifier, the last 2 bits are key control information, the 5th-6th bytes are the ciphertext data length, and the 7th byte is the key checksum. This enables encrypted control during the FC to Ethernet protocol conversion process. However, this scheme uses the secure field for encryption key management, not message authentication. Although it utilizes the ASM secure field, its purpose is limited to encryption key management (key identifier, key control information, ciphertext length, key checksum), and it does not utilize this field for message authentication and integrity protection. Furthermore, this scheme is designed for FC to Ethernet protocol conversion scenarios, not for security enhancement within FC-AE-ASM networks.

[0007] Application number CN202010484926.8, entitled "A Data Encryption Algorithm Based on FC-AE-ASM Protocol Communication," describes a simple data integrity check that performs data verification between the sender and receiver under the standard FC-AE-ASM data communication frame format, discarding data when the comparison results are inconsistent. However, this scheme only provides simple data verification similar to a checksum and lacks cryptographically strong message authentication capabilities. It cannot resist active tampering attacks and lacks a replay protection mechanism. Although the scheme achieves simple data verification, the verification mechanism does not employ a cryptographic algorithm, resulting in insufficient security strength and inability to resist malicious tampering. Furthermore, it lacks replay protection, allowing attackers to replay legitimate messages and pass the verification.

[0008] Application number CN109672632A, entitled "FC-AE-ASM Network Data Communication Method and System," implements an FC-AE-ASM multicast communication method based on a publish-subscribe approach, but does not involve security mechanisms. Although this solution achieves dynamic multicast communication, it lacks security mechanisms.

[0009] In summary, the long-term idleness of the security fields (bytes 4-7) in the existing FC-AE-ASM protocol has resulted in ASM messages transmitted in the network lacking passive authentication, integrity verification, and replay protection, posing a serious security risk. Summary of the Invention

[0010] The present invention aims to solve the problem that the security information field of the FC-AE-ASM protocol is only used for encryption key management or simple data verification in the prior art, and does not achieve cryptographically strong message authentication and integrity protection.

[0011] Therefore, in view of the shortcomings of the existing technology, the purpose of this invention is to provide a lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field.

[0012] To achieve the above objectives, the first aspect of the present invention provides a lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field. The method includes: Step S01: Establishing several ASM channels and assigning a corresponding channel key to each ASM channel through an airborne network security management center; Step S02: Selecting the ASM frame header, message payload, and SEQ_ID in the FC frame header as authentication data by the sending end, and generating a truncated message authentication code for the ASM message using the corresponding channel key and performing HMAC-SHA256 calculation; Step S03: Embedding the truncated message authentication code into the security information field of bytes 4-7 of the FC-AE-ASM frame header.

[0013] Step S04: Receive the ASM message at the receiving end and extract the truncated message authentication code tMAC_received from the security information field. Then, recalculate the received ASM message using the same authentication data, channel key, and HMAC-SHA256 operation as the sending end to generate a local truncated message authentication code tMAC_computed. Verify whether tMAC_received and tMAC_computed match. If they match, proceed to step S05; otherwise, proceed to step S07. Step S05: Receive the FC... The SEQ_ID sequence maintains a sliding window with a range of [lower bound, upper bound]. Based on the sequence number position of the ASM message, it is determined whether the ASM message is a normal message or a replay message, thus achieving replay protection. Step S06: If the ASM message authentication and replay protection check pass, the message is received and delivered to the upper layer. Step S07: If it is determined that the ASM message has been tampered with or the message source is untrustworthy, the message is directly discarded, and a security alarm process is triggered. Step S08: Periodic key rotation is supported through the airborne network security management center. Step S09: When an ASM channel fails authentication continuously for more than a preset threshold within a preset time window, it is determined that the ASM channel has been attacked. The isolation operation of the ASM channel is performed to suspend the reception of messages from the ASM channel and send an emergency alarm to the network security management center.

[0014] Preferably, in step S01, each ASM channel is uniquely identified by a triple consisting of Message ID, SID, and DID.

[0015] Preferably, in step S02, the corresponding channel key is used to perform HMAC-SHA256 operation to generate the truncated message authentication code of the ASM message. Specifically, the corresponding channel key is used to perform HMAC-SHA256 operation to obtain the first HMAC result, and then the high 32 bits of the first HMAC result are truncated to generate the truncated message authentication code of the ASM message.

[0016] Preferably, in step S04, the same authentication data, channel key, and HMAC-SHA256 operation as the sending end are used to generate a local truncated message authentication code tMAC_computed. Specifically, the received ASM message is recalculated using the same authentication data, channel key, and HMAC-SHA256 operation as the sending end to obtain a second HMAC result. The high 32 bits of the second HMAC result are then truncated to generate the local truncated message authentication code tMAC_computed.

[0017] Preferably, in step S05, the ASM message is determined to be a normal message or a replay message based on its sequence number position to achieve replay protection. Specifically, this includes: if the sequence number SEQ_ID of the ASM message is less than the lower bound of the window, it is determined to be a replay message and is discarded directly; if the sequence number SEQ_ID of the ASM message is within the sliding window range, it is further checked whether the sequence number has been received before. If not, the message is received; if it has been received, it is determined to be a replay message; if the sequence number SEQ_ID of the ASM message is greater than the upper bound of the window, the receiving window is updated and the message is received to achieve replay protection for the ASM message.

[0018] The beneficial technical effects of this invention are as follows:

[0019] (1) Unlike the prior art CN117499146A, which uses the security field for encryption key control, this invention uses the security information field of the 4th to 7th bytes of the ASM frame header to embed the truncated message authentication code (tMAC) based on HMAC-SHA256 to realize message source authentication and integrity verification.

[0020] (2) Unlike the simple data verification of the existing technology CN202010484926.8, the present invention adopts a cryptographic authentication algorithm, which has the ability to resist active tampering attacks, and combines the FC frame header sequence number to achieve anti-replay protection. At the same time, a key rotation mechanism is introduced to ensure long-term security.

[0021] (3) Without changing the ASM protocol communication mode or adding extra communication overhead, the present invention realizes three major security functions: message source authentication, integrity verification and anti-replay, thus meeting the dual requirements of airborne networks for real-time performance and security.

[0022] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 A flowchart illustrating a message authentication and integrity protection method based on the FC-AE-ASM security information field according to an embodiment of the present invention is shown.

[0025] Figure 2 A schematic diagram illustrating ASM channel initialization and key pre-allocation according to an embodiment of the present invention is shown;

[0026] Figure 3 A flowchart illustrating the calculation of a truncated message authentication code according to an embodiment of the present invention is shown;

[0027] Figure 4 A flowchart illustrating verification via truncated message authentication codes according to an embodiment of the present invention is shown;

[0028] Figure 5 A schematic diagram of an anti-replay serial number window mechanism according to an embodiment of the present invention is shown. Detailed Implementation

[0029] To better understand the above-mentioned objects, features, and advantages of the present invention, such as Figures 1 to 5 As shown in the accompanying drawings and specific embodiments, the present invention will be further described in detail below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0031] The following specific embodiment will demonstrate the message authentication and integrity protection method based on the FC-AE-ASM security information field of the present invention. For example... Figure 1 As shown, the message authentication and integrity protection method based on the FC-AE-ASM security information field in this specific embodiment is implemented through the following steps:

[0032] (1) Step S01: Perform ASM channel initialization and key pre-allocation.

[0033] In step S01, during the ASM channel establishment phase, a pre-shared channel key is assigned to each ASM channel (identified by the triplet of Message ID, SID, and DID). The key is uniformly generated and distributed by the airborne network security management center.

[0034] Furthermore, the key distribution adopts a key negotiation protocol based on asymmetric encryption. The sender and receiver negotiate a channel-specific symmetric key K_channel through the Diffie-Hellman key exchange protocol. This key is only used for message authentication of the corresponding ASM channel.

[0035] Furthermore, the airborne network security management center maintains a channel-key mapping table, recording the key identifier Key_ID and key status corresponding to each ASM channel, supporting regular key rotation and emergency updates.

[0036] Specifically, such as Figure 2 As shown, the Airborne Network Security Management Center is responsible for generating the channel key K_channel corresponding to the ASM channel and maintaining the channel-key mapping table. The Airborne Network Security Management Center distributes the channel key K_channel to FC node A (the sender) and FC node B (the receiver) through a key distribution process. An ASM channel is established between FC node A and FC node B, and this ASM channel is identified by a triplet of Message ID, SID, and DID. FC node A receives the channel key K_channel for subsequent message authentication code calculation; FC node B receives the channel key K_channel for subsequent message authentication code verification.

[0037] (2) Step S02: Calculate the truncated message authentication code (tMAC) of the ASM message through the sending end.

[0038] In step S02, when assembling the ASM message, the sending end uses the Message ID field, reserved field, L / priority / message payload length field and ASM message payload in the ASM frame header, together with the SEQ_ID field in the FC frame header, as authentication data, and uses the channel key K_channel allocated in step S01 to calculate the message authentication code using the HMAC-SHA256 algorithm.

[0039] Furthermore, during the HMAC calculation process, the SID (source FCID) and DID (destination FCID) in the FC frame header are included in the calculation as associated data to ensure that the source and destination addresses of the message cannot be tampered with.

[0040] Furthermore, for multi-frame ASM messages, HMAC is calculated independently for each frame, but the HMAC calculation for all frames includes a complete copy of the ASM frame header, ensuring that tampering in any frame of the multi-frame sequence can be detected.

[0041] Specifically, such as Figure 3 As shown, at the sending end, the ASM frame header, message payload, and FC SEQ_ID are first selected as authentication data, and HMAC-SHA256 operation is performed in combination with the channel key K_channel; then the high 32 bits of the calculated HMAC result are truncated to generate the truncated message authentication code tMAC, so that the subsequent step S03 can embed the tMAC into the security information field of the 4th to 7th bytes of the FC-AE-ASM frame header.

[0042] (3) Step S03: Embed the truncated message authentication code (tMAC) into the ASM security information field.

[0043] In step S03, the 256-bit HMAC value calculated in step S02 is truncated to the high 32 bits, which are used as the truncated message authentication code (tMAC) and filled into the security information field of bytes 4-7 in the ASM frame header.

[0044] Furthermore, the unauthorized generation probability of a 32-bit truncated message authentication code is 1 / 2^32, approximately 2.3 × 10^-10. Under typical message transmission volumes in airborne networks (hundreds of messages per second per channel), the average number of attempts required for an attacker to successfully construct a message exceeds 4 billion, and the corresponding average cracking time far exceeds the duration of a single flight mission. Therefore, this security level meets the engineering application requirements of airborne environments.

[0045] Furthermore, the truncation operation takes the high 32 bits of HMAC as the authentication tag. This truncation method has equivalent security strength in cryptography as taking the low 32 bits. The high-bit truncation is chosen to maintain consistency with the byte order of the security field in the ASM frame header, which is convenient for hardware implementation.

[0046] (4) Step S04: Extract and verify the truncated message authentication code (tMAC) through the receiving end. When the verification result is a tMAC match, proceed to step S05; when the verification result is a tMAC mismatch, proceed to step S07.

[0047] In step S04, specifically, after receiving the ASM message, the receiving end extracts the truncated message authentication code tMAC_received from bytes 4-7 of the ASM frame header, and then uses the same channel key K_channel and the same HMAC-SHA256 algorithm as the sending end to recalculate the HMAC of the received message and truncate the high 32 bits to obtain tMAC_computed.

[0048] Furthermore, tMAC_received and tMAC_computed are compared. If they match, the message authentication is successful, and the upper-layer application is allowed to process the message. If they do not match, it is determined that the message has been tampered with or that the source is untrusted. The message is then discarded and a security alarm is triggered.

[0049] Furthermore, when message authentication fails, the receiving end records a failure event log, including the message ID, SID, DID, SEQ_ID, timestamp, and reason for failure, and reports it to the airborne network security management center.

[0050] Specifically, such as Figure 4 As shown, at the receiving end, the ASM message is first received, and the truncated message authentication code tMAC_received is extracted and received from the security information field. The same authentication data, channel key K_channel, and HMAC-SHA256 algorithm as the sending end are used to recalculate and generate the local truncated message authentication code tMAC_computed. tMAC_received and tMAC_computed are compared: if they match, the message authentication is successful, the message is received, and delivered to the upper layer; if they do not match, the message is determined to have the risk of being tampered with or generated without authorization, the message is directly discarded, and subsequent security alarm procedures may be triggered.

[0051] (5) Step S05: Perform anti-replay protection based on FC serial number (i.e. Figure 1 The steps in the "sliding window anti-replay check" are as follows.

[0052] In step S05, the receiver maintains a receive sequence number window for each ASM channel and records the most recently received FC SEQ_ID value; when a new message is received, it first checks whether the SEQ_ID of the new message falls within the sequence number window;

[0053] Furthermore, if SEQ_ID is less than the lower bound of the window, the new message is determined to be a replay message and is discarded directly; if SEQ_ID is greater than the upper bound of the window, the window is slid and the message is accepted; if SEQ_ID falls within the window and has not been received before, the message is accepted and the SEQ_ID is marked as received.

[0054] Furthermore, the serial number window size is configured based on the communication cycle and message rate of the airborne network, with a default setting of 64, covering a message serial number range of approximately 8 communication cycles.

[0055] Specifically, such as Figure 5 As shown, the receiver maintains a sliding window with a range of [lower bound, upper bound] for the FC SEQ_ID sequence; wherein the FC SEQ_ID sequence includes: SEQ_0, SEQ_1, SEQ_2, SEQ_3, ...

[0056] SEQ_4, SEQ_5, SEQ_6 and SEQ_7.

[0057] Upon receiving a message and obtaining its SEQ_ID, three scenarios are considered: if the SEQ_ID is less than the lower bound of the window, it is determined to be a replay message and is discarded directly; if the SEQ_ID is within the sliding window range, it is further checked whether the sequence number has already been received; if not, the message is received; if it has been received, it is determined to be a replay message; if the SEQ_ID is greater than the upper bound of the window, the receiving window is updated and the message is received, thereby achieving anti-replay protection for ASM messages.

[0058] (6) Step S06: Message reception and delivery (i.e. Figure 1 The steps in the document are "receiving and delivering the message to the upper layer".

[0059] When the truncated message authentication code verification in step S04 passes and the anti-replay check in step S05 determines it to be a normal message, step S06 is executed, that is, the receiving end receives the ASM message and delivers the message to the upper layer application.

[0060] (7) Step S07: Discard messages and security alerts (i.e. Figure 1 The "Discard Message and Alert" step in the process.

[0061] When the verification result of step S04 is a tMAC mismatch, it is determined that the ASM message has been tampered with or the message source is untrustworthy. Step S07 is then executed, that is, the receiving end directly discards the message and triggers a security alarm process. The security alarm process includes recording the failure event log and reporting it to the airborne network security management center. The content of the failure event log is as described in step S04.

[0062] If the truncated message authentication code verification in step S04 passes, but the anti-replay check in step S05 determines it to be an abnormal message, then step S07 is also executed.

[0063] (8) Step S08: Perform key update and rotation.

[0064] In step S08, the airborne network security management center automatically triggers key rotation according to the preset key update cycle (default 24 hours or per flight). Furthermore, the key update adopts a strategy of distribution before activation—the new key does not take effect immediately after issuance, but is activated uniformly at a preset switching time to ensure that all nodes switch synchronously and avoid authentication failure due to key inconsistency.

[0065] Furthermore, when the security detection module reports that the number of authentication failures exceeds the threshold, an emergency key update is triggered, immediately discarding the current key and enabling a backup key.

[0066] (9) Step S09: Channel isolation and emergency alarm.

[0067] In step S09, when the receiving end detects that the number of consecutive authentication failures exceeds the threshold N (default N=3) within a preset time window, step S09 is executed, that is, it is determined that the ASM channel has been attacked, and a channel isolation operation is performed—the reception of messages on the channel is suspended, and an emergency alarm is sent to the network security management center.

[0068] Furthermore, after receiving the alarm, the network security management center comprehensively analyzes the alarm information from multiple channels to determine the scope and type of the attack, and decides whether to perform a network-wide key update or channel reconstruction.

[0069] Furthermore, after security verification, the isolated channel can resume communication after key updates and channel reinitialization.

[0070] In this specific embodiment, the present invention utilizes the security information field of bytes 4-7 of the ASM frame header to embed a truncated message authentication code (tMAC) based on HMAC-SHA256 to achieve message source authentication and integrity verification.

[0071] In this specific embodiment, the present invention employs a cryptographic authentication algorithm, which has the ability to resist active tampering attacks, and combines it with the FC frame header sequence number to achieve anti-replay protection. At the same time, a key rotation mechanism is introduced to ensure long-term security.

[0072] In this specific embodiment, the present invention achieves three major security functions—message source authentication, integrity verification, and replay protection—without changing the ASM protocol communication mode or adding additional communication overhead, thus meeting the dual requirements of airborne networks for real-time performance and security.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lightweight message authentication and integrity protection method based on FC-AE-ASM security information fields, characterized in that, include: Step S01: Establish several ASM channels and assign a corresponding channel key to each ASM channel through the airborne network security management center; Step S02: The sending end selects the SEQ_ID in the ASM frame header, message payload, and FC frame header as authentication data, uses the corresponding channel key and performs HMAC-SHA256 operation to generate the truncated message authentication code of the ASM message; Step S03: Embed the truncated message authentication code into the security information field of bytes 4-7 of the FC-AE-ASM frame header; Step S04: Receive the ASM message at the receiving end and extract the truncated message authentication code tMAC_received from the security information field. Then, recalculate the received ASM message using the same authentication data, channel key, and HMAC-SHA256 operation as the sending end to generate a local truncated message authentication code tMAC_computed. Verify whether tMAC_received and tMAC_computed match. If they match, proceed to step S05; otherwise, proceed to step S07. Step S05: The receiving end maintains a sliding window with a range of [lower bound, upper bound] for the FC SEQ_ID sequence, and then determines whether the ASM message is a normal message or a replay message based on the sequence number position of the ASM message, thereby achieving anti-replay protection; Step S06: If the ASM message authentication and anti-replay check pass, receive and deliver the message to the upper layer; Step S07: If it is determined that the ASM message has been tampered with or that the message source is untrustworthy, the message is discarded directly, and a security alarm process is triggered; Step S08: Support periodic key rotation through the airborne network security management center; Step S09: When an ASM channel fails to authenticate continuously for more than a preset threshold within a preset time window, it is determined that the ASM channel has been attacked. An isolation operation is performed on the ASM channel to suspend receiving messages from the ASM channel and send an emergency alarm to the network security management center.

2. The lightweight message authentication and integrity protection method based on FC-AE-ASM security information fields according to claim 1, characterized in that, In step S01, each ASM channel is uniquely identified by a triple consisting of Message ID, SID, and DID.

3. The lightweight message authentication and integrity protection method based on FC-AE-ASM security information fields according to claim 1, characterized in that, In step S02, the corresponding channel key is used to perform HMAC-SHA256 operation to obtain the first HMAC result. Then, the high 32 bits of the first HMAC result are truncated to generate the truncated message authentication code of the ASM message.

4. The lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field according to claim 3, characterized in that, In step S04, the received ASM message is recalculated using the same authentication data, channel key, and HMAC-SHA256 operation as the sending end to obtain the second HMAC result. Then, the high 32 bits of the second HMAC result are truncated to generate the local truncated message authentication code tMAC_computed.

5. The lightweight message authentication and integrity protection method based on the FC-AE-ASM security information field according to any one of claims 1 to 4, characterized in that, In step S05, based on the sequence number position of the ASM message, it is determined whether the ASM message is a normal message or a replay message, thereby implementing replay protection. Specifically, this includes: If the sequence number SEQ_ID of an ASM message is less than the lower bound of the window, it is determined to be a replay message and is discarded directly. If the sequence number SEQ_ID of the ASM message is within the sliding window range, then further check whether the sequence number has been received. If not, then receive the message; if it has been received, then determine it as a replay message. If the sequence number SEQ_ID of the ASM message is greater than the upper limit of the window, the receiving window is updated by sliding and the message is received to achieve anti-replay protection for the ASM message.

Images