Inter-ship communication method based on digital certificate and symmetric key identity authentication

Abstract

The invention discloses an inter-ship communication method based on digital certificate and symmetric key identity authentication. In an initialization stage, a communication initiating ship selects to broadcast a complete digital certificate or a hash abstract thereof according to a preset strategy, and generates a signature in combination with a private key to perform identity broadcasting; and the communication response ship verifies the broadcast identity through the offline identity record table. The two parties exchange identity binding information through random numbers, independently generate the same shared symmetric key by using a key derivation function, and further derive an identity binding key. And based on the key, the two parties perform three-wheel handshake authentication to complete identity verification and key consistency confirmation. And after verification succeeds, the two parties derive encryption and authentication sub-keys from the identity binding keys for encryption and integrity protection of subsequent communication data. The method has the capability of resisting man-in-the-middle attack and replay attack, is suitable for a dynamic and weak-connection marine communication environment, and improves the safety and reliability of communication between ships.

Description

Technical Field

[0001] The present invention belongs to the technical field of inter-ship communication, and in particular relates to an inter-ship communication method based on digital certificates and symmetric key identity authentication. Background Art

[0002] Currently, the vast majority of ships worldwide are equipped with AIS, which is used to exchange information between ships or between ships and shore-based facilities, including key data such as identity, geographic location, speed, and course. The AIS system uses VHF radio channels and time division multiple access (TDMA) for communication. Each ship periodically broadcasts its status information, enabling other ships to obtain and establish situational awareness in real time, ensuring maritime safety.

[0003] However, existing AIS and similar ship wireless communication systems have serious security flaws, especially the lack of an effective identity authentication mechanism, as shown below:

[0004] AIS messages are broadcast entirely in plain text. Any third party with ordinary wireless receiving equipment can monitor, record, and even replay them, posing the risk of eavesdropping, counterfeiting, and interference.

[0005] Currently, the MMSI number carried in AIS messages is filled in by the device itself, and the receiver lacks an effective authenticity verification mechanism for this identity information. This allows attackers to easily construct forged messages through software radio devices and impersonate any ship to carry out "ghost ship" attacks and "identity drift" attacks.

[0006] Since traditional PKI systems usually rely on real-time online access to CA and CRL services, and ocean-going ships are often in a network isolation state, it is difficult to ensure connection. In addition, embedded devices such as AIS have limited processing capabilities and are not suitable for complete use of public key cryptography for encrypted communication. Online verification mechanisms (such as OCSP) rely on external infrastructure and are not suitable for point-to-point, self-organizing communication environments between ships.

[0007] In the prior art, Chinese patent CN115037465A discloses an intelligent ship identity authentication and false identity warning system based on ship digital certificates. This system includes three types of entities in the maritime system and a maritime certificate authority center. Each entity has its own local database, which stores a list of MCAs that it considers trustworthy and the digital certificates issued to it. All entities follow the principle of upward trust and also store a certificate revocation list (CRL) consisting of revoked certificate numbers broadcast by all MCAs. Authentication between any two entities is completed with the help of digital certificates issued by the MCA, and the entity identity and location are associated with the ship's movement characteristics.

[0008] However, this approach has the following limitations: 1. It still relies on the traditional public key infrastructure (PKI) model based on certificate revocation lists (CRLs). CRL information requires constant updating to ensure its validity, which is difficult to implement for ships operating in ocean-going, disconnected environments. This can lead to authentication failures or the use of expired certificates, compromising the system's real-time performance and security. 2. In this scheme, each entity locally stores its own list of trusted MCAs, resulting in a fragmented and inconsistent trust system. Disparities in trust in MCAs between different entities can lead to inconsistent authentication results, reducing the system's interoperability and robustness. Furthermore, the scheme employs a static trust model and lacks dynamic adjustment capabilities, making it difficult to adapt to the complex and ever-changing maritime communication environment. 3. In practical deployment, this approach requires high coordination and information sharing among multiple maritime entities, including digital certificates, revocation information, and motion data. However, current AIS equipment generally has limited computing resources and is difficult to upgrade. This approach places high demands on device performance and system integration, and lacks a feasible path for seamless integration and deployment within existing AIS systems.

[0009] Therefore, the existing AIS authentication scheme based on traditional PKI still has much room for improvement in terms of offline environment adaptability, trust model consistency, anti-counterfeiting ability and deployment complexity. There is an urgent need for an AIS identity authentication mechanism that takes into account security, real-time performance and deployability to enhance the overall anti-attack capability and credibility of the maritime communication system. Summary of the Invention

[0010] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for inter-ship communication based on digital certificates and symmetric key identity authentication.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] The present invention provides a method for inter-vessel communication based on digital certificates and symmetric key identity authentication, comprising the following steps:

[0013] Before going out to sea, each ship submits information including the ship's unique identification number and public key to the maritime trust agency, obtains a digital certificate issued by the maritime trust agency, and stores the digital certificate, private key and identity record table locally;

[0014] When initializing communication, the communication initiating ship selects a digital certificate or digital certificate summary according to the communication preset strategy, signs it with the private key, obtains the identity information formed after the signature, and broadcasts it;

[0015] After the communication response ship receives the identity information, if the received data packet is a digital certificate summary data packet, the digital certificate summary field is compared and verified through the locally stored identity record table; if the received data packet is a complete digital certificate data packet, the root certificate or certificate chain of the pre-stored maritime trust authority is used to locally verify the signature and validity of the contained digital certificate, and further verify whether the authentication signature is consistent with the broadcast content;

[0016] After successful verification, both communicating parties independently generate the same shared symmetric key through a sharing mechanism. Both communicating parties use the shared symmetric key and their respective ship identity information as input and obtain the identity binding key through a key derivation function;

[0017] The communicating parties perform a three-round handshake interaction based on the identity binding key to verify the consistency of the identities of the communicating parties and the shared symmetric key;

[0018] After successful authentication, both communicating parties input the identity-binding key into a key derivation function to obtain an encryption subkey and a message authentication subkey, respectively. The sender uses the encryption subkey to symmetrically encrypt the communication data, and uses the message authentication subkey to generate a message authentication code for the ciphertext containing the sequence number field and sends it. The encrypted communication data packet is verified and decrypted by the receiver.

[0019] When a preset time interval, data volume threshold or policy condition is reached, the communicating parties use a key derivation function and an updated random number to derive a new identity binding key, and simultaneously update the encryption subkey and message authentication subkey;

[0020] When a communication session ends or times out, both parties destroy all key materials related to the current session.

[0021] Furthermore, each vessel submits information including the vessel's unique identification number and public key to the maritime trust agency before setting sail, and obtains a digital certificate issued by the maritime trust agency, specifically including:

[0022] Each ship generates a pair of public and private keys locally. The private key is generated and protected by a security module in the ship's local equipment and cannot be exported.

[0023] The shipowner or the representative of the ship operation and management organization submits the registration information including the ship's unique identification number, flag state registration information, ship operating unit or management company information, public key, and administrator signature confirmation to the maritime trust agency. The registration information is authenticated and stamped by the competent authority to form a certificate issuance request;

[0024] The ship signs the certificate issuance request using its local private key and sends the signed request to the maritime trust authority;

[0025] The maritime trust agency verifies the validity of the registration information and signature in the request. Once the verification is passed, the maritime trust agency uses its private key to sign the ship's public key and registration information, generates a digital certificate, and returns the digital certificate to the ship.

[0026] The ship stores the digital certificate, identity record table and locally generated private key in a local system, wherein the identity record table is used to store and quickly verify the hash information, public key, certificate validity period, certificate status, ship unique identification number and issuing agency information of other ships' digital certificates;

[0027] The digital certificate adopts a short-term validity control method and is considered credible within the validity period of the certificate. It needs to be re-applied after the expiration date.

[0028] Furthermore, the ship stores the digital certificate, identity record table and locally generated private key in a local system, wherein the identity record table is used to store and quickly verify hash information, public key, certificate validity period, certificate status, ship unique identification number and issuing agency information of other ship digital certificates;

[0029] The digital certificate adopts a short-term validity control method and is considered credible within the validity period of the certificate. It needs to be re-applied after the expiration date.

[0030] Furthermore, the communication preset strategy includes the following two identity broadcast modes and supports automatic switching:

[0031] The complete digital certificate broadcast method is that the communication initiating vessel broadcasts an identity authentication data packet containing the following fields to the communication responding vessel during the initialization phase: the vessel's unique identification number, digital certificate, current timestamp or random number, and an authentication signature generated by the vessel's local private key for the aforementioned fields. After receiving the data packet, the communication responding vessel uses the pre-stored identity record table of the maritime trust agency to locally verify the signature and validity of the digital certificate, and further verify whether the authentication signature is consistent with the broadcast fields, thereby confirming the identity authenticity and data integrity of the communication initiating vessel.

[0032] Digital certificate summary broadcast mode: the communication initiating vessel broadcasts an identity summary data packet containing the following fields during the initialization phase: the vessel's unique identification number, the digital certificate summary value processed by a hash function, the current timestamp or random number, and an authentication signature generated using a private key for the aforementioned fields. After receiving the summary data packet, the communication responding vessel uses a locally stored identity record table to compare the digital certificate summary fields with the local record to ensure consistency.

[0033] The complete digital certificate broadcasting method is suitable for wide-area distribution and highly dynamic maritime communication environments; the digital certificate summary broadcasting method is suitable for scenarios where the scope of communication objects is known and the update cycle is controllable.

[0034] Furthermore, the communicating parties independently generate the same shared symmetric key through a sharing mechanism, specifically including:

[0035] The communication initiating ship generates a first random number, combines the first random number with the ship's unique identification number and the digital certificate digest to obtain a first key negotiation data packet, and sends the first key negotiation data packet to the communication responding ship;

[0036] After receiving the first key negotiation data packet, the communication responding ship generates a second random number, and combines the first random number, the unique identification number of the ship, and the digital certificate digest to generate a second key negotiation data packet and returns it to the communication initiating ship;

[0037] After receiving the second key negotiation data packet, the communication initiating ship uses a preset key derivation function to calculate and generate a shared symmetric key based on the first random number, the second random number, the unique identification numbers of both parties' ships, and the digital certificate digest:

[0038] K=KDF(R1||R2||MMSI A ||MMSI B ||H A ||H B )

[0039] Among them, K is the shared symmetric key, R1 and R2 are the first and second random numbers respectively, MMSI A MMSI B are the unique identification numbers of the communication initiating ship and the communication responding ship, respectively. A 、H B are the hash digest values of the digital certificates of the communication initiating ship and the communication responding ship respectively. KDF is the key derivation function, including HKDF or BLAKE2b;

[0040] The communication responding ship generates the same shared symmetric key as the communication initiating ship by using the same key derivation function and the same parameter sequence based on the second random number, the first random number, the unique ship identification numbers of both parties and the digital certificate summary.

[0041] Furthermore, the communicating parties use the shared symmetric key and their respective ship identity information as input and obtain an identity binding key through a key derivation function, specifically including:

[0042] After both communicating parties have calculated and obtained the shared symmetric key K, they use the following identity binding function to generate the identity binding key:

[0043] K ID =KDF(K||MMSI A ||MMSI B )

[0044] Among them, K ID is the identity binding key for the generated ship ID, K is the shared symmetric key negotiated by both parties, and MMSI A The unique identification number of the ship initiating the communication, MMSI B is the unique identification number of the responding ship, || represents a bit-level concatenation operation, and KDF is a key derivation function, including HKDF or BLAKE2b.

[0045] Furthermore, the communicating parties perform a three-round handshake interaction based on the identity binding key, specifically including:

[0046] Communication initiator ship A binds key K based on identity ID Generate the first authentication random number N1 and construct the authentication request message:

[0047] M1=MMSI A ||N1

[0048]

[0049] Among them, M1 is the first message payload in the authentication process, MAC1 is the identity binding key K ID The authentication request message obtained by calculating the first message payload, To bind the key K to the identity ID HMAC authentication function for the key;

[0050] After receiving the authentication request message, the communication response ship B uses its own calculated identity binding key K ID Verify the legitimacy of MAC1. If the verification is successful, generate the second authentication random number N2 and construct a response message:

[0051] M2=MMSI B ||N1||N2

[0052]

[0053] Among them, M2 is the second message payload in the authentication process, MAC2 is the identity binding key K ID a response message calculated based on the payload of the second message;

[0054] After receiving the response message, the communication initiator ship A uses the identity binding key K IDVerify the legitimacy of MAC2. Once the verification is successful, use N2 as input to construct the final authentication confirmation message:

[0055]

[0056] Among them, MAC3 is the final authentication confirmation message;

[0057] The communication initiating ship A sends MAC3 to the communication responding ship B. After receiving it, the communication responding ship B verifies the validity of MAC3. If the verification is successful, the three-round handshake authentication process is completed.

[0058] Furthermore, in the three-round handshake interaction, if the communicating parties fail to verify the message authentication in any round of messages, or the identity information does not meet expectations, or if timestamp expiration or signs of replay attack are detected, the communication session will be immediately interrupted, the session will be marked as illegal, and the subsequent exchange of sensitive data will be stopped.

[0059] Furthermore, the step of inputting the identity binding key into a key derivation function to obtain an encryption subkey and a message authentication subkey, respectively, specifically includes:

[0060] Bind the identity to the key K OD Input the key derivation function to obtain the encryption subkey K enc and the message authentication subkey K mac :

[0061] K enc =KDF enc (K ID )

[0062] K mac =KDF mac (K ID )

[0063] Among them, K enc K is the encryption subkey used to symmetric encrypt communication data. mac is the message authentication subkey used to generate the message authentication code, KDF enc 、KDF mac The key derivation functions used to derive encryption subkeys and message authentication subkeys, respectively, use the HKDF or BLAKE2b algorithm;

[0064] The two communicating parties are based on K enc Encrypt communication data based on K mac Generate a message authentication code for the ciphertext containing the sequence number field. The specific communication data packet structure is:

[0065]

[0066] Among them, SeqID The sequence number field is used to uniquely identify the order of each communication data packet to prevent replay attacks. The sequence number field can be an incremental count value or a timestamp. Ciphertext is the encrypted subkey K of the communication data. enc Encrypted ciphertext; Indicates the use of message authentication subkey K mac A message authentication code is calculated on the concatenation of the sequence number field and the ciphertext;

[0067] The communication initiator ship A sends the communication data packet to the receiver; after receiving the communication data packet, the receiver first uses K mac Verify the message authentication code, confirm the data integrity and the legitimacy of the message source, and use K after verification enc Decrypt the ciphertext to restore the communication data.

[0068] Furthermore, when a preset time interval, data volume threshold, or policy condition is reached, the communicating parties use a key derivation function and an updated random number to derive a new identity binding key, specifically including:

[0069] The communicating parties regularly monitor the following parameters based on pre-set key update trigger conditions: whether the elapsed communication time reaches the preset time interval threshold, whether the cumulative amount of data sent or received exceeds the preset threshold, and whether a key refresh request triggered manually or by system policy is received;

[0070] When any trigger condition is met, both communicating parties will simultaneously initiate the key update process, specifically:

[0071] The communication parties negotiate or pre-agreed on the update parameter UpdateNonce i , the update parameter is an incremental number or a random number; based on the identity binding key of the previous round and update parameter UpdateNonce i , generate a new identity-bound key through the key derivation function:

[0072]

[0073] in, The identity binding key after the update in round i+1;

[0074] The two communicating parties bind keys based on their new identities Derive new encryption subkeys and message authentication subkeys;

[0075] The communicating parties switch to the new encryption subkey and message authentication subkey for subsequent data encryption and authentication, and securely destroy the old encryption subkey and message authentication subkey and the old identity binding key.

[0076] Compared with the prior art, the present invention has the following advantages:

[0077] (1) The present invention proposes a lightweight offline identity authentication method suitable for ship AIS systems. Addressing the problem of the lack of an effective identity authentication mechanism in existing AIS communications, the present invention introduces an offline verifiable identity credential mechanism, enabling identity authenticity verification between ships even without a network connection. This method does not rely on the traditional online PKI architecture and its real-time certificate revocation checking mechanism, solves the problem of identity authentication failure caused by network unreachability in maritime communication scenarios, and enhances the reliability and security of the AIS communication system in an offline environment.

[0078] (2) The present invention utilizes a key-pair-based digital signature mechanism to generate a vessel identity certificate. Vessels pre-register in the trusted environment of the host system and receive a signed certificate containing authoritatively signed identity information and a bound public key fingerprint. This technical feature addresses the existing issues of MMSI numbers being easily forged and identity information lacking an authenticity verification mechanism. It achieves non-repudiation of the identity-signature binding, fundamentally preventing attacks such as forged messages and "ghost ship" attacks.

[0079] (3) To address the high computational complexity of traditional public-key cryptography and the difficulty of supporting it in embedded AIS devices, this invention employs a lightweight signature algorithm and a simplified verification process. This algorithm uses a digital certificate digest for verification, combined with a fixed-format signature structure design, to adapt it to the computing power and communication load constraints of the AIS embedded environment. This technical feature overcomes the limitation that existing AIS devices cannot afford the traditional encryption and decryption overhead, and improves the feasibility and deployability of the authentication mechanism on existing shipboard systems.

[0080] (4) To prevent the risk of abuse caused by the long-term validity of identity credentials, the present invention designs an offline verifiable credential validity mechanism. Combined with ship motion trajectory and timestamp verification, this mechanism automatically invalidates credentials upon expiration. This technical feature effectively solves the problem of inaccessible revocation mechanisms such as CRL / OCSP in offline environments, ensuring that authentication security is not compromised by credential abuse and enhancing the dynamic protection capabilities of AIS identity authentication.

[0081] (5) The present invention solves the problem of identity information being broadcast in plain text, lacking an effective authentication mechanism, and being easily counterfeited in traditional AIS communication systems by selecting a digital certificate or digital certificate digest during the communication initialization phase, generating a signature based on a private key, and broadcasting identity information. The responding ship then uses a local identity record table for offline verification. The present invention uses a digital certificate or its digest based on the PKI system, combined with a timestamp / random number and signature mechanism, to achieve strong verification of the communication identity and tamper-proof protection of the broadcast data, significantly enhancing the authenticity of identity recognition and data integrity.

[0082] (6) The complete digital certificate broadcasting method of the present invention can fully transmit the digital certificate of the initiating ship in the initial stage of communication. It is suitable for situations where the communication object is uncertain in wide-area distribution and high-dynamic scenarios, such as the need to verify the identity of a newly contacted ship during the first communication on an ocean voyage. By broadcasting the complete certificate in conjunction with the authentication signature, the communication response ship can use the identity record table issued by the maritime trust agency locally to perform digital certificate chain verification, signature verification and timestamp consistency confirmation, thereby completing the confirmation of the authenticity of the initiating ship's identity offline, solving the problem of lack of CA online service support in offline, self-organizing maritime environments. On the other hand, the digital certificate summary broadcasting method only broadcasts the certificate hash value, identity identifier, timestamp and signature, and is suitable for application scenarios where the communication object is known, the environment is stable, and the update cycle is controllable, such as regular communications in ports, near-shore formations or designated route areas. In this scenario, the communication response ship can quickly compare the summary hash through the local record table to see if it is consistent, complete identity authentication, significantly reduce communication bandwidth overhead, and improve response efficiency.

[0083] (7) The dual-mode identity broadcast strategy of the present invention can be dynamically switched according to the current communication environment, number of objects, and system resources, achieving a flexible balance between bandwidth efficiency and strong identity authentication, thereby improving the overall adaptability and scalability of the communication system. By introducing an offline authentication mechanism based on certificates and their digests, the present invention effectively avoids the authentication unavailability problem caused by the traditional PKI's reliance on online CA and CRL services, taking into account the actual network isolation and computing resource constraints in maritime communication scenarios, improving the security, practicality, and robustness of AIS-type ship wireless communication systems in identity authentication, and enhancing the system's resistance to security threats such as "ghost ships", man-in-the-middle attacks, and disguised ships.

[0084] (8) The present invention introduces a three-round handshake authentication mechanism based on identity binding keys, which enables the two devices in the maritime communication scenario to complete peer identity authentication and shared key consistency confirmation safely and efficiently without relying on third-party online services, without the need for pre-shared keys. This solves the problem of the lack of authentication, key negotiation and data encryption capabilities in traditional AIS communications, and improves the anti-tampering and anti-counterfeiting capabilities of the ship communication system.

[0085] (9) On the basis of successful identity authentication, the present invention enables the communicating parties to independently generate completely consistent shared symmetric keys through a sharing mechanism, effectively solving the problem of difficulty in securely synchronizing keys through traditional key exchange protocols (such as Diffie-Hellman) under conditions of heterogeneous equipment, large communication delays, and unstable networks in maritime communication environments. The sharing mechanism adopts a two-way random number exchange mechanism, combined with the unique identification number of each ship and the summary of the digital certificate, to form a key negotiation data packet, which does not expose the actual key information in the public channel and prevents man-in-the-middle attacks or offline replay attacks. At the same time, all input parameters are hashed through a preset key derivation function (such as HKDF or BLAKE2b) to ensure the randomness and unpredictability of the shared symmetric key, thereby improving the security of the key negotiation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a diagram showing the overall architecture of a method for secure communication between ships according to an embodiment of the present invention;

[0087] Figure 2 A schematic diagram of a dual authentication mode according to an embodiment of the present invention;

[0088] Figure 3 This is a flowchart of the symmetric authentication interaction in an embodiment of the present invention. DETAILED DESCRIPTION

[0089] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0090] Example 1:

[0091] This embodiment provides a method for inter-vessel communication based on digital certificates and symmetric key identity authentication, such as Figure 1 As shown, the following steps are included:

[0092] Step S1: Before going out to sea, each ship submits information including the ship's unique identification number and public key to the maritime trust agency, obtains a digital certificate issued by the maritime trust agency, and stores the digital certificate, private key, and identity record table locally;

[0093] This embodiment requires each ship to complete registration with the Maritime Certificate Service System in advance, obtain a digital certificate issued by an authoritative maritime authority (MCA), and store it locally;

[0094] Before going to sea, each ship should generate a public-private key pair in the local system, and the shipowner or the representative of the ship operation management agency shall submit the following registration information to the authoritative trust agency MCA. The content of the registration information shall at least include: the ship's unique identification number (MMSI), flag state registration information, ship operating unit or management company information, equipment public key, and administrator signature confirmation. This information should be certified and stamped by the Maritime Administration or the registration country agency to enhance authority. The private key should be generated and protected by the security module in the ship's local equipment and must not be exported; anti-tampering and anti-copying mechanisms should be enabled to prevent the private key from being leaked during physical intrusion or remote attacks. The system will package the basic information of the ship and its public key into a certificate issuance request. The request content shall at least include: registration information, validity period requirements, signature of the ship's private key on the request information, and signature algorithm.

[0095] As an authoritative trust authority, the MCA, upon receiving a certificate issuance request, must perform at least the following operations: verify the authenticity of the registration information, review the validity of the signature, sign the ship's public key information using the MCA private key to form a formal digital certificate, and store the certificate in the MCA's certificate issuance directory. The certificate content should at least include: version number, serial number, signature algorithm identifier, issuer, validity period, ship identity information, ship's public key, the address where the superior MCA certificate is obtained, and the MCA's signature on all of the above fields. The certificate and root certificate chain are then distributed locally to the ship. The ship must also store: its own private key, MCA certificate chain, its own digital certificate, and the identity record table downloaded from the MCA. The identity record table is a local database stored locally on the ship for quickly verifying the hash information and validity period of other ship certificates. This table should contain: certificate hash value, public key, certificate validity period, certificate status (authenticated, pending authentication, and revoked), ship's MMSI, and issuing MCA. To adapt to offline communication environments, the present invention uses short-term validity period control instead of the traditional revocation mechanism. Ship certificates are considered credible within their validity period and need to be renewed ashore after expiration. This eliminates the need to rely on online CRL or OCSP mechanisms, reduces device burden, simplifies protocol processes, and improves applicability in offline scenarios.

[0096] Step S2: When initializing communication, the communication initiating ship selects a digital certificate or digital certificate digest according to the communication preset strategy, signs it with the private key, obtains the identity information formed after the signature, and broadcasts it. After receiving the identity information, the communication responding ship uses the identity record table to verify the identity information offline;

[0097] The identity authentication mechanism proposed in this embodiment supports two identity broadcast and verification methods, which are suitable for different communication environments and system load requirements, so as to achieve efficient identity authentication, flexible adaptation and optimal resource allocation between ships.

[0098] In the first implementation of the identity broadcast of this embodiment, each ship actively broadcasts its own identity authentication data packet to the communicating party when initializing communication. The data packet contains at least: the ship's unique identifier, the ship's digital certificate, the current timestamp or random number, and an authentication signature generated using the ship's local private key for the above fields. After receiving the identity broadcast, the receiving ship will use the pre-stored MCA root certificate or certificate chain to verify the signature and validity of the digital certificate locally and offline, and further verify whether the signature content is consistent with the broadcast content, completing the confirmation of the authenticity of the communicating party's identity and the integrity of the data. This method is suitable for the first communication between ships or scenarios where there is no preset identity data. It has the advantages of strong flexibility, high real-time performance, and no need to rely on external network synchronization. It is particularly suitable for wide-area distribution and highly dynamic maritime communication environments.

[0099] In the second implementation of identity broadcasting in this embodiment, to further reduce the data volume of identity broadcasts, lower processing overhead, and improve authentication efficiency, each vessel can choose to broadcast a summary of its identity information. The broadcast content includes, but is not limited to, the vessel's unique identifier, a digital certificate summary, a timestamp, or a random number. The digital certificate summary is the hash value obtained by processing the digital certificate using a hash function. The content of digital certificates is described in patents. Since digital certificates are often large (hundreds to kilobytes), they can be mapped into a short sequence of fixed length after hashing. Therefore, sending this digital certificate summary can reduce overhead. Simultaneously, each vessel pre-populates an "identity record table" in its local system. This table can be obtained through docking updates, broadcast synchronization, or pre-provisioning mechanisms. Upon receiving the summary broadcast, the recipient compares the broadcast summary with the pre-configured information in the local identity record table to confirm the authenticity of the other party, eliminating the need for real-time parsing and verification of the digital certificate signature. This approach is suitable for scenarios where the scope of communication targets is known and the update cycle is controllable, such as port operations and scheduled shipping fleets. It can significantly reduce broadcast bandwidth and local processing resource consumption.

[0100] This embodiment supports the automatic compatibility and on-demand switching design of the above two identity broadcast mechanisms: when the local identity record table cannot be hit, the system can fall back to the "broadcast complete certificate" mode; the system automatically adopts the complete certificate broadcast process by default in the first communication, identity table missing, summary inconsistency, or bilateral negotiation failure; supports automatic switching of broadcast strategies based on configuration strategies or communication scenarios (such as wide area / port). Appendix Figure 2 The work and switching process of full certificate broadcast and summary broadcast are demonstrated. By combining the two identity broadcast methods and the switching mechanism, this invention takes into account the actual needs of ship communication systems in terms of identity authentication strength, system resource overhead, broadcast data length, dynamic adaptability, etc., and has high practicality and deployment flexibility.

[0101] In this embodiment, after completing identity information broadcast and verification, both communicating parties need to generate a session symmetric key based on a shared mechanism and then perform identity confirmation and key consistency verification based on this key. This process includes the following three steps: shared symmetric key generation, key-identity binding, and symmetric authentication interaction verification.

[0102] Step S4: After successful verification, both communicating parties independently generate the same shared symmetric key through a sharing mechanism. Both communicating parties use the shared symmetric key and their respective ship identity information as input and obtain the identity binding key through a key derivation function, which specifically includes:

[0103] Specifically include:

[0104] The communication initiating ship generates a first random number, combines the first random number with the unique identification number of the ship and the digital certificate digest to obtain a first key negotiation data packet, and sends the first key negotiation data packet to the communication responding ship;

[0105] After receiving the first key negotiation data packet, the communication responding ship generates a second random number, and combines the first random number, the unique identification number of the ship and the digital certificate digest to generate a second key negotiation data packet and returns it to the communication initiating ship;

[0106] After the communication initiating ship receives the second key negotiation data packet, it uses the preset key derivation function to calculate and generate a shared symmetric key based on the first random number, the second random number, the unique identification number of both parties' ships, and the digital certificate digest:

[0107] K=KDF(R1||R2||MMSI A ||MMSI B ||H A ||H B )

[0108] Among them, K is the shared symmetric key, R1 and R2 are the first and second random numbers respectively, MMSI A MMSI B are the unique identification numbers of the communication initiating ship and the communication responding ship, respectively. A 、H B are the hash digest values of the digital certificates of the communication initiating ship and the communication responding ship respectively. KDF is the key derivation function, including HKDF or BLAKE2b;

[0109] The communication responding ship generates the same shared symmetric key as the communication initiating ship by using the same key derivation function and the same parameter sequence based on the second random number, the first random number, the unique ship identification numbers of both parties and the digital certificate summary.

[0110] The symmetric key used in this embodiment is generated by negotiation between the communicating parties based on a shared mechanism. This mechanism may include, but is not limited to, physical layer feature extraction; random negotiation between devices; pre-shared key updates; or other key generation methods. The present invention does not limit the specific method for generating this key; it only requires that the communicating parties independently generate the same symmetric key without exposing the key content. This key will serve as the basis for subsequent authentication and data encryption communications. To enhance system adaptability and scalability, the key negotiation module can be integrated into the communication module or deployed independently, and can support on-demand updates.

[0111] In order to prevent attackers from impersonating others to participate in the session during the key negotiation process, this paper proposes a key and identity joint derivation mechanism. After generating the shared key K, the identity binding function is used to derive the authentication key K. ID The derived method is as follows:

[0112] K ID =KDF(K||MMSI A ||MMSI B )

[0113] Where K is the shared symmetric key obtained through negotiation between the two parties; MMSI A ,MMSI B It is the ship identity code of each communicating party; KDF is the key derivation function, which can use lightweight algorithms such as HKDF and BLAKE2b.

[0114] By embedding identity information into the derivation process, the authentication key K is ensured ID This mechanism is not only related to the channel characteristics and negotiation process, but also strongly bound to the identity pair. This mechanism can effectively prevent attackers from forging identities in advance to participate in key negotiation and cause "identity mismatch".

[0115] To prevent the potential risks of shared keys being copied or reused, this invention binds the shared symmetric key to the identities of both parties and generates an identity-bound key using a key derivation function. This identity-binding mechanism ensures that the key is not solely dependent on the content of the negotiation but is also tightly coupled to the identities of the two parties in the current communication session. This ensures that the generated key can only be used by the devices currently participating in the session, preventing the key from being misused or abused across multiple communicating parties and enhancing the uniqueness and identity relevance of the communication channel.

[0116] On this basis, the present invention designs a three-round handshake mechanism based on identity binding key, uses HMAC function to generate authentication messages in rounds, and gradually verifies the identities of both parties and the consistency of shared keys through three stages of authentication request, response and confirmation. This mechanism has the following advantages: First, no plaintext keys or identity credentials are leaked during the authentication process, and it has strong anti-replay and anti-counterfeiting capabilities; second, the MAC value generated by the identity binding key ensures the integrity and non-forgeability of the message; third, the authentication logic is symmetrical, and both parties can verify whether the identity of the other party is consistent with the key used, eliminating the asymmetric trust problem caused by one-way authentication. Through this three-round authentication mechanism, the communicating parties have completed the dual verification of identity consistency and key synchronization before establishing a secure channel, which significantly improves the security and reliability of the communication.

[0117] In summary, the proposed mechanism addresses the three core security shortcomings of existing ship communication systems: inability to verify identity, inability to negotiate keys, and inability to encrypt data. It does not rely on online CAs or key servers, nor does it require the physical deployment of shared keys. This significantly enhances the system's adaptability, scalability, and practicality, making it particularly suitable for dynamic, wide-area, and heterogeneous maritime communication environments. This technical solution not only improves the confidentiality, integrity, and authentication of data transmission, but also provides a reliable key foundation and identity trust root for subsequent high-speed encrypted communications based on symmetric encryption, anti-denial of service attack mechanisms, and safe navigation collaboration.

[0118] Step S5: The communicating parties perform a three-round handshake interaction based on the identity binding key to verify the consistency of the identities of the communicating parties and the shared symmetric key;

[0119] After completing the identity binding key derivation, the two communicating parties use K ID The authentication handshake process is initiated to verify: whether the other party is the actual communication entity that possesses the key; whether the other party is the identity claimed during key negotiation; and whether the current key is consistent (anti-middleman interference). The authentication process uses a three-round handshake mechanism, and the specific process is as follows:

[0120] The first step is to start the authentication:

[0121] The communication initiator (ship A) generates a random number N1 and constructs the message:

[0122] M1=MMSI A ||N1

[0123]

[0124] Send {M1, MAC1} to the communication responder (ship B).

[0125] Step 2: Response confirmation:

[0126] After receiving M1, ship B verifies whether MAC1 is correct and confirms that the other party has the correct key. It then generates a new random number N2 and constructs a response message:

[0127] M2=MMSI B ||N1||N2

[0128]

[0129] Send {M2, MAC2} back to ship A.

[0130] Step 3: Final confirmation:

[0131] After receiving M2, ship A verifies whether MAC2 is correct and generates the following code using N2 as input:

[0132]

[0133] The final response is returned to ship B.

[0134] Both communicating parties complete key verification, identity confirmation and entity authentication in three rounds of interaction to ensure the security of session establishment. Figure 3 The complete symmetric authentication interaction process is demonstrated.

[0135] If any of the following is found in any authentication round: HMAC verification fails; identity information does not match expectations; timestamp expires or there are signs of replay attacks; the communication process is immediately terminated and the session is marked as illegal to prevent subsequent sensitive data exchange.

[0136] After completing symmetric key negotiation, identity authentication, and key consistency verification, the present invention enters the secure communication phase. The communicating parties use the authenticated session key to encrypt and authenticate subsequent communication data, ensuring the confidentiality and integrity of the communication content. Furthermore, to mitigate the security risks associated with long-term use of the same key, the present invention incorporates a lightweight key update and session derivation mechanism to achieve periodic symmetric key refresh and forward secrecy.

[0137] Step S5, through the technical feature of a three-round handshake interaction between the communicating parties based on an identity-bound key, specifically addresses current challenges in maritime ship communications, such as the difficulty in verifying the authenticity of the communicating parties, the lack of a verification mechanism during the shared key negotiation process, and the vulnerability of communications to man-in-the-middle and replay attacks. In traditional ship-to-ship communications, communicating entities often cannot confirm whether the other party is the node corresponding to their true identity, and there is a lack of effective verification of the negotiated key consistency. This makes it easy for spoofed nodes to impersonate the other party in a maritime environment without a central authentication server, or for malicious middlemen to insert false messages, posing the risk of communication tampering, eavesdropping, or hijacking. This ensures that both communicating parties possess the correct keys and that their identities remain consistent with previously exchanged identity information. The initiator initiates the initial handshake by sending an authentication request message bound to its own identity and a random number. The responder, after verifying the legitimacy of the request, constructs a response message containing both parties' identities and a bidirectional random number to further confirm the other party's identity and its own claims. Finally, the initiator returns an authentication confirmation message, completing bidirectional authentication and key verification. Each round of authentication messages incorporates a random number and identity information, which are bound via HMAC, making the entire handshake process resistant to replay, tampering, and man-in-the-middle attacks. It ensures the consistency of key negotiation and the authenticity of the identities of both communicating parties, effectively preventing illegal nodes or attackers from forging identities or inserting incorrect keys during the handshake phase; through a three-round interactive process, it ensures that sufficient security verification has been completed before communication is established, greatly improving the system's resistance to security threats such as session hijacking, man-in-the-middle forgery, and replay attacks; the entire handshake process uses symmetric encryption and hash algorithms, and can operate in offline scenarios without relying on external trust agencies. It is suitable for dynamic, high-latency, and weak infrastructure maritime communication environments. In addition, the mechanism can immediately interrupt communication and mark the session as illegal when authentication fails, avoiding the occurrence of unauthorized data exchange, and ensure session uniqueness by binding random numbers to identities, providing confidentiality and integrity for subsequent communications, while also laying the foundation for subsequent key updates and forward security.

[0138] Step S6: After successful authentication, both communicating parties input their identity-binding keys into a key derivation function to derive an encryption subkey and a message authentication subkey. The sender uses the encryption subkey to symmetrically encrypt the communication data and uses the message authentication subkey to generate a message authentication code for the ciphertext containing the sequence number field and sends it. The encrypted communication data packet is then verified and decrypted by the receiver.

[0139] The communicating parties complete the identity binding key K ID After the derivation of the key, two sub-keys are further generated based on the key through the key derivation function (KDF):

[0140] K enc =KDF enc (K ID )

[0141] K mac =KDF mac (K ID )

[0142] in:

[0143] K enc : Used to encrypt communication data; K mac : Used to generate message authentication code (HMAC); KDF enc and KDF mac These are the corresponding key derivation functions. This design follows the "one key, one use" principle in cryptography, preventing a single key from being used for multiple security objectives simultaneously, thus enhancing key isolation, attack resistance, and overall system robustness.

[0144] After communication is established, both parties use the derived subkey to encrypt and protect the integrity of the communication data. The structure of each encrypted communication data packet is as follows:

[0145]

[0146] where Seq ID It is the sequence number field (or timestamp) to prevent replay attacks; Ciphertext is the original communication data encrypted by K enc Encrypted ciphertext; A message authentication code generated for a data packet using the authentication subkey.

[0147] The specific process is: the sender uses a symmetric encryption algorithm to enc Encrypt communication data; use K mac Seq ID and ciphertext to generate HMAC value; combine the three and broadcast to the receiver; the receiver verifies HMAC in the same way to confirm data integrity and key consistency; if the verification passes, use K enc Decrypt data. This mechanism ensures that each communication message has the security properties of being unforgeable, tamper-proof, and non-replayable.

[0148] In the present invention, after the identity authentication is successful, the communicating parties further derive an encryption subkey and a message authentication subkey based on the identity binding key, and use these two subkeys to perform data encryption and integrity verification respectively. This technical feature solves the technical problem that data in traditional maritime communications is easily eavesdropped, tampered with, forged or replayed during transmission. Especially in the highly dynamic and weak infrastructure maritime environment, the traditional mechanism that relies on central trust structure and static keys is difficult to provide continuous and reliable data security protection.

[0149] Step S7: When a preset time interval, data volume threshold, or policy condition is reached, the communicating parties use a key derivation function and an updated random number to derive a new identity-binding key, and simultaneously update the encryption subkey and message authentication subkey;

[0150] To prevent the risk of security degradation and key leakage caused by long-term use of the same key, the present invention provides a lightweight session key update mechanism to ensure forward secrecy.

[0151] The key update triggering conditions of the present invention are: reaching a fixed time interval; the cumulative amount of sent data exceeds a preset threshold; and a key refresh request is triggered manually or by policy.

[0152] The key update process of the present invention is: both parties agree to update the parameter UpdateNonce i (can be an incremental number or a random number); based on the master key of the previous round Derive a new master key: Use the new master key to derive a new and Communications switch to the new key group for data encryption and authentication, discarding the old key to prevent backtracking attacks. This process allows secure session renewal without re-authentication and key negotiation, effectively improving long-term communication security.

[0153] Step S8: When the communication session ends or is interrupted due to timeout, both communicating parties destroy all key materials related to the current session.

[0154] When a communication session is terminated or interrupted due to timeout, the system should immediately destroy all key materials related to the current session, including: the master key K ID ; Subkey K enc and K mac ; Derived context (such as KDF intermediate states). If the device supports a security chip (such as a TPM or HSM), a security interface should be called to perform a physical key erase operation to ensure that the key is completely unrecoverable in the storage medium or cache to prevent the risk of leakage.

[0155] This paper addresses key issues in existing ship communication systems, such as the lack of effective identity authentication mechanisms, the unsuitability for deploying traditional encryption systems, and the risk of identity forgery during symmetric key negotiation. By proposing a lightweight identity authentication and secure communication method suitable for ship-to-ship wireless communication environments, this method balances security, deployment feasibility, and resource overhead control without relying on persistent network connections or heavy computing platforms. It offers the following significant advantages and positive effects:

[0156] Compared with traditional PKI, the present invention adopts a lightweight digital certificate mechanism that does not rely on online CA, CRL or OCSP, solving the problem that traditional digital certificates are difficult to deploy in offshore environments.

[0157] After completing the symmetric key negotiation, the present invention uses the identity information of both parties of the communication as input and derives the session master key K together with the negotiated key. ID , achieving a strong binding between keys and identities. This effectively prevents the "correct key but forged identity" problem that exists in traditional symmetric authentication protocols, ensuring that "who owns the key" is authenticated and that "the key was indeed generated by that identity."

[0158] The present invention adopts HMAC authentication to complete entity verification and key consistency confirmation, with low computational cost, short message length, no need for large integer operations, and fully adaptable to the performance constraints of AIS equipment or other shipborne communication modules.

[0159] This invention provides two identity broadcast modes: full certificate broadcast is suitable for initial communication and unfamiliar vessels; certificate summary broadcast combined with local record matching is suitable for port areas, regular shipping routes, and other scenarios. The system supports automatic switching and compatible operation, maintaining authentication strength while controlling bandwidth consumption.

[0160] The present invention rolls over the master key through a lightweight derivation function without the need for re-authentication or negotiation; each round of communication can use an independent subkey group (encryption / authentication separation), effectively preventing key leakage from causing cascading security risks.

[0161] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0162] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for inter-vessel communication based on digital certificates and symmetric key identity authentication, characterized in that: The following steps are involved: Before going out to sea, each ship submits information including the ship's unique identification number and public key to the maritime trust agency, obtains a digital certificate issued by the maritime trust agency, and stores the digital certificate, private key and identity record table locally; When initializing communication, the communication initiating ship selects a digital certificate or digital certificate digest according to the communication preset strategy, signs it with the private key, obtains the identity information formed after the signature, and broadcasts it; After the communication response ship receives the identity information, if the received data packet is a digital certificate summary data packet, the digital certificate summary field is compared and verified through the locally stored identity record table; if the received data packet is a complete digital certificate data packet, the root certificate or certificate chain of the pre-stored maritime trust authority is used to locally verify the signature and validity of the contained digital certificate, and further verify whether the authentication signature is consistent with the broadcast content; After successful verification, both communicating parties independently generate the same shared symmetric key through a sharing mechanism. Both communicating parties use the shared symmetric key and their respective ship identity information as input and obtain the identity binding key through a key derivation function; The communicating parties perform a three-round handshake interaction based on the identity binding key to verify the consistency of the identities of the communicating parties and the shared symmetric key; After successful authentication, both communicating parties input the identity-binding key into a key derivation function to obtain an encryption subkey and a message authentication subkey, respectively. The sender uses the encryption subkey to symmetrically encrypt the communication data, and uses the message authentication subkey to generate a message authentication code for the ciphertext containing the sequence number field and sends it. The encrypted communication data packet is verified and decrypted by the receiver. When a preset time interval, data volume threshold or policy condition is reached, the communicating parties use a key derivation function and an updated random number to derive a new identity binding key, and simultaneously update the encryption subkey and message authentication subkey; When a communication session ends or times out, both parties destroy all key materials related to the current session.

2. A method for inter-ship communication based on digital certificates and symmetric key identity authentication according to claim 1, characterized in that: Each vessel shall submit information including the vessel's unique identification number and public key to the maritime trust agency before setting sail, and obtain a digital certificate issued by the maritime trust agency, specifically including: Each ship generates a pair of public and private keys locally. The private key is generated and protected by a security module in the ship's local equipment and cannot be exported. The shipowner or the representative of the ship operation and management organization submits the registration information including the ship's unique identification number, flag state registration information, ship operating unit or management company information, public key, and administrator signature confirmation to the maritime trust agency. The registration information is authenticated and stamped by the competent authority to form a certificate issuance request; The ship signs the certificate issuance request using its local private key and sends the signed request to the maritime trust authority; The maritime trust authority verifies the validity of the registration information and signature in the request. Once the verification is successful, the maritime trust authority uses its private key to sign the ship's public key and registration information to generate a digital certificate, which is then returned to the ship. The ship stores the digital certificate, identity record table and locally generated private key in a local system, wherein the identity record table is used to store and quickly verify the hash information, public key, certificate validity period, certificate status, ship unique identification number and issuing agency information of other ships' digital certificates; The digital certificate adopts a short-term validity control method and is considered credible within the validity period of the certificate. It needs to be re-applied after the expiration date.

3. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: The ship stores the digital certificate, identity record table and locally generated private key in a local system, wherein the identity record table is used to store and quickly verify the hash information, public key, certificate validity period, certificate status, ship unique identification number and issuing agency information of other ships' digital certificates; The digital certificate adopts a short-term validity control method and is considered credible within the validity period of the certificate. It needs to be re-applied after the expiration date.

4. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: The communication preset strategy includes the following two identity broadcast modes and supports automatic switching: The complete digital certificate broadcast mode is that the communication initiating ship broadcasts an identity authentication data packet containing the following fields to the communication responding ship during the initialization phase: the ship's unique identification number, digital certificate, current timestamp or random number, and the authentication signature generated by the ship's local private key for the aforementioned fields; After receiving the data packet, the communication responding ship uses the pre-stored identity record table of the maritime trust agency to locally verify the signature and validity of the digital certificate, and further verify whether the authentication signature is consistent with the broadcast field to confirm the identity authenticity and data integrity of the communication initiating ship; Digital certificate summary broadcast mode, that is, the communication initiating ship broadcasts an identity summary data packet containing the following fields during the initialization phase: the ship's unique identification number, the summary value of the digital certificate processed by the hash function, the current timestamp or random number, and the authentication signature generated by the private key for the above fields; After receiving the summary data packet, the communication response ship uses the locally stored identity record table to compare the digital certificate summary field with the local record to see if they are consistent; The complete digital certificate broadcasting method is suitable for wide-area distribution and highly dynamic maritime communication environments; the digital certificate summary broadcasting method is suitable for scenarios where the scope of communication objects is known and the update cycle is controllable.

5. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: The two communicating parties independently generate the same shared symmetric key through a sharing mechanism, specifically including: The communication initiating ship generates a first random number, combines the first random number with the ship's unique identification number and the digital certificate digest to obtain a first key negotiation data packet, and sends the first key negotiation data packet to the communication responding ship; After receiving the first key negotiation data packet, the communication responding ship generates a second random number, and combines the first random number, the unique identification number of the ship, and the digital certificate digest to generate a second key negotiation data packet and returns it to the communication initiating ship; After receiving the second key negotiation data packet, the communication initiating ship uses a preset key derivation function to calculate and generate a shared symmetric key based on the first random number, the second random number, the unique identification numbers of both parties' ships, and the digital certificate digest: K=KDF(R1||R2||MMSI A ||MMSI B ||H A ||H B ) Among them, K is the shared symmetric key, R1 and R2 are the first and second random numbers respectively, MMSI A MMSI B are the unique identification numbers of the communication initiating ship and the communication responding ship, respectively. A 、H B are the hash digest values of the digital certificates of the communication initiating ship and the communication responding ship respectively. KDF is the key derivation function, including HKDF or BLAKE2b; The communication responding ship generates the same shared symmetric key as the communication initiating ship by using the same key derivation function and the same parameter sequence based on the second random number, the first random number, the unique ship identification numbers of both parties and the digital certificate summary.

6. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: The communicating parties use the shared symmetric key and their respective ship identity information as input and obtain the identity binding key through a key derivation function, specifically including: After both communicating parties have calculated and obtained the shared symmetric key K, they use the following identity binding function to generate the identity binding key: K ID =KDF(K||MMSI A ||MMSI B ) Among them, K ID is the identity binding key for the generated ship ID, K is the shared symmetric key negotiated by both parties, and MMSI A The unique identification number of the ship initiating the communication, MMSI B is the unique identification number of the responding ship, || represents a bit-level concatenation operation, and KDF is a key derivation function, including HKDF or BLAKE2b.

7. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: The communicating parties perform a three-round handshake interaction based on the identity binding key, specifically including: Communication initiator ship A binds key K based on identity ID Generate the first authentication random number N1 and construct the authentication request message: M1=MMSI A ||N1 Among them, M1 is the first message payload in the authentication process, MAC1 is the identity binding key K ID The authentication request message obtained by calculating the first message payload, To bind the key K to the identity ID HMAC authentication function for the key; After receiving the authentication request message, the communication response ship B uses its own calculated identity binding key K ID Verify the legitimacy of MAC1. If the verification is successful, generate the second authentication random number N2 and construct a response message: <h2 style=";text-align:left;direction:ltr">M2 = MMSI<h2 style=";text-align:left;direction:ltr"> B <h2 style=";text-align:left;direction:ltr"> ||N1||N2 Among them, M2 is the second message payload in the authentication process, MAC2 is the identity binding key K ID a response message calculated based on the payload of the second message; After receiving the response message, the communication initiator ship A uses the identity binding key K ID Verify the legitimacy of MAC2. Once the verification is successful, use N2 as input to construct the final authentication confirmation message: Among them, MAC3 is the final authentication confirmation message; The communication initiating ship A sends MAC3 to the communication responding ship B. After receiving it, the communication responding ship B verifies the validity of MAC3. If the verification is successful, the three-round handshake authentication process is completed.

8. The method for inter-vessel communication based on digital certificates and symmetric key identity authentication according to claim 1, characterized in that: In the three-round handshake interaction, if the communicating parties fail to verify the message authentication in any round of messages, or the identity information does not match the expectations, or if the timestamp expires or signs of replay attack are detected, the communication session will be immediately interrupted, the session will be marked as illegal, and the subsequent exchange of sensitive data will be stopped.

9. The method for inter-vessel communication based on digital certificates and symmetric key identity authentication according to claim 1, characterized in that: Inputting the identity binding key into a key derivation function to obtain an encryption subkey and a message authentication subkey, respectively, specifically includes: Bind the identity to the key K ID Input the key derivation function to obtain the encryption subkey K enc and the message authentication subkey K mac : K enc =KDF enc (K ID ) K mac =KDF mac (K ID ) Among them, K enc K is the encryption subkey used to symmetric encrypt communication data. mac is the message authentication subkey used to generate the message authentication code, KDF enc 、KDF mac The key derivation functions used to derive encryption subkeys and message authentication subkeys, respectively, use the HKDF or BLAKE2b algorithm; The two communicating parties are based on K enc Encrypt communication data based on K mac Generate a message authentication code for the ciphertext containing the sequence number field. The specific communication data packet structure is: Among them, Seq ID The sequence number field is used to uniquely identify the order of each communication data packet to prevent replay attacks. The sequence number field can be an incremental count value or a timestamp; Ciphertext is the encrypted subkey K of the communication data. enc Encrypted ciphertext; Indicates the use of message authentication subkey K mac A message authentication code is calculated on the concatenation of the sequence number field and the ciphertext; The communication initiator ship A sends the communication data packet to the receiver; after receiving the communication data packet, the receiver first uses K mac Verify the message authentication code, confirm the data integrity and the legitimacy of the message source, and use K after verification enc Decrypt the ciphertext to restore the communication data.

10. The method for inter-vessel communication based on digital certificate and symmetric key identity authentication according to claim 1, characterized in that: When a preset time interval, data volume threshold, or policy condition is reached, the communicating parties use a key derivation function and an updated random number to derive a new identity binding key, specifically including: The communicating parties regularly monitor the following parameters based on pre-set key update trigger conditions: whether the elapsed communication time reaches the preset time interval threshold, whether the cumulative amount of data sent or received exceeds the preset threshold, and whether a key refresh request triggered manually or by system policy is received; When any trigger condition is met, both communicating parties will simultaneously initiate the key update process, specifically: The communication parties negotiate or pre-agreed on the update parameter UpdateNonce i , the update parameter is an incremental number or a random number; based on the identity binding key of the previous round and update parameter UpdateNonce i , generate a new identity-bound key through the key derivation function: in, The identity binding key after the update in round i+1; The two communicating parties bind keys based on their new identities Derive new encryption subkeys and message authentication subkeys; The communicating parties switch to the new encryption subkey and message authentication subkey for subsequent data encryption and authentication, and securely destroy the old encryption subkey and message authentication subkey and the old identity binding key.

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