A low-altitude data encryption method integrating spatiotemporal attributes

Abstract

This invention belongs to the field of communication security and unmanned aerial vehicle (UAV) system applications, specifically relating to a low-altitude data encryption method that integrates spatiotemporal attributes. The invention includes: constructing a spatial grid index table for the mission airspace; acquiring the UAV's location information, current Coordinated Universal Time (UTC), and mission type in real time to construct a UAV attribute set; deriving a session key for the current communication cycle using a hash algorithm based on the UAV attribute set and a dedicated key; triggering an update of the session key based on preset trigger conditions; encrypting the session key using a preset access control policy to generate ciphertext; encrypting UAV service data to generate ciphertext payload; and decrypting the data using a dedicated private key held by the ground control station to obtain the session key and restore the UAV service data. This invention improves the data confidentiality and access controllability of the communication link, enhancing the security protection capabilities and airspace compliance of the UAV system.

Description

Technical Field

[0001] This invention belongs to the field of communication security and unmanned aerial vehicle (UAV) system applications, and specifically relates to a low-altitude data encryption method that integrates spatiotemporal attributes. Background Technology

[0002] With the rapid development of the low-altitude economy and intelligent unmanned systems, the application of unmanned aerial vehicles (UAVs) in fields such as emergency rescue, power line inspection, urban security, and agricultural surveying is constantly expanding. During missions, UAVs need to interact with ground control units via wireless communication links for data exchange and status feedback; therefore, communication security is a crucial aspect of ensuring reliable system operation. Existing UAV communication encryption schemes are mostly designed for two-dimensional planar areas or general network scenarios, typically employing fixed keys or static encryption mechanisms, providing security protection only for latitude and longitude ranges or communication channels.

[0003] However, these solutions fail to consider the precise three-dimensional airspace control requirements of low-altitude missions and lack a dynamic key management mechanism adapted to changes in flight attitude, altitude, and airspace layering restrictions. Once a UAV crosses a predetermined airspace boundary or enters a restricted area, traditional communication systems may still maintain connectivity, leading to security risks such as encryption failure after airspace incursion, data link loss of control, and even exploitation. Currently, most mainstream encryption systems are based on internationally recognized algorithms (such as the symmetric encryption algorithm AES and the asymmetric encryption algorithm RSA). The algorithm implementation and key distribution architecture lack controllability and auditability, exhibiting significant shortcomings in national cryptographic compliance, security traceability, and independent controllability. These factors combined result in three major problems prevalent in the UAV communication field: first, the risk of long-term key reuse and leakage is high, allowing attackers to replay or forge attacks once they capture communication traffic; second, the lack of airspace-related access control mechanisms makes it impossible to adjust key strategies in real time based on dynamic flight positions or mission area boundaries; and third, the high complexity of encryption algorithm systems, inconsistent algorithm combinations, and poor compatibility between different manufacturers or systems make it difficult to form a unified national cryptographic encryption mechanism.

[0004] Therefore, there is an urgent need for a new UAV communication encryption method that can integrate spatiotemporal attributes and national cryptographic algorithm system to achieve integrated design of communication security strategy and airspace supervision. This method can complete precise airspace constraints, dynamic key derivation and policy-based access control throughout the entire flight cycle of the UAV, thereby ensuring data confidentiality while strengthening the system's autonomy, controllability and compliance with national cryptographic standards. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and to propose a low-altitude data encryption method that integrates spatiotemporal attributes.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] A low-altitude data encryption method integrating spatiotemporal attributes includes:

[0008] The National Cryptography Trust Center constructs a spatial grid index table for the mission airspace based on a preset three-dimensional spatial grid standard, distributes exclusive keys generated by the SM9 identity cryptography algorithm to UAVs, distributes exclusive private keys generated by the SM9 identity cryptography algorithm to ground control stations, and generates mission policies in the policy center.

[0009] The UAV acquires its own location information, current Coordinated Universal Time and mission type in real time, and constructs a UAV attribute set that includes a three-dimensional mesh code of the current location, the mission type of the current mission cycle and the time discretization result;

[0010] The drone derives the session key for the current communication cycle using a hash algorithm based on the drone attribute set and exclusive key. A task cycle contains at least one communication cycle, and a communication cycle consists of a preset number of consecutive time slices. When the preset number of time slices is reached, or when a change in the version number of the task policy is detected, the session key is updated and the next communication cycle begins.

[0011] The drone uses an attribute-based encryption algorithm, combined with access control policies, to encrypt the session key and generate session key ciphertext.

[0012] The drone encrypts its service data based on the session key, generating a ciphertext payload. The returned data frame, including the ciphertext of the session key and the ciphertext payload, is synchronized to the ground control station. The ground control station, which meets the access control policy, decrypts the data using its exclusive private key to obtain the session key and restore the drone's service data.

[0013] Furthermore, the National Cryptographic Trust Center constructs a spatial grid index table for the mission airspace based on a preset three-dimensional spatial grid standard, including:

[0014] Import the coordinate data of the task's airspace;

[0015] By mapping coordinate data to the corresponding three-dimensional grid using a preset three-dimensional spatial grid standard, a three-dimensional grid code for each grid is generated, resulting in a spatial grid index table.

[0016] Furthermore, the time discretization result is obtained by discretizing the time slice based on the current Coordinated Universal Time.

[0017] Furthermore, before deriving the session key, the process also includes:

[0018] Verify whether the authorization constraints are met. The authorization constraints include: the 3D mesh code of the current position is within the task authorization spatial mesh set corresponding to the mesh index table; and the current Coordinated World Time is during the task authorization period.

[0019] If the authorization constraints are met, a session key is derived; otherwise, no session key is derived.

[0020] Furthermore, the drone derives the session key for the current communication period using a hash algorithm based on its attribute set and proprietary key, including:

[0021] Based on the UAV attribute set and mission strategy version number, a hash algorithm is used to calculate the local attribute hash.

[0022] Based on local attribute hashing and a private key, a temporary key is calculated using a hash algorithm;

[0023] Multiply the temporary key by the base point of the elliptic curve to obtain the local key;

[0024] A true random number generator is invoked to generate a random factor, and the session key for the current communication period is derived based on the random factor, the local key, and the time discretization result.

[0025] Furthermore, the step of encrypting the session key using an attribute-based encryption algorithm in conjunction with an access control policy to generate session key ciphertext includes:

[0026] The session key is encrypted only if the drone's unique identifier, the current 3D mesh encoding, and the current task type all match the access control policy, as expressed by the formula:

[0027]

[0028] in, This represents the ciphertext of the session key; Indicates the session key; Indicates the access control policy; Indicates the master public key; This indicates an encryption operation using an attribute-based encryption algorithm;

[0029] The access control policy is as follows: The drone's unique identifier belongs to a drone registered with the trust center. The current 3D mesh encoding of the UAV belongs to the task region set defined by the task strategy; the current task type is a predefined task type.

[0030] Furthermore, the encryption of UAV service data based on the session key to generate a ciphertext payload includes:

[0031] The drone service data is encapsulated with a pre-formatted message header to obtain a plaintext payload; the message header includes: session identifier, time discretization result, and message sequence number;

[0032] Using the session key as the master key, the plaintext payload is encrypted using the SM4_GCM block cipher algorithm, generating the ciphertext payload and the corresponding authentication tag.

[0033] Furthermore, after the return data frame including the session key ciphertext and the ciphertext payload is synchronized to the ground control station, the ground control station locates the access control policy corresponding to the current session based on the session identifier, time discretization result and the UAV's unique identifier in the return data frame.

[0034] When the UAV's unique identifier meets the access control policy, the ground control station decrypts it; otherwise, it discards the current transmitted data frame and records it as an abnormal event.

[0035] Compared with existing technologies, the significant advantages of this invention are as follows: By introducing airspace attribute authentication and policy-based access control into the system, this invention achieves dynamic binding between encrypted boundaries and physical airspace boundaries, effectively solving the problems of static keys, out-of-bounds communication, and access lag in UAV communication scenarios. This method improves the data confidentiality and access controllability of the communication link, and enhances the security protection capabilities and airspace compliance of the UAV system. Attached Figure Description

[0036] Figure 1 This is a flowchart of the flight preparation phase of the present invention;

[0037] Figure 2 This is a flowchart of the flight execution phase of the present invention;

[0038] Figure 3 This is a flowchart of the data landing stage of the present invention;

[0039] Figure 4 This is a graph showing the fluctuation of CPU utilization and memory overhead in a desktop-based simulation test environment. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] This invention aims to address the problems of static key usage, decoupling of security and airspace boundaries, and lagging access control in existing UAV communication processes. It proposes a low-altitude data encryption method that integrates spatiotemporal attributes. This method encodes the mission airspace in a three-dimensional grid and, based on this, combines the national cryptographic algorithm system SM9, SM3, and SM4_GCM to establish a dynamic key collaboration mechanism that integrates location, time, and mission, achieving security, controllability, and traceability of the UAV communication link under the national cryptographic system. This method achieves integrated management and control throughout the entire process by collaboratively constructing a central control platform (running the national cryptographic trust center and policy center), the UAV, and the ground control station.

[0042] like Figures 1-3 As shown, the present invention provides a low-altitude data encryption method that integrates spatiotemporal attributes, comprising the following steps:

[0043] 1. Flight preparation phase: National cryptographic trust initialization and policy binding pre-configuration mechanism based on three-dimensional spatial grid.

[0044] This stage involves system initialization and mission planning. By establishing a three-dimensional spatial grid system consistent with the GB / T40087-2021 standard, the initial binding of the UAV mission space with the national cryptographic encryption system is achieved. This stage uses spatial coding, mission strategies, and national cryptographic keys as the core to achieve pre-alignment between the encryption system and the airspace supervision system, ensuring security consistency from the source of flight missions.

[0045] The main steps include:

[0046] (1) Initialization of national cryptographic trust and binding of master key for three-dimensional spatial grid.

[0047] (1-1) Trust Center Deployment and Master Key Generation.

[0048] Deploy the National Cryptographic Trust Center (KGC) in a system security environment and establish the system root key based on the national commercial cryptographic algorithm framework. Select security parameters. The system generates a master key (MSK) and a master public key (MPK) using the SM9 identity cryptography algorithm. The master key (MSK) is permanently stored within the Hardware Security Module (HSM) and is not exported from the system. The master public key (MPK) is a public key generated by the China Cryptography Trust Center (KGC) and is located at the top level of the key hierarchy, forming an asymmetric key pair with the master private key. The master public key is publicly released to internal device nodes within the system.

[0049] (1-2) Identity registration and key distribution.

[0050] Each device node (drone, ground control station) submits its identity identifier (ID), device serial number (SN), and certificate (Certificate) to the National Cryptographic Trust Center. After authentication, the National Cryptographic Trust Center uses the master key MSK to calculate the drone node's exclusive key.

[0051]

[0052] in, MSK is the exclusive key for the drone node, and it is the master key. To map identity IDs to groups A hash function for a set of points on an elliptic curve.

[0053] After the calculation is completed, the National Cryptographic Trust Center distributes the node private key information packet (including the node private key, identity identifier, certificate information, etc.) through a secure channel. The node's internal security module completes the writing and saving, realizing trusted binding of the node identity and initial key distribution. In addition, based on the access scope of the ground control station (GCS), the Trust Center generates the ground control station's exclusive private key using the same method as generating the exclusive key for the UAV node, and pre-distributes exclusive private keys that meet access control policies to it.

[0054] (1-3) Initialization of the spatial grid system.

[0055] After the National Cryptographic Trust Center completes the master key deployment, the system performs three-dimensional meshing and encoding of the task spatial domain according to the national standard GB / T40087-2021. The system imports coordinate data of the task spatial domain in the CGC2000 coordinate system and sets the mesh level. (The grid hierarchy can be adjusted according to the finer granularity of the task), and a spatial grid index table is generated using a standard encoding function. This spatial grid index table contains the geographical extent of each grid cell and is synchronized to the UAV and ground control station (GCS) to support precise positioning and boundary constraints in the mission airspace.

[0056] (2) Task strategy configuration and algorithm parameter release.

[0057] (2-1) Task strategy definition and loading.

[0058] During the mission planning phase, the system defines mission policies based on the mission type. The policy content includes parameters such as version number, mission identifier, mission type, and mission time window. After the mission policy is configured via the ground control terminal, it is signed and verified by the National Cryptographic Trust Center and simultaneously distributed to the UAV and ground control station (GCS) to ensure the consistency of policy information before mission initiation.

[0059] (2-2) Parameter release.

[0060] The National Cryptography Trust Center packages the three-dimensional grid encoding mapping relationship (spatial grid index table) and algorithm templates (SM3, SM4_GCM, SM9) into a parameter file, which is automatically called and verified by UAV during the task loading stage, realizing an integrated process of spatial mapping and master key initialization binding.

[0061] 2. Flight execution phase: Three-dimensional mesh coding-driven national cryptographic dynamic key derivation and real-time data encryption mechanism.

[0062] During mission execution, the UAV calculates the 3D grid code in real time and uses this code as a dynamic variable in the communication session key. It is derived from the identity system in the hash algorithm (SM3) and the identity cryptography algorithm of SM9 to generate dynamic keys, so that the keys are tightly coupled with location, time and task policy; the SM4_GCM (SM4in Galois / Counter Mode) algorithm is used to implement end-to-end encryption of the data link, and the key update is dynamically triggered by the change of the spatial boundary, so as to achieve full synchronization between the physical boundary and the encryption boundary.

[0063] The main steps include:

[0064] (3) Real-time positioning and attribute set construction.

[0065] (3-1) Acquisition and fusion of multi-source positioning signals.

[0066] After the UAV mission is initiated, it collects location information in real time through a GPS / BeiDou dual-mode positioning module, and performs dynamic attitude compensation by combining data from the onboard IMU (Inertial Measurement Unit) and barometric altimeter. The system uses a weighted fusion algorithm to correct the multi-source data and outputs high-precision spatial coordinates (lat, lon, alt).

[0067] (3-2) Construction of attribute set.

[0068] The system generates a UAV attribute set based on real-time location and mission control parameters (mission type, time discretization result). This set of drone attributes describes the spatiotemporal and mission characteristics of the drone during its mission cycle. It is defined as follows:

[0069]

[0070] Wherein, GridCode represents the 3D grid encoding, a spatially unique identifier generated according to the preset 3D spatial grid standard (GB / T40087-2021 grid encoding algorithm); MissionType represents the current task type; TimeSlot represents the time discretization result, used for time-series index calculation:

[0071]

[0072] in, In order to harmonize the world in the present time, For time slices (e.g., 10s).

[0073] Drone Attribute Set The basic semantic structure that constitutes the UAV mission data not only provides mission scenario context information, but also serves as a key input for encrypted indexes and on-chain identifiers.

[0074] (3-3) Dynamic updating and validation of attributes.

[0075] The system dynamically updates based on real-time trajectory and task status changes (spatial grid location, time). Content. When GridCode or TimeSlot is updated, the system automatically triggers an update event to ensure that the drone attribute set is accurate, valid, and time-trackable throughout its entire lifecycle.

[0076] (4) Dynamic key derivation and dynamic policy update mechanism.

[0077] (4-1) Task validity verification and attribute derivation.

[0078] This stage is the root node of the dynamic key system. The system first verifies the legitimacy of the task context, and only allows the UAV to derive a local key specific to the task cycle if both the task space and time meet the authorization constraints. It is used for subsequent key derivation and encryption operations.

[0079] Calculate the 3D mesh code of the current location In the verification phase, GridCode, a 3D grid encoding algorithm, represents the real-time position mapping result of the UAV. ):

[0080]

[0081] in, This is the location mapping function; lat, lon, and alt represent the latitude, longitude, and elevation of the UAV's current location, respectively.

[0082] Verify whether the space and time constraints meet the authorization requirements:

[0083]

[0084] Among them, AuthorizedGridSet is a collection of task authorization spatial grids; and These represent the start and end times (default values) of the task authorization, respectively.

[0085] Task access is considered valid only if the conditions are met. If the authorization constraints are not met, the system determines that the current state is out of bounds or in violation and does not derive a session key.

[0086] The system generates only under authorized constraints. This ensures that each key is bound to the task execution environment, preventing cross-domain use and temporal / spatial tampering.

[0087] After completing the mission validity verification, the drone uses the drone attribute set for the current mission. Calculate the local attribute hash h and derive a local key specific to the task cycle. It is used for subsequent key derivation and encryption operations.

[0088] The calculation formula is as follows:

[0089]

[0090]

[0091]

[0092] in, The base point of the elliptic curve It is a temporary key. For hash operation, A unique key for each drone node. It integrates four factors: space (GridCode), task (MissionType), time (TimeSlot), and task policy version (PolicyVersion), ensuring its uniqueness and non-reusability in different task scenarios.

[0093] (4-2) Short-cycle session key derivation and isolation design.

[0094] After completing the task and attribute validity verification, the local key... Used to generate short-lived session keys By finely partitioning the key space in terms of both the time discretization result and the random factor dimension, the system ensures that each communication cycle corresponds to a unique key. This isolates key replay and association attacks in both physical space and time dimensions.

[0095] First, the system calls the True Random Number Generator (TRNG) to generate a 256-bit random factor r:

[0096]

[0097] The random factor r has independent and high-entropy randomness, providing unpredictable random input for each session key derivation process, ensuring that multiple key derivations under the same task context are independent of each other.

[0098] Subsequently, the system utilizes the local key The session key is derived from the random factor r and the time discretization result TimeSlot. :

[0099]

[0100] in, This refers to the SM3 function, a Chinese national cryptographic hash algorithm. is the local key, r is the random factor generated by TRNG, and the output of the above operation is a 256-bit hash result.

[0101] The dynamic input space, formed by different combinations of r and TimeSlot, allows each session key to... Maintaining complete independence across different time slices and different derived instances. Through this short-cycle key segmentation design, the system achieves both "intra-task domain independence" and "time-slice key isolation": even within a single time slice... Even if the attacker obtains the key, they will not be able to deduce the session key in other time slices or other task scenarios, thus significantly improving the overall key system's resistance to attacks.

[0102] (4-3) Attribute-based policy-driven key encryption and secure distribution.

[0103] To prevent unauthorized ground terminals or intermediate agents from resuming operations. The system uses the IB-ABE (identity-based attribute encryption) mechanism for policy encapsulation.

[0104] Access control policy construction:

[0105]

[0106] Among them, Policy is the mission access control policy; ID is the unique identifier of the drone; This represents the intersection of two sets; GridCode is the current 3D grid code of the UAV; AllowedRegions is the set of task regions defined by the task strategy; MissionType is the current task type. When simultaneously satisfying (1) the UAV's unique identifier belongs to a UAV registered with the trust center... (2) The current three-dimensional mesh encoding of the UAV belongs to the task area set defined by the task policy; (3) When the current task type is a predefined task type, the access control policy result is true (Policy=True).

[0107] This access control policy specifies the target GCS identity, spatial authorization scope, and task type matching conditions.

[0108] Key encryption:

[0109]

[0110] in, Session key The session key ciphertext generated after attribute-based encryption; It is the session key used during communication; Policy is the access control policy, which defines the attribute conditions that a user must possess to decrypt the data; MPK is the master public key, which is generated by the attribute management center and made public to all nodes; This indicates an encryption operation using an attribute-based encryption algorithm. The session key can only be obtained by decrypting using the corresponding private key if and only if the user attributes at the ground control station satisfy the access control policy. .

[0111] After encryption, the session key is converted into a ciphertext object carrying access attributes, which can only be decrypted by GCS that meets the access control policy.

[0112] Table 1. Ciphertext Structure

[0113]

[0114] This attribute-driven encryption design embeds key access control logic into the cryptographic system, ensuring that the generation, distribution, and use of session keys are all subject to a unified policy, thereby naturally blocking unauthorized access at the protocol level.

[0115] (4-4) The session key is sent up and synchronized with the ground control station.

[0116] when After generation, the UAV encapsulates it into a synchronization frame and sends it to the ground control station (GCS) via a secure channel to complete air-to-ground key consistency synchronization. The synchronization transmission uses a secure communication link based on the SM9 algorithm for encryption throughout the process. Plaintext must never appear in the wireless link.

[0117] GCS received Then, decryption is performed using the exclusive private key:

[0118]

[0119] in, It is the session key obtained through decryption; It is a session key ciphertext generated using an attribute-based encryption algorithm; It is a private key owned by the ground control station, used to perform decryption according to the access policy; For attribute-based encryption and decryption functions, the session key can be successfully recovered only if the user attributes of the ground control station satisfy the access control policy. It also passes the cache; otherwise, it returns an error receipt and requests resynchronization.

[0120] This automatic air-to-ground two-way synchronization ensures that the UAV and GCS maintain secure and consistent encryption parameters in each time slice, thereby effectively preventing time slot misalignment attacks and delayed replay behavior.

[0121] (4-5) Key rolling mechanism that links periodic updates with policies.

[0122] To ensure that session keys have the ability to be updated on a rolling basis and remain sensitive to policy changes, the system achieves key rolling and continuous link security through a dual triggering method of time slice accumulation and policy version change.

[0123] The system deploys scheduled update logic, and the update trigger conditions include:

[0124] (1) The total number of task time slices reaches 6 cycles (e.g., 60s);

[0125] (2) The Policy Center detected a change in PolicyVersion (such as task area migration, access permission adjustment or revocation).

[0126] When any condition is met, the system triggers a session key refresh process. After the refresh, the UAV and the ground control station (GCS) automatically negotiate and derive a new session key within the new time slice. Synchronization is achieved through receipts, enabling seamless password switching in the underlying protocol without any noticeable disruption to business communication or requiring manual intervention.

[0127] To enable the linkage between policy changes and key updates, the system introduces the task policy version number, PolicyVersion, into the session key derivation function.

[0128] When the Policy Center updates the PolicyVersion, the UAV is re-forged locally based on the new version. The original session key and its identifier become invalid immediately and will no longer be used for subsequent encryption and decryption related communication sessions. The session will be automatically terminated or renegotiated.

[0129] Through periodic updates and policy linkage design, the session key remains short-cycled, unpredictable, and bound to the current policy throughout the entire mission lifecycle. Even if a single time-slice key is leaked, it is impossible to deduce the key under other time-slices or policy versions, effectively resisting replay, cross-domain abuse, and unauthorized access, and ensuring the continuous security of the UAV communication link.

[0130] 3. Data landing stage: National cryptographic decryption and access control mechanism based on spatial domain attributes.

[0131] After the encrypted data from the UAV is transmitted back to the ground control center or storage node, the system simultaneously verifies the "validity of the national cryptographic key" and the "consistency of three-dimensional airspace attributes" during the data reception and decryption phases to ensure that data access permissions strictly correspond to the generated airspace. Through mechanisms such as key validity verification, attribute matching, and policy version comparison, data security is guaranteed throughout the entire mission lifecycle.

[0132] The main steps include:

[0133] (5) Encrypted data transmission.

[0134] After completing session key negotiation and synchronization, the UAV will use the session key valid within the current time slice during subsequent tasks. Business data is encrypted and encapsulated, and then transmitted back to the ground control station (GCS) via the drone link to achieve end-to-end secure data transmission.

[0135] Before encryption, the UAV encapsulates the business data into plaintext payload according to a preset message format. The message format includes at least two parts: a message header and business data. The message header field carries control fields such as the session ID, time slot, and message sequence number (MsgSeq), which are used to identify the message type and associate it with the current session key. The message header marks the effective time slice of the key and supports replay detection; the service data section carries the specific telemetry data or mission payload content. By explicitly carrying the SessionID and TimeSlot fields in the message header, the receiving end can quickly locate the corresponding session key, which works in conjunction with the aforementioned key rolling and access control mechanisms.

[0136] In obtaining Then, the UAV uses the session key As the master key for the symmetric cryptography algorithm, the SM4_GCM block cipher algorithm is invoked to encrypt and protect the plaintext payload, generating the corresponding ciphertext payload. :

[0137]

[0138] in, It is an abstract representation of "SM4 encryption functionality in GCM mode".

[0139] The SM4_GCM mode generates an authentication tag while encrypting the data to ensure that it has not been tampered with or forged during transmission. The UAV encapsulates the ciphertext payload along with the aforementioned message header fields into a return data frame, which is then sent to the GCS through the currently established secure link.

[0140] During the session, if a periodic update or policy linkage is triggered, resulting in a loss of the session key... With rolling updates, the UAV automatically switches to the latest session key for subsequent data encryption in each new time slice. Since the key negotiation and update process is transparent to upper-layer services, the encrypted data transmission appears continuous and stable, avoiding link interruptions or data loss due to key changes. This ensures both security and real-time performance and reliability.

[0141] (6) Access control and data decryption.

[0142] After receiving encrypted data from the UAV, the Ground Control Station (GCS) first performs session context identification and access control checks based on the message header information. Then, provided the policy verification passes, it uses the corresponding session key. Decrypt the data and restore the original business load.

[0143] Upon receiving the returned data frame, GCS uses the SessionID, TimeSlot, and UAV identification information carried in the message to locate the access control policy corresponding to the current session. The system first matches and verifies the UAV's identity attributes, task type, and spatial grid location against the locally stored access control policy to determine if it has the permission to access and return this type of data under the current policy version (PolicyVersion). Only if the access control policy is satisfied will GCS proceed to the subsequent decryption process; otherwise, the data frame is discarded and recorded as an abnormal event.

[0144] After access control is granted, GCS retrieves or re-derives a session key from the local key management module that matches the current SessionID, TimeSlot, and PolicyVersion. And use it as the master key for the SM4_GCM decryption module to decrypt the ciphertext payload. Perform decryption and integrity verification:

[0145]

[0146] in, It is an abstract representation of "SM4's decryption function in GCM mode".

[0147] If the authentication tag verification fails during decryption, it indicates that the data has been tampered with or forged during transmission. The system will reject the data frame and may trigger an alarm. Only if the key matches correctly and the integrity verification passes will the system receive and send the decrypted plaintext data. Up to the upper-level task processing module.

[0148] By introducing access control and policy verification on the decryption side, the system tightly binds decryption permissions to key validity: even if an attacker intercepts the returned ciphertext and attempts to replay or forward it across domains, they will be unable to decrypt because they do not possess a session key that matches the current time slice and policy version. Furthermore, it cannot pass the authentication verification of SM4_GCM, and it is impossible to recover valid plaintext. Combined with the aforementioned periodic update and policy linkage mechanism, the access control and data decryption process remains consistent with the latest policy and session key throughout the entire task cycle, thereby achieving fine-grained control and secure implementation of data access at the receiving end.

[0149] This invention underwent performance evaluation in a desktop-based simulation environment: the processor was an Intel Core i5-12400F, and the flight control, link transmission, and command and dispatch processes were all reproduced in this simulation environment. Without altering the original "physical link abstraction" and service protocol stack logic, the SM9 identity system, SM3 hashing, SM4_GCM encryption / decryption, and attribute-based access control logic were embedded into the communication security module. The performance of this solution was tested through typical mission airspace flight tasks.

[0150] The experiment selected a three-dimensional spatial grid divided according to the GB / T40087-2021 standard to observe the communication behavior of UAVs in scenarios such as normal cruise within the authorized grid, deliberate flight into the unauthorized grid, rapid boundary crossing and boundary crossing. The experiment focused on recording indicators such as control message overhead, CPU utilization and memory overhead of the UAV terminal (simulation terminal).

[0151] Experimental results show that on the above simulation platform, control messages introduced by key negotiation and policy distribution account for less than 1% of the total communication volume (affected by the policy and key update frequency). Figure 4 The top chart is a line graph of CPU utilization, and the bottom chart is a line graph of memory usage. Figure 4As shown, during the flight execution phase, even during multiple policy adjustments and key updates, the single-core CPU utilization of the communication security module remained stable at approximately 30% on the UAV, with fluctuations of less than 5%; memory usage also remained at approximately 9.27MB, showing only slight fluctuations with policy and key updates. These results demonstrate that even with frequent security attribute and key maintenance, the CPU and memory resource consumption of this solution remains stable and controllable, and the overall performance overhead is within the acceptable range of current mainstream UAV platforms, providing valuable reference for practical engineering deployments.

[0152] Based on this, the session key is tightly bound to attributes such as 3D spatial grid encoding, task type, and time slice: once the UAV goes out of the authorized grid or the policy version is updated, the key and data frame generated under the old attributes or old policies will automatically become invalid. Out-of-bounds data cannot be decrypted on the ground station side, and replay attack data packets cannot pass the authentication tag verification due to inconsistent attributes. This demonstrates that this solution has the comprehensive advantages of strong spatiotemporal fine access control capabilities, high security, and easy engineering implementation in existing UAV systems, under the premise of controllable resource consumption.

[0153] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-altitude data encryption method integrating spatiotemporal attributes, characterized in that, The low-altitude data encryption method that integrates spatiotemporal attributes includes: The National Cryptography Trust Center constructs a spatial grid index table for the mission airspace based on a preset three-dimensional spatial grid standard, distributes exclusive keys generated by the SM9 identity cryptography algorithm to UAVs, distributes exclusive private keys generated by the SM9 identity cryptography algorithm to ground control stations, and generates mission policies in the policy center. The UAV acquires its own location information, current Coordinated Universal Time and mission type in real time, and constructs a UAV attribute set that includes a three-dimensional mesh code of the current location, the mission type of the current mission cycle and the time discretization result; The drone derives the session key for the current communication cycle using a hash algorithm based on the drone attribute set and exclusive key. A task cycle contains at least one communication cycle, and a communication cycle consists of a preset number of consecutive time slices. When the preset number of time slices is reached, or when a change in the version number of the task policy is detected, the session key is updated and the next communication cycle begins. The drone uses an attribute-based encryption algorithm, combined with access control policies, to encrypt the session key and generate session key ciphertext. The drone encrypts its service data based on the session key, generating a ciphertext payload. The returned data frame, including the ciphertext of the session key and the ciphertext payload, is synchronized to the ground control station. The ground control station, which meets the access control policy, decrypts the data using its exclusive private key to obtain the session key and restore the drone's service data.

2. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, The National Cryptography Trust Center constructs a spatial grid index table for the mission airspace based on a preset three-dimensional spatial grid standard, including: Import the coordinate data of the task's airspace; By mapping coordinate data to the corresponding three-dimensional grid using a preset three-dimensional spatial grid standard, a three-dimensional grid code for each grid is generated, resulting in a spatial grid index table.

3. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, The time discretization result is obtained by discretizing the time slice based on the current Coordinated Universal Time.

4. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, Before deriving the session key, the following is also included: Verify whether the authorization constraints are met. The authorization constraints include: the 3D mesh code of the current position is within the task authorization spatial mesh set corresponding to the mesh index table; and the current Coordinated World Time is during the task authorization period. If the authorization constraints are met, a session key is derived; otherwise, no session key is derived.

5. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, The drone derives the session key for the current communication period using a hash algorithm based on its attribute set and proprietary key, including: Based on the UAV attribute set and mission strategy version number, a hash algorithm is used to calculate the local attribute hash. Based on local attribute hashing and a private key, a temporary key is calculated using a hash algorithm; Multiply the temporary key by the base point of the elliptic curve to obtain the local key; A true random number generator is invoked to generate a random factor, and the session key for the current communication period is derived based on the random factor, the local key, and the time discretization result.

6. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 4, characterized in that, The method of encrypting the session key using an attribute-based encryption algorithm in conjunction with an access control policy to generate session key ciphertext includes: The session key is encrypted only if the drone's unique identifier, the current 3D mesh encoding, and the current task type all match the access control policy, as expressed by the formula: in, This represents the ciphertext of the session key; Indicates the session key; Indicates the access control policy; Indicates the master public key; This indicates an encryption operation using an attribute-based encryption algorithm; The access control policy is as follows: The drone's unique identifier belongs to a drone registered with the trust center. The current 3D mesh encoding of the UAV belongs to the task region set defined by the task strategy; the current task type is a predefined task type.

7. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, The encryption of UAV service data based on the session key to generate a ciphertext payload includes: The drone service data is encapsulated with a pre-formatted message header to obtain a plaintext payload; the message header includes: session identifier, time discretization result, and message sequence number; Using the session key as the master key, the plaintext payload is encrypted using the SM4_GCM block cipher algorithm, generating the ciphertext payload and the corresponding authentication tag.

8. The low-altitude data encryption method integrating spatiotemporal attributes according to claim 1, characterized in that, After the return data frame, which includes the session key ciphertext and the ciphertext payload, is synchronized to the ground control station, the ground control station locates the access control policy corresponding to the current session based on the session identifier, time discretization result and the UAV's unique identifier in the return data frame. When the UAV's unique identifier meets the access control policy, the ground control station decrypts it; otherwise, it discards the current transmitted data frame and records it as an abnormal event.

Images