Passive intelligent lock based on NFC radio frequency power supply and security authentication method thereof

Abstract

The application relates to a passive intelligent lock based on NFC radio frequency power supply and a security authentication method thereof. The intelligent lock comprises an energy collection and storage module, which collects energy from an external radio frequency field through a near-field electromagnetic coupling mode, stores the energy in an energy storage unit after resonance matching, rectification and voltage stabilization, a low-power mechanical transmission mechanism, which sequentially performs state switching and power transmission under the constraint of limited instantaneous power, state switching is electromagnetically driven at a first energy consumption level, and the state switching is converted between two states of blocking and conducting a torque output path, power transmission is at a second energy consumption level, a worm gear transmission pair driven by a motor amplifies and outputs torque to drive a lock bolt, a security authentication and communication module, which completes identity authentication and outputs a control instruction within a limited time window, and the low-power mechanical transmission mechanism is configured to start step-by-step energy supply based on limited instantaneous power only when the control instruction is allowed to be executed. The application realizes safe, reliable and intelligent management of the lock under a passive environment.

Description

Technical Field

[0001] This invention relates to the field of smart locks and Internet of Things security technology; in particular, it relates to a passive smart lock based on NFC radio frequency power supply and its security authentication method, which is suitable for passive or low-energy environments such as underground power transmission channels and integrated utility tunnels. Background Technology

[0002] Existing smart locks for underground passages face the following technical bottlenecks: Energy supply dilemma: Locks are usually deployed in environments without a stable power source. Battery power has a limited lifespan, high maintenance costs, and cannot meet the high energy consumption requirements of security calculations and mechanical drives.

[0003] Conflict between security authentication and real-time management: In an environment where internal and external networks are isolated, smart locks are in an "information island" state, making it difficult to achieve real-time synchronization of online identity authentication, authorization control, and operation logs.

[0004] Insufficient mechanical structure reliability: Traditional locks are prone to mechanical jamming in dirty or humid environments, and have weak anti-pry and tensile strength, making it difficult to meet the high-level security requirements of GA / T73-2015 "Mechanical Anti-theft Locks".

[0005] Security and energy efficiency are difficult to balance: high-strength encryption algorithms (such as asymmetric encryption) consume a lot of computing power, which is in stark contrast to the limited energy supply in passive environments.

[0006] Therefore, there is an urgent need for an intelligent lock system that can achieve secure authentication, reliable driving, and information synchronization under passive conditions. Summary of the Invention

[0007] Based on the above analysis, this invention aims to disclose a passive smart lock based on NFC radio frequency power supply and its security authentication method. Through efficient wireless energy harvesting, low-power mechanical transmission, lightweight two-way authentication and asynchronous information synchronization mechanism, it enables safe, reliable and intelligent management of locks in the current passive environment.

[0008] This invention discloses a passive smart lock based on NFC radio frequency power supply, comprising: The energy harvesting and storage module is used to harvest energy from an external radio frequency field through near-field electromagnetic coupling, and store it in the energy storage unit after resonant matching, rectification and voltage regulation, so as to provide limited instantaneous power output within a limited time window; A low-power mechanical transmission mechanism is used to sequentially perform state switching and power transmission under limited instantaneous power constraints. The state switching is electromagnetically driven at a first energy consumption level, switching between two states: blocking and opening the torque output path. The power transmission is amplified and output to drive the locking tongue through a worm gear transmission pair driven by a motor at a second energy consumption level. The sequential execution is manifested in the energy supply sequence of first opening the torque output path and then driving the locking tongue. The security authentication and communication module is used to complete identity authentication and output control commands within the limited time window; the low-power mechanical transmission mechanism is configured to start step-by-step energy supply based on the limited instantaneous power only when the control command is allowed to be executed.

[0009] Furthermore, the low-power mechanical transmission mechanism includes a state switching unit, a power transmission unit, and an energy distribution unit; The state switching unit is configured to switch between a first state and a second state at a first energy consumption level under the action of electromagnetic force. The first state is to block the torque output path of the power transmission unit, and the second state is to connect the torque output path. The power transmission unit, including the worm gear transmission pair and its drive motor, is configured to amplify the input torque and output it to the locking tongue at a second energy consumption level. The energy distribution unit is configured to distribute energy to the state switching unit and the drive motor in a preset sequence based on the constraint of the limited instantaneous power, so that the state switching unit completes the state switching before the power transmission unit.

[0010] Furthermore, the state switching unit includes: The first movable component is linked to the torque output path; An elastic reset element is used to drive the first movable element to the blocking position; An electromagnetic drive is used to overcome the elastic force of the elastic reset member and drive the first movable member to the conducting position.

[0011] Furthermore, the first movable member is arranged orthogonally to the output end of the worm gear transmission pair. When the first movable member is in the blocking position, it radially engages with the circumferential groove of the output end to form a mechanical lock. When it is in the conducting position, it radially disengages from the groove to release the lock.

[0012] Furthermore, the elastic reset member is configured to automatically drive the first movable member back to the blocking position when the electromagnetic drive member is de-energized, so as to restore the mechanical locking state.

[0013] Furthermore, the low-power mechanical transmission mechanism includes a brake shaft, a control shaft, a drive shaft, a locking ball, an electromagnet, a return spring, a worm gear transmission pair, and a drive motor; The brake shaft is arranged longitudinally, with its upper end fixedly connected to the locking tongue and its lower end connected to the output end of the worm gear of the worm gear transmission pair. The brake shaft is provided with an annular groove in the circumferential direction. The control shaft is arranged laterally and is orthogonal to the brake shaft. One end is abutted against the lock housing by a return spring, and the other end is coaxially aligned with the electromagnet. The cylindrical surface of the control shaft is provided with a locking ball receiving hole. The drive shaft is arranged laterally, with one end coaxially connected to the output shaft of the drive motor and the other end connected to the worm input end of the worm gear transmission pair. The locking ball is configured to partially embed into the receiving hole and partially engage with the brake shaft slot under the thrust of the return spring to form a radial mechanical lock, blocking the torque output path of the brake shaft, or to displace laterally with the control shaft under the axial attraction force generated by the electromagnet being energized, thereby releasing the lock and opening the torque output path of the brake shaft. The drive motor is configured to consume electrical energy at the second energy consumption level to output initial torque, which is transmitted to the worm gear transmission pair via the drive shaft, amplified, and then output to the locking tongue via the brake shaft.

[0014] Furthermore, the security authentication and communication module is configured to employ a hybrid encryption strategy of first asymmetric and then symmetric encryption, wherein, The authentication phase employs asymmetric encryption: it uses two-way identity authentication based on public key infrastructure, and achieves strong identity authentication through the exchange of digital certificates between electronic keys and locks, random number challenges and two-way signature verification; Symmetric encryption is used during the communication phase: After authentication, a temporary session key is generated through negotiation based on the ECDH protocol, and subsequent unlocking operation commands are transmitted using AES-128 / 256 symmetric encryption.

[0015] Another aspect of the present invention discloses a security authentication and drive control method for a passive smart lock based on NFC radio frequency power supply as described above, characterized in that it includes: Within a limited time window, energy is harvested and stored through near-field electromagnetic coupling to provide limited instantaneous power; Within the specified time window, identity authentication is completed and control commands are generated; Only when the control command is allowed to be executed, based on the limited instantaneous power, the state switching and power transmission are executed sequentially: first, electromagnetic drive at the first energy consumption level is used to conduct the torque output path, and then the torque is amplified and output through the worm gear transmission pair driven by the motor at the second energy consumption level to drive the locking tongue.

[0016] Furthermore, the process of completing identity authentication and generating control commands includes the following steps: The offline two-way authentication step involves exchanging digital certificates with an external electronic key and performing two-way signature verification within the limited time window. The session key negotiation step involves negotiating and generating a temporary session key based on the ECDH protocol after successful authentication. The command encryption transmission step involves using the temporary session key to encrypt and transmit the control commands. In the asynchronous information synchronization step, the operation log is temporarily stored in local non-volatile memory and uploaded in batches when communication is established with the electronic key next time, and then synchronized to the background management system by the electronic key.

[0017] Furthermore, the asynchronous information synchronization step also includes: The log management sub-step divides the local non-volatile memory into a circular buffer, stores operation logs in time sequence and adds priority identifiers; when the storage capacity reaches a preset threshold, high-priority logs are retained first, and the earliest low-priority logs are overwritten in time sequence. The differential synchronization sub-step adds a unique lock identifier, timestamp, and verification hash to each operation log; after the electronic key is read in batches, it is sorted locally based on the unique lock identifier and timestamp, and only incremental data is uploaded when it is synchronized to the background management system.

[0018] The present invention has at least the following beneficial effects: Completely passive: Powered by NFC radio frequency and stored in supercapacitors, the lock operates without batteries, eliminating maintenance and adapting to extreme environments.

[0019] High security and low energy consumption are combined: a hybrid encryption strategy of "asymmetric first and then symmetric" is adopted, which reduces the authentication energy consumption by an order of magnitude while ensuring strong security authentication.

[0020] Highly reliable mechanical drive: Optimized transmission mechanism and step-by-step drive strategy achieve high torque output with minimal current, and the lock tongue can withstand static pressure ≥6000N, meeting the highest level of anti-theft requirements.

[0021] Intelligent information management: By using the "electronic key intermediary" model, the problem of information synchronization for passive island locks is solved, and the operation is traceable and the management is closed-loop in an offline environment. Attached Figure Description

[0022] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 This is a schematic block diagram of the passive smart lock based on NFC radio frequency power supply in an embodiment of the present invention; Figure 2 This is a schematic diagram of the mechanical structure of the smart lock in an embodiment of the present invention; Figure 3This is a timing diagram of smart key authorization for unlocking and information synchronization in the smart lock system of this invention embodiment. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0024] Example 1 One embodiment of the present invention discloses a passive smart lock based on NFC radio frequency power supply, such as... Figure 1 As shown, it includes: The energy harvesting and storage module is used to harvest energy from an external radio frequency field through near-field electromagnetic coupling, and store it in the energy storage unit after resonant matching, rectification and voltage regulation, so as to provide limited instantaneous power output within a limited time window; A low-power mechanical transmission mechanism is used to sequentially perform state switching and power transmission under limited instantaneous power constraints. The state switching is electromagnetically driven at a first energy consumption level, switching between two states: blocking and opening the torque output path. The power transmission is amplified and output through a worm gear transmission pair driven by a motor at a second energy consumption level to drive the locking tongue. The sequential execution is arranged in a step-by-step energy supply sequence, which first opens the torque output path and then drives the locking tongue. The security authentication and communication module is used to complete identity authentication and output control commands within the limited time window; the low-power mechanical transmission mechanism is configured to start the step-by-step energy supply based on the limited instantaneous power only when the control command is allowed to be executed.

[0025] The solution in this embodiment also includes a lock control module, which is used to coordinate the working timing of the energy harvesting and storage module, the security authentication and communication module, and the low-power mechanical transmission mechanism.

[0026] Specifically, the energy harvesting and storage module includes a double-layer spiral energy antenna, an LC resonant matching circuit, and a supercapacitor; Among them, the double-layer spiral energy antenna (approximately 32mm in diameter) enhances the inductance value (approximately 4.68µH) through electromagnetic coupling, with a coupling coefficient k≈0.9; the LC resonant matching circuit (resonant capacitor approximately 30pF) operates at a frequency of 13.56MHz, maximizing wireless energy transmission efficiency; and an integrated 1000µF / 16V supercapacitor serves as an energy storage unit to meet the short-term high-current drive requirements.

[0027] When the smart key is brought close to the lock within the effective NFC communication range (typically ≤4cm), the double-layer spiral energy antenna collects radio frequency energy through electromagnetic induction, which is then rectified, regulated, and used to charge the supercapacitor and activate the lock control circuit.

[0028] Specifically, the lock control module is configured to: wake up the security authentication and communication module to enter the authentication process when the supercapacitor voltage reaches the working threshold; output a timing control signal to the energy distribution unit of the low-power mechanical transmission mechanism when the security authentication and communication module outputs the permission to execute control command; and switch to the energy supply of the power transmission stage after detecting the state switching completion signal.

[0029] More specifically, the lock control module includes a microcontroller unit (MCU), a voltage detection circuit, and a timing control circuit. The voltage detection circuit monitors the voltage at the supercapacitor terminals in real time. When the terminal voltage reaches a first threshold (e.g., 8V), it allows the power supply to the state switching unit to be activated. When the terminal voltage reaches a second threshold (e.g., 10V) and a state switching completion signal is received, it allows the power transmission unit to be activated.

[0030] The timing control circuit includes a first electronic switch and a second electronic switch. The first electronic switch is connected in series in the power supply circuit of the electromagnetically driven electromagnet and is controlled by the first GPIO port of the lock control module. The second electronic switch is connected in series in the power supply circuit of the drive motor and is controlled by the second GPIO port of the lock control module. A dead time (e.g., 10ms-20ms) is set between the high-level signals output by the two ports to ensure that the motor starts only after the electromagnet is completely de-energized, avoiding the superposition of peak currents caused by the simultaneous conduction of the two circuits.

[0031] Specifically, the low-power mechanical transmission mechanism adopts a step-by-step drive design of first electromagnetic unlocking and then worm gear transmission. The core purpose is to balance the high reliability and high torque requirements of mechanical drive with low power consumption control under the constraints of a passive environment.

[0032] The low-power mechanical transmission mechanism includes a state switching unit, a power transmission unit, and an energy distribution unit; it completes the step-by-step energy supply according to the timing sequence of "first guiding the torque path, then driving the locking tongue action".

[0033] The state switching unit is configured to switch between a first state and a second state at a first energy consumption level under the action of electromagnetic force. The first state is to block the torque output path of the power transmission unit, and the second state is to connect the torque output path. The state switching unit includes a first movable component, an elastic reset component, and an electromagnetic drive component.

[0034] The first moving part is linked to the torque output path; Specifically, the first movable member is arranged orthogonally to the output end of the worm gear transmission pair. When the first movable member is in the blocking position, it radially engages with the circumferential groove of the output end to form a mechanical lock, and when it is in the conducting position, it radially disengages from the groove to release the lock.

[0035] The elastic reset element is used to drive the first movable element to the blocking position; Specifically, the elastic reset member is configured to automatically drive the first movable member back to the blocking position when the electromagnetic drive member is de-energized, so as to restore the mechanical locking state.

[0036] The electromagnetic drive component is used to overcome the elastic force of the elastic reset component and drive the first movable component to the conducting position.

[0037] The electromagnetic drive requires only a short-term, small current to complete the unlocking action, with an operating current of approximately 50mA and a duration of 50ms–100ms, resulting in extremely low energy consumption.

[0038] The power transmission unit includes a drive shaft, a worm gear transmission pair, and a drive motor; it enables small torque input and large torque output.

[0039] The drive motor is configured to consume electrical energy at a second energy consumption level to output initial torque; The drive shaft is configured to transmit the initial torque to the worm input end of the worm gear transmission pair; The worm gear transmission pair is configured to amplify the initial torque and transmit it to the locking tongue to drive the locking tongue to move; In a worm gear drive, the helix angle of the worm is smaller than the equivalent friction angle to achieve reverse self-locking. The worm is made of hardened alloy steel, and the worm wheel is made of tin bronze to achieve high torque transmission and low wear within a compact structure.

[0040] The energy distribution unit is configured to distribute energy to the state switching unit and the drive motor sequentially according to a preset timing sequence based on the constraint of the limited instantaneous power, so that the state switching unit completes the state switching before the power transmission unit; thereby realizing step-by-step driving. The sequential execution of the energy supply timing is arranged as follows: first, the torque output path is activated, and then the locking tongue is driven.

[0041] In a more specific plan, The low-power mechanical transmission mechanism includes a brake shaft, a control shaft, a drive shaft, a locking ball, an electromagnet, a return spring, a worm gear transmission pair, and a drive motor; the mechanical structure can be referred to as follows. Figure 2 .

[0042] The brake shaft is arranged longitudinally, with its upper end fixedly connected to the locking tongue and its lower end connected to the output end of the worm gear of the worm gear transmission pair. The brake shaft is provided with an annular groove in the circumferential direction. The control shaft is arranged laterally and is orthogonal to the brake shaft. One end abuts against the lock housing through a return spring, and the other end is coaxially aligned with the electromagnet. The cylindrical surface of the control shaft is provided with a locking bead receiving hole. The drive shaft is arranged laterally, with one end coaxially connected to the output shaft of the drive motor and the other end connected to the worm input end of the worm gear transmission pair. The locking ball is configured to partially embed into the receiving hole and partially engage with the brake shaft slot under the thrust of the return spring to form a radial mechanical lock, blocking the torque output path of the brake shaft, or to displace laterally with the control shaft under the axial attraction force generated by the electromagnet being energized to release the lock and open the torque output path of the brake shaft. The drive motor is configured to consume electrical energy at the second energy consumption level to output initial torque, which is transmitted to the worm gear transmission pair via the drive shaft, amplified, and then output to the locking tongue via the brake shaft.

[0043] After the unlocking operation is completed, the power supply to the motor and electromagnet is cut off. The brake shaft return spring and control shaft return spring release their elastic potential energy, driving the brake shaft and control shaft back to their initial positions. The locking ball re-locks under the spring force, restoring the mechanical self-locking state. Snap rings axially position each shaft component to prevent loosening and ensure the stability of the lock in subsequent operations.

[0044] The lock is suitable for harsh environments through a multi-level sealing system. It uses sealing rings to seal key parts, and seals gaskets and rubber plugs to seal reserved holes, so that the overall structure has a protection level of ≥IP65 and can withstand high and low temperatures of -20℃ to 60℃, as well as humid and dirty environments.

[0045] Step-by-step energy supply timing has the following four technical benefits: First, reduce startup energy consumption to adapt to the energy limitations of passive power supply; Passive smart locks rely on NFC radio frequency to harvest energy, but the power supply is limited and cannot support the instantaneous start-up of high-power drive modules. Using a miniature electromagnet for initial operation: a brief attraction of the locking bead is all it takes to release the mechanical self-locking mechanism. This action is simple, consumes extremely low energy, does not require continuous high torque output, and is compatible with the low-power supply capability of NFC.

[0046] If the unlocking is directly driven by the motor, it is necessary to overcome both the self-locking resistance and the transmission load simultaneously. The instantaneous energy consumption will exceed the NFC power supply limit, causing the drive to fail. The step-by-step design breaks down the self-locking and output torque into two low-energy-consumption steps, ensuring sufficient energy.

[0047] The electromagnet operates at a current of approximately 50mA for a duration of 50ms-100ms, and its adsorption stroke is designed to match the radial displacement of the locking beads.

[0048] Second, increase the output torque to meet the requirements of high-safety-level mechanical drive. In scenarios such as underground power transmission channels and utility tunnels, locks have extremely high requirements for anti-pry and tensile strength. However, in passive environments, only low-power micro motors can be used, which cannot directly drive the lock body.

[0049] The torque is amplified by a worm gear mechanism: the motor torque is increased from 0.02 N·m to 1.2 N·m, and the transmission efficiency reaches 88.7%. High torque output is achieved in a compact structure to meet the mechanical force requirements when unlocking.

[0050] Meanwhile, the irreversible transmission characteristics of the worm gear structure can enhance the lock's anti-pry capability. Combined with the logic of unlocking before transmission, it can prevent unauthorized external forces from directly driving the lock tongue, thus improving mechanical security.

[0051] Third, ensure mechanical reliability and adaptability to harsh environments; In underground passages, utility tunnels, and other similar environments, there are issues such as dirt accumulation and dampness. Traditional integrated drive mechanisms are prone to jamming due to increased resistance and lack sufficient strength.

[0052] Step-by-step drive separates the self-locking and drive latches: the electromagnet is only responsible for precisely attracting the locking ball, with a short stroke and less prone to jamming; the worm gear focuses on torque transmission, avoiding a single mechanism from bearing the dual load of unlocking and driving at the same time, reducing the risk of jamming.

[0053] The enclosed structure of the worm gear reduces the impact of dirt accumulation, and combined with a high strength safety factor, it ensures long-term reliable operation in harsh environments, solving the problem of insufficient reliability of traditional lock mechanical structures.

[0054] The high torque output by the worm gear is transmitted to the lock tongue through the lock core transmission assembly. The drive shaft, control shaft, and brake shaft are all made of high-hardness alloy parts. The clearance between each shaft part is ≤0.05mm, and the coaxiality error of the transmission is ≤0.1mm, ensuring accurate torque transmission.

[0055] The final drive of the lock tongue completes the unlocking action. The lock tongue is made of 304 stainless steel and can withstand static pressure ≥6000N, meeting the high-level security requirements of GA / T73-2015 "Mechanical Anti-theft Locks". The unlocking stroke is ≤8mm.

[0056] Fourth, it balances low power consumption and high security, supporting the practical application of passive locks. The core contradiction of passive locks is the conflict between the demand for high security and the low energy supply. Step-by-step driving achieves a balance through division of labor and cooperation.

[0057] The electromagnet is responsible for precise unlocking, solving the problem of high driving resistance in the self-locking state; the worm gear is responsible for stable force transmission, overcoming the shortcoming of low torque in small motors. The combination of the two not only controls the peak unlocking current within the NFC power supply capacity, but also achieves high torque and high security level drive.

[0058] The peak current is controlled within 214mA throughout the entire process.

[0059] Specifically, the security authentication and communication module is used to complete identity authentication and output control commands within the limited time window. The low-power mechanical transmission mechanism is configured to activate the step-by-step energy supply based on the limited instantaneous power only when the control command is allowed to be executed.

[0060] Specifically, the security authentication and communication module integrates an independent security chip and an NFC communication unit to quickly complete two-way authentication of the lock and electronic key within a limited time window powered by NFC radio frequency, and output authorized control commands.

[0061] The security authentication and communication module establishes a data link through the NFC antenna and immediately enters the authentication process after energy acquisition is completed. The entire process is executed within the radio frequency power supply window and does not consume additional lock energy.

[0062] The security chip has built-in digital certificates and keys, supporting PKI two-way authentication, random number challenge, two-way signature verification, and ECDH key negotiation.

[0063] After successful authentication, the security authentication and communication module generates an unlocking control command and outputs a timing control signal to the energy distribution unit of the low-power mechanical transmission mechanism.

[0064] The energy distribution unit supplies power to the electromagnet and drive motor sequentially in time only after receiving a valid enable command, thus completing the step-by-step drive; if no valid enable command is received, the power supply to the mechanical drive is continuously cut off, and any unlocking action is refused.

[0065] The security authentication and communication module adopts a hybrid encryption strategy of "asymmetric first, then symmetric" to balance high security and low power consumption. Asymmetric encryption phase (authentication phase): Employs two-way authentication based on Public Key Infrastructure (PKI), achieving strong authentication through the exchange of digital certificates between electronic keys and locks, random number challenges, and two-way signature verification. This phase uses the Elliptic Curve Cryptography (ECC) algorithm, which, compared to the RSA algorithm, has a shorter key length and lower computational cost for the same security strength, making it suitable for the computational resource constraints of passive environments.

[0066] Symmetric encryption phase (communication phase): After successful authentication, a temporary session key is negotiated and generated based on the ECDH protocol. Subsequent unlocking and other operation commands are transmitted using AES-128 / 256 symmetric encryption. The computational complexity of symmetric encryption is far lower than that of asymmetric encryption, reducing communication energy consumption by an order of magnitude while ensuring the real-time performance and security of data transmission.

[0067] Energy consumption optimization: Asymmetric encryption is used only during the initial authentication phase (once per session), while symmetric encryption is used for subsequent command transmissions (which can be repeated). Compared to using asymmetric encryption throughout, the hybrid strategy reduces the total encryption energy consumption of a single unlocking session by approximately 90%, significantly extending the effective operating time within the NFC RF power supply window.

[0068] The security authentication and communication module is also equipped with an asynchronous information synchronization mechanism, using an electronic key as an intermediary to solve the information synchronization problem of passive islanded locks: Circular Log Management: The lock is configured with local non-volatile memory as a circular buffer to store operation logs in chronological order. Each log entry includes a timestamp, user ID, operation type, execution result, and priority identifier. When the storage capacity reaches a preset threshold (e.g., 80%), high-priority logs such as abnormal unlocking and brute-force attempts are retained first, while the earliest regular operation logs are overwritten in chronological order to ensure the traceability of critical events.

[0069] Differential synchronization mechanism: Each operation log is appended with a unique lock identifier, timestamp, and verification hash, forming an immutable data record. When a legitimate electronic key approaches and completes two-way authentication, the lock automatically uploads the backlog logs in batches to the electronic key. The electronic key performs deduplication and sorting based on the lock's unique identifier and timestamp locally, and only uploads incremental data when synchronizing to the backend management system, avoiding duplicate transmissions and reducing communication energy consumption and network load.

[0070] Offline Closed-Loop Management: The electronic key acts as a "mobile data transfer carrier," establishing a spatiotemporal bridge between offline locks and the online back-end management system. Each NFC communication window serves as both a power supply window and a data exchange window, achieving the integration of energy, data, and control flows. The back-end management system indirectly obtains the operation records of each lock through the electronic key, enabling traceable operations, auditable permissions, and closed-loop management in an offline environment.

[0071] In summary, the passive smart lock of this embodiment has the following advantages: Completely passive: Powered by NFC radio frequency and stored by supercapacitors, the lock can operate without batteries, eliminating maintenance and adapting to extreme environments.

[0072] High security and low energy consumption: It adopts a hybrid encryption strategy of "asymmetric first and then symmetric", which significantly reduces the energy consumption of authentication and communication while ensuring strong security authentication.

[0073] Highly reliable mechanical drive: Step-by-step drive achieves high torque output with minimal current, and the static pressure of the lock tongue can withstand ≥6000N, meeting high-level anti-theft security requirements.

[0074] Intelligent information management: Through cyclic log management and differential synchronization mechanism, using electronic keys as an intermediary, it efficiently solves the information synchronization problem of passive islanded locks, and realizes traceable operation and closed-loop management in offline environment.

[0075] Example 2 This invention discloses a security authentication and drive control method for the passive smart lock described in Embodiment 1, comprising: Within a limited time window, energy is harvested and stored through near-field electromagnetic coupling to provide limited instantaneous power; Within the specified time window, identity authentication is completed and control commands are generated; Only when the control command is allowed to be executed, based on the limited instantaneous power, the state switching and power transmission are executed sequentially: first, the torque output path is turned on by electromagnetic drive at the first energy consumption level, and then the torque is amplified and output by the worm gear transmission pair driven by the motor at the second energy consumption level to drive the locking tongue.

[0076] The process of completing identity authentication and generating control commands includes the following steps: S1. Offline two-way authentication step: Exchange digital certificates with external electronic keys and perform two-way signature verification within the limited time window; S2, Session Key Negotiation Step: After successful authentication, a temporary session key is negotiated and generated based on the ECDH protocol. S3. Command encryption transmission step: The control command is transmitted in encrypted form using the temporary session key; S4. Asynchronous information synchronization step: The operation log is temporarily stored in local non-volatile memory and uploaded in batches when communication is established with the electronic key next time. The electronic key then synchronizes the log to the background management system.

[0077] In the offline two-way authentication process, within the NFC communication window, the lock and electronic key complete certificate exchange, random number challenge, and two-way signature verification to achieve two-way confirmation of identity legitimacy. Simultaneously, a forward-secure session key negotiation mechanism is established, dynamically generating a temporary key valid only for that instance after successful authentication to ensure communication security. Through an asynchronous information synchronization mechanism mediated by the electronic key, logs such as operation instructions, timestamps, and user identities are temporarily stored locally on the lock, and then uploaded in batches to the backend management system during the next authentication, resolving the contradiction between "information silos" and real-time management in passive environments. Specifically, this includes: S101, Energy Harvesting Phase; When the smart key is brought close to the lock within the effective NFC communication range (usually ≤4cm), the energy antenna collects radio frequency energy through electromagnetic induction, which is then rectified and regulated to charge the supercapacitor, while simultaneously waking up the lock control circuit to enter working mode.

[0078] S102, Security Certification Phase; The NFC communication antenna establishes a data link, and the lock and electronic key exchange pre-set digital certificates and perform two-way signature verification. If the verification fails, the session is terminated immediately; if the verification succeeds, the ECDH key negotiation process is initiated to generate a temporary session key.

[0079] S103, Two-way signature authentication process; 1) Certificate exchange and validity verification; The lock sends its digital certificate to the electronic key via an NFC link and requests the electronic key to return its certificate; both the lock and the electronic key perform dual verification on the received certificate. Signature validity verification: Decrypt the certificate signature using the issuing authority's public key to verify that the certificate has not been tampered with; Compliance verification: Check the certificate validity period, equipment type (lock / electronic key) matching, and equipment scene permissions (such as underground power transmission channels and integrated utility tunnel area permissions).

[0080] If any certificate verification fails, the session will be terminated immediately, and subsequent operations will be rejected.

[0081] 2) Random number challenge mechanism; The lock generates a one-time random number R1 valid only for this session and sends it to the electronic key; the electronic key simultaneously generates a one-time random number R2 valid only for this session and sends it to the lock. This dynamic random number identification ensures the uniqueness of the session, effectively resisting replay attacks and guaranteeing the real-time nature of authentication interactions.

[0082] 3) Two-way signature and verification; Electronic key: Call the local private key SK_Key to digitally sign “R1+R2”, generate signature data S_Key, and send R2 and S_Key to the lock; Lock: Call the security chip private key SK_Lock to digitally sign “R2+R1”, generate signature data S_Lock, and send R1 and S_Lock to the electronic key.

[0083] Among them, the two-way verification rules are as follows: The lock uses the public key PK_Key of the electronic key certificate to decrypt S_Key, and checks whether the result matches "R1+R2"; The electronic key uses the lock certificate public key PK_Lock to decrypt S_Lock, and checks whether the result matches "R1+R2".

[0084] Result determination: If the signatures of either party do not match, the authentication fails and the session is terminated; if both parties pass, the identity is legitimate, the two-way authentication is completed, and the key negotiation phase begins.

[0085] Specifically, the session key negotiation step S2 includes: 1) Temporary key pair generation; The lock's security chip generates a temporary key pair based on predefined elliptic curve parameters. This pair is valid only for the current session and is destroyed when the session ends: a temporary private key SK_Temp_Lock (stored locally) and a temporary public key PK_Temp_Lock (can be publicly transmitted).

[0086] The electronic key uses the same elliptic curve parameters to synchronously generate a temporary key pair: a temporary private key SK_Temp_Key (stored locally) and a temporary public key PK_Temp_Key (can be publicly transmitted).

[0087] Temporary key pairs are independent of the device's long-term key and are used only for key negotiation in this session to ensure forward security.

[0088] 2) Temporary public key exchange and validity verification; The lock sends the temporary public key PK_Temp_Lock to the electronic key, and the electronic key sends the temporary public key PK_Temp_Key to the lock; both parties verify the legality of the received temporary public key: checking whether the temporary public key meets the preset elliptic curve domain parameter requirements to prevent public key substitution attacks.

[0089] 3) Shared key calculation; The lock uses the ECDH algorithm to perform an elliptic curve multiplication operation with its own temporary private key SK_Temp_Lock and the received electronic key's temporary public key PK_Temp_Key to generate the original shared key K_RAW. The electronic key uses the same ECDH algorithm to perform an elliptic curve multiplication operation with its own temporary private key SK_Temp_Key and the received lock's temporary public key PK_Temp_Lock to generate the same original shared key K_RAW. Based on the mathematical properties of the ECDH algorithm, both parties achieve secure generation of the same shared key without directly transmitting the key.

[0090] 4) Temporary session key derivation; The original shared key K_RAW is processed using a key derivation function (KDF). The derivation input parameters include K_RAW and random numbers R1 and R2 generated during the two-way authentication phase to improve the randomness of the key. A temporary session key K_Session conforming to the AES-128 / 256 encryption standard is generated. The temporary session key K_Session is only valid for the current session. After the session ends (such as when the lock is unlocked or the NFC link is disconnected), the lock and electronic key immediately destroy K_Session and the corresponding temporary key pair. The key negotiation process must be re-executed during the next communication to ensure forward security.

[0091] S3, Command Encryption Transmission Steps; The electronic key uses a temporary session key K_Session to encrypt the unlocking control command using the AES-128 / 256 symmetric encryption algorithm and sends it to the lock via the NFC link. After receiving the encrypted command, the lock uses the same temporary session key K_Session to decrypt it and verify the integrity, legality and timeliness of the command.

[0092] Authorized users can issue encrypted unlocking commands via electronic keys. After the lock control module verifies the validity of the command, it first activates the miniature electromagnet to release the mechanical self-lock, and then drives the worm gear mechanism to perform the unlocking action. The peak current is controlled within 214mA throughout the process. If decryption fails, the command is illegal, or the timeout occurs, the command is discarded and the locked state is maintained.

[0093] S4, asynchronous information synchronization steps; The operation logs are temporarily stored in local non-volatile memory and uploaded in batches when a legitimate communication is established with the electronic key next time. The electronic key then relays and synchronizes the logs to the background management system.

[0094] After the unlocking operation is completed, the lock immediately writes the time, user ID, operation type, execution result, and other logs of this operation to the local non-volatile memory. When the next legitimate electronic key approaches and completes two-way authentication, the accumulated logs are automatically uploaded in batches to the electronic key, which then relays them to the backend management system, realizing traceability of operations and closed-loop management in offline scenarios.

[0095] The asynchronous information synchronization step also includes: S401, Log Management Sub-step: Divide the local non-volatile memory into a circular buffer, store operation logs in time sequence and attach priority identifiers; when the storage capacity reaches a preset threshold, prioritize the retention of high-priority logs and overwrite the earliest low-priority logs in time sequence. S402, Differential Synchronization Sub-step: Attach a unique lock identifier, timestamp, and verification hash to each operation log; After the electronic key is read in batches, it is sorted locally based on the unique lock identifier and timestamp, and only incremental data is uploaded when synchronized to the background management system.

[0096] Example 3 This embodiment discloses a passive smart lock system, including: The passive smart lock based on NFC radio frequency power supply as described in Example 1; and The electronic key provides radio frequency power to the passive smart lock via near-field electromagnetic coupling and employs the security authentication and drive control method described in Embodiment 2 to complete two-way identity authentication, temporary session key negotiation, and encrypted command transmission with the lock within the NFC limited time window. Simultaneously, the electronic key receives the operation logs temporarily stored locally by the passive smart lock, verifies, deduplicates, and sorts them, and then synchronizes the log data to the backend management system, achieving full traceability and management of the lock operation process in a passive environment.

[0097] like Figure 3 The diagram shown is a sequence diagram of the system's smart key authorization unlocking and information synchronization; the process in the diagram can be divided into the following stages: Triggering phase: Electronic key approaches lock → Energy harvesting → Establishment of NFC data link Authentication phases: Certificate verification (session terminates if failure occurs) → Random number verification → Two-way signature verification Key negotiation: ECDH negotiates and generates temporary session keys. Command execution: Electronic key issues unlock command → Lock unlocks step by step → Operation log recorded. Asynchronous / Synchronous: Wait for the next valid key interaction → Upload backlog logs → Synchronize electronic key logs to the platform → End.

[0098] This enables a closed-loop process of "energy supply - security authentication - mechanical drive - log recording" to be completed within a single NFC communication window. Furthermore, the periodic interaction of the electronic key breaks the information silo dilemma of passive locks, achieving traceable operation and closed-loop management in offline environments.

[0099] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A passive smart lock based on NFC radio frequency power supply, characterized in that, include: The energy harvesting and storage module is used to harvest energy from an external radio frequency field through near-field electromagnetic coupling, and store it in the energy storage unit after resonant matching, rectification and voltage regulation, so as to provide limited instantaneous power output within a limited time window; A low-power mechanical transmission mechanism is used to sequentially perform state switching and power transmission under limited instantaneous power constraints. The state switching is electromagnetically driven at a first energy consumption level, switching between two states: blocking and opening the torque output path. The power transmission is amplified and output to drive the locking tongue through a worm gear transmission pair driven by a motor at a second energy consumption level. The sequential execution is manifested in the energy supply sequence of first opening the torque output path and then driving the locking tongue. The security authentication and communication module is used to complete identity authentication and output control commands within the limited time window; the low-power mechanical transmission mechanism is configured to start step-by-step energy supply based on the limited instantaneous power only when the control command is allowed to be executed.

2. The passive smart lock based on NFC radio frequency power supply according to claim 1, characterized in that, The low-power mechanical transmission mechanism includes a state switching unit, a power transmission unit, and an energy distribution unit; The state switching unit is configured to switch between a first state and a second state at a first energy consumption level under the action of electromagnetic force. The first state is to block the torque output path of the power transmission unit, and the second state is to connect the torque output path. The power transmission unit, including the worm gear transmission pair and its drive motor, is configured to amplify the input torque and output it to the locking tongue at a second energy consumption level. The energy distribution unit is configured to distribute energy to the state switching unit and the drive motor in a preset sequence based on the constraint of the limited instantaneous power, so that the state switching unit completes the state switching before the power transmission unit.

3. The passive smart lock based on NFC radio frequency power supply according to claim 2, characterized in that, The state switching unit includes: The first movable component is linked to the torque output path; An elastic reset element is used to drive the first movable element to the blocking position; An electromagnetic drive is used to overcome the elastic force of the elastic reset member and drive the first movable member to the conducting position.

4. The passive smart lock based on NFC radio frequency power supply according to claim 3, characterized in that, The first movable component is arranged orthogonally to the output end of the worm gear transmission pair. When the first movable component is in the blocking position, it radially engages with the circumferential groove of the output end to form a mechanical lock. When it is in the conducting position, it radially disengages from the groove to release the lock.

5. The passive smart lock based on NFC radio frequency power supply according to claim 3, characterized in that, The elastic reset member is configured to automatically drive the first movable member back to the blocking position when the electromagnetic drive member is de-energized, so as to restore the mechanical locking state.

6. The passive smart lock based on NFC radio frequency power supply according to claim 1, characterized in that, The low-power mechanical transmission mechanism includes a brake shaft, a control shaft, a drive shaft, a locking ball, an electromagnet, a return spring, a worm gear transmission pair, and a drive motor. The brake shaft is arranged longitudinally, with its upper end fixedly connected to the locking tongue and its lower end connected to the output end of the worm gear of the worm gear transmission pair. The brake shaft is provided with an annular groove in the circumferential direction. The control shaft is arranged laterally and is orthogonal to the brake shaft. One end is abutted against the lock housing by a return spring, and the other end is coaxially aligned with the electromagnet. The cylindrical surface of the control shaft is provided with a locking ball receiving hole. The drive shaft is arranged laterally, with one end coaxially connected to the output shaft of the drive motor and the other end connected to the worm input end of the worm gear transmission pair. The locking ball is configured to partially embed into the receiving hole and partially engage with the brake shaft slot under the thrust of the return spring to form a radial mechanical lock, blocking the torque output path of the brake shaft, or to displace laterally with the control shaft under the axial attraction force generated by the electromagnet being energized, thereby releasing the lock and opening the torque output path of the brake shaft. The drive motor is configured to consume electrical energy at the second energy consumption level to output initial torque, which is transmitted to the worm gear transmission pair via the drive shaft, amplified, and then output to the locking tongue via the brake shaft.

7. The passive smart lock based on NFC radio frequency power supply according to any one of claims 1-6, characterized in that, The security authentication and communication module is configured to employ a hybrid encryption strategy, first asymmetric and then symmetric. The authentication phase employs asymmetric encryption: based on public key infrastructure, two-way identity authentication is achieved through the exchange of digital certificates between electronic keys and locks, random number challenges, and two-way signature verification to achieve strong identity authentication; Symmetric encryption is used during the communication phase: After authentication, a temporary session key is generated through negotiation based on the ECDH protocol, and subsequent unlocking operation commands are transmitted using AES-128 / 256 symmetric encryption.

8. A security authentication and drive control method for a passive smart lock based on NFC radio frequency power supply as described in any one of claims 1-7, characterized in that, include: Within a limited time window, energy is harvested and stored through near-field electromagnetic coupling to provide limited instantaneous power; Within the specified time window, identity authentication is completed and control commands are generated; Only when the control command is allowed to be executed, based on the limited instantaneous power, the state switching and power transmission are executed sequentially: first, electromagnetic drive at the first energy consumption level is used to conduct the torque output path, and then the torque is amplified and output through the worm gear transmission pair driven by the motor at the second energy consumption level to drive the locking tongue.

9. The security authentication and drive control method according to claim 8, characterized in that, The process of completing identity authentication and generating control commands includes the following steps: The offline two-way authentication step involves exchanging digital certificates with an external electronic key and performing two-way signature verification within the limited time window. The session key negotiation step involves negotiating and generating a temporary session key based on the ECDH protocol after successful authentication. The command encryption transmission step involves using the temporary session key to encrypt and transmit the control commands. In the asynchronous information synchronization step, the operation log is temporarily stored in local non-volatile memory and uploaded in batches when communication is established with the electronic key next time, and then synchronized to the background management system by the electronic key.

10. The security authentication and drive control method according to claim 9, characterized in that, The asynchronous information synchronization step also includes: The log management sub-step divides the local non-volatile memory into a circular buffer, stores operation logs in time sequence and adds priority identifiers; when the storage capacity reaches a preset threshold, high-priority logs are retained first, and the earliest low-priority logs are overwritten in time sequence. The differential synchronization sub-step adds a unique lock identifier, timestamp, and verification hash to each operation log; after the electronic key is read in batches, it is sorted locally based on the unique lock identifier and timestamp, and only incremental data is uploaded when it is synchronized to the background management system.

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