Design of anti-theft remote control based on living fingerprint sensor MBF310

Anti-theft remote controls are mainly used in access control devices such as cars, garage doors, anti-theft doors, interior doors, and safes. They can control the opening and closing of access control devices. In anti-theft mode, they send out anti-theft alarm signals when the access control is illegally opened, collided, moved, or vibrated. The fingerprint recognition anti-theft remote controls currently on the market use the first generation of optical fingerprint recognition technology, which can only scan the surface of the finger skin (also known as the "dead skin layer") and cannot penetrate the dermis. Therefore, the cleanliness of the finger surface directly affects the recognition effect. In addition, if people make a fingerprint hand model based on the fingerprint of the finger, it may also pass the recognition system. Although this fingerprint recognition technology can identify the identity of the user, it is neither safe nor stable to use.

The scratch-type live fingerprint reader sends out an electronic signal through a capacitive sensor. The electronic signal passes through the surface of the finger and reaches the live layer of the finger skin (also known as the "dermis") to directly read the fingerprint pattern, thereby greatly improving the security of the system. Using the scratch-type live fingerprint recognition technology, the anti-theft remote control collects the user's fingerprint live layer and sends it to the remote control receiver for comparison with the legal fingerprint stored in the remote control receiver. Only when they match can the user perform other operations on the remote control; otherwise, an anti-theft alarm signal is issued. The use of live fingerprint recognition technology to verify the identity of the user improves the system's anti-theft level, security and stability.

1 Design of anti-theft remote control transmitter

The scratch-type live fingerprint identification anti-theft remote control is divided into two parts: the anti-theft remote control transmitter and the anti-theft remote control receiver. The anti-theft remote control transmitter is carried by the user, and the anti-theft remote control receiver is placed in the access control device to be protected. The anti-theft remote control transmitter uses the MSP430F12X processor as the core, and configures the working status of the scratch-type live fingerprint sensor MBF310, the wireless transmission/reception chip nRF401, the parameter configuration chip AT93C46, etc., including fingerprint data reading, fingerprint data and encrypted data wireless transmission, and wireless transmission of control instructions.

AT93C46 stores 256 bits of parameter configuration data for encryption of transmitted data; nRF401 works in wireless transmission mode. MBF310 uses SPI working mode to connect to the SPI bus of MSP430F12X processor. MSP430F12X initializes the working state of MBF310 sensor through SPI bus and configures it to enable SPI mode of FIFO interrupt. When the finger slides over MBF310, MBF310 collects fingerprint data and stores it in FIFO buffer; when FIFO buffer is full, an interrupt signal is generated. After receiving the FIFO buffer full interrupt signal, MSP430F12X processor immediately reads the fingerprint data collected by MBF310 through SPI bus; and encrypts the read fingerprint data and the configuration word in AT93C46 by "OR" operation, and transmits the encrypted data through nRF401, so as to realize the functions of fingerprint collection, fingerprint data reading, encryption and wireless transmission, as well as wireless transmission of control instructions. The circuit connection diagram of anti-theft remote control transmitter is shown in Figure 1.

Figure 1 Circuit connection diagram of anti-theft remote control transmitter

2 Design of anti-theft remote control receiver

The anti-theft remote control receiver is composed of MSP430F12X processor, wireless transmitter/receiver chip nRF401, parameter configuration chip AT93C46, fingerprint template memory FM24C64, buttons and indicator lights. When the anti-theft remote control receiver works normally, the MSP430F12X processor selects nRF401 as the wireless receiving mode to receive the data and instructions transmitted by the anti-theft remote control transmitter in a timely manner. When receiving the fingerprint data, the MSP430F12X processor uses the 256-bit configuration word in AT93C46 to decode the received encrypted fingerprint and obtain the real live fingerprint data collected by MBF310 in the anti-theft remote control transmitter. Then the decoded fingerprint data is compared with the fingerprint template data pre-stored in the fingerprint template memory FM24C64. If the comparison result is true, it means that the legal identity authentication is obtained, then the anti-theft remote control receiver can receive the control command of the anti-theft remote control transmitter (the command set by the button on the anti-theft remote control transmitter), otherwise it will not respond to the command data transmitted by the anti-theft remote control transmitter. The anti-theft remote control receiver button is used to establish a fingerprint template, and the indicator light indicates the current working status of the anti-theft remote control receiver. Output ports 1 to 6 are output control signals generated according to remote control commands. The circuit connection diagram of the anti-theft remote control receiver is shown in Figure 2.

[page]

Taking this design as a car anti-theft remote control as an example, the car anti-theft remote control consists of two parts: a car anti-theft remote control transmitter and a car anti-theft remote control receiver. The car anti-theft remote control transmitter is carried by the car owner, and the car anti-theft remote control receiver is installed in the car. The three command operation buttons of the car anti-theft remote control transmitter are defined as turning on the car system (KEY1), turning off the car system (KEY2) and finding the car (KEY3). The output control port outputs 1 to 6 of the car anti-theft remote control receiver are defined as: alarm sounding, headlight flashing, door lock opening/closing, rear hatch opening, total circuit on/off, and car ignition/off control signal.

All operations of the car anti-theft remote control are based on fingerprint recognition. First, the remote control operator's finger (the remote control operator's finger that has established a fingerprint template in the car anti-theft remote control receiver) slides gently over the fingerprint recognition window; after the car anti-theft remote control transmitter collects the fingerprint, it encrypts the fingerprint data through the encoding encryption algorithm and transmits it through the FSK method; the car anti-theft remote control receiver within the effective distance receives the encrypted data, and obtains the decrypted fingerprint data through the decoding algorithm, and then compares it with the stored fingerprint template data one by one. If the comparison result is true, the operator's identity is confirmed to be successful and the command data of the remote control transmitter can be received. Otherwise, the remote control transmitter's command will not be received. If the car is forcibly operated without obtaining the operator's legal identity, the anti-theft remote control receiver will send an alarm control signal (such as the alarm ringing, the headlights flashing), and execute other anti-theft control signals (such as the main circuit disconnection, the car is turned off, the door locks are closed, etc.).

Conclusion

The anti-theft remote control transmitter designed in this paper adopts the scratch-type live fingerprint recognition chip MBF310, which belongs to the second-generation fingerprint recognition technology. It effectively overcomes the shortcomings and deficiencies of the first-generation fingerprint recognition technology, such as low recognition rate and recognition of rubber molded fingerprints, and improves the security level and correct recognition rate.

The nRF401 wireless transceiver chip uses FSK technology and can reach a remote control distance of 800 m. In the anti-theft remote control transmitter and anti-theft remote control receiver, AT93C46 is a codec configuration chip that stores 256 bits of codec data. The remote control transmitter uses a 256-bit encoding encryption algorithm when transmitting data, which can prevent the remote control data from being intercepted and cracked and the remote control transmitter from being imitated. Only when the codec data of the remote control transmitter and the remote control receiver are the same can the remote control operation be performed, which improves the security level. The fingerprint template memory in the anti-theft remote control receiver uses an 8 KB high-speed ferroelectric memory FM24C64, which can read and write 1 010 times without failure and keep the data without loss for 10 years in the case of power failure. The remote control transmitter and receiver use the ultra-low power 16-bit processor MSP430F12X as the data processing and control core, which improves the data calculation speed and the intelligence of the system and reduces power consumption.

References

[1] Hu Dake. MSP430 series FLASH ultra-low power 16-bit microcontroller [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2001.

[2] Hu Dake. MSP430 series microcontroller C language programming and development [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2003.

[3] Wei Xiaolong. MSP430 series microcontroller interface technology and system related examples [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2002.