Low-overhead passive sensing safety terminal

Abstract

The invention discloses a low-overhead passive sensing security terminal, which is applied to the field of Internet of Things, and aims at solving the problems that a special true random number generation circuit is needed for generating true random numbers in the prior art, the overhead is relatively high, and the terminal is not suitable for a low-overhead passive sensing terminal. The true random number is generated based on specific sensing and radio frequency signals of the passive terminal, a chaotic mapping function is realized by combining an ADC (Analog to Digital Converter) built in the sensing terminal, a special true random number generator circuit is not needed, the system cost and power consumption can be reduced, and support is provided for realizing passivity and miniaturization of the terminal.

Description

Technical Field

[0001] The invention belongs to the field of Internet of Things, and in particular relates to a technology for generating true random numbers. Background Art

[0002] With the widespread development of Internet of Things technology, wireless passive sensor networks based on RFID technology have received widespread attention, which has the advantages of low power consumption, low cost, miniaturization, etc. However, with the continuous expansion of Internet of Things application scenarios, especially in the application fields of tobacco, alcohol, tea, etc., people are very concerned about whether the products are genuine, and the encryption algorithms of traditional passive sensor terminals often use pseudo-random numbers to encrypt data, which has security risks.

[0003] The existing passive sensor terminal architecture is as follows: Figure 1 As shown, the antenna is used to receive radio frequency signals; the matching module is used for impedance matching between the antenna and subsequent circuits to achieve the maximum transmission function of the antenna receiving power; the power divider distributes the radio frequency signal received by the antenna to the rectifier circuit for energy collection and to the demodulation circuit to achieve the signal demodulation function; the energy collection and management module realizes the boost, energy storage and power supply management functions; the sensor circuit realizes the information perception function, which is the basic function of the passive sensor terminal; the processor adopts a low-power and low-cost MCU, which mainly realizes the wireless communication protocol, sensor information collection, pseudo-random number generation, encryption algorithm and other functions; the modulation circuit adopts backscattering technology to realize the passive terminal data transmission function with near zero power consumption.

[0004] Existing passive sensor terminals often use pseudo-random numbers. There are also some application scenarios with high security levels that require the generation of true random numbers and data encryption processing (using existing encryption algorithms). The traditional methods for generating true random numbers are shown below (A) to (D), including: (A) a noise comparison method based on thermal noise; (B) a method based on clock jitter; (C) a residual recycling method based on ADC (analog-to-digital conversion), also known as chaotic mapping; (D) a method based on quantum effects.

[0005] (A) Method based on thermal noise comparison

[0006] Thermal noise is the most common type of white noise, which is caused by electronic It is caused by thermal shock, which is the result of temperature change and the basis of other noises. The circuit structure of the true random number generator based on thermal noise is as follows Figure 2 shown.

[0007] (B) Clock jitter-based method

[0008] The clock jitter-based method mainly uses a low-frequency clock to sample the output of a high-frequency oscillator. The most commonly used method is to use a D flip-flop. The low-frequency clock is used as the input clock of the D flip-flop, and the high-frequency oscillator is used as the input data of the D flip-flop. Its structure is as follows: Figure 3shown.

[0009] (C) Chaotic circuit-based method

[0010] A chaotic system refers to a deterministic system with irregular motion, uncertainty, non-repeatability, unpredictability, and extreme sensitivity to initial conditions. Chaos is an inherent characteristic of nonlinear dynamic systems and a common phenomenon in nonlinear systems. Chaotic systems can be implemented through computer systems or analog circuits. Analog circuit chaotic systems are often implemented based on ADCs. The structure of a true random number generator based on ADC and DAC residuals is as follows: Figure 4 shown.

[0011] (D) Methods based on quantum effects

[0012] The structure of a true random number generator based on quantum effects is as follows: Figure 5 As shown, a single photon is detected at two output ends of a balanced beam splitter (having the same transmittance and reflectance), and a true random number can be obtained after the detected photon information is digitized.

[0013] Among them, the voltage amplitude of thermal noise is very small, and it needs to be amplified by a high-gain amplifier before it can be quantized by the ADC, or it needs an ADC with a very high bit width, which has high cost and power consumption. In addition, the bandwidth of the amplifier is limited, which will reduce the randomness of the thermal noise. The entropy source circuit of the true random number generator based on clock jitter is composed of inverters, which requires more inverter resources to increase the randomness of the system, and has high power consumption and cost. The true random number generator based on quantum effects requires equipment that can generate and measure quantum effects, which is not suitable for passive sensor terminals. At the same time, the above methods all require a dedicated true random number generation circuit, which has a large overhead and is not suitable for low-overhead passive sensor terminals. Summary of the invention

[0014] In view of the problem that the existing passive sensor terminals have high cost, power consumption, volume and complexity in generating true random numbers, the present invention, for the first time, proposes a low-overhead passive sensor security terminal based on the inherent ADC (converting the analog signal output by the sensor) and radio frequency signal of the passive sensor terminal. The terminal is powered by radio frequency energy harvesting and uses its own sensor output signal and radio frequency signal to realize the entropy source of true random numbers. There is no need to design a special circuit structure, thereby reducing the cost, power consumption, volume and design complexity of the passive sensor security terminal.

[0015] The technical solution adopted by the present invention is: a low-overhead passive sensing safety terminal, including: an antenna, a matching module, a power divider, a rectifier circuit, an energy collection and management module, a sensing circuit, a processor, a modulation circuit, and a demodulation circuit;

[0016] The RF signal received by the antenna enters the power divider after passing through the matching module;

[0017] The power divider divides the input RF signal into two paths, one of which is input into the rectifier circuit and the other is input into the demodulation circuit;

[0018] The output end of the rectifier circuit is connected to the energy collection and management module;

[0019] The energy collection and management module provides power for the demodulation circuit, sensor circuit, and processor respectively;

[0020] The processor includes an ADC, a true random number controller, an encryption module and a memory; the sensing circuit is connected to the processor to provide a sensing entropy source; the demodulation circuit is connected to the processor to provide a radio frequency entropy source; the ADC samples the sensing entropy source and the radio frequency entropy source, and then generates true random numbers through the true random number controller, and stores the true random numbers in the memory; the encryption module performs data encryption based on the true random numbers stored in the memory;

[0021] The modulation circuit is connected to the processor and is used to modulate the modulation signal transmitted from the processor and then transmit it to the antenna for transmission.

[0022] The demodulation circuit comprises a detector, a low-pass filter and a comparator which are connected in sequence; a radio frequency entropy source is provided through the output of the detector.

[0023] Beneficial effects of the present invention: A low-overhead passive sensor security terminal design method proposed in the present invention can be used to solve the problems of high cost, high power consumption, and large size of passive sensor terminals. The ADC, sensor circuit, and radio frequency circuit of the passive sensor tag are used to implement a compatible true random number generator. An enhanced SM7 encryption algorithm implementation method based on true random numbers is also proposed, which can be used to improve the security performance of such encryption algorithms. The present invention can be used to improve the recognition performance of ultra-high frequency RFID anti-collision algorithms, mainly to solve the problem that a large number of tags implemented using pseudo-random numbers are prone to output the same random number sequence, resulting in continuous collisions of these tags that cannot be identified. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is an existing passive sensor terminal architecture.

[0025] Figure 2 It is a true random number generator structure based on thermal noise.

[0026] Figure 3 It is a true random number generator structure based on clock jitter.

[0027] Figure 4 It is a true random number generator circuit structure based on ADC and DAC residuals.

[0028] Figure 5It is a true random number generator structure based on quantum effects.

[0029] Figure 6 A low-overhead passive sensing security terminal architecture.

[0030] Figure 7 True random number generator architecture for compatibility.

[0031] Figure 8 The invention provides a compatible true random number generator workflow based on RF signal and ADC residual.

[0032] Fig. 9 This is the overall architecture diagram of the SM7 algorithm.

[0033] Fig.10 This is a flow chart of the enhanced SM7 encryption algorithm based on true random numbers. DETAILED DESCRIPTION

[0034] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0035] The low-cost passive sensor security terminal architecture proposed by the present invention is as follows Figure 6 As shown, the antenna receives the radio frequency signal; the matching module is used for impedance matching between the antenna and the subsequent circuit to realize the maximum transmission function of the antenna receiving power; the power divider divides the radio frequency signal received by the antenna to the rectifier circuit for energy collection and to the demodulation circuit to realize the signal demodulation function; the energy collection and management module realizes the energy storage and power supply management functions; the energy storage capacitor is used to store the energy collected by the energy collection and management module, and to power the subsequent modules through the energy collection and management circuit; the sensor circuit realizes the information perception function, which is the basic function of the passive sensor security terminal; the processor can adopt a low-power and low-cost MCU, which mainly realizes the functions of wireless communication protocol, sensor information collection, true random number generation, enhanced encryption algorithm, etc.; the modulation circuit adopts backscattering technology to realize the passive terminal data transmission function with near zero power consumption; the true random number generator uses the existing resources of the sensor terminal to generate true random numbers; the enhanced SM7 encryption algorithm uses the generated true random numbers to improve the S transform in the encryption algorithm, thereby improving the security performance of the SM7 encryption algorithm.

[0036] The compatible true random number generator architecture proposed by the present invention is as follows: Figure 7As shown, it includes an entropy source and a processor. The entropy source includes a sensor entropy source and a radio frequency entropy source. The sensor entropy source is composed of a sensor circuit, and the radio frequency entropy source comes from the detection output of the radio frequency transceiver circuit. The processor has a built-in ADC, which is mainly used for analog-to-digital conversion of passive sensor terminals to realize the sensor data acquisition function. The true random number controller uses the built-in ADC to sample the sensor entropy source and the radio frequency entropy source, and then generates true random numbers through post-processing by the true random number controller, and stores the true random numbers in the memory. The true random numbers in the memory can be used to further iterate and improve the randomness of the number of cyclic shift bits in the post-processing process, thereby iteratively improving the true randomness of the system.

[0037] The workflow of the compatible true random number generator based on RF signal and ADC residual is as follows: Figure 8 shown.

[0038] The working steps of the compatible true random number generator based on RF signal and ADC residual are as follows:

[0039] 1. First, according to the actual application requirements, set the initial values ​​of the variables required in the system, such as the total number of true random numbers RN required all , the number of operations to generate 16-bit true random numbers RN times = 0, total number of runs k = 0, total number of true random numbers generated RN sum = 0, and by setting Power to high, the sensing circuit is powered and the RF entropy source voltage is sampled to generate D RF0 , with D RF0 is the offset address, and a random number is read from the memory to generate the initial random delay time t 0 , and delay t 0 Time. Initially, the random number in the memory is 0.

[0040] 2. Then use ADC to convert the sensor entropy source voltage to obtain the ADC output digital signal D affected by thermal noise sensor , judge D sensor Is it greater than the high threshold D? HT Is the sum less than the lower threshold D? LT , used to control whether the power is high or low, thereby controlling the charging or discharging of the sensing circuit, so that the output voltage of the sensing entropy source changes continuously. HT With D LT Explanation of the value: For example, if the power supply voltage is 2V and the corresponding ADC bit width is 8 bits, then the maximum value of the ADC output is FF, and the maximum threshold value that can be set is F0; the minimum threshold value is 0F.

[0041] 3. Further use ADC to convert the RF entropy source voltage to output digital signal by For the offset address, read a random number in the memory to generate a random delay time And delay time.

[0042] 4. Further For the offset address, a random number is read from the memory to generate the cyclic shift number SBS k , D sensor Circular right shift SBS k Get Then use The lowest 4 bits generate a 4-bit true random number and set RN times =RN times +1, RN sum =RN sum +4, k=k+1.

[0043] 5. Further concatenate the 4-bit true random number with the 4-bit true random number generated in the previous iteration. If the number of true random numbers generated is RN times =4, the generated 16-bit true random number is saved in the memory and RN is set times =0.

[0044] 6. Determine the total number of true random numbers RN generated sum Does it meet the needs? If RN sum ≥ RN all , then the process of generating true random numbers ends, and all generated true random numbers are sent to the enhanced SM7 encryption algorithm, otherwise continue to step 2.

[0045] Implementation method of enhanced SM7 encryption algorithm based on true random numbers

[0046] In wireless passive RFID systems, there are multiple air interface protocol standards, among which ISO / IEC 18000-6C is the most widely used RFID air interface protocol. ISO / IEC 18000 uses technologies such as password authentication, access control, and transmission masking to protect tag information. However, the security performance of these protection measures is very weak and cannot provide effective protection for the wireless communication of IoT sensor tags. It is easy to clone or forge tags, leak personal privacy, and tamper with information.

[0047] In view of the security issues of ISO / IEC 18000 standard, my country's GB / T 29768 protocol adds a two-way authentication mechanism and SM7 encryption algorithm to improve the security performance of passive terminal wireless communication. SM7 is a commercial encryption algorithm specially designed for electronic tags approved by the State Cryptography Administration. The overall structure of the original SM7 algorithm is as follows: Fig. 9As shown, the encryption or decryption function is selected according to the application needs. SM7 encryption and decryption requires generating 16 sub-keys and implementing 16 F functions. The F function requires multiple S transformations, where S1, S2, S3 and S4 represent sub-transformations of S.

[0048] By performing a simple logical operation on the input data and a 16-bit true random number before the S transform, the randomness of the S transform output data can be improved, thereby improving the security performance of the SM7 encryption algorithm. The tag generates a true random number that is directly used to change the S transform. The collector can read the data of this address at any time for encryption and decryption operations. Each time the collector reads, the tag regenerates a new true random number for encryption and decryption. The collector can control the reading rate to control the rate at which the tag generates true random numbers.

[0049] The overall architecture of the enhanced SM7 encryption algorithm based on true random numbers is as follows Fig.10 As shown by Fig.10 It can be seen that the enhanced SM7 encryption algorithm is more secure than the original SM7 encryption algorithm and is fully compatible with the original SM7 encryption algorithm (when sampling logical OR operation, the true random number is all 0 and is compatible with the original encryption algorithm). In addition, users can choose different logical operations according to different application scenarios, so that completely different encrypted data can be generated under the same data, key and true random number.

[0050] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A low-cost passive sensing security terminal, characterized in that: include: Antenna, matching module, power divider, rectifier circuit, energy collection and management module, sensor circuit, processor, modulation circuit, demodulation circuit; The RF signal received by the antenna enters the power divider after passing through the matching module; The power divider divides the input RF signal into two paths, one of which is input into the rectifier circuit and the other is input into the demodulation circuit; The output end of the rectifier circuit is connected to the energy collection and management module; The energy collection and management module provides power for the demodulation circuit, sensor circuit, and processor respectively; The processor includes an ADC, a true random number controller, an encryption module and a memory; the sensing circuit is connected to the processor to provide a sensing entropy source; the demodulation circuit is connected to the processor to provide a radio frequency entropy source; the ADC samples the sensing entropy source and the radio frequency entropy source, and then generates true random numbers through the true random number controller, and stores the true random numbers in the memory; The encryption module performs data encryption based on the true random number stored in the memory; The modulation circuit is connected to the processor and is used to modulate the modulation signal transmitted from the processor and then transmit it to the antenna for transmission.

2. A low-cost passive sensing security terminal according to claim 1, characterized in that: The demodulation circuit comprises a detector, a low-pass filter and a comparator which are connected in sequence; a radio frequency entropy source is provided through the output of the detector.

3. A low-cost passive sensing security terminal according to claim 2, characterized in that: The process of generating true random numbers is: A1. First, according to the actual application requirements, set the initial values ​​of the variables required in the system, including: the total number of true random numbers RN all , the number of operations to generate 16-bit true random numbers RN times = 0, total number of runs k = 0, total number of true random numbers generated RN sum = 0, and by setting Power to high, the sensor circuit is powered, and the ADC is used to sample the RF entropy source voltage to obtain the ADC output digital signal D RF0 , with D RF0 For the offset address, a random number is read from the memory to generate an initial random delay time t0, and the delay time t0 is used; A2. Use ADC to sample the sensor entropy source voltage and obtain the ADC output digital signal D affected by thermal noise. sensor , if D sensor is greater than the high threshold, the sensor circuit is controlled to discharge; if D sensor If the value is less than the low threshold, the sensor circuit is controlled to charge; otherwise, step A3 is executed; A3. Use ADC to sample the RF entropy source voltage and obtain the ADC output digital signal by For the offset address, read a random number in the memory to generate a random delay time And delay time; A4. For the offset address, a random number is read from the memory to generate the cyclic shift number SBS k , D sensor Circular right shift SBS k Get Then use The lowest 4 bits generate a 4-bit true random number and set RN times =RN times +1, RN sum =RN sum +4, k=k+1; A5. Concatenate the 4-bit true random number with the previously generated true random number. If the number of true random numbers generated is RN times =4, the generated 16-bit true random number is saved in the memory and RN is set times =0, then execute step A6; otherwise return to step A2; A6. If RN sum ≥ RN all , then the process of generating true random numbers ends, and all generated true random numbers are sent to the encryption module, otherwise continue to execute step A2.

4. A low-cost passive sensing security terminal according to claim 3, characterized in that: It also includes a first voltage stabilizing circuit and a second voltage stabilizing circuit; the energy collection and management module supplies power to the processor and the comparator in the demodulation circuit through the first voltage stabilizing circuit, and the energy collection and management module supplies power to the sensor circuit through the second voltage stabilizing circuit.

5. A low-cost passive sensing security terminal according to claim 4, characterized in that: The encryption module specifically adopts the SM7 encryption algorithm.

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