PCB safety protection structure and method
By using a method of tilting zebra strips and comparing real-time electrical signals from the MCU, the problem of traditional POS terminal physical security measures being easily bypassed is solved, achieving more efficient physical attack protection and system security.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN XINGUODU TECH
- Filing Date
- 2023-09-20
- Publication Date
- 2026-05-15
AI Technical Summary
Traditional POS terminal physical security measures, such as zebra stripes, are easily bypassed by attackers, and solutions to increase protection effectiveness and reduce costs are insufficient.
The conductive layer of the zebra strip is tilted, and a random electrical signal is generated by the MCU and compared with the expected return electrical signal to detect physical attacks in real time.
This increases the difficulty of physical attacks on POS terminals and enhances their protection flexibility, thereby improving the overall security of the system and reducing implementation complexity and cost.
Smart Images
Figure CN117456669B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of physical protection technology for financial terminals, and in particular to a PCB security protection structure and method. Background Technology
[0002] With the increasing volume of digital financial transactions, POS terminals, as key financial transaction devices, are facing more and more physical attacks and security threats. Traditional physical security measures, such as the use of zebra stripes and metal pins, can provide a certain degree of protection, but still have some limitations.
[0003] Traditional zebra strips feature vertically stacked conductive layers connecting pads on both sides to transmit and connect electrical signals. However, attackers can bypass the zebra strip protection by directly inserting metal pins vertically to short-circuit the pads, thus compromising device security. Furthermore, increasing the number of zebra strips, adding more PCB layers, or using blind-buried processes to enhance protection increases manufacturing costs and may reduce product reliability.
[0004] Therefore, existing technologies still have some shortcomings in protecting POS terminals from physical attacks, and more innovative and cost-effective solutions are needed. Summary of the Invention
[0005] To address the aforementioned technical problems, this application provides a PCB security protection structure and method, aiming to enhance the protection effect of POS terminals and improve product reliability. The solution in this application tilts the conductive layer layout of the zebra strip, so that the zebra strip layout between the two pads is no longer the traditional vertical placement, but tilted within a certain angle range. This layout makes it difficult for attackers to short-circuit signals using conventional vertical insertion methods, thereby increasing the difficulty of physical attacks. The technical solution in this application is described below:
[0006] The first aspect of this application provides a PCB security protection structure, including:
[0007] A first pad, a second pad, and a zebra strip, wherein one end of the zebra strip is connected to the first pad and the other end is connected to the second pad, and the zebra strip contains multiple layers of insulating and conductive layers, the insulating and conductive layers are spaced apart, and the conductive layers are arranged at an angle to both the first and second pads.
[0008] Optionally, the multiple conductive layers are parallel to each other.
[0009] Optionally, a zebra strip bracket is also included, which is disposed between the first pad and the second pad to support the zebra strip.
[0010] Optionally, a plurality of conductive channels are formed by conductive layers disposed between adjacent insulating layers, and each conductive channel is isolated from the insulating layer, wherein the width and spacing of the conductive channels are equal.
[0011] Optionally, the first pad is a pad on the cover PCB, and the second pad is a pad on the motherboard PCB.
[0012] A second aspect of this application provides a PCB security protection method, applied in the first aspect and any optional security protection structure of the first aspect, wherein the security protection structure is further coupled with an MCU, and the method includes:
[0013] The MCU generates random electrical signals;
[0014] The MCU sends the random electrical signal to the loop formed by the first pad, the zebra stripe, and the second pad;
[0015] The MCU generates the desired return electrical signal based on pre-configured circuit configuration information using the same random seed as in the step of generating random electrical signals by the MCU.
[0016] The MCU receives the actual return electrical signal transmitted through the loop.
[0017] The MCU compares the returned electrical signal with the expected returned electrical signal to obtain a comparison result.
[0018] The MCU determines whether the PCB has been physically attacked based on the comparison results.
[0019] If so, then perform protective measures.
[0020] Optionally, the MCU compares the return electrical signal with the desired return electrical signal to obtain the comparison result, including:
[0021] The MCUs are compared in the following way:
[0022] The difference between each sampling point of the actual returned electrical signal and the expected returned electrical signal is calculated in the following manner:
[0023] The difference dn = xn - yn;
[0024] The actual returned electrical signal is represented as xn, and the expected returned electrical signal is represented as yn. There are a total of N sampling points.
[0025] The squared difference of dn is calculated as follows:
[0026] Squared difference en = dn^2;
[0027] The mean square error is calculated as follows:
[0028] Mean squared error (MSE) = (1 / N) * Σ(en);
[0029] Where Σ represents the summation over all sampling points;
[0030] The comparison results include MSE.
[0031] Optionally, the MCU compares the return electrical signal with the desired return electrical signal to obtain the comparison result, including:
[0032] The MCUs are compared in the following way:
[0033] Collect the actual returned electrical signal xn and determine the expected returned electrical signal yn. There are a total of N sampling points.
[0034] The covariance of all differences is calculated as follows:
[0035] Covariance Cov=(1 / N)*Σ(xn) μ_x)(yn μ_y);
[0036] Where Σ represents summing over all sampling points, and μ_x and μ_y are the mean values of the actual returned electrical signal and the expected returned electrical signal, respectively;
[0037] Calculate the standard deviations of the actual return signal and the expected return signal respectively:
[0038] Standard deviation σ_x = sqrt((1 / N)*Σ(xn-μ_x)^2);
[0039] Standard deviation σ_y=sqrt((1 / N)*Σ(yn-μ_y)^2);
[0040] The correlation coefficient is calculated as follows:
[0041] The correlation coefficient ρ = Cov / (σ_x*σ_y).
[0042] The optional comparison result includes the correlation coefficient ρ.
[0043] Optionally, the protection operation includes:
[0044] Remove sensitive data and transaction records from memory;
[0045] or
[0046] Users or administrators will be alerted via sound, light indicators, and alarm messages;
[0047] or
[0048] Suspend the current transaction.
[0049] As can be seen from the above technical solutions, this application has the following advantages:
[0050] With its angled zebra stripes, this security structure effectively defends against physical attacks, such as needle punctures. This helps protect critical components and sensitive data inside the equipment.
[0051] Based on this protective structure, different tilt angles can be set between different product units, making it difficult for attackers to attack the PCB using specially designed jigs.
[0052] In the method provided in this application, the MCU generates a random electrical signal and compares it with the expected return electrical signal to achieve real-time detection. Once a significant difference is detected between the actual return signal and the expected signal, the MCU can quickly take protective measures to prevent potential attacks in a timely manner.
[0053] Pre-configured circuit information allows the system to adjust to different environments and operating conditions. This enables the system to dynamically adapt to different attack methods and environmental factors, improving the flexibility and effectiveness of protection.
[0054] This protective structure combines physical and circuit layer security measures. By comparing tilted zebra strips, random electrical signals, and expected return electrical signals, it constructs multi-layered protection, enhancing the overall security of the system. Attached Figure Description
[0055] Figure 1 This is a schematic diagram of an embodiment of the PCB security protection structure provided in this application;
[0056] Figure 2 This is a schematic diagram of an installation structure for the PCB safety protection structure provided in this application.
[0057] Figure 3 This is a schematic diagram of the PCB safety protection structure provided in this application after installation.
[0058] Figure 4 This is a schematic flowchart of an embodiment of the PCB security protection method provided in this application;
[0059] Figure 5 This is a schematic diagram of the information flow for the PCB security protection method provided in this application. Detailed Implementation
[0060] In this application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and other terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to describe the relative positional relationship between the components or parts and do not specifically limit the specific installation orientation of each component or part.
[0061] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.
[0062] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.
[0063] Furthermore, the structures, proportions, sizes, etc., drawn in the accompanying drawings of this application are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modification to the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that this application can produce, should still fall within the scope of the technical content disclosed in this application.
[0064] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0065] This application first provides an embodiment of a PCB security protection structure, which is described in detail below. Please refer to [link / reference]. Figures 1 to 3 This embodiment includes:
[0066] A first pad 01, a second pad 02, and a zebra strip 03. One end of the zebra strip 03 is connected to the first pad 01, and the other end is connected to the second pad 02. The zebra strip 03 contains multiple layers of insulating layer 04 and conductive layer 05. The insulating layer 04 and the conductive layer 05 are spaced apart, and the conductive layer 05 is arranged at an angle so as to form an angle with both the first pad and the second pad.
[0067] The following is a description of each component in this embodiment:
[0068] First pad 01: The first pad 01 on the PCB is the starting point for connecting the circuit; it can be a metal pad or a connector. In this embodiment, the first pad 01 is used to connect to one end of the zebra strip 03.
[0069] Second pad 02: Similar to the first pad 01, the second pad 02 is also located on the PCB and is used to connect to the other end of the zebra strip 03. A circuit path is formed between the first pad 01 and the second pad 02.
[0070] Zebra Strip 03: Zebra Strip 03 is a key component connecting the first pad 01 and the second pad 02. It is composed of multiple layers of insulating layer 04 and conductive layer 05, with gaps between the insulating layer 04 and the conductive layer 05. In this embodiment, the conductive layer 05 is arranged at an angle, forming an angle with the first pad 01 and the second pad 02.
[0071] After the PCB security protection structure provided in this embodiment is assembled, the MCU on one of the PCBs will generate a randomly changing signal, which will be transmitted to Zebra Strip 03 via the line, and then from Zebra Strip 03 to the other PCB. The signal will then return to the MCU signal receiving pin through the entire loop, where the MCU will determine whether the received signal matches the expected signal. If they match, the terminal can operate normally; otherwise, it is considered that the PCB has been physically attacked, and the terminal will enter protection mode, preventing further financial transactions. This protection principle protects sensitive product information, preventing attackers from obtaining or tampering with sensitive data in memory. Specific embodiments of the PCB security protection method are also provided in this application, and subsequent embodiments will describe the specific method based on this structure in detail.
[0072] The PCB security protection structure provided in this embodiment increases the difficulty for physical attackers to attack the zebra stripe 03 through the design of the inclined conductive layer 05 and the multi-layer insulating layer 04. The inclined arrangement of the conductive layer 05 makes traditional vertical penetration attack methods difficult, thereby effectively preventing physical attacks from damaging the motherboard.
[0073] Based on the structure provided in this embodiment, more variables and complexity can be introduced by setting different tilt angles for different product units, increasing the difficulty for attackers. This strategy can effectively improve system security because attackers cannot attack multiple product units using a single, universal attack method.
[0074] In an optional embodiment, the plurality of conductive layers 05 are parallel to each other.
[0075] This optional embodiment incorporates multiple parallel conductive layers 05 in the zebra stripe 03 design. Each conductive layer 05 is located between insulating layers 04 and is arranged parallel to the other conductive layers 05. These conductive layers 05 can be used to transmit signals or current, while also providing some protection against physical attacks.
[0076] An insulating layer 04 is included between every two conductive layers 05. These insulating layers 04 are used to isolate the different conductive layers 05 to prevent short circuits and interference. The spacing between the conductive layers 05 and the insulating layers 04 can be adjusted as needed.
[0077] The parallel arrangement of multiple conductive layers 05 enhances physical security. Attackers find it difficult to directly penetrate multiple conductive layers 05 using traditional attack methods because the parallel arrangement increases the complexity of the attack path. Furthermore, the design of the conductive layers 05 not only provides physical security but also allows for signal transmission. By transmitting signals between different conductive layers 05, the possibility of signal interference can be reduced, thereby improving circuit reliability.
[0078] In an optional embodiment, a zebra strip 03 bracket is further included, which is disposed between the first pad 01 and the second pad 02 to support the zebra strip 03.
[0079] In this optional embodiment, in addition to the first pad 01, second pad 02, conductive layer 05, and insulating layer 04 described above, a zebra strip 03 bracket is introduced. The zebra strip 03 bracket is disposed between the first pad 01 and the second pad 02 to support and fix the position of the zebra strip 03. See also... Figure 2 The zebra strip 03 bracket can be provided with a fixing hole 08, in which the zebra strip 03 is installed.
[0080] Furthermore, to ensure a more secure installation of the Zebra Strip 03, the Zebra Strip 03 bracket can be fixed to other components (such as the PCB or housing) using screws 07.
[0081] In this embodiment, the use of the zebra strip 03 bracket increases the stability of the zebra strip 03, preventing it from moving or falling off due to external forces or vibrations. Simultaneously, combined with the inclined arrangement of the conductive layer 05 and the zebra strip 03 bracket, this design provides enhanced physical security, making it more difficult for attackers to compromise the PCB.
[0082] In an optional embodiment, each insulating layer 04 forms a conductive channel, and each conductive channel is isolated from each other by the insulating layer 04, and the width and spacing of the conductive channels are equal.
[0083] In this optional embodiment, each insulating layer 04 is designed as a conductive channel, with insulating layers 04 used to isolate different conductive channels. Specifically, the width and spacing of each conductive channel can be equal. That is, each conductive channel has the same width within the insulating layer 04, and the distance between adjacent conductive channels is also equal. The design of the insulating layer 04 provides physical isolation between each conductive channel. This isolation prevents interference and disturbance between conductive channels, thereby maintaining the stability and reliability of the circuit. The design of equal width and spacing of the conductive channels provides uniformity, thereby simplifying the manufacturing process and reducing design variations.
[0084] In an optional embodiment, the first pad 01 is a pad on the cover PCB, and the second pad 02 is a pad on the motherboard PCB.
[0085] In this optional embodiment, the first pad 01 is a pad located on the cover plate PCB, while the second pad 02 is a pad located on the motherboard PCB. These two pads are located on different PCBs.
[0086] In this embodiment, the structure connects the first pad 01 and the second pad 02 together via zebra strip 03, forming a secure protective loop, increasing physical isolation and improving physical security. It is suitable for various applications requiring cross-PCB connections, such as terminal devices that need to establish a connection between the cover PCB and the motherboard PCB.
[0087] The above embodiments provide a detailed description of the PCB security protection structure provided in this application. The following describes in detail the PCB security protection method provided in this application. This method is applied to the above-mentioned PCB security protection structure. To execute the method, one PCB in the structure needs to be coupled with an MCU (Microcontroller Unit). The following describes an embodiment of this method:
[0088] See Figure 4 and Figure 5 :
[0089] This application first provides an embodiment of a method, which includes:
[0090] S101, The MCU generates a random electrical signal;
[0091] In this step, the MCU generates a random electrical signal. The random electrical signal is generated based on a random number generation algorithm and can be an electrical signal with random amplitude and frequency.
[0092] S102, the MCU sends the random electrical signal to the loop formed by the first pad, the zebra strip and the second pad;
[0093] The MCU sends random electrical signals to a loop in the PCB structure, which is formed by the connection of the first pad, the zebra strip, and the second pad. The random electrical signals are transmitted through this loop, following the circuit path. For example, when the MCU is placed on the PCB corresponding to the first pad, the transmission loop of the random electrical signals is: MCU - PCB corresponding to the first pad - zebra strip - PCB corresponding to the second pad - zebra strip - MCU.
[0094] S103. The MCU generates the desired return electrical signal based on the pre-configured circuit configuration information using the same random seed as in the previous steps.
[0095] In this step, the MCU generates an expected return signal using the same random seed as the previously generated random signal, based on the pre-configured circuit configuration information. This expected return signal is pre-calculated and anticipated, and is defined in this application as circuit configuration information based on the characteristics and configuration of the circuit. This circuit configuration information may include information about various electronic components in the circuit, such as resistors, capacitors, and inductors. If the circuit includes components such as amplifiers and filters, the circuit configuration information may also include settings such as their gain and cutoff frequency.
[0096] S104. The MCU receives the actual return electrical signal transmitted through the loop.
[0097] The MCU receives the actual return electrical signal transmitted through the loop. This actual return electrical signal is the result of the random electrical signal being transmitted through the loop.
[0098] S105. The MCU compares the return electrical signal with the expected return electrical signal to obtain a comparison result.
[0099] The MCU compares the actual returned electrical signal with the expected returned electrical signal. This comparison can involve various methods, such as waveform comparison and correlation coefficient calculation. Through this comparison, the MCU can determine the differences between the actual and expected returned electrical signals.
[0100] The following are two specific examples of electrical signal comparison:
[0101] Example 1:
[0102] The difference between each sampling point of the actual returned electrical signal and the expected returned electrical signal is calculated in the following manner:
[0103] The difference dn = xn - yn;
[0104] The actual returned electrical signal is represented as xn, and the expected returned electrical signal is represented as yn. There are a total of N sampling points.
[0105] The squared difference of dn is calculated as follows:
[0106] Squared difference en = dn^2;
[0107] The mean square error is calculated as follows:
[0108] Mean squared error (MSE) = (1 / N) * Σ(en);
[0109] Where Σ represents the summation over all sampling points;
[0110] The comparison results include the MSE value.
[0111] In this embodiment of electrical signal comparison, the similarity between the actual returned electrical signal and the expected returned electrical signal is compared by calculating the difference, squared difference, and mean square error of each sampling point.
[0112] For each sampling point, calculate the difference between the actual returned electrical signal and the expected returned electrical signal. The difference is denoted by the symbol dn, where xn represents the value of the actual returned electrical signal and yn represents the value of the expected returned electrical signal.
[0113] Square each difference dn to get the squared difference en = dn^2. This represents the square of the difference at each sampling point.
[0114] Sum all the squared differences en (Σ denotes the summation sign), then divide by the number of sampling points N to obtain the mean square error MSE = (1 / N)*Σ(en). The mean square error is the average of the squared differences at each sampling point, used to measure the overall difference between the actual returned electrical signal and the expected returned electrical signal.
[0115] The comparison result is the mean squared error (MSE) value. A smaller MSE value indicates a closer similarity between the actual and expected returned electrical signals; a larger MSE value indicates a greater difference between the two. If the MSE value becomes too large, for example, exceeding a pre-set threshold, the PCB can be considered to have suffered a physical attack. The advantage of using mean squared error as a comparison metric is that it comprehensively considers the differences at each sampling point and squares the differences, giving greater emphasis to larger differences. This makes it particularly suitable for situations where the zebra stripe experiences a sudden change in electrical signal due to a physical attack.
[0116] Example 2:
[0117] The MCUs are compared in the following way:
[0118] Collect the actual returned electrical signal xn and determine the expected returned electrical signal yn. There are a total of N sampling points.
[0119] The covariance of all differences is calculated as follows:
[0120] Covariance Cov=(1 / N)*Σ(xn) μ_x)(yn μ_y);
[0121] Where Σ represents summing over all sampling points, and μ_x and μ_y are the mean values of the actual returned electrical signal and the expected returned electrical signal, respectively;
[0122] Calculate the standard deviations of the actual return signal and the expected return signal respectively:
[0123] Standard deviation σ_x = sqrt((1 / N)*Σ(xn-μ_x)^2);
[0124] Standard deviation σ_y=sqrt((1 / N)*Σ(yn-μ_y)^2);
[0125] The correlation coefficient is calculated as follows:
[0126] The correlation coefficient ρ = Cov / (σ_x*σ_y).
[0127] The correlation coefficient ρ = Cov / (σ_x*σ_y) is calculated using the covariance, the standard deviation of the actual returned electrical signal, and the standard deviation of the expected returned electrical signal. The correlation coefficient represents the degree of linearity between the actual returned electrical signal and the expected returned electrical signal.
[0128] The comparison result is the correlation coefficient (ρ) value. The correlation coefficient ranges between -1 and 1; a value close to 1 indicates a high positive correlation between the two signals, close to -1 indicates a high negative correlation, and close to 0 indicates no correlation. The advantage of using the correlation coefficient as an indicator for electrical signal comparison is that it considers not only the magnitude of the differences between the electrical signals but also their linear relationship. The correlation coefficient can reveal common trends in signal variation and is an effective method for determining whether a physical attack has occurred.
[0129] S106. The MCU determines whether the PCB has been physically attacked based on the comparison result.
[0130] Based on the comparison results, the MCU determines whether the PCB has been subjected to a physical attack. If the difference between the actual returned electrical signal and the expected returned electrical signal exceeds a predetermined threshold, it may indicate that the PCB has been subjected to a physical attack. If a physical attack is determined, step S107 is executed; otherwise, step S108 is executed.
[0131] S107. Perform protective measures.
[0132] If the MCU determines that the PCB has been subjected to a physical attack, it will execute pre-set protective actions. These actions may include triggering alarms, clearing critical information, locking the device, and suspending transactions to ensure the security and protection functions of the PCB.
[0133] S108. Execute the normal procedure.
[0134] If the MCU determines that the PCB has not been physically attacked, it will continue to perform normal workflows, such as continuing to process financial transactions or other tasks.
[0135] In summary, the method provided in the above embodiments can effectively detect physical attack attempts, such as attacks that attempt to interfere with, alter, or short-circuit electrical signals, by comparing the actual returned electrical signal with the expected returned electrical signal in real time. This helps protect the device from malicious attacks and damage.
[0136] The generation of both the random electrical signal and the expected return electrical signal in the method are based on pre-configured circuit configuration information. This makes the method adaptive, allowing it to adapt to different circuit configurations and devices. Furthermore, by using a random seed, different electrical signals can be generated in different instances, increasing the difficulty for attackers.
[0137] This method compares electrical signals in real time during equipment operation, enabling timely detection of potential physical attacks. Once a physical attack is detected, the system can immediately trigger corresponding protective measures, thereby reducing the damage caused by the attack.
[0138] This method generates and compares electrical signals internally within the device, requiring no additional hardware or external support. This reduces implementation complexity and cost. Upon detecting a physical attack, the system can perform protective actions, such as erasing critical information or locking the device, to protect user data and sensitive information.
[0139] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A PCB safety protection structure, characterized in that, include: A first pad, a second pad, and a zebra strip, wherein one end of the zebra strip is connected to the first pad and the other end is connected to the second pad, and the zebra strip contains multiple layers of insulating and conductive layers, the insulating and conductive layers are spaced apart, and the conductive layers are arranged at an angle to both the first and second pads.
2. The PCB safety protection structure according to claim 1, characterized in that, The multiple conductive layers are parallel to each other.
3. The PCB safety protection structure according to claim 1, characterized in that, It also includes a zebra strip bracket, which is disposed between the first pad and the second pad to support the zebra strip.
4. The PCB safety protection structure according to claim 1, characterized in that, Multiple conductive channels are formed by conductive layers disposed between adjacent insulating layers, and each conductive channel is isolated from the insulating layer. The width and spacing of the conductive channels are equal.
5. The PCB safety protection structure according to claim 1, characterized in that, The first pad is a pad on the cover plate PCB, and the second pad is a pad on the motherboard PCB.
6. A PCB security protection method, characterized in that, Applied to the PCB security protection structure according to any one of claims 1 to 5, wherein the PCB security protection structure is further coupled with an MCU, the method includes: The MCU generates random electrical signals; The MCU sends the random electrical signal to the loop formed by the first pad, the zebra stripe, and the second pad; The MCU generates the desired return electrical signal based on pre-configured circuit configuration information using the same random seed as in the step of generating random electrical signals by the MCU. The MCU receives the actual return electrical signal transmitted through the loop. The MCU compares the returned electrical signal with the expected returned electrical signal to obtain a comparison result. The MCU determines whether the PCB has been physically attacked based on the comparison results. If so, then perform protective measures.
7. The PCB security protection method according to claim 6, characterized in that, The MCU compares the returned electrical signal with the desired returned electrical signal to obtain the comparison result, including: The MCUs are compared in the following way: The difference between each sampling point of the actual returned electrical signal and the expected returned electrical signal is calculated in the following manner: The difference dn = xn - yn; The actual returned electrical signal is represented as xn, and the expected returned electrical signal is represented as yn. There are a total of N sampling points. The squared difference of dn is calculated as follows: Squared difference en = dn^2; The mean square error is calculated as follows: Mean squared error (MSE) = (1 / N) * Σ(en); Where Σ represents the summation over all sampling points; The comparison results include MSE.
8. The PCB security protection method according to claim 6, characterized in that, The MCU compares the returned electrical signal with the desired returned electrical signal to obtain the comparison result, including: The MCUs are compared in the following way: Collect the actual returned electrical signal xn and determine the expected returned electrical signal yn. There are a total of N sampling points. The covariance of all differences is calculated as follows: Covariance Cov = (1 / N) * Σ(xn μ_x)(yn μ_y); Where Σ represents summing over all sampling points, and μ_x and μ_y are the mean values of the actual returned electrical signal and the expected returned electrical signal, respectively; Calculate the standard deviations of the actual return signal and the expected return signal respectively: Standard deviation σ_x = sqrt((1 / N)*Σ(xn-μ_x)^2); Standard deviation σ_y=sqrt((1 / N)*Σ(yn-μ_y)^2); The correlation coefficient ρ is calculated as follows: The correlation coefficient ρ = Cov / (σ_x*σ_y).
9. The PCB security protection method according to claim 8, characterized in that, The comparison results include the correlation coefficient ρ.
10. The PCB security protection method according to claim 6, characterized in that, The protective operations include: Remove sensitive data and transaction records from memory; or The system alerts users or administrators through sound, light indicators, and alarm messages. or Suspend the current transaction.