TWI864389B - Power supplying device, method and secure system - Google Patents

Abstract

A power supplying device is provided with a secure power supply device, a voltage detection circuit, a stable voltage source and a switch. By using the voltage detection circuit, whether a driving voltage of the encryption/decryption device is insufficient is determined to control the on and off the switch, so as to determine whether only the security power supply device provides the supply voltage to the encryption/decryption device as the driving voltage, or the supply voltage of the secure power supply device and the stable voltage of the stable voltage source are provided simultaneously to the encryption/decryption device as the driving voltage. In other words, once the driving voltage drops (that is, the encryption/decryption device consumes a large current for encryption/decryption), the stable voltage source immediately provides the stable voltage to the encryption/decryption device as part of the driving voltage to ensure that the encryption/decryption device can normally work.

Description

Power supply device, method and safety system

The present invention relates to a power supply device, method and security system, and in particular to a power supply device, method and security system that can prevent hackers from maliciously stealing security information by detecting changes in system voltage of a power supply and changes in corresponding current values.

In recent years, security applications have been implemented in many areas, including identity cards, credit cards, computer access control, and mobile phones (e.g., SIM cards). These applications usually rely on cryptographic calculations based on keys embedded in memory to achieve high security. Hackers will try to extract these keys from the card to generate unauthorized transactions. Side channel attacks are the most common method to collect information from a card or computer system during normal operation. It can decrypt the keys based on timing information, power consumption, and electromagnetic fields. Therefore, keeping data secure and avoiding side channel attacks are factors that need to be considered when designing a secure system.

The power side channel attack scenario is as follows. During the switching of the logic gates of the encryption device (implemented by multiple logic gates), the hacker can detect the current change and the power characteristics generated by the current change. Usually, the driving voltage applied to the encryption device will also change with the current change. These power characteristics can be monitored by the power pins and used to recover the key. In order to prohibit the reading of power and ground signals from the logic gate, the power pins and ground pins are usually isolated from the external pads.

Please refer to FIG. 1, which is a circuit diagram of a security system of the prior art. The security system 1 includes a power supply 10, a power supply device 12, and an encryption device 14, wherein the power supply device 12 is electrically connected between the power supply 10 and the encryption device 14 to prevent hackers from obtaining power supply characteristics related to security information by detecting the power pins and ground pins of the power supply 10. The power supply device 12 includes a plurality of switches SW1 to SW5 and a charge storage capacitor CS. One end of the switch SW1 is electrically connected to the system voltage of the power supply 10, and the other end of the switch SW1 is electrically connected to one end of the switch SW2, one end of the switch SW5, and one end of the charge storage capacitor CS. The other end of the switch SW2 is electrically connected to one end of the encryption device 14, thereby outputting a supply voltage to the encryption device 14 as a driving voltage of the encryption device 14. One end of the switch SW3 is electrically connected to the ground voltage of the power source 10. The other end of the switch SW3 is electrically connected to one end of the switch SW4, the other end of the switch SW5 and the other end of the charge storage capacitor CS. The other end of the switch SW4 is electrically connected to the other end of the encryption device 14 to provide a ground voltage to the encryption device 14.

The process of the power supply device 12 providing the supply voltage is as follows. First, in the first stage, only the switch SW5 is turned on, and the other switches SW1 to SW4 are turned off to discharge the charge storage capacitor CS to a specific voltage level, that is, the switch SW5 is used as a reset switch. In the second stage, the switches SW1 and SW3 are turned on, and the other switches SW2, SW4, and SW5 are turned off, so the system voltage of the power supply 10 can charge the charge storage capacitor CS. After charging to the voltage level of the system voltage, it enters the third stage. In the third stage, the switches SW2 and SW4 are turned on, and the other switches SW1, SW3, and SW5 are turned off, and the charge storage capacitor CS provides the supply voltage to the encryption and decryption device 14 as a driving voltage. Then, in the fourth stage, the encryption and decryption device 14 is allowed to perform encryption and decryption. After the fourth stage is finished, it returns to the first stage again.

Through the above method, although it is possible to prevent hackers from obtaining power supply characteristics related to security information through the power pin and the ground pin of the detection power supply 10, the above method must ensure that the amount of charge stored in the charge storage capacitor CS must be able to supply the large amount of charge consumed by the encryption and decryption device 14 during encryption and decryption, so this results in the size of the charge storage capacitor CS must be large enough. Furthermore, the above method is not a power-saving solution, because the above method must discharge the charge storage capacitor CS to a predetermined voltage level in the first stage. In addition, the larger the size of the charge storage capacitor CS, the longer the charging and discharging time will be, which will be more time-consuming overall, not to mention that the above method requires a total of four stages to ensure that the encryption and decryption device 14 can work normally.

The embodiment of the present invention provides a power supply device for providing power to an encryption device of a security system, and includes a security power supply device, a stable voltage source, a voltage detection circuit and a switch. The security power supply device is used to provide a supply voltage according to a system voltage. The stable voltage source is used to provide a stable voltage. The voltage selection device is electrically connected to the encryption device, the safety power supply device and the stable voltage source, and is used to select the stable voltage and the supply voltage as the driving voltage of the encryption device when the driving voltage of the encryption device is less than the lower limit voltage, and to select the supply voltage as the driving voltage when the driving voltage of the encryption device is not less than the lower limit voltage.

The embodiment of the present invention also provides a security system, which includes the power supply device and the encryption and decryption device.

The embodiment of the present invention also provides a power supply method, which is used to provide power to the encryption and decryption device of the security system, and has the following steps. Determine whether the driving voltage of the encryption and decryption device is less than the lower limit voltage. If the driving voltage of the encryption and decryption device is less than the lower limit voltage, the supply voltage of the security power supply device and the stable voltage of the stable voltage source are used as the driving voltage at the same time. If the driving voltage of the encryption and decryption device is not less than the lower limit voltage, the supply voltage is used as the driving voltage.

In summary, compared with the prior art, the various power supply devices, methods and security systems provided by the embodiments of the present invention can achieve at least one of the technical effects of reducing the size, operation time, power consumption current and circuit area required for the charge storage capacitor. The power supply device of the embodiments of the present invention can effectively protect the security system and prevent hackers from obtaining security information through the power characteristics detected by the power pins and the ground pins.

In order to further understand the technology, means and effects of the present invention, reference may be made to the following detailed description and accompanying drawings, so that the purpose, features and concepts of the present invention can be thoroughly and specifically understood. However, the following detailed description and accompanying drawings are only used for reference and explanation of the implementation of the present invention, and are not used to limit the present invention.

Reference will now be made in detail to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Where possible, the same reference numerals are used in the drawings and the specification to refer to the same or similar components. In addition, the exemplary embodiments are only one of the implementation methods of the design concept of the present invention, and the following examples are not intended to limit the present invention.

To solve the problems of the prior art, the various power supply devices, methods and security systems provided by the embodiments of the present invention can prevent hackers from obtaining security information through the power characteristics detected by the power pins and the ground pins, and while achieving the security protection effect, can also achieve at least one of the technical effects of reducing the size, operation time, power consumption current and circuit area required for the charge storage capacitor.

In the embodiment of the present invention, the power supply device includes a safety power supply device, a voltage detection circuit, a stable voltage source and a switch. The voltage detection circuit determines whether the driving voltage of the encryption device is insufficient to control the on and off of the switch to determine whether only the safety power supply device provides the supply voltage to the encryption device as the driving voltage, or whether the safety power supply device and the stable voltage source simultaneously provide the supply voltage and the stable voltage encryption device as the driving voltage. In other words, once the driving voltage drops (i.e., the encryption device performs encryption and decryption and consumes a large current), the stable voltage source (for example, implemented by a DC-to-DC converter such as a bandgap voltage generator or a low-dropout voltage regulator) immediately provides the stable voltage to the encryption device as part of the driving voltage to ensure that the encryption device can work normally. Since the voltage detection circuit detects the encryption device in real time, the safe power supply device does not have to perform four stages of charging and discharging as in the prior art, thereby effectively reducing the size, operation time, power consumption current and circuit area required for the charge storage capacitor.

Incidentally, the switching switch and the voltage detection circuit can be integrated into a voltage selection device. The voltage selection device is electrically connected to the encryption device, the safety power supply device and the stable voltage source. When the driving voltage of the encryption device is not less than the lower limit voltage, the voltage selection device selects the supply voltage as the driving voltage; and when the driving voltage of the encryption device is less than the lower limit voltage, the voltage selection device selects the supply voltage and the stable voltage as the driving voltage at the same time. Furthermore, in another embodiment, it can also be designed that when the driving voltage of the encryption device is less than the lower limit voltage, the voltage selection device only selects the stable voltage as the driving voltage at the same time.

First, please refer to FIG. 2, which is a circuit diagram of a security system according to an embodiment of the present invention. The security system 2 includes a power supply device 20 and an encryption device 22, wherein the power supply device 20 includes a stable voltage source 200, a safe power supply device 202, a voltage detection circuit 204, and a switching switch 206. The power supply device 20 is used to provide power to the encryption device 22 of the security system 2, and its main purpose is to prevent hackers from obtaining security information by detecting changes in power characteristics obtained by the power pin and the ground pin (i.e., changes in the power characteristics of the system voltage). In other words, during the encryption and decryption process of the encryption device 22, the power characteristics of the system voltage will not change significantly.

The safety power supply device 202 is used to generate a supply voltage according to the system voltage and provide the supply voltage, wherein the supply voltage is applied to the encryption device 22 to serve as part or all of the driving voltage VDIG for driving the encryption device 22 (related to the on and off of the switching switch 206). Through the safety power supply device 202, when the encryption device 22 performs encryption and decryption, the power supply characteristic variation of the system voltage is less than a specific range, for example, the current or voltage variation is less than 5%, but the present invention is not limited to this. However, when only the safety power supply device 202 provides the supply voltage as the driving voltage VDIG of the encryption device 22, it may not be able to provide enough total output current to the encryption device 22 as the current consumed in encryption (if the safety power supply device 202 does not have a large charge storage capacitor or does not have enough switching current units). Therefore, the stable voltage source 200, the switching switch 206 and the voltage detection circuit 204 are set in the power supply device 20 to solve the above technical problems.

The stabilized voltage source 200 is used to provide a stable voltage that is not susceptible to changes, wherein the stabilized voltage source 200 can be implemented by a DC-to-DC converter such as a bandgap voltage generator, a low-dropout voltage regulator, etc., for example but not limited to the stabilized voltage source 300 of FIG. 6 , which is implemented by a bandgap reference voltage circuit composed of a PMOS transistor MP1, a comparator CMP1, and a resistor R1, and is used to provide a lower system voltage DVDD (lower than the system voltage VDD) as a stable voltage. The voltage detection circuit 204 is electrically connected to the encryption device 22, and is used to generate a switch signal according to the drive voltage VDIG of the encryption device 22. The voltage detection circuit 204 can be implemented using a comparator, wherein the comparator is used to receive the driving voltage VDIG of the encryption device 22, and the positive input terminal of the comparator is used to receive the lower limit voltage VTG-Δ, and the voltage value of the lower limit voltage VTG-Δ is the target voltage value VTG of the driving voltage VDIG minus the difference voltage value Δ. It should be noted that the implementation of the voltage detection circuit 204 of the present invention is not limited to the comparator. The switching switch 206 has a first end, a second end and a control end, wherein the first end is electrically connected to the stable voltage source 200, the second end is electrically connected to the encryption device 22, and the control end is electrically connected to the voltage detection circuit 204 to receive the first switch signal. The conduction or disconnection of the switch 206 (ie, the conduction or disconnection between the first terminal and the second terminal) is controlled by the first switch signal.

When the encryption and decryption device 22 performs encryption and decryption, the current consumption of the encryption and decryption device 22 increases, and the driving voltage VDIG of the encryption and decryption device 22 decreases. When the driving voltage VDIG is less than the lower limit voltage VTG-Δ, the first switch signal turns on the switching switch 206, and the encryption and decryption device 22 receives the stable voltage and the supply voltage as the driving voltage VDIG, that is, the driving voltage VDIG consists of two parts, one of which is the stable voltage and the other is the supply voltage. In this way, it can be ensured that the encryption and decryption device 22 has sufficient current to use and can perform encryption and decryption normally.

When the driving voltage VDIG is still greater than the lower limit voltage VTG-Δ, the first switch signal will cause the switching switch 206 to be disconnected, so the supply voltage is still provided by the safety power providing device 202 as the entire driving voltage VDIG. Preferably, the safety power providing device 202 is designed to increase the total output current of the safety power providing device 202 to increase the voltage value of the driving voltage VDIG when the driving voltage VDIG decreases but is still greater than the lower limit voltage VTG-Δ.

Incidentally, the power supply device 20 may further include a capacitor connected in parallel to the encryption device 22 and/or a ripple suppression unit connected in parallel to the encryption device 22 (not shown). The capacitor connected in parallel to the encryption device 22 and/or the ripple suppression unit connected in parallel to the encryption device 22 can more effectively maintain the stability of the driving voltage, wherein the ripple suppression unit may be a transistor whose gate receives a fixed bias, and the source and drain of the transistor receive the driving voltage VDIG and a low voltage (e.g., a ground voltage) respectively, so that the ripple when the driving voltage VDIG changes can be reduced.

Next, please refer to Figure 3, which is a circuit diagram of a safe power supply device of an embodiment of the present invention. One implementation of the safe power supply device 202 is shown in Figure 3, but the present invention is not limited to this. The safe power supply device 202 includes switches SW1~SW5 and a charge storage capacitor CS. The two ends of switch SW1 are electrically connected to the system voltage VDD and one end of switch SW2 respectively. The other end of switch SW2 is used to output the supply voltage as part or all of the driving voltage VDIG. The two ends of switch SW3 are electrically connected to a low voltage (for example, a ground voltage) and one end of switch SW4. The other end of switch SW4 is electrically connected to the other end of switch SW3. The two ends of switch SW5 are electrically connected to the two ends of the charge storage capacitor CS respectively. The switch SW5 is used as a discharge switch to provide a discharge path, but it is not an essential component in the present invention and can be selectively removed.

One end of the charge storage capacitor CS is electrically connected to the other end of the switch SW1 and one end of the switch SW2, and the other end of the charge storage capacitor CS is electrically connected to the other end of the switch SW3 and one end of the switch SW3. The switches SW1 to SW4 are controlled by a plurality of second switch signals, and the switch SW5 is controlled by a reset signal, wherein the plurality of second switch signals can be used to control the charge storage capacitor CS to charge and discharge in four stages as described in the prior art. Incidentally, the switch SW5 is not a necessary component in the present invention, and can be selectively removed, that is, the voltage level of the charge storage capacitor CS does not need to be reset.

Next, please refer to FIG. 4, which is another circuit diagram of the safety power supply device of the embodiment of the present invention. Another implementation of the safety power supply device 202 is shown in FIG. 3, but the present invention is not limited thereto. The safety power supply device 202 includes a plurality of switching current units CU1-CUn, wherein a plurality of ends of the plurality of switching current units CU1-CUn are electrically connected to the system voltage VDD, and another plurality of ends of the plurality of switching current units CU1-CUn are electrically connected to each other and used to output the supply voltage as part or all of the driving voltage VDIG, and the plurality of switching current units CU1-CUn are controlled by a plurality of second switch signals.

The switching current unit CU1 includes a current source CR1 and a switch SC1, wherein one end of the current source CR1 is electrically connected to the system voltage VDD, two ends of the switch SC1 are electrically connected to the other end of the current source CR1 and the system voltage VDD, and the switch SC1 is controlled by a second switch signal. Similarly, the switching current unit CUn includes a current source CRn and a switch SCn, and the electrical connection method of the current source CRn and the switch SCn is similar to the electrical connection method of the current source CR1 and the switch SC1, so it is not repeated. When the encryption and decryption device 22 performs encryption and decryption, causing the driving voltage VDIG to decrease but not less than the lower limit voltage VTG-Δ, multiple switching current units CU1~CUn are controlled by multiple second switch signals to increase the total output current of the multiple switching current units CU1~CUn to increase the voltage value of the driving voltage VDIG.

Please refer to FIG. 5, which is a flow chart of a power supply method of an embodiment of the present invention. This power supply method is used to provide power to the encryption and decryption device of the security system, which can be executed by the above-mentioned power supply device and includes the following steps. First, in step S102, the initial state is that the security power supply device provides a supply voltage to the encryption and decryption device as a driving voltage. Then, in step S104, the encryption and decryption device starts encryption and decryption. In step S106, it is determined whether the driving voltage of the encryption and decryption device is less than the lower limit voltage. If the driving voltage of the encryption/decryption device is not less than the lower limit voltage, step S108A is executed; on the contrary, if the driving voltage of the encryption/decryption device is less than the lower limit voltage, step S108B is executed.

In step S108A, since the driving voltage of the encryption device is not less than the lower limit voltage, the safety power supply device continues to provide the supply voltage to the encryption device as the driving voltage. In step S108B, since the driving voltage of the encryption device is not less than the lower limit voltage, the safety power supply device and the stable voltage source respectively provide the supply voltage and the stable voltage to the encryption device as the driving voltage, so as to avoid the encryption device being unable to perform encryption and decryption smoothly due to insufficient driving current or driving voltage.

Please note that although the above method is limited to selecting the source of the driving voltage when the encryption device is performing encryption and decryption, the present invention is not limited to this. In other embodiments, it is not necessary to consider whether encryption and decryption are being performed. When the driving voltage is less than the lower limit voltage, the stable voltage and the supply voltage are used as the driving voltage at the same time.

In summary, the various power supply devices, methods and security systems provided by the embodiments of the present invention can achieve the technical effect of preventing hackers from detecting power pins and ground pins to obtain security information. Moreover, compared with the prior art, the various power supply devices, methods and security systems of the embodiments of the present invention can also effectively reduce the size, operation time, power consumption current and circuit area required for the charge storage capacitor. In addition, it is mentioned that the system complexity of the various power supply devices, methods and security systems of the embodiments of the present invention is not high, so it is easy to implement and does not require a huge manufacturing cost. Therefore, the various power supply devices, methods and security systems of the embodiments of the present invention have extremely high practicality and market value.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes thereto will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the scope of the appended claims.

1~3, 3': Security system 10: Power supply 12, 20: Power supply device 14, 22: Encryption device 200: Stable voltage source 202: Safety power supply device 204: Voltage detection circuit 206: Switch SW1~SW5: Switch CS: Charge storage capacitor VDIG: Driving voltage VTG-Δ: Lower limit voltage DVDD, VDD: System voltage CU1~CUn: Switching current unit CR1~CRn: Current source SC1~SCn: Switch S102, S104, S106, S108A, S108B: Step MP1: PMOS transistor CMP1: Comparator R1: resistor

The accompanying drawings are provided to enable a person with ordinary knowledge in the technical field to which the present invention belongs to further understand the present invention, and are incorporated into and constitute a part of the specification of the present invention. The accompanying drawings show exemplary embodiments of the present invention, and are used together with the specification of the present invention to explain the principle of the present invention.

FIG. 1 is a circuit diagram of a safety system of the prior art.

FIG. 2 is a circuit diagram of a safety system according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a safe power supply device according to an embodiment of the present invention.

FIG. 4 is another circuit diagram of the safety power supply device according to the embodiment of the present invention.

FIG5 is a flow chart of a power supply method according to an embodiment of the present invention.

FIG6 is a circuit diagram of a stable voltage source according to an embodiment of the present invention.

2: Security system

20: Power supply device

22: Encryption and decryption device

200:Stable voltage source

202: Safe power supply device

204: Voltage detection circuit

206: Switch

VDIG: driving voltage

VTG-Δ: lower limit voltage

Claims (10)

A power supply device is used to provide power to an encryption device of a security system, comprising: A safety power supply device, used to provide a supply voltage according to a system voltage; A stable voltage source, used to provide a stable voltage; A voltage selection device, electrically connecting the encryption device, the safety power supply device and the stable voltage source, used to select the stable voltage and the supply voltage as the driving voltage of the encryption device when the driving voltage of the encryption device is less than a lower limit voltage, and used to select the supply voltage as the driving voltage when the driving voltage of the encryption device is not less than the lower limit voltage. A power supply device as described in claim 1, wherein the voltage selection device comprises: a voltage detection circuit electrically connected to the encryption device, for comparing the driving voltage with the lower limit voltage to generate a first switch signal; and a switching switch having a first end, a second end and a control end, wherein the first end is electrically connected to the stable voltage source, the second end is electrically connected to the encryption device, and the control end is electrically connected to the voltage detection circuit to receive the first switch signal; The first end and the second end are connected or disconnected according to the first switch signal. When the first end and the second end are connected, the encryption and decryption device receives the stable voltage and the supply voltage as the driving voltage. When the first end and the second end are disconnected, the encryption and decryption device receives the supply voltage as the driving voltage. A power supply device as described in claim 2, wherein the voltage detection circuit is a comparator, the negative input terminal of the comparator is used to receive the driving voltage, the positive input terminal of the comparator is used to receive the lower limit voltage, and the voltage value of the lower limit voltage is the target voltage value of the driving voltage minus the difference voltage value. A power supply device as described in claim 1, wherein the safety power supply device comprises: a first switch, a second switch, a third switch, and a fourth switch, wherein two ends of the first switch are electrically connected to the system voltage and one end of the second switch, respectively, and the other end of the second switch is used to output the supply voltage, two ends of the third switch are electrically connected to the low voltage and one end of the fourth switch, and the other end of the fourth switch is electrically connected to the other end of the third switch; and a charge storage capacitor, wherein one end of the charge storage capacitor is electrically connected to the other end of the first switch and the one end of the second switch, and the other end of the charge storage capacitor is electrically connected to the other end of the third switch and the one end of the fourth switch; wherein the first switch, the second switch, the third switch, and the fourth switch are controlled by a plurality of second switch signals. The power supply device as described in claim 4, wherein the safety power supply device further comprises: A discharge switch, wherein two ends of the discharge switch are electrically connected to the two ends of the charge storage capacitor, and the discharge switch is controlled by a reset signal. A power supply device as described in claim 1, wherein the safety power supply device comprises: A plurality of switching current units, wherein a plurality of ends of the plurality of switching current units are electrically connected to the system voltage, another plurality of ends of the plurality of switching current units are electrically connected to each other and used to output the supply voltage, and the plurality of switching current units are controlled by a plurality of second switch signals. A power supply device as described in claim 6, wherein the switching current unit comprises: a current source, wherein one end of the current source is electrically connected to the system voltage; and a switch, wherein two ends of the switch are electrically connected to the other end of the current source and the supply voltage, respectively, and the switch is controlled by the second switch signal. A security system, comprising: a power supply device as described in any one of claim items 1 to 8; and the encryption and decryption device. A power supply method is used to provide power to an encryption device of a security system, comprising: Determining whether the driving voltage of the encryption device is less than a lower limit voltage; When the driving voltage of the encryption device is less than the lower limit voltage, using the supply voltage of a safety power supply device and the stable voltage of a stable voltage source as the driving voltage; and When the driving voltage of the encryption device is not less than the lower limit voltage, using the supply voltage as the driving voltage. A power supply device is used to provide power to an encryption device of a security system, comprising: A safety power supply device, used to provide a supply voltage according to a system voltage; A stable voltage source, used to provide a stable voltage; A voltage selection device, electrically connecting the encryption device, the safety power supply device and the stable voltage source, used to select the stable voltage as the driving voltage of the encryption device when the driving voltage of the encryption device is less than a lower limit voltage, and used to select the supply voltage as the driving voltage when the driving voltage of the encryption device is not less than the lower limit voltage.

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