阅读说明：本技术 一种支持环境感知的puf单元、puf和混合puf (PUF unit, PUF and mixed PUF supporting environment perception ) 是由 郑朝霞 蒋思航 徐尚成 郑刚 刘谦 于 2020-06-22 设计创作，主要内容包括：本发明公开了一种支持环境感知的PUF单元、PUF和混合PUF,属于数字集成电路设计以及安全防伪领域,包括：基于环形振荡器的第一基本PUF单元和感知外部环境变化的片外电路；片外电路串联在所述第一基本PUF单元的反馈环之间。本发明通过将感知外部环境变化的片外电路串联在所述第一基本PUF单元的反馈环之间,由于外部环境的变化改变对应的寄生RC值,寄生RC值的变化导致所述片外电路延时的差异,所述片外电路延时计入环形振荡器的总体延时,该时延变化导致PUF单位的频率发生变化,从而实现外部环境信息耦合到PUF电路内,产生环境变化相关的唯一输出,任何改变外部物理环境的尝试都会导致输出结果永久失效,且无法重建。(The invention discloses a PUF unit, a PUF and a mixed PUF supporting environment perception, which belong to the field of digital integrated circuit design and security and anti-counterfeiting, and comprise the following steps: a first basic PUF unit based on a ring oscillator and an off-chip circuit for sensing external environment change; an off-chip circuit is connected in series between the feedback loops of the first basic PUF cell. According to the invention, the off-chip circuit for sensing the external environment change is connected in series between the feedback loops of the first basic PUF unit, the corresponding parasitic RC value is changed due to the change of the external environment, the change of the parasitic RC value causes the difference of the off-chip circuit delay, the off-chip circuit delay accounts for the total delay of the ring oscillator, the change of the delay causes the change of the frequency of the PUF unit, so that the external environment information is coupled into the PUF circuit to generate the unique output related to the environment change, and any attempt of changing the external physical environment can cause the output result to be permanently invalid and can not be reconstructed.)

1. A PUF cell that supports environmental sensing, comprising: a first basic PUF unit based on a ring oscillator and an off-chip circuit for sensing external environment change; the off-chip circuit is connected in series between feedback loops of the first basic PUF cell.

2. The PUF cell that supports sensing of the environment according to claim 1, wherein a change in the external environment changes a corresponding parasitic RC value, the change in the parasitic RC value resulting in a difference in the off-chip circuit delay that accounts for the overall delay of the ring oscillator to produce an output related to the change in the external environment.

3. The PUF cell supporting sensing of the environment according to claim 1 or 2, wherein the off-chip circuitry is using circuitry on a PCB board or conductive stickers.

4. The PUF cell capable of environmental sensing according to any one of claims 1 to 3, wherein the ring oscillator is connected off-chip at any one of the inverter outputs through a PAD pin of the chip, passes through an off-chip circuit, and then returns to the inverter chain on-chip through another PAD pin of the chip.

5. A PUF supporting environmental perception, comprising:

n independent oscillator rings, each oscillator ring being a PUF cell supporting environmental sensing according to any one of claims 1 to 4;

the output end of each PUF unit is connected to the first multiplexer and the second multiplexer, and the two multiplexers are used for selecting two different PUF units and outputting oscillation waveforms;

the first counter is connected with the output end of the first multiplexer, the second counter is connected with the output end of the second multiplexer, and the counting result is used for reflecting the frequency of the corresponding oscillator ring;

and two input ends of the 1 comparator are respectively connected with the output end of the first counter and the output end of the second counter, and the comparator is used for comparing the counting results of the two counters and generating a response signal of one bit.

6. A hybrid PUF supporting environmental perception, comprising: a second basic PUF based on a ring oscillator and the PUF supporting environmental perception as claimed in claim 5, wherein the first basic PUF and the second basic PUF are identical in structure, and an oscillator ring in the second basic PUF is a first basic PUF unit based on the ring oscillator;

and the multi-bit response signal generated by the second basic PUF and the multi-bit response signal generated by the PUF supporting the environmental perception are mixed through logic operation to obtain a final result of the mixed PUF supporting the environmental perception.

7. The context aware hybrid PUF according to claim 6, wherein the context aware hybrid PUF further comprises a register to store results of the context aware PUF.

Technical Field

The invention belongs to the field of digital integrated circuit design and security anti-counterfeiting, and particularly relates to a PUF unit, a PUF and a hybrid PUF supporting environment sensing.

Background

Since the 21 st century, information technology has been rapidly developed, various smart cards, RFID and the like are widely applied, and the physical entities have high requirements on safety as small as bank cards, bus cards and even smart phones with built-in NFC everywhere in life. These physical entities are limited by their resource limitations, computing power and reproducibility, and it is difficult to achieve higher security authentication standards based on the requirements of traditional cryptography. Currently, fingerprint identification, iris identification and even voiceprint identification based on biological unique features are a safe and effective authentication idea for performing unique identity authentication on an individual, and by the aid of the idea, a concept of a Physical Unclonable Function (PUF) is proposed.

Just as there are no two identical leaves in the world, the PUF does so depending on the irreversible errors in the chip manufacturing process, and by using the randomness and uniqueness of these errors, they are extracted as the characteristics of the chip in a special way, so as to realize a unique correspondence between the excitation signal and the response signal, thus forming a "chip fingerprint" similar to a human fingerprint. The PUF concept greatly enriches the application scenes and the safety of the traditional cryptography.

PUFs can be broadly divided into two major classes, one being an unitegrable PUF; another class is the integratable electronic class of PUFs, including both analog and digital circuit PUFs. Examples of unitegrable PUFs include optical PUFs, paper PUFs, and CD PUFs. Such PUFs tend to possess good randomness and uniqueness, but the disadvantage is that these PUFs cannot be well integrated into a circuit, which is difficult to apply. Electronic PUFs are mainly based on random characteristics such as asymmetry of some processes, or memory-based unsteady state, or delay-based randomness, which are generated randomly but can be stabilized and continued once generated.

Besides the PUFs described above, researchers have proposed corresponding PUFs based on the fundamental theory of quantum mechanics, such as "spintronic PUFs" by utilizing the difference in the electron spin direction, but although the PUF in this form meets the requirement of integration in size, it still needs to be considered how to integrate it into a circuit.

In summary, the most widely used at present are integratable electronic PUFs. The PUF has the main characteristic that the output corresponds to the chip real objects one to one, cannot be influenced by an external environment, and is really suitable for generating the unique ID of the chip. However, in actual products, not only one chip is included, but also all environments required for the chip to work are provided, and sometimes the environments are even higher than the value of the chip, so that the counterfeiting focuses on the counterfeiting of the environments. At this time, the PUF cannot provide support for environmental anti-counterfeiting.

Disclosure of Invention

Aiming at the problem that the existing PUF can not be applied to the anti-counterfeiting of the environment outside a chip only by generating a result through the process deviation inside the chip, the invention provides a PUF unit, a PUF and a mixed PUF supporting environment perception, and aims to couple specific physical environment information outside the chip into the internal PUF generation flow, and the unique physical environment of the PUF can be damaged by any counterfeiting attempt such as chip detachment or external circuit damage, so that the output of the PUF is damaged.

To achieve the above object, according to a first aspect of the present invention, there is provided a PUF cell supporting environmental sensing, comprising: a first basic PUF unit based on a ring oscillator and an off-chip circuit for sensing external environment change; the off-chip circuit is connected in series between feedback loops of the first basic PUF cell.

Preferably, changes in the external environment change corresponding parasitic RC values, the changes in the parasitic RC values resulting in differences in the off-chip circuit delays that account for the overall delay of the ring oscillator to produce an output related to the external environment change.

Preferably, the off-chip circuitry is using circuitry on a PCB board, or conductive stickers.

Preferably, the ring oscillator is connected to the outside of the chip through a PAD pin of the chip at the output end of any one inverter, and returns to an inverter chain inside the chip through another PAD pin of the chip after passing through an off-chip circuit.

To achieve the above object, according to a second aspect of the present invention, there is provided a PUF supporting environmental perception, comprising:

n independent oscillator rings, each oscillator ring being a PUF cell supporting environmental sensing as described in the first aspect;

the output end of each PUF unit is connected to the first multiplexer and the second multiplexer, and the two multiplexers are used for selecting two different PUF units and outputting oscillation waveforms;

the first counter is connected with the output end of the first multiplexer, the second counter is connected with the output end of the second multiplexer, and the counting result is used for reflecting the frequency of the corresponding oscillator ring;

and two input ends of the 1 comparator are respectively connected with the output end of the first counter and the output end of the second counter, and the comparator is used for comparing the counting results of the two counters and generating a response signal of one bit.

To achieve the above object, according to a third aspect of the present invention, there is provided a hybrid PUF supporting environmental perception, comprising: a second basic PUF based on a ring oscillator and the PUF supporting environmental sensing as described in the second aspect, the first basic PUF and the second basic PUF being identical in structure, the oscillator ring in the second basic PUF being a first basic PUF cell based on the ring oscillator;

and the multi-bit response signal generated by the second basic PUF and the multi-bit response signal generated by the PUF supporting the environmental perception are mixed through logic operation to obtain a final result of the mixed PUF supporting the environmental perception.

Preferably, the hybrid PUF supporting environmental sensing further includes a register for storing a result of the PUF supporting environmental sensing.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

(1) the invention provides a PUF unit supporting environment sensing, wherein an off-chip circuit sensing external environment change is connected in series between feedback loops of a first basic PUF unit, the off-chip circuit delay is counted into the total delay of a ring oscillator, the delay change causes the change of the unit frequency of the PUF, and therefore the external environment information is coupled into the PUF circuit to generate unique output related to environment change, and any attempt of changing the external physical environment can cause the output result to be permanently invalid and incapable of being reconstructed.

(2) The invention provides a PUF supporting environment sensing, because time delay is mainly generated by parasitic resistance and capacitance of a line, factors such as environment temperature and power supply voltage can uniformly influence all external circuits RC, common mode change is brought, the change can be eliminated when frequency comparison is carried out, and the final result cannot be influenced. Therefore, only the specific line is changed, which affects the comparison result, and the stability of the environmental perception can be ensured.

(3) The invention relates to a mixed PUF supporting environmental perception, which consists of a single PUF structure and a PUF structure supporting environmental perception, and response results of the two are mixed through logic operation, so that an output sequence has better random characteristics.

Drawings

Fig. 1 is a schematic diagram of a PUF cell structure supporting environmental sensing according to the present invention;

FIG. 2 is a block diagram of a PUF supporting environmental sensing according to the present invention;

fig. 3 is a structural diagram of a hybrid PUF supporting environmental sensing provided in the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a mixed Physical Unclonable Function (PUF) implementation scheme supporting environment perception, which comprises a basic PUF structure and an environment perception PUF structure. The basic PUF is a PUF based on a ring oscillator, and the environment sensing PUF structure is realized by connecting the basic PUF to a circuit which is connected to the outside of a chip through a PAD of the chip and can sense the change of the physical environment. A context-aware PUF pattern may couple external environmental information into a PUF circuit to produce a unique output that is context dependent, and any attempt to change the external physical environment may result in the output being permanently disabled and unable to be reconstructed. And finally, mixing the single PUF structure and the environment perception PUF structure to generate a unique output result. The responses (response signals) generated by both PUFs are required to be of the same length AND implemented by specific logic operations (XOR, AND, OR, etc.).

The ring oscillator based PUF consists of N ring oscillators, generated by comparing the magnitude of each two ring oscillator frequencies. The ring oscillator uses a common inverter end-to-end mode, and different paths of delay caused by process deviation are utilized to generate oscillation with different frequencies, so that output is obtained through comparison. Because every two oscillators can be used for generating 1-bit output, in order to realize multi-bit output, the number of the oscillators can be expanded according to actual requirements.

As shown in fig. 1, the PUF supporting environmental sensing is implemented on the basis of a ring oscillator PUF. The oscillator path is disconnected at one stage in the middle of the inverter chain, reaches the outside of the chip through the PAD pin of the chip, and returns to the inverter chain in the chip through another PAD pin of the chip after passing through a specific line outside the chip. The environmental perception is realized by the PAD foot and the off-chip line.

One input end of an AND gate is used as a switch control, and the output end of the AND gate is connected with an odd number of inverters; at the output end of the last phase inverter, the output end is connected to the outside of the chip through the PAD of the chip; after passing through the off-chip line, it is returned to the chip through another PAD and connected to the other input of the and gate, completing an oscillator loop. In the oscillator, a signal is output from the output end of any inverter as a starting point, and the delay generated after the signal passes through a circuit and returns to the starting point is 1/2 oscillation period. The time delay of a part of circuits in a chip is determined by process deviation in the manufacturing process, each chip has time delay with different lengths, and the basic PUF utilizes the time delay to generate relevant chip output; the context awareness is reflected by the delay introduced by the off-chip circuitry, which will also calculate the delay of the off-chip circuitry into the overall delay of the oscillator to produce an output related to the context.

The off-chip line is most simply represented by a parasitic series resistance R and a parasitic parallel capacitance C. Environmental factors can affect the value of the parasitic RC, which can cause changes in line delay, thereby correlating environmental factors with line delay. Various line-independent noises in the environment, such as temperature, can have the same effect on all such RC values connected to off-chip loops; only the physical properties of the off-chip line, such as the pin soldering condition and the line implementation manner, bring unique RC changes to the loop. Therefore, the invention defines the environmental perception as the change of the line outside the sensing chip. Where off-chip circuitry is defined as any relevant circuitry that exits the PAD pin of the chip for environmental sensing. The off-chip circuit can be flexibly realized according to specific physical environment, such as using a circuit on a PCB (printed Circuit Board), or using a conductive sticker, and the like.

The specific principle is as follows: in the actual implementation process, even if the PAD pin is designed exactly the same, some slight deviations must be introduced, which causes the parasitic parameters to change. The change of the parasitic parameters can cause the delay of the line to change, and the line is connected into a loop of the oscillator, so that the delay information can be introduced into a process generated by the PUF to generate a PUF value related to a physical environment. Since these slight deviations can be stably maintained after the implementation, any chip detachment or physical environment change will change the corresponding parasitic parameters, and further change the delay of the line, resulting in a change in the PUF output. Since the generation of these subtle differences is completely random in the manufacturing process, the reconstruction of the physical environment is not possible. Thus, a unique correspondence of the physical object to the PUF output can be achieved. For example, when the chip pin is soldered to the PCB pad, the process will cause unique RC parasitics and thus unique delay, which will inevitably change after the chip is detached and soldered again; in another example, attaching the output to a conductive sticker and then applying the sticker to a particular product surface will necessarily change the time delay information once the sticker is torn.

As shown in fig. 2, RO1 through ROn are n independent oscillator rings and are connected to two n-input multiplexers MUX. The outputs of the multiplexers are selected by changers, each of which selects two different ROs and outputs an oscillating waveform from the multiplexer. The two oscillations drive two independent counters CNT1 and CNT2, respectively, which are clocked using a standard clock ref clk. When a period of time has elapsed, the REF _ CNT output stop signal stops the counting of CNTs 1 and CNTs 2. The final count values of CNT1 and CNT2 may reflect the frequency of the corresponding RO, and a final 0/1 comparison value may be obtained by comparing the count values.

RO in fig. 2, which is a common ring oscillator, the structure is used as a common PUF; when the ring oscillator is a ring oscillator supporting environmental sensing as shown in fig. 1, the structure is used as a PUF supporting environmental sensing.

As shown in fig. 3, the hybrid PUF is mainly composed of the basic PUF and the PUF supporting the environmental sensing, and its output is multi-bit. The PUF configuration shown in fig. 2 can only output 1bit at a time, so a register configuration is required to store the PUF result shown in fig. 2, and different outputs are generated by inputting different changees for multiple times to obtain a multi-bit result. Finally, the output results of the two PUFs are mixed by logical operation, usually by exclusive or operation, to obtain the final output.