JP2003108364A - Random number generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a random number generation circuit that generates intrinsic random numbers and can be rendered as a small integrated circuit. SOLUTION: The random number generation circuit generates digital random numbers based on a noise acquired from a noise source. If a tunnel element is used as the noise source, a thermal noise and a shot noise can be simultaneously acquired on a high level, accordingly, the size and configuration of an amplifier can be simplified considerably, and random numbers of high genuineness can be generated. In addition, by providing a feedback circuit for automatically holding the output distribution of the noises acquired with the tunnel element constant by feeding a feedback signal to a control terminal that can control the maximum value of the tunnel current, it can be realized to automatically correct the deviation of the distribution of the random numbers to improve the degree of genuineness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a random number generation circuit, and more particularly, to a small and lightweight random number generation circuit capable of generating random numbers with high authenticity.

[0002]

2. Description of the Related Art Digital random numbers are used for simulation of phenomena involving stochastic processes, generation of cryptographic keys in cryptographic algorithms used for security, and the like. Conventionally, as the digital random number, a "pseudo-random number" created by a CPU has been used. This pseudo random number is typically made by a logic circuit called a “feedback shift register”.

On the other hand, when a random number is generated by using noise generated in an element, it is a "true random number" with no periodicity or bias.
It is known that a product close to the above can be obtained, and some of them have already been put to practical use for large-scale computers.

FIG. 13 is a schematic diagram illustrating a circuit configuration for generating random numbers from noise generated in the element. That is, in the case of the circuit illustrated in the figure, noise generated by causing a constant current to flow through the element 110 as a noise source is passed through a high-pass filter circuit to extract an AC component. Next, after being amplified by the analog circuit 112, it is AD-converted by the A / D converter 114 and digitized. At this time, a certain value is set as a threshold value, and a value exceeding that is set to “1”,
Digits below that are digitized as "0".
Further, since the generated random number sequence is biased, it is used after being corrected by the digital circuit 116.

A resistor, a diode, or the like is used for the element 110 which is a noise source. Thermal noise (Johnson noise), which is white noise, or the like is used as the noise.

[0006]

The "pseudo-random number" created by the CPU generates the same random number if the numbers (seed) given at the beginning are the same, and the periodicity based on the number of registers. Therefore, it is known that it is not suitable as a random number. In particular, when used for security, it causes a risk of breaking the encryption key.

On the other hand, in the case of the type that amplifies noise, the output of thermal noise and shot noise of resistors and diodes is generally small, so that the circuit configuration becomes large in scale, and integration and miniaturization are difficult. For example, thermal noise in a normal resistor or diode is a weak signal of about 1 microvolt peak-to-peak, so that amplification of about 10 ⁶ times is required to generate a signal for random number generation. To be done. However, in order to obtain such a high amplification factor, a large-scale operation amplifier is required, and there are cases where there are restrictions in terms of size and price. In particular, it is difficult to incorporate such a circuit in an IC card equipped with a cryptographic security function.

The present invention has been made based on the recognition of such a problem. That is, an object thereof is to provide a random number generation circuit that generates a true random number and can be made into a small integrated circuit.

In order to achieve the above object, a random number generation circuit of the present invention is a random number generation circuit for generating digital random numbers based on noise obtained from a noise source. A tunnel element is used.

According to the above structure, thermal noise and shot noise can be obtained at a large level at the same time, so that the size and structure of the amplifier can be greatly simplified, and a random number with high authenticity can be generated.

Alternatively, the random number generating circuit of the present invention comprises a tunnel element, an amplifying means for amplifying noise obtained from the tunnel element, and a converting means for converting an analog signal amplified by the amplifying means into a digital signal. Digital processing means for extracting a part of the digital signal converted by the converting means.

Also with the above configuration, thermal noise and shot noise can be obtained at a large level at the same time, so that the size and configuration of the amplifier can be greatly simplified, and a random number with high authenticity can be generated.

Here, in the first and second random number generating circuits, the tunnel element is an element having a maximum value in a current obtained by applying a voltage, whereby thermal noise and shot noise are generated. And can be obtained at a large level at the same time.

Alternatively, the tunnel element is an element having an upwardly convex portion in a current curve obtained by applying a voltage, so that thermal noise and shot noise can be simultaneously obtained at a large level. You can

Further, the tunnel element has a control terminal capable of controlling the maximum value of the flowing tunnel current, and by applying a feedback signal to the control terminal, the output distribution of the noise obtained from the tunnel element is automatically determined. If a feedback circuit for keeping constant is further provided, it is possible to automatically correct the “deviation” of the random number distribution and increase the authenticity.

More specifically, for example, the tunnel element is a three-terminal type element having a control terminal capable of controlling the maximum value of a tunneling current flowing, and converts an analog signal obtained from the tunnel element. When the ratio of the number of peaks to the total number of data in the obtained digital signal is larger than a predetermined value, a signal is given to the control terminal to increase the tunnel current, and the ratio of the number of peaks to the total number of data in the digital signal is When it becomes smaller than a predetermined value, a feedback circuit for giving a signal to the control terminal is further provided so as to reduce the tunnel current, thereby automatically correcting the “deviation” of the random number distribution. Can increase the authenticity.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to specific examples.

FIG. 1 is a schematic diagram illustrating the basic configuration of the random number generation circuit of the present invention. That is, in the present invention, the tunnel element 10 is used as a noise source. As will be described later in detail, the tunnel element 10 has a feature that thermal noise and shot noise can be simultaneously increased.

The high-level thermal noise and shot noise obtained from the tunnel element 10 have their DC components cut off in the high-pass filter circuit, and then the analog circuit 12
Is amplified by. Since the levels of thermal noise and shot noise obtained from the tunnel element 10 are very high, a high amplification factor is not required for the analog circuit 12, and the circuit can be made much smaller.
Can be simplified.

The signal amplified by the analog circuit 12 is digitized in the A / D converter 14.
That is, with respect to the predetermined threshold value, those exceeding the threshold value are digitized, and those below the threshold value are digitized into "0". Further, since the generated random number sequence is biased, it is used as a random number after being corrected by the digital circuit 16.

Before describing the characteristics of the tunnel element 10 used in the present invention, the technical background of the element for generating thermal noise and shot noise will be described below.

The thermal noise voltage output <v ² > is given by the following equation. <V ² > = 4kRTΔf (1) Here, Δf represents a band. Therefore, the thermal noise is
Alternatively, the larger the reciprocal of the conductance, the larger simply. However, in general, for a noise source exceeding several mega ohms, since the magnitude is about the same as the input impedance of the amplifier circuit 112, amplification is not sufficient and is not suitable. Taking these into consideration, the thermal noise <v ² > that can be stably amplified at room temperature is 1.65 × at the maximum from the equation (1).
It remains at about 10 ^{−1 3} Δf (V ² ).

Shot noise is generated when electrons or holes cross an energy barrier and is given by the following equation. <I ² > = 2eIΔf (2) Therefore, the shot noise simply increases as the current increases. However, in an element in which electrons or holes have an energy barrier, the shot noise cannot be so large because the amount of current is essentially small. Since thermal noise is also generated in an element that generates shot noise, combining them increases noise output.

Thermal noise component <v ² > under the bias
Is proportional to the differential resistance r (ΔV / ΔI) and is given by the following equation. <V ² > = 4 kTrΔf (3) In an element under a certain bias condition, <v ² > and <i
^The following relationship is approximately established with ² >. <V ² > ≈ r ² <i ² > (4) Therefore, when the sum of thermal noise and shot noise is represented by the voltage output, the following equation is obtained. <I ² > = (4kTr + 2eIr ² ) Δf (5) Here, in the general diode used in the conventional random number generation circuit as illustrated in FIG.
And the differential resistance r have a negative correlation.

FIG. 2 is a graph showing the current-voltage characteristics of a normal diode used in the conventional random number generating circuit as shown in FIG.

As can be seen from the figure, in the region A of the portion biased in the forward direction, the differential resistance is relatively large, but the current is small. When the differential resistance r is large, the thermal noise is large, but the shot noise is small because the current I is small.

On the other hand, in the forward biased region B, the current is large but the differential resistance is small. The shot noise increases as the current increases, but the thermal noise decreases because the differential resistance is small.

As described above, in a normal diode, it is impossible to increase the thermal noise and the shot noise at the same time. The same situation applies to the case where a normal resistance element is used as a noise source.

As a result, in the conventional random number generating circuit using the noise source as illustrated in FIG. 13, the level of the noise obtained from the noise source 110 is small, so that the amplifier 112 circuit portion for amplifying the noise is provided. It becomes a large scale. That is, if the output from the noise source can be increased, the noise amplification circuit can be downsized and the entire circuit can be downsized.

On the other hand, as shown in FIG. 1, in the random number generation circuit of the present invention, a tunnel element is used as the noise source 10 to increase thermal noise and shot noise at the same time. In the tunnel element 10, as a typical example in which the thermal noise and the shot noise can be increased at the same time, there is an operating region in which the current has a maximum value with respect to the voltage in the element having the negative resistance.

FIG. 3 is a current-voltage characteristic diagram under forward bias illustrating the negative resistance observed in the tunnel element.

Generally, in the case of a tunnel element exhibiting negative resistance, as shown in FIG. 3, in the range of tunnel current, there is always a maximum portion P immediately before the transition from positive differential resistance to negative differential resistance. . In principle, the value of the differential resistance increases to infinity in this maximum portion P. Therefore, large thermal noise is generated.

At the same time, if the flowing current is a tunnel current, shot noise proportional to the current is generated, so that shot noise also becomes large in the maximum portion P where the amount of current is large. That is, thermal noise and shot noise can be increased at the same time in the maximum portion P and its vicinity.

Further, the tunnel element 10 used in the present invention is not limited to the one exhibiting the negative resistance characteristic as illustrated in FIG. 3, and in the current-voltage characteristic at the time of forward bias, the current curve shows "upper". It is sufficient if there is a "convex part".

FIG. 4 is a graph showing another specific example of the current-voltage characteristics obtained in the tunnel element. In the tunnel element shown in the figure, when the forward bias voltage is increased, the normal pn junction forward current component and the tunnel current component are superposed, and the “upward convex portion” in the current curve. Is formed. In the vicinity of this inflection point P, the differential resistance is extremely high and the current is relatively large. Of course, not only the shape of the current-voltage curve is important, but it is necessary that the tunnel current occupy most of the current component. This is because shot noise is caused by variations in electron motion when overcoming the energy barrier of electrons, and shot noise does not occur with a current flowing through a normal resistor.

Therefore, the thermal noise and the shot noise can be increased at the same time, so that the random number generating circuit of the present invention can be used as a tunnel element.

On the other hand, when the circuit of FIG. 1 is used, the random number distribution is disturbed unless the noise output from the tunnel element 10 is always constant. Therefore, as will be described later in detail with reference to the embodiments, a three-terminal tunnel element can be used to increase the stability of random numbers. In this case, if the tunnel current flowing between the two terminals is controlled by the voltage applied to the third terminal, the “deviation amount” of the random number distribution can be negatively fed back and stabilized.

Specifically, the true random number shows a normal distribution, and if the distribution is monitored in the circuit and deviates from a predetermined distribution, a voltage change proportional to the deviation may be given to the tunnel current control terminal. Specific examples will be described later in detail as examples.

[0038]

Embodiments of the present invention will be described in more detail below with reference to embodiments.

(First Embodiment) First, as a first embodiment of the present invention, a random number generating circuit using a pn junction type tunnel diode will be described.

FIG. 5 is a schematic diagram showing the overall configuration of the random number generation circuit of this embodiment.

In this figure, elements similar to those in FIG. 1 are assigned the same reference numerals and detailed explanations thereof are omitted.

As shown in FIG. 5, the tunnel diode 10A is used as a noise source in this embodiment.

FIG. 6 is a schematic view showing the cross-sectional structure of the tunnel diode 10A used in this embodiment. This diode was formed by the following process.

First, in the silicon substrate 32, boron (B) is ion-implanted at a volume density of about 10 ²⁰ cm ^{−3 in a} region where a diode is to be provided while masking with a resist. Next, the resist is masked again, and phosphorus (P) is ion-implanted inside the boron-implanted region at a volume density of about 10 ²⁰ cm ⁻³ . After that, by annealing at an appropriate temperature, ap ⁺ type region 32 and an n ⁺ type region 34 are formed. By forming the electrodes 36 on the respective surfaces, a highly doped pn junction type tunnel diode can be obtained. This electrode 36, 3
When a proper bias is applied to 6, a tunnel current flows.

FIG. 7 is a graph showing a typical current-voltage characteristic of the tunnel diode thus obtained.

In this case, the tunnel current flows in the region of 0 to 0.3 V, and the negative resistance is observed in the region of 0.05 to 0.3 V.

When an arbitrary bias is applied to the tunnel diode 10A, thermal noise is generated in proportion to the differential resistance r at that point, as expressed in the above equation (1), and at the same time proportional to the tunnel current I. As a result, shot noise is generated as shown in (2).

The differential resistance theoretically becomes infinite when the current-voltage characteristic reaches the maximum P, so that large thermal noise can be obtained. At the same time, since the current continues to flow due to the tunnel current, shot noise also increases. That is, the thermal noise and the shot noise can be increased at the same time. Actually, as will be described below, even if the differential resistance is brought to infinity and the thermal noise is increased, the large noise output cannot be amplified as it is. Can also be used as a large noise source.

In this embodiment, by using the tunnel diode 10A as the noise source of the random number generation circuit, the digital random number generation circuit can be constructed as shown in FIG.

The random number generation circuit of FIG. 5 will be described below.

First, the output of the tunnel diode 10A is passed through the filter 11, the DC component is cut, and the noise A
Only the C component is used. Next, the operational amplifier 12 performs analog amplification. At this time, the input impedance of the operational amplifier 12 is usually several MΩ (mega ohms) to several tens MΩ, and if the differential resistance exceeds that, it cannot be linearly amplified and the operational amplifier output is distorted and cannot be used as a random number source. The bias applied to the diode is designed so that the differential resistance is several 10 MΩ or less. The bias setting is determined by the size of the resistance between the power supply and the tunnel diode.

For example, a tunnel diode 10A having a current-voltage characteristic as shown in FIG.
When a voltage of 5 V was applied, the differential resistance became approximately 1 MΩ and the tunnel current flowed at approximately 5 μA. In this case, the voltage output of noise is about 0.6 μV × (Δf) ^1/2 . That is, the noise output is 10 times or more as compared with a normal resistance element having the same resistance value of 1 MΩ. Therefore, the size of the circuit forming the amplifier circuit 12 can be significantly reduced, or the number of elements can be significantly reduced.

The magnitude of the tunnel current depends on the p ⁺ type region 32.
And the impurity concentration profile of the n ⁺ type region 34. Therefore, if these are controlled to make a diode with an increased tunnel current, the noise output increases according to the equation (5).

The change in the noise signal obtained from the tunnel diode 10A is completely random. Therefore, a digital random number is obtained by converting the analog-amplified noise signal into a digital signal by the AD converter 14, but if converted as it is, the analog signal has a normal distribution, so that a digital signal reflecting the normal distribution is formed. It does not become a true random number.

Therefore, when creating an N-bit digital random number, it is advisable to adopt a method in which after digitizing using an L-bit (where L> N) AD converter 14, only the lower L bits are taken out and used. For example, with an 8-bit AD converter 14, 00000000-11111
Create a normal distribution up to 111, and the lower 2 bits 00-11
Is used as a 2-bit random number sequence.

Further, the bias applied to the tunnel diode 10A has the same effect as described above when the absolute value of the resistance is a large resistance exceeding 1 MΩ even in the region where the differential resistance is negative.

Further, since the tunnel diode 10A in this embodiment can obtain a large noise output at a low voltage and a low current, an effect of reducing the low power consumption of the random number generation circuit can also be obtained.

(Second Embodiment) Next, as a second embodiment of the present invention, a random number generating circuit using a three-terminal tunnel element will be described. That is, the tunnel diode 10A used in the first embodiment described above is a two-terminal element having a pn junction, and it is difficult to adjust the current value of the element other than changing the bias voltage between the two terminals. is there.

On the other hand, the surface junction transistor (Su
A three-terminal element called an rface junction transistor (SJT) changes the voltage applied to the third terminal (called the "gate electrode") by changing the thickness of the tunnel insulating layer (inversion layer) at the pn junction interface. Therefore, the amount of tunnel current can be changed.

FIG. 8 is a schematic view illustrating the configuration of the main part of SJT.

That is, the SJT shown in the figure has an n ⁺ type source region 44, an i type channel region 46, ap ⁺ type drain region 4 on a silicon substrate 40 with a silicon oxide film 42 interposed therebetween.
8 is formed. The gate electrode 50 is provided on the channel region 46 with a gate insulating film interposed therebetween.

When a predetermined bias voltage is applied to the gate electrode 50, the electron inversion layer 46A is formed on the surface of the channel region 46.
Is formed, and a pin diode is formed between the source and the drain via the inversion layer.

FIG. 9 is a graph showing the current-voltage characteristics of this SJT.

In the two-terminal element tunnel diode as illustrated in FIG. 6, the same noise output cannot be obtained unless the initial element characteristics are all the same. When the noise output changes, the output distribution after AD conversion changes. Therefore, in order to create a large number of the same random number generation circuits, precise control is required in the manufacturing process.

On the other hand, when SJT is used as a noise source, when the output distribution after AD conversion on the gate electrode deviates from the desired distribution, the amount of "deviation" is fed back and corrected. be able to.

FIG. 10 is a schematic diagram showing the structure of the main part of the random number generation circuit of this embodiment. Also in this figure, elements similar to those described above with reference to FIGS. 1 to 9 are marked with the same reference numerals and not described in detail.

Hereinafter, the case of performing 8-bit AD conversion in this random number generation circuit will be specifically described as an example.

In the case of this circuit, the DC component of the output voltage of the SJT 10B is removed by the high-pass filter 11 and only the AC component is amplified. For example, the maximum value is 1.5 V, the minimum value is -1.5 V, and 0 Design to have a normal distribution around the bolt.

[0069] separating the analog signal, and AD conversion by the AD converter 14 into ^{2 eight} digital signals. The analog signal itself does not break the normal distribution in principle, and the center point is always 0. When this is digitally converted, a normal distribution having constant peak values at 2 ⁷ and 2 ⁷ +1 is obtained.

If the digital counter 16 counts the number of peaks / total number, the “deviation” of the noise output of the SJT 10B from the design value can be detected. When the number of peaks / total number increases, the noise output decreases. Therefore, in this case, in the feedback circuit 18, the value of the "deviation" is converted into a voltage by a comparator or the like, and SJ
Positive feedback may be applied to the gate voltage of T10B. That is, it is possible to increase the gate voltage, increase the tunnel current, and correct the “deviation” of the normal distribution.

When the number of peaks / total number is small, the feedback circuit 18 can correct the deviation of the normal distribution by applying feedback in the direction of reducing the tunnel current.

(Third Embodiment) Next, as a third embodiment of the present invention, a random number generation circuit using a quantum well tunnel element will be described.

That is, in the above-described first and second embodiments, the random number generation circuit is constructed by using the tunnel element using the tunnel current that passes through the single energy barrier.

On the other hand, an energy level called “quantum level” is formed in a semiconductor layer of several nanometers surrounded by two or more energy barriers called “quantum well”.

FIG. 11 is a conceptual diagram illustrating a quantum well structure.

As shown in FIG. 9A, in the quantum well structure, the quantum level Q1 is formed in the quantum well W sandwiched between the energy barriers B1 and B2. When the quantum level Q1 and the energy C of conduction electrons are separated,
No current flows across it.

However, as shown in FIG. 10B, when a voltage is applied between A and B so that the quantum level Q1 and the energy C of conduction electrons are close to each other, the tunnel probability increases and the tunnel current increases. Flows.

When the voltage between AB is further increased, as shown in FIG.
As shown in 0 (c), the quantum level Q1 and the energy C of the conduction electron are separated again, and the tunnel current becomes small. Therefore, the tunnel element having such a quantum well structure exhibits a negative resistance due to the tunnel current, like the tunnel elements of the first and second embodiments. This is what is known as a "resonant tunnel diode".

Generally, in the resonant tunnel diode, it is easier to obtain a large peak of the tunnel current than in the tunnel elements of the first and second embodiments. Therefore, by using such a resonant tunneling diode as a noise source in the same manner as in the first embodiment, a random number generation circuit can be made.

The tunnel barriers B1 and B2 and the quantum well W are
SiO ₂ and Si combination, Si and SiGe combination, AlGaAs and GaAs combination, InAl
A combination of GaAs or InGaAlP and InP, a combination of various kinds of materials such as a quantum well formed of a metal and an oxide thin film, and the like can be considered.

Further, as illustrated in FIG. 12, three tunnel barriers B1, B2 and B3 and two quantum wells W1 and W are provided.
By arranging 2 to form a quantum well and further providing an electrode also on one of the semiconductor layers C so that the energy level can be changed, a three-terminal element in which the peak amount of the tunnel current is variable can be formed. By using this, it is possible to realize a random number generation circuit capable of correcting the "deviation" as in the second embodiment.

The embodiments of the present invention have been described with reference to specific examples. However, the present invention is not limited to the above specific examples.

For example, the tunnel element used in the present invention is not limited to the above specific examples, and includes all elements that can be appropriately selected by those skilled in the art. In short, as long as the thermal noise and the shot noise can be obtained at a high level at the same time, an element having a portion similar to a peak or a terrace-shaped inflection point in the current-voltage characteristics is referred to as a “tunnel element” in the present invention. The same effect can be obtained by using the same.

There are various methods for amplifying the noise obtained from the tunnel element and digitizing it, in addition to the above-mentioned specific examples. For example, as described in JP-A-3-235007, a method of extracting the least significant 2 bits of normal distribution data and creating a digital random number with an arbitrary number of bits, and JP-A-2000-66592. As described, a method of binarizing an amplified signal with a comparator, a method of sampling a digitized signal at a desired cycle to form a digital random number sequence, or a method disclosed in Japanese Patent Laid-Open No. 2000-83019 As described above, a method of directly inputting the voltage output and noise component of the element to the comparator without passing through the amplifier circuit and digitizing it,
The above embodiments can be appropriately combined and used.

Although the digital random number generated by the random number generating circuit of the present invention can be used as it is, a new random number can be generated by using it as a seed of the feedback shift register.

[0086]

As described in detail above, according to the present invention,
By using a tunnel element as a noise source, thermal noise and shot noise can be obtained at a large level at the same time, so that the size and configuration of the amplifier can be greatly simplified, and a random number with high authenticity can be generated.

Further, according to the present invention, a feedback signal is applied to the control terminal capable of controlling the maximum value of the tunnel current, so that the feedback distribution for automatically keeping the output distribution of the noise obtained from the tunnel element constant. By providing the circuit, it is possible to automatically correct the “deviation” of the random number distribution and increase the authenticity.

That is, according to the present invention, it is possible to realize a random number having a high degree of authenticity in a compact size and at a low price.
For example, the industrial advantage is great in that an inexpensive card system with reliable security can be realized by applying it to an IC card or the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the basic configuration of a random number generation circuit of the present invention.

FIG. 2 is a graph showing current-voltage characteristics of a normal diode used in the conventional random number generation circuit as shown in FIG.

FIG. 3 is a current-voltage characteristic diagram at the time of forward bias illustrating the negative resistance observed in the tunnel element.

FIG. 4 is a graph showing another specific example of current-voltage characteristics obtained in the tunnel element.

FIG. 5 is a schematic diagram showing an overall configuration of a random number generation circuit according to an exemplary embodiment of the present invention.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a tunnel diode 10A used in an example of the present invention.

FIG. 7 is a graph illustrating a typical current / voltage characteristic of the tunnel diode obtained in the example of the present invention.

FIG. 8 is a schematic view illustrating the configuration of a main part of SJT.

FIG. 9 is a graph showing current-voltage characteristics of SJT.

FIG. 10 is a schematic diagram illustrating a configuration of a main part of a random number generation circuit according to an exemplary embodiment of the present invention.

FIG. 11 is a conceptual diagram illustrating a quantum well structure.

FIG. 12 is a conceptual diagram showing a quantum well in which three tunnel barriers B1, B2, B3 and two quantum wells W1, W2 are arranged.

FIG. 13 is a schematic diagram illustrating a circuit configuration for generating random numbers from noise generated in an element.

[Explanation of symbols]

10, 10A, 10B Tunnel element 10A Tunnel diode 11 High-pass filter 12 Amplifier circuit 14 Converter 16 Digital counter 30 Silicon substrate 32 p ⁺ type region 34 n ⁺ type region 36 Electrode 40 Silicon substrate 42 Silicon oxide film 44 n ⁺ type source region 46 i-type channel region 46A electron inversion layer 48 p ⁺ type drain region 50 gate electrode 110 noise source 112 amplifier 114 converter 116 digital circuit B1 and B2 energy barrier C semiconductor layer P maximum part Q1 quantum level W1 and W2 quantum well

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toru Onodera             2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Ceremony Company Toshiba Hamakawasaki Factory F term (reference) 5J049 AA13 AA20 BB02 CA03 CA09

Claims (4)

[Claims] 1. A tunnel element, amplification means for amplifying noise obtained from the tunnel element, conversion means for converting an analog signal amplified by the amplification means into a digital signal, and the conversion means converted by the conversion means. A random number generation circuit comprising: a digital processing unit for extracting a part of a digital signal; 2. The random number generating circuit according to claim 1, wherein the tunnel element is an element having an upwardly convex portion in a current curve obtained by applying a voltage. 3. The tunnel element has a control terminal capable of controlling a maximum value of a flowing tunnel current, and a feedback signal is given to the control terminal to automatically output an output distribution of the noise obtained from the tunnel element. 3. The random number generation circuit according to claim 1, further comprising a feedback circuit for keeping it constant. 4. The tunnel element is a three-terminal type element having a control terminal capable of controlling the maximum value of a flowing tunnel current, and in a digital signal obtained by converting an analog signal obtained from the tunnel element. When the ratio of the number of peaks to the total number of data becomes larger than a predetermined value, a signal is given to the control terminal to increase the tunnel current, and the ratio of the number of peaks to the total number of data in the digital signal becomes smaller than a predetermined value. 3. The random number generation circuit according to claim 1, further comprising a feedback circuit for applying a signal to the control terminal so as to reduce the tunnel current.