JP2011034397A - Device and method for making random number generated - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a random number generation technique that is simpler than conventional techniques. <P>SOLUTION: A device for generating random numbers includes a light source that outputs amplified natural emission light; a branching means for branching the light from the light source; a delay means for providing a time difference between the branched light beams; a combination means for combining the light beams, given the time difference; a detection means for detecting the strength of the light beams combined; and a threshold means for generating random numbers, by comparing the detected strength of the light beams with a threshold. This allows obtaining a noise signal having fluctuations that are three digits or more greater than those obtained by the conventional techniques that utilize electrical noise. Furthermore, the light frequency bandwidth of an ASE light source is as wide as 1 THz or higher, enabling generation of random numbers of high generation speed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a random number generator. More specifically, the present invention relates to a random number generator that generates a random bit string of “0” and “1”.

  Random numbers are basic elements used in cryptographic systems and authentication systems, and random number generators are basic devices for constructing these systems. Usually, the random number is a random bit string of {0, 1}. Methods for generating random numbers are roughly divided into an arithmetic method using a computer algorithm and a method using a physical phenomenon. A truly random bit string is generated by the latter.

  There are various physical random number generation methods. The most common and commercialized method is a method using noise of an electric circuit (see Non-Patent Document 1). As electrons move as particles in a conductor, random motion that occurs in individual electrons causes electrical noise. Therefore, a random number is obtained by passing this noise signal through a threshold circuit and outputting a bit “1” if it is above a certain level and a bit “0” if it is below that level.

True random number (physical random number) generation IC RPG100 / RPG100B catalog, [online], September 2005, FDK Corporation, [July 15, 2009 search], Internet <http://www.fdk.co.jp /cyber-j/pdf/HM-RAJ001.pdf>

  The amplitude of such an electric noise signal is generally not large and is about several tens of μV. In order to threshold this, it must be amplified by 4 to 5 digits. In particular, when it is desired to generate random numbers at a high speed, a broadband circuit and an amplifier are required, which increases the circuit scale and power consumption. Therefore, in order to obtain a simpler random number generator, a means for generating a noise signal having a large amplitude and a wide band is desired.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a technique for generating random numbers that is simpler than before. In particular, a random number generation technique including means for generating a noise signal having a large amplitude and a wide band is provided.

  In order to achieve such an object, the present invention is an apparatus for generating a random number, wherein a light source for outputting amplified spontaneous emission light and light from the light source are branched. Branching means; delay means for giving a time difference between the branched lights; multiplexing means for multiplexing the light given the time difference; detecting means for detecting the intensity of the combined light; Threshold means for generating a random number by comparing the detected light intensity with a threshold is provided.

  The invention according to claim 2 is the apparatus according to claim 1, wherein the branching unit branches light from the light source into two.

  The invention according to claim 3 is a method for generating a random number, wherein the amplified spontaneous emission light is branched, a time difference is given between the branched light, and the time difference is given. And a random number is generated by comparing the intensity of the combined light with a threshold value.

  As described above, according to the present invention, it is possible to generate a noise signal having a wide fluctuation width and a wide band. Thereby, it is possible to provide a random number generator that is simpler than before. More specifically, according to the present invention, it is possible to obtain a noise signal having a fluctuation that is three orders of magnitude greater than that of the prior art using electrical noise. Further, by using an ASE light source having a wide optical frequency band, it is possible to generate a random number at a high generation speed.

It is a figure which shows the structural example of the random number generator by one Embodiment of this invention.

  FIG. 1 shows a basic configuration of a random number generator according to an embodiment of the present invention. The random number generator 100 includes a light source 101 that generates amplified spontaneous emission (AES) light, an optical coupler 102 that is coupled to the output of the AES light source 101, and a delay that is coupled to one output of the optical coupler 102. Means 103, an optical coupler 104 coupled to the other output of optical coupler 102 and the output of delay means 103, an optical intensity detector 105 coupled to the output of optical coupler 104, and an output of optical intensity detector 105 And a connected threshold circuit 106.

  The ASE light source 101 generates amplified spontaneous emission (AES) light. Specifically, an optical amplifier to which signal light is not input, a super luminescent diode (SLD), or the like corresponds to this. The output light from the ASE light source is branched into two by the optical coupler 102, one of which is given a time delay by the delay means 103, and then multiplexed again by the optical coupler 104. The combined light is converted into an electric signal by the light intensity detector 105, and the bit of the electric signal from the light intensity detector is determined by the threshold circuit 106 according to the level of the electric signal. Then, the bit string from the threshold circuit 106 becomes an output of the random number generator 100. Note that the electrical signal from the light intensity detector 105 may be amplified by an amplifier as necessary.

  The signal flow in such a configuration will be described using equations.

First, light having a random phase (spontaneously emitted light) is output from an ASE light source over a wide wavelength range. When the wavelength range of the output light is divided into minute wavelength ranges, and the output light in the kth wavelength range is expressed as A _k exp [i (ω _k t + θ _k )], the total output light is the sum of the following: It is expressed as follows.

Here, ω _k is the angular frequency of light in the kth wavelength region, θ _k is its phase, A _k is its amplitude, and Σ represents the sum of the output wavelength ranges of the ASE light source. While A _k is constant over time, the phase θ _k varies randomly.

  The output from the ASE light source is branched into two, and after being given a delay time τ, it is combined again. The combined light is expressed as follows.

The first term represents light passing through a short path, and the second term represents light passing through a long path. The light passing through the long path is shifted by τ by the amount of delay.

  The combined light is converted into an electrical signal by a light intensity detector. This electrical signal is expressed as follows.

The phase θ _k of each minute wavelength region varies randomly with time, and the relative phase (θ _k −θ _{k ′} ) between different wavelength regions is also random. Therefore, the second to fourth terms of Equation (1) vary randomly. Therefore, if this electric signal is input to the threshold circuit and the bit is “1” if it is above a certain level and bit “0” if it is less than that level, a random number can be obtained.

  In the formula (1), all except the first term are terms that randomly vary. The size of each term is almost the same order. Therefore, the entire signal of the electrical signal represented by Equation (1) varies greatly. By the way, the photoelectric conversion efficiency of an avalanche photodiode (APD), which is a general light intensity detector, is about 1 A / W. That is, an electric signal of several mA is generated from an optical signal of several mW. This corresponds to 100 mV or more in the 50Ω circuit system. Moreover, it is easy to obtain ASE light of about several mW from an optical amplifier or a super luminescent diode. From these facts, it can be seen that in the present embodiment, a noise signal having a fluctuation that is three orders of magnitude larger than that of the prior art using electrical noise can be obtained.

  Further, regarding the band, the frequency band of the signal of the formula (1) covers the optical frequency band of the ASE light. The optical frequency band of the ASE light source is 1 THz or more, and the signal frequency band of Expression (1) is considered to be the same level. By using this, it is possible to generate random numbers at a high generation speed.

  Although the present invention has been specifically described above with reference to specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied. It is not intended to limit the scope of the invention. The configuration and details of the embodiment exemplified here can be changed without departing from the spirit of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 100 Random number generator 101 AES light source 102 Optical coupler 103 Delay means 104 Optical coupler 105 Optical intensity detector 106 Threshold circuit

Claims (3)

A device for generating random numbers,
A light source that outputs amplified spontaneous emission light;
Branching means for branching light from the light source;
Delay means for providing a time difference between the branched lights;
A multiplexing means for multiplexing the light given the time difference;
Detecting means for detecting the intensity of the combined light;
An apparatus comprising: threshold means for comparing the detected light intensity with a threshold to generate a random number. The apparatus of claim 1, comprising:
The branching means branches the light from the light source into two. A method for generating random numbers,
Branching the amplified spontaneous emission; and
Providing a time difference between the branched lights;
Combining the light given the time difference;
Comparing the intensity of the combined light with a threshold to generate a random number.

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