JP4725462B2 - Communication apparatus and program - Google Patents

Description

  The present invention relates to a communication device connected to a network and having a random number generation function.

  2. Description of the Related Art Conventionally, communication devices that perform cryptographic communication or user authentication using random numbers are known. For example, in encryption communication such as SSL communication, when a session is established, the server device and the client device exchange random number data generated by them, and generate an encryption key (session key) based on these random number data. And realizes cryptographic communication.

  Further, as a random number generation method, there is known a method of generating a random number in a pseudo manner by applying a predetermined arithmetic process to a bit pattern (so-called seed) which is a seed of a random number. Etc., a method of generating random number data by the above bit pattern and finally generating an encryption key is widely adopted.

  Specifically, when generating a random number by the above method, the input parameter is subjected to arithmetic processing by a predetermined algorithm, and the random number is generated by giving the bit pattern as an input parameter to a program for generating the random number. To do.

  Note that the above-described bit pattern called a seed is basic information from which a random number is generated. Therefore, when a certain bit pattern is given to the program for generating the random number, the random number is generated in a specific pattern. Will be generated.

Therefore, when generating random numbers by the above method, a more ideal random number is generated by giving a random bit pattern to the program. In this regard, as a conventional technique, a technique is known in which a packet is reciprocated between a first communication apparatus and a second communication apparatus, and a random bit pattern is generated using fluctuation of the reciprocation time. (For example, refer to Patent Document 1).
JP 2004-206025 A

  However, the conventional random number generation method has the following problems. For example, as described in Patent Document 1, the method of generating a random number (seed) based on the round trip time of a packet can predict the round trip time of the packet by observing the quality of the communication path. When cryptographic communication or the like is realized by using a random number generated by the method as a seed, the seed is predicted by a malicious person, and as a result, the encryption key may be overlooked.

  Further, in the above method, since the random number is generated by utilizing the fact that the fluctuation of the packet round trip time due to the quality of the communication path is larger than the time resolution of the timer that measures the round trip time of the packet, the quality of the communication path is sufficient. When the value is too high, fluctuations in the packet round-trip time are reduced, and a sufficiently random value cannot be generated based on the packet round-trip time.

  That is, in the conventional method for generating random numbers using the relationship between the accuracy of the measuring device and the fluctuation of the physical quantity to be measured as described above, the random numbers are generated in a biased manner without being generated with a uniform probability. There is a high possibility that this has an adverse effect on a program that realizes a predetermined process using a random number, such as an encryption communication program, and there is a possibility that a function that should be originally realized cannot be realized.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique capable of realizing highly secure communication by enabling generation of a more ideal random number than in the past.

A first invention made to achieve such an object is a communication device connected to a network, and receiving means for receiving data transmitted from a plurality of other devices on the network via the network, Received data number measuring means for measuring the number of data received by the receiving means, and receiving means when the number of data received by the receiving means reaches a preset threshold based on the measurement result of the received data number measuring means A reception time detection means for detecting the reception time of the data by the reception means, and a random number output means for outputting a value corresponding to the reception time detected by the reception time detection means as a random number. Features.

Further, the second invention is a communication device connected to a network, the receiving means for receiving data transmitted from another device on the network via the network, and the reception time of the data by the receiving means The number of data received by the receiving means is preset based on the measurement result of the reception time detecting means, the received data number measuring means for measuring the number of data received by the receiving means, and the received data number measuring means. A value corresponding to the reception time detected by the reception time detection means for the reception data determined by the determination means and the reception data determined by the determination means for determining the reception data of the reception means when the threshold is reached. And random number output means for outputting as random numbers.

According to these communication devices, it is possible to generate (output) an ideal random number as compared with the conventional case, and by using this random number as a seed, it is possible to realize highly secure encrypted communication.

  More specifically, a plurality of communication devices are normally connected to the network, and on the network, the plurality of communication devices operate individually, and the communication devices interact with each other through communication, etc. Etc. change from moment to moment. For this reason, it is difficult to predict the reception amount and reception timing of data in each communication device.

  That is, when a communication device on the network receives data transmitted from the other device through the network, the data reception timing such as the operation content of each communication device on the network, the communication delay according to the network traffic, etc. There are a number of external factors that affect these factors.

  For this reason, as in the present invention, if the reception time and the number of received data transmitted from other devices through the network are used for generating random numbers, random numbers can be generated uniformly and generated by the communication device. The random number prediction can be made difficult. Therefore, according to the communication apparatus of the present invention, it is possible to generate an ideal random number than before.

In particular, according to the communication device of the present invention, since a random number is generated based on the data reception time and the number of received data, a malicious person transmits data from the communication device on the network to generate the random number of the communication device. Even if it is intended to influence, the act is unlikely to affect the random number generation of the communication device. Further, since data is transmitted from a plurality of communication devices on the network, it is difficult to know the reception time of the reception data when the number of reception data reaches the threshold from the outside. For this reason, according to the communication apparatus of the present invention, it is not necessary for a malicious person to know the generated random number, and high-security communication can be realized in the case of performing cryptographic communication using the random number.

Incidentally, the above-mentioned random number output means, a reception time reception time detecting means detects the least significant values corresponding to the bit when expressed in binary, Ru can be configured to output as a random number.

In the present invention, the reception time of the corresponding data when the number of data received by the receiving means reaches a preset threshold value is used for generation of random numbers. However, the number of data corresponding to the threshold value is used. Since the time required for reception changes under the influence of network traffic, the communication apparatus cannot be configured to generate random numbers periodically if the threshold value is a fixed value.

Therefore, to generate a periodic random number, as the threshold value, the threshold value setting means for setting a value corresponding to the network traffic, has good when provided to the communication device. According to the communication apparatus configured in this way, random numbers can be generated almost regularly, and it is possible to prevent the generation interval of random numbers from becoming longer due to network traffic. In addition, as a result, it is possible to further prevent the malicious person from knowing the random number. Therefore, highly secure communication can be realized.

In order to set a value corresponding to the network traffic as the threshold and to be able to generate a random number periodically, the communication device may be specifically configured as follows.
That is, the communication device uses a storage unit that stores a value larger than the minimum unit of reception time that can be detected by the reception time detection unit as a random number generation interval, and a threshold value that is currently set. A unit for calculating the number of receivable data per unit time based on the reception time measuring means for measuring the time required to receive the corresponding number of data and the time required for receiving the data measured by the reception time measuring means. The number of data that can be received within the time corresponding to the generation interval stored in the storage means is calculated from the number of time calculation means and the number of data that can be received per unit time calculated by the unit time number calculation means. a receivable number calculating means, the provided threshold value setting means, the threshold, the number calculated by the receivable number calculating means, have good when it is in the configuration to be updated.

  According to the communication apparatus configured as described above, the number of pieces of data that can be received per unit time is measured, and based on the result, the threshold value is set so that the random number generation interval becomes a preset time interval. Therefore, random numbers can be generated almost regularly regardless of network traffic.

Also, when the receiving unit is configured to receive data transmitted from other devices on the network regardless of the destination, determine the destination of the data, and discard the data other than the address to the own device as data other than destined for the own device not only the data destined for the own device also interest, to detect the reception time, as well as constitute a reception time detecting means, not only the data destined for the own apparatus other than destined for the own device data as target, so as to measure the number of data received by the receiving means, have good to constitute reception data number measuring means.

  In this way, if the reception time detection means and the reception data number measurement means are configured, the external factors affecting the generation of random numbers increase, and the reception time and the number of reception data are detected only for the data addressed to the own device, An ideal random number can be generated more than when a random number is generated based on this. Moreover, in a network environment that can receive data other than that addressed to the device itself, there is a high possibility that the contents of the data will be known by a third party. It is possible to further prevent the random number from being known. Therefore, highly secure communication can be realized.

The functions of the respective means in the above-mentioned communication apparatus, the program, Ru can be realized on the computer.

For example, the program is connected to a network, and the number of data received by the receiving means is set in a computer of a communication apparatus having receiving means for receiving data transmitted from a plurality of other devices on the network via the network. Based on the reception data number measurement function to be measured and the measurement result by the reception data number measurement function, the reception means receives the data when the number of data received by the reception means reaches a preset threshold. And a random number output function for outputting a value corresponding to the least significant bit of the reception time detected by the reception time detection means as a random number. be able to.

In addition, the program is connected to the network, and the reception time of the data received by the receiving means is transmitted to the computer of the communication apparatus provided with the receiving means for receiving data transmitted from other devices on the network via the network. The number of data received by the receiving means is set in advance based on the measurement result by the reception time detecting function for detecting, the received data number measuring function for measuring the number of data received by the receiving means, and the received data number measuring function. A function that determines the received data of the receiving means when it reaches the threshold value as the received data used for generating random numbers, and the received data determined by the determining function corresponds to the received time detected by the received time detection function Required to receive the number of data corresponding to the currently set threshold value A reception time measurement function that measures time, a unit time number calculation function that calculates the number of receivable data per unit time based on the time required to receive data measured by the reception time measurement function, and unit time Corresponds to a random number generation interval predetermined as a value larger than the minimum unit of the reception time that can be detected by the reception time detection function from the number of data that can be received per unit time calculated by the number calculation function. Configured as a program for realizing a receivable number calculating function for calculating the number of receivable data within a time period and a threshold setting function for updating the threshold value to the number calculated by the receivable number calculating function. be able to.

  Each of the above programs can be recorded on a computer-readable recording medium such as an optical disk or a magnetic disk and provided to the user.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a communication system 1 according to the present embodiment. The communication system 1 according to this embodiment includes a plurality of communication devices 3 connected to a network NT. Examples of the network NT include a wired network and a wireless network, and examples of the communication device 3 include various communication devices such as a personal computer (PC), a digital multifunction peripheral, and a database server device.

  However, in this embodiment, as the communication device 3, a personal computer 5 and a digital multifunction device 10 are connected to the network NT, and the personal computer 5 and the digital multifunction device 10 are configured to be capable of SSL communication. It is assumed that the digital multi-function peripheral 10 is provided with a function of generating a seed that is a seed of random numbers used for SSL communication or the like by the method of the present invention.

  The digital multifunction machine 10 of this embodiment is a multi-function device having a network printer function, a scanner function, a copy function, and the like. Mainly, a CPU 11 that executes various programs, a ROM 13 that stores programs executed by the CPU 11, and A RAM 15 as a working memory, an NVRAM 17 for storing various setting information, a printing unit 19, a reading unit 21, a display operation unit 23, and a communication interface 25 are provided.

  The printing unit 19 is controlled by the CPU 11 and prints image data designated by the CPU 11 by an ink jet method or a laser printer method, and forms an image based on the image data on a sheet. The printing unit 19 is used when realizing a network printer function or a copy function. On the other hand, the reading unit 21 is controlled by the CPU 11 to optically read a document placed on the placement unit, generate image data representing a read image, and provide the image data to the CPU 11. It is. The reading unit 21 is used when realizing a scanner function or a copy function.

  In addition, the display operation unit 23 includes various keys that can be operated by the user and also includes a display unit including a liquid crystal display, and functions as a user interface that receives commands from the user and displays various information for the user. To do.

  The communication interface 25 is connected to the network NT, and is configured to be capable of bidirectional communication with the communication device 3 on the network NT. FIG. 2 is an explanatory diagram showing the processing operation of the communication interface 25.

  The communication interface 25 provided in the MFP 10 of the present embodiment sequentially receives packets transmitted from other devices on the network NT and flows through the network NT, and based on the destination address attached to the packet, the received packet is automatically transmitted. It is determined whether the packet is addressed to the device. If the received packet is a packet addressed to the own device, the packet is forwarded to a higher-level communication module, and the received packet is a packet other than the addressed device itself In such a case, this packet is discarded and the packet is not transferred to the upper communication module.

  In addition, the communication interface 25 stores the transmission target data input from the communication module and sends the packet with the destination address to the network NT so that the transmission target data corresponds to the destination address. To the communication device 3 to be transmitted.

  The communication module may be an IP (Internet Protocol) module, and the packet transmitted and received by the communication interface 25 may be an Ethernet (registered trademark) frame having a destination MAC address as a destination address. it can.

  The packet transferred from the communication interface 25 to the communication module is processed by the communication module and then provided to the upper communication application software. In addition, the transmission target data generated by the higher-level communication application software is input to the communication interface 25 via the communication module, thereby realizing communication between the MFP 10 and other communication devices. . Examples of the communication application software include application software that realizes SSL communication.

  The multifunction machine 10 according to the present embodiment has a function of monitoring a reception operation of the communication interface 25 and generating a seed that is a seed of random numbers necessary for SSL communication or the like as a function according to the present invention. That is, in this embodiment, the MFP 10 executes a seed generation program (see FIG. 2) by the CPU 11, and based on the number n of packets received by the communication interface 25 and the reception time of the packets, Is generated. Thereby, in the multifunction machine 10 of the present embodiment, it is possible to generate a more appropriate seed than in the past.

Hereinafter, this function will be described with reference to FIGS. FIG. 3 is a flowchart showing a seed generation process executed by the CPU 11 based on a seed generation program.
When the sheet generation process is started, the CPU 11 first performs an initialization process (S110), initializes a parameter n representing the number of received packets to zero, and sets a threshold value TH described later to a default value. The default value of the threshold value TH is stored in the NVRAM 17 as setting information. In addition, in S110, the CPU 11 sets a random number generation interval Ts, which will be described later, to a designated value stored in the NVRAM 17, and sets the current time indicated by the system clock CLK in the RAM 15 as an initial value of the random number generation time and the seed update time. Remember.

  When the processing in S110 is completed, the CPU 11 proceeds to S120, and the communication interface 25 transmits the packet flowing through the network NT via the network NT because another device on the network NT sends the packet to the network NT. It is determined whether it has been received (S120). Here, whether or not a packet has been received is determined not only for packets addressed to the own apparatus but also for packets other than the addressed to the own apparatus.

  If no packet is received by the communication interface 25 (No in S120), the process waits until a packet is received by the communication interface 25, and if a packet is received by the communication interface 25 (Yes in S120). In step S130, the value of parameter n is incremented by 1 (n ← n + 1), and the number n of received packets is counted up.

  When this process is finished, the CPU 11 proceeds to S140 and determines whether or not the number n of received packets is equal to or greater than the threshold value TH. If it is determined that the number n of received packets is less than the threshold value TH (No in S140), the process proceeds to S120 and waits until the communication interface 25 newly receives a packet. When the communication interface 25 newly receives a packet, the number n of received packets is counted up (S130), and the determination in S140 is performed again.

  If it is determined in S140 that the number of received packets n is equal to or greater than the threshold value TH (Yes in S140), the CPU 11 refers to the least significant bit of the bit string representing the current time in the system clock CLK (S150), and the reference value (minimum order). (Bit value) is written as a random number in a seed generation area prepared in the RAM 15. Thereby, the reference value is temporarily stored (S160).

  The multi-function device 10 of this embodiment is configured to generate a seed having a data length of several bytes (for example, 4 bytes), and the reference value temporarily stored in S160 is used as a constituent bit of the seed. In this embodiment, since the seed configuration bits are determined in this way, the time required for the number n of received packets to reach the threshold value TH is sufficiently longer than the minimum unit of time that the system clock CLK ticks. Thus, the threshold value TH is set (details will be described later).

  When the process in S160 is completed, the CPU 11 determines whether or not the number of random numbers corresponding to the data length of the seed to be generated has been generated in S160 (S170). That is, it is determined whether or not the process of S160 has been executed a number of times corresponding to the seed data (bit) length. For example, when the seed is 32 bits (4 bytes), whether or not the process of S160 has been executed 32 times since the time when the seed was set in S175 or S185 last time (the seed generation process was started only for the first time). Determine whether.

  If it is determined that the number of random numbers corresponding to the data length has been generated (Yes in S170), the CPU 11 generates the latest random number of the number corresponding to the seed data length temporarily stored in the seed generation area of the RAM 15. A random number sequence arranged in order is set as a new seed (S175). Thereafter, the process proceeds to S190.

  On the other hand, if it is determined that the number of random numbers corresponding to the data length has not been generated (No in S170), the CPU 11 has passed a predetermined time TL from the time of setting the previous seed based on the seed update time stored in the RAM 15. (S180), if it is determined that the predetermined time TL has not elapsed (No in S180), the process proceeds to S200, and if it is determined that the predetermined time TL has elapsed (Yes in S180), S185 Migrate to

  After shifting to S185, the CPU 11 sets a new seed based on the random number temporarily stored in the seed generation area of the RAM 15. Here, since the number of newly generated random numbers does not reach the seed data length, for example, the lower bits of the number of bits corresponding to the shortage in the previously set seed are set to the upper bits of the seed set this time. Used for. That is, a random number sequence formed by arranging the latest random numbers temporarily stored in the seed generation area of the RAM 15 in the order of generation is combined with the end of the lower bits of the previously set seed corresponding to the shortage, A random number sequence having a length corresponding to the data length is generated and set as a new seed.

  However, when the process of S185 is executed at the time of initial seed generation, since the previously set seed does not exist, for example, the upper bits of the amount corresponding to the shortage are set to all zeros, and the seed generation of the RAM 15 is added to this. A random number sequence formed by arranging the random numbers temporarily stored in the area in the order of generation is added to generate a random number sequence having a length corresponding to the data length of the seed, and this random number sequence is set as a new seed.

  Further, when the process of S185 is completed in this way, the CPU 11 proceeds to S190, and temporarily stores the current time in the RAM 15 as the seed update time. Thereafter, the process proceeds to S200.

  In addition, when the process proceeds to S200, the CPU 11 calculates the elapsed time from the time when the last random number was generated (or the time when the seed generation process was started) based on the random number generation time stored in the RAM 15 in S110 or S250. . Based on this elapsed time and the current number of received packets n, the number of received packets NT per unit time is calculated as the current network traffic (S210).

NT = number of received packets n / elapsed time When the processing in S210 is completed, the CPU 11 proceeds to S220, and multiplies the calculated number of received packets NT per unit time by the random number generation interval Ts. A threshold value TH1 to be set is calculated.

Threshold TH1 = number of received packets per unit time NT × random number generation interval Ts
When this process ends, the CPU 11 proceeds to S230 and sets the calculated threshold TH1 as a new threshold TH (TH ← TH1). Since the threshold TH needs to satisfy the above-described requirements, in this embodiment, the random number generation interval Ts is greater than the time resolution of the system clock CLK (the minimum unit of time that the system clock CLK ticks). It is assumed that the time interval is set sufficiently long.

  When the processing in S230 is completed, the CPU 11 proceeds to S240, resets the number of received packets n (parameter n) to zero, and then stores the current time in the RAM 15 as a new random number generation time ( S250).

  When this process is completed, the CPU 11 proceeds to S120 and waits until the communication interface 25 newly receives a packet. When the communication interface 25 newly receives a packet, the processing after S130 is executed again. Thus, in the seed generation process, the value of the least significant bit of the packet reception time when the number n of received packets reaches the threshold value TH is output to the RAM 15 as a random number, and this random number sequence is , S175 or S185 is set as a seed.

  Although the present embodiment has been described above, according to the MFP 10 of the present embodiment, the number of packets received by the communication interface 25 is measured, and the minimum time when the number of received packets reaches a threshold value is measured. The order bit is output as a random number. Then, the seed is generated by repeating this operation. Therefore, according to the multifunction machine 10 of the present embodiment, an ideal random number can be generated, and encrypted communication with high security can be realized by using a seed composed of this random number sequence.

  In other words, according to the present embodiment, since there are a large number of external factors that influence the generation of random numbers, there is no bias and ideal random numbers can be generated. For example, in the present embodiment, the external factors that influence the generation of random numbers include packet transmission operation of each communication device, network traffic, and the like. It changes under the influence of the packet transmission operation by the communication device. For this reason, as in this embodiment, if the reception time and the number of packets received are used for generating random numbers, random numbers can be generated uniformly. Seed prediction can be difficult. Therefore, according to the present embodiment, for example, in SSL communication, random data that is difficult to predict maliciously can be used for generating an encryption key, and encryption communication with high security can be realized.

  In addition, according to the present embodiment, since a random number is generated based on the packet reception time and the number of received packets, a malicious person transmits a packet from the communication device 3 on the network NT to generate the random number of the multifunction machine 10. Even if it is intended to influence the random number, the act is unlikely to affect the random number generation of the multifunction device 10. For this reason, according to the multifunction machine 10 of the present embodiment, it is possible to realize communication with higher security than before when performing cryptographic communication using a random number (seed).

  In addition, in this embodiment, since the time required to receive the number of packets corresponding to the threshold value TH changes due to the influence of network traffic, the threshold value TH is updated according to the network traffic. A seed can be generated at a constant cycle. Therefore, according to the present embodiment, it is possible to appropriately generate a seed using a packet flowing through the network while preventing a seed update interval from becoming long due to a change in network traffic. Encrypted communication can be realized.

  In addition, according to the present embodiment, since the random number generation is realized by software, an external physical quantity (external temperature, etc.) is detected by a sensor, and a random number is generated based on a detection value of the sensor. Compared to a technology that realizes random number generation using hardware, a sensor failure or the like does not occur, and a more reliable product can be manufactured. In addition, according to the present embodiment, when random number generation is impossible, communication is also impossible, and therefore it is difficult to generate a random number, so that it is difficult to perform communication with high security, and a more reliable product is obtained. Can be manufactured.

  Note that the receiving means of the present invention corresponds to the communication interface 25. The reception time detection means is realized by the processing of S150, the reception data number measurement means is realized by the processing of S130, the determination means is realized by the processing of S140, and the random number output means is the processing of S160. It is realized by processing. The threshold setting means is realized by the process of S230, the reception time measuring means is realized by the process of S200, the unit time number calculating means is realized by the process of S210, and the receivable number calculating means is , S220 is realized.

  Further, the present invention is not limited to the above-described embodiments, and can take various forms. For example, in the above-described embodiment, an example in which the present invention is applied to a digital multifunction peripheral has been described. However, the present invention can also be applied to various other communication devices 3 such as a personal computer 5 having a communication function. .

  In addition, in the said Example, although the seed was used for SSL communication as an example, the effect of invention was demonstrated, However, The use of a seed is not limited to the said use. For example, since the seed is used also in the case of wireless communication, the above-described effect on security can be similarly applied to the wireless network.

  In addition, the technique of the present invention can generate random numbers uniformly as compared with the conventional technique, but it cannot reliably eliminate the bias, so in the seed generation process described above, May replace the processing of S150 and S160 with the random number correction processing shown in FIG. 4 (modified example).

  FIG. 4 is a flowchart showing random number correction processing executed by the CPU 11 in the multifunction machine 10 according to the modification. Note that the modified multifunction machine 10 is such that the random number correction process shown in FIG. 4 is executed instead of the processes of S150 and S160 in the seed generation process shown in FIG. And basically the same configuration. Therefore, in the following description, the random number correction process will be described only as an explanation of the modification.

  When the random number correction process is started, the CPU 11 in the multifunction machine 10 of the modified example refers to the least significant bit of the bit string representing the current time in the system clock CLK, similarly to the process in S150 (S310). Then, this reference value (value of the least significant bit) is written in a reference value recording area prepared in the RAM 15, and this reference value is temporarily stored (S320).

  When the process in S320 is completed, the value m of the parameter m is incremented by 1, thereby incrementing the reference count m, which is the execution count of S310 (S330), and then the process proceeds to S340. It is assumed that the parameter m is reset to zero during the initialization process in S110.

  In S340, the CPU 11 determines whether or not the reference count m is the predetermined count M. If the CPU 11 determines that the reference count m is not the predetermined count M (No in S340), the procedure proceeds to S400. If it is determined that the reference count m is the predetermined count M (Yes in S340), the process proceeds to S350.

  In S350, the CPU 11 calculates the occurrence probability P1 of the event whose reference value is 1 from the past reference result in S310 stored in the reference value recording area of the RAM 15. For example, when the reference value recording area stores a sample (reference value) a times the predetermined number M, the number of samples whose reference value is 1 is set to the total number of samples (a × M). Then, the occurrence probability P1 of the event whose reference value is 1 is calculated.

  When this process is finished, the CPU 11 proceeds to S360, calculates the occurrence probability P0 of the event whose reference value is 0 (P0 = 1−P1), and then the probability P1 is greater than the probability P0. Whether or not (S370).

  If it is determined that the probability P1 is greater than the probability P0 (Yes in S370), the CPU 11 proceeds to S380, and the probability of (P1-0.5) / P1 is obtained in the replacement process executed in the subsequent S400. Then, the condition parameter for the replacement process is set so that the reference value 1 is replaced with the value 0. For example, when P1 = 0.7, the replacement process condition parameter is set so that the reference value 1 is replaced with the value 0 with a probability of 2/7. The reference value 0 is set so as not to be replaced with the value 1. Thereafter, the process proceeds to S390.

  On the other hand, if it is determined in S370 that the probability P1 is less than or equal to the probability P0 (No in S370), the CPU 11 proceeds to S385, and the reference value 0 becomes the value 1 with the probability of (P0−0.5) / P0. After setting the condition parameter of the replacement process so as to be replaced, the process proceeds to S390. In S385, the reference value 1 is set not to be replaced with the value 0.

In S390, the CPU 11 resets the reference count m to zero, and then proceeds to S400.
When the process proceeds to S400, the CPU 11 performs a replacement process on the reference value obtained by the process of S310 immediately before, and replaces the reference value 1 with 0 with a probability corresponding to a preset condition parameter, or the reference value 0. Is replaced with 1. Thereafter, the process proceeds to S410. As a result, in the reference value after the replacement process, the probability that the value is 1 and the probability that the value is 0 are 0.5. Note that immediately after the seed generation process is executed, the process of S380 or S385 is not executed. In this state, the replacement process is not substantially executed in S400, and the process proceeds to S410.

  In S410, the CPU 11 writes the reference value after the replacement process as a random number in a seed generation area prepared in the RAM 15, and temporarily stores this reference value. When the process in S410 is completed, the CPU 11 ends the random number correction process and proceeds to S170.

  Although the modification has been described above, according to the modification, when the random number is not uniformly generated, the reference value is replaced as necessary so that the apparent random number is generated. . Therefore, according to this modified example, seeds can be generated more suitably.

1 is a block diagram illustrating a configuration of a communication system 1. FIG. FIG. 6 is an explanatory diagram showing a processing operation of a communication interface 25. It is a flowchart showing the seed production | generation process which CPU11 performs. It is a flowchart showing the random number correction process which CPU11 performs.

DESCRIPTION OF SYMBOLS 1 ... Communication system, 3 ... Communication apparatus, 5 ... Personal computer, 10 ... Digital compound machine, 11 ... CPU, 13 ... ROM, 15 ... RAM, 17 ... NVRAM, 19 ... Printing part, 21 ... Reading part, 23 ... Display Operation unit, 25 ... communication interface, CLK ... system clock, NT ... network

Claims (10)

A communication device connected to a network,
Receiving means for receiving data transmitted from a plurality of other devices on the network via the network ;
A received data number measuring means before Symbol receiving means for measuring the number of received data,
Based on the measurement result of the received data number measuring means, regarding the received data of the receiving means when the number of data received by the receiving means reaches a preset threshold, the reception time of this data by the receiving means is calculated. Receiving time detecting means for detecting;
A random number output means for outputting a value corresponding to the least significant bit of the reception time detected by the reception time detection means as a random number;
A communication apparatus comprising: The communication apparatus according to claim 1 , further comprising a threshold setting unit configured to set a value according to traffic of the network as the threshold. Storage means for storing a value larger than the minimum unit of reception time that can be detected by the reception time detection means as a random number generation interval;
A reception time measuring means for measuring a time required to receive a number of data corresponding to the currently set threshold value;
Unit time number calculating means for calculating the number of receivable data per unit time based on the time required for receiving the data measured by the reception time measuring means;
The receivable number for calculating the number of receivable data within the time corresponding to the generation interval stored in the storage means from the number of data receivable per unit time calculated by the unit time number calculating means. A calculation means;
With
The communication apparatus according to claim 2 , wherein the threshold setting unit sets the number calculated by the receivable number calculating unit as a new threshold. A communication device connected to a network,
  Receiving means for receiving data transmitted from another device on the network via the network;
  A reception time detecting means for detecting a reception time of data by the receiving means;
  Received data number measuring means for measuring the number of data received by the receiving means;
  Based on the measurement result of the received data number measuring means, the received data of the receiving means when the number of data received by the receiving means reaches a preset threshold is determined as received data used for generating random numbers. A decision means to
  Random number output means for outputting, as a random number, a value corresponding to the reception time detected by the reception time detection means for the reception data determined by the determination means;
  Storage means for storing a value larger than the minimum unit of reception time that can be detected by the reception time detection means as a random number generation interval;
  A reception time measuring means for measuring a time required to receive a number of data corresponding to the currently set threshold value;
  Unit time number calculating means for calculating the number of receivable data per unit time based on the time required for receiving the data measured by the reception time measuring means;
  The receivable number for calculating the number of receivable data within the time corresponding to the generation interval stored in the storage means from the number of data receivable per unit time calculated by the unit time number calculating means. A calculation means;
  Threshold setting means for updating the threshold to the number calculated by the receivable number calculating means;
  A communication apparatus comprising: The receiving unit is configured to receive data transmitted from another device on the network regardless of the destination, determine the destination of the data, and discard data other than the device itself,
The reception time detecting means is configured to detect the reception time not only for data addressed to the own device but also for data other than the addressed to the own device,
The received data number measuring means is configured to measure the number of data received by the receiving means for not only data addressed to the own apparatus but also data other than the addressed to the own apparatus. The communication apparatus according to any one of claims 1 to 4. A computer connected to a network and having a receiving means for receiving data transmitted from a plurality of other devices on the network via the network.
A received data number measurement function to measure the number of data received by the receiving means,
Based on the I that measurement result to the reception data counting function for the received data of the receiving means when the number of data received by the receiving means reaches a preset threshold, received by said receiving means of the data A reception time detection function for detecting time;
A random number output function for outputting a value corresponding to the least significant bit of the reception time detected by the reception time detection means as a random number;
A program to realize The program according to claim 6 , further causing a computer to realize a threshold setting function for setting a value according to traffic of the network as the threshold. On the computer,
A reception time measuring function for measuring the time required to receive the number of data corresponding to the currently set threshold value;
A unit time number calculation function for calculating the number of data that can be received per unit time based on the time required to receive the data measured by the reception time measurement function;
A random number generation interval predetermined as a value larger than the minimum unit of the reception time detectable by the reception time detection function from the number of data receivable per unit time calculated by the unit time number calculation function A receivable number calculating function for calculating the number of receivable data within a time corresponding to
In addition,
The program according to claim 7 for causing a computer to realize, as the threshold setting function, a function of updating the threshold to the number calculated by the receivable number calculation function.   A computer connected to a network and having a receiving means for receiving data transmitted from another device on the network via the network.
  A reception time detection function for detecting a reception time of data received by the reception means;
  A received data number measuring function for measuring the number of data received by the receiving means;
  Based on the measurement result of the received data number measurement function, the received data of the receiving means when the number of data received by the receiving means reaches a preset threshold is determined as the received data used for generating random numbers. A decision function to
  A random number output function for outputting a value corresponding to the reception time detected by the reception time detection function as a random number for the reception data determined by the determination function;
  A reception time measuring function for measuring the time required to receive the number of data corresponding to the currently set threshold value;
  A unit time number calculation function for calculating the number of data that can be received per unit time based on the time required to receive the data measured by the reception time measurement function;
  A random number generation interval predetermined as a value larger than the minimum unit of the reception time detectable by the reception time detection function from the number of data receivable per unit time calculated by the unit time number calculation function A receivable number calculating function for calculating the number of receivable data within a time corresponding to
  A threshold value setting function for updating the threshold value to the number calculated by the receivable number calculating function;
  A program to realize The receiving unit is configured to receive data transmitted from another device on the network regardless of the destination, determine the destination of the data, and discard data other than the device itself,
The program is
A function for detecting the reception time for not only data addressed to the device itself but also data other than the device addressed to the device is implemented in the computer as the reception time detection function,
A program for causing a computer to realize the function of measuring the number of data received by the receiving unit as the received data number measuring function for not only data addressed to the own device but also data other than the addressed to the own device. The program according to any one of claims 6 to 9, wherein:

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