Open key distributing method, and open key transmitting device and open key receiving device used for the same method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention is a public key distribution method for distributing a public key used in cryptography for preventing the original information communicated between an information transmitting side and an information receiving side from being leaked or tampered with by a third party. The present invention relates to a public key transmitting device and a public key receiving device used in a public key distribution method.

【0002】

[Conventional technology]

In the field of information communication systems, public key cryptography and digital signature cryptography have come to be widely used as a means of secure and reliable information transmission. The public key and private key used here are public and private keys in public key cryptography and digital signature cryptography, and the public key is made public so that anyone can know it. On the other hand, the private key is determined and kept secret by a cryptographic algorithm that is difficult to infer from the public key.

【0003】

It is customary among cryptographic engineers to encrypt the process using the public key and decrypt the process using the private key. In the public key cryptosystem, it is described that "the sender (information sender) of information encrypts information with a private key, and the receiver (receiver of information) decrypts it with a public key". On the other hand, in the digital signature method, the sender of the information is processed by the private key, and the receiver is processed by the public key. Therefore, it is described that "the signal decrypted by the sender of the information is encrypted by the receiver". These statements are technically correct, but difficult for anyone other than a crypto engineer to intuitively understand.

【0004】

Therefore, in the description of the public encryption method in this specification, "encryption" is used to obtain encryption by processing the information that the sender of the information wants to send with a public key, and the encryption that receives the information Obtaining the original information by performing processing with the private key is called "decryption". On the other hand, in the explanation of digital signature, the information receiver receives "conversion" that the information sender processes the information (or hashed version) that the information sender wants to send with a private key to obtain an authenticator. "Reverse conversion" is to obtain the original information (or hashed version of it) by processing the authenticator with a public key. Here, the hash refers to a process of generating fixed-length output data from non-infinite length input data. This fixed-length output data is called a hash value. As the hash processing used in the cryptographic technique, a method is used in which it is not easy to obtain a plurality of input data having the same hash value. How to create a public key and an encryption key and how to perform hash processing are disclosed in detail in "Introduction to Information Security" published by Shokodo (issued in March 1999).

【0005】

Figure 5 shows an overview of the conventional public key cryptosystem. This method is a cryptographic technique for transmitting information from an unspecified number of senders (information senders) to a receiver (information receiver) without being known to a third party. First, the information receiver 110R creates a method of encrypting information (public key 102E) and a method of decrypting the encryption (private key 102D) by the key pair creation device 102. The private key 102D is kept secret from others, while the public key 102E is widely distributed publicly. In the example shown in FIG. 5, the case where the public key 102E is published on the Internet 101 is shown.

【0006】

In the conventional public key cryptosystem, first, the information sender 110S encrypts the original information 111a to be sent using the public public key 102E, and sends the information as encrypted information 111b to the information receiver 110R. Next, the information receiver 110R decrypts the sent encryption information 111b with the private key 102D to obtain the decryption information 111c. The decryption information 111c obtained here is equal to the original original information 111a. Even if a third party intercepts the encrypted information 111b while the encrypted information 111b is transmitted through the Internet 101, the original original information 111a cannot be obtained unless the private key 102D is known.

【0007】

Figure 6 shows an overview of the conventional digital signature method. This method is a cryptographic technology for the information receiver to detect that the information from the information sender (information sender) has been tampered with when it is transmitted to an unspecified number of receivers (information receiver). .. First, the information sender 130S creates a method of converting the information to be transmitted to create an authenticator (private key 102D) and a method of inversely converting the authenticator to obtain the original information (public key 102E). .. The private key 102D is kept secret so that it is not known to others, while the public key 102E is widely distributed publicly. The example shown here shows the case where a physical medium such as a CD-ROM containing the public key 102E is distributed.

【0008】

In the conventional digital signature method, first, the information sender 130S creates the authenticator 131b by using the private key 102D as follows. That is, the original information 131a to be sent is input to the hash processing device 161, the hash value 131ah is generated, and the hash value 131a is input to the conversion device 132D. When the amount of information of the original information 131a is small, the information 131a may be input to the conversion device 132D as it is instead of the hash value. Next, the conversion device 132D generates an authenticator 131b from the input information 131ah using the private key 102D. Then, the original original information 131a and the authenticator 131b are sent to the information receiver 130R via the Internet 101.

【0009】

In the conventional digital signature method, the original original information 131a and the authenticator 131b may be tampered with by a third party while the original original information 131a and the authenticator 131b pass through the Internet 101. The original information 131a and the authenticator 131b received by the receiver 130R of the above are represented by different codes 131a # and 131b #, respectively.

【0010】

For the received original information 131a #, a hash value 131a # h is generated by the hash processing device 162 (same as the hash processing device 161), and the hash value 131a # h is input to the comparison device 136. When the authenticator 131b is generated on the information sender 130S side without hash processing, the original information 131a # received on the information receiver 130R side is input to the comparison device 136 as it is. On the other hand, the received authenticator 131b # is inversely converted by the inverse conversion device 132E using the public key 102E, and the information 131ah # after the inverse conversion is input to the comparison device 136.

【0011】

The comparison device 136 compares the input information 131ah # with the information 131a # h. As a result of comparison, when both are equal, both the received information 131a # and the authenticator 131b # have not been tampered with, or the received information 131a # and the authenticator 131b # have both been tampered with. Either. However, even if the information 131a # is tampered with, in order to create the corresponding authenticator 131b #, it is necessary to know the conversion method in the conversion device 132D, that is, the private key 102D. Since the third party does not know the private key 102D, it is not possible to create an authenticator 131b # corresponding to the original information 131a # which is a falsification of the original information 131a.

【0012】

Summarizing the above, in this digital signature method, if the comparison results of the comparison device 136 are equal, it is determined that the information 131a # has not been tampered with and is equal to the original original information 131a. In this case, the switching device 137 is controlled to transmit the information 131a to the information receiver 130R as it is. Further, in this digital signature method, if the comparison results of the comparison device 136 are not equal, it is determined that the information 131a # has been tampered with and is not equal to the original original information 131a. In this case, the switching device 137 is controlled, and the error message 103e indicating that the information 131a has been tampered with is transmitted to the information receiver 130R, and the tampered information is not transmitted to the information receiver 130R.

【0013】

[Problems to be Solved by the Invention]

By the way, in the conventional public key cryptosystem shown in FIG. 5, it is necessary that the public key 102E is transmitted from the information receiver 110R to the information sender 110S without being tampered with. In this case, using the Internet 101 as a means of distributing the public key 102E is dangerous. This is because the propagation path of the information sender 110S and the information receiver 110R is not fixed in the Internet 101, and the public key 102E does not always pass through only a reliable relay device, so it is tampered with by a third party on the way. There is no guarantee that it has not been done.

【0014】

For example, FIG. 7 shows a case where a third party 170 impersonates the information receiver 110R (public key creator) in the middle of the route of the Internet 101 connecting the information sender 110S and the information receiver 110R. .. As is clear from comparison with FIG. 5, the information from the information sender 110S is drawn to the third party 170 in the middle of the Internet 101 shown in FIG. This can happen if the settings on the Internet 101 router (not shown) are rewritten by a third party.

【0015】

First, the third party 170 stores the public key 102E sent from the information receiver 110R to the information sender 110S and uses it as the public key of its own encryption device 172E, while the fake public key 102E. Send # to the information sender 110S. Since the information sender 110S believes that the public key 102E # was created by the information receiver 110R, the original information 111a to be transmitted is encrypted using the public key 102E #, and the encrypted information 111b # Send to recipient 110R.

【0016】

Here, the encrypted information 111b # is drawn to the third party 170. Since the third party 170 creates the fake public key 102E # and the corresponding fake private key 102D # by the key pair creation device 162, the encryption information 111b # can be correctly decrypted. That is, the information 111d obtained by decrypting the encryption information 111b # by the decryption device 172D is equal to the original original information 111a.

【0017】

Further, the third party 170 encrypts the obtained information 111d (111a) with the public key 102E obtained from the information receiver 110R to generate the encrypted information 111b, and transmits the encrypted information 111b to the receiver 110R. This encrypted information 111b is decrypted in the same manner as in the example shown in FIG. 5, and the information receiver 110R obtains the original information 111a sent. Therefore, neither the information sender 110S nor the information receiver 110R notices that the encrypted information is leaked on the way. Therefore, distributing the public key 102E on the Internet 101 is dangerous.

【0018】

Further, in the conventional digital signature method shown in FIG. 6, since the public key 102E is distributed on a CD-ROM, the information tampered with by the above-mentioned "spoofing" is not transmitted to the information receiver 130R. .. However, the information 131ah before conversion by the public key 102E and the private key 102D (which is obtained as the input 131ah # of the comparison device when the information was not tampered with on the Internet 101) and the authenticater 131b after conversion (this). Can be obtained as the received authenticator 131b #) when the information has not been tampered with on the Internet 101), which could lead to the decryption of the private key 102D. Therefore, the pair of private key 102D and public key 102E needs to be changed before the private key 102D is decrypted. However, every time the pair of private key 102D and public key 102E is changed, it is troublesome to redistribute physical media such as CD-ROM, so in reality, we are aware of the danger of being tampered with on the way. The reality is that the new public key 102E is redistributed on the Internet 101.

【0019】

The present invention has been made in view of the above circumstances, and a public key distribution method capable of immediately distributing a new public key without the public key being tampered with in the middle, a public key transmitting device used for this method, and public disclosure. It is an object of the present invention to provide a key receiving device.

【0020】

[Means for solving problems]

In order to solve the above-mentioned problems, the invention according to claim 1 distributes a radio wave as a medium from the side that distributes the public key to the side that receives the public key in the public key distribution method that distributes the public key in the asymmetric cryptosystem. This is a public key distribution method.

【0021】

As a result, since the public key in the asymmetric cryptosystem is distributed using radio waves as a medium, the public key is directly distributed from the distribution side to the receiving side without being tampered with by a third party.

【0022】

The private key and the public key are generally composed of a computer program. The radio wave may be a terrestrial wave (broadcast radio wave), a satellite communication wave, or the like. Further, the public key received by the radio wave may be transmitted to a device using a plurality of public keys by using a communication line in which it is difficult to falsify the information. In addition, the private / public key pair changes irregularly or periodically.

【0023】

If the private key and public key are computer programs that describe the calculation method for performing operations on the input data and outputting it, the cryptographic algorithm can be changed as appropriate, and when simply changing the pair of private key and public key. It is even safer than that.

【0024】

Among radio waves, broadcast radio waves in particular have a larger transmission power than other wireless communications, and are therefore less susceptible to jamming radio waves. Radio waves from communication or broadcasting satellites (satellite communication waves) are not disturbed unless fake radio waves are transmitted from the satellites, so they are not easily affected by disturbing radio waves.

【0025】

When transmitting a public key received by radio waves to a device that uses multiple public keys using a communication line that is difficult to tamper with, the public key transmitted by radio waves is not received individually at one location. Received at.

【0026】

Since the private key can be decrypted if the same one is used for a long period of time, it will not be affected even if it is decrypted by changing to a new private key and public key pair before it is decrypted, and the security function is enhanced. Can be planned.

【0027】

Further, in the invention according to claim 2, in the public key distribution method according to claim 1, the side that distributes the public key is the information receiving side, and the side that receives the public key is the information transmitting side, and the public key. Is the first public key that encrypts the original information held by the information transmitting side into encrypted information.

【0028】

As a result, the first public key that encrypts the original information held by the information transmitting side into encrypted information is distributed using radio waves as a medium, so that the first public key can be obtained from the distribution side without being tampered with by a third party. It will be distributed directly to the recipient.

【0029】

Further, in the invention according to claim 3, in the public key distribution method according to claim 1, the side that distributes the public key is the information transmitting side, and the side that receives the public key is the information receiving side, and the public key. Is the second public key that reversely converts the original information converted into the encrypted information received by the information receiving side into the original original information.

【0030】

As a result, the second public key, which reversely converts the original information converted into the encrypted information received by the information receiving side into the original original information, is tampered with by a third party in order to distribute the radio wave as a medium. The second public key will be distributed directly from the distributor to the recipient.

【0031】

The invention according to claim 4 is a public key transmitting device used in the public key distribution method according to claim 2, and is a first public key that encrypts the original information held by the information transmitting side into encrypted information, and A key pair creation means for creating a first private key corresponding to this first public key and decrypting the encrypted information received by the information receiving side into the original information, and a radio wave of the first public key to the information transmitting side. The radio wave transmitting means for transmitting, the information receiving means for receiving the encrypted information transmitted from the information transmitting side to the information receiving side, and the encrypted information are subjected to the first private key to obtain the original information. It is a public key transmitting device used in a public key distribution method characterized by having a decryption means.

【0032】

As a result, the information receiving side equipped with the public key transmitting device transmits the first public key that encrypts the original information held by the information transmitting side into encrypted information using radio waves as a medium without being tampered with by a third party. Then, the original information is obtained by the decryption means for applying the first private key to the encrypted information transmitted from the information transmitting side.

【0033】

Further, the invention according to claim 5 is a public key receiving device used in the public key distribution method according to claim 2, wherein the original information held by the information transmitting side, which is transmitted by radio waves, is encrypted into encrypted information. (I) A radio wave receiving means for receiving a public key, an encryption means for applying the first public key to the original information to obtain the encrypted information, and transmitting the encrypted information from the information transmitting side to the information receiving side. It is a public key receiving device used in a public key distribution method, which is characterized by being provided with an information transmitting means.

【0034】

As a result, the information transmitting side equipped with the public key receiving device receives the first public key that encrypts the original information held by the information transmitting side into encrypted information using radio waves as a medium without being tampered with by a third party. Then, the original information is converted into encrypted information by an encryption means that applies the received first public key to the original information, and this encrypted information is transmitted to the information receiving side by the information transmitting means.

【0035】

The invention according to claim 6 is a public key transmitting device used in the public key distribution method according to claim 3, which is a second private key that converts the original information held by the information transmitting side into an authenticator, and this. A key pair creation means for creating a second public key corresponding to the second private key and converting the authenticator received by the information receiving side back into the original information, and transmitting the second public key to the information receiving side by radio wave. The radio wave transmitting means, the conversion means for converting the original information into the authenticator by applying the second private key, and the original information and the authenticator possessed by the information transmitting side from the information transmitting side to the information receiving side. It is a public key transmitting device used in a public key distribution method characterized by being provided with an information transmitting means for transmitting.

【0036】

As a result, the information transmitting side equipped with the public key transmitting device transmits and has the second public key that reversely converts the authenticator using the radio wave as a medium without being tampered with by a third party. An authenticator is obtained by a conversion means that applies a second private key to the original information, and the original information and the authenticator are transmitted to the information receiving side by the information transmitting means.

【0037】

The invention according to claim 7 is a public key receiving device used in the public key distribution method according to claim 3, which reversely converts the original information possessed by the information transmitting side transmitted by radio waves into a converted authenticator. The radio wave receiving means for receiving the public key, the information receiving means for receiving the original information and the authenticator transmitted from the information transmitting side to the information receiving side, and the authenticator are subjected to the second public key. It is a public key receiving device used in a public key distribution method, which comprises an inverse conversion means for obtaining an inverse conversion original information and a comparison means for comparing the inverse conversion original information with the original information.

【0038】

As a result, the information receiving side equipped with the public key receiving device receives the second public key that reversely converts the authenticator using the radio wave as a medium without being tampered with by a third party, and transmits it from the information transmitting side. The original information and the authenticator are received by the information receiving means, and the inverse conversion original information is obtained by the inverse conversion means that applies the second public key to the received authenticator. Is compared by a comparison means.

【0039】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. An embodiment of the present invention will be described with reference to FIG. The first embodiment shown here is a case where the information sender 10S sends the information 11a to the information receiver 10R, and the broadcasting satellite 14 is used to distribute the public key at that time.

【0040】

In FIG. 1, the information receiver 10R is the side that distributes the public key, and is equipped with the public key transmitting device 40. Further, the information sender 10S is a side that receives the public key, and is provided with the public key receiving device 42.

【0041】

The public key transmitting device 40 includes a key pair creating device (key pair creating means) 2, a decoding device (decoding means) 12D, a satellite uplink device (radio wave transmitting means) 13, and an information receiving device (information receiving means). It is configured with.

【0042】

The key pair creation device 2 creates the first public key 2E that encrypts the information into the encrypted information, and also creates the first private key 2D that decrypts the encrypted information corresponding to the first public key 2E. It is a thing.

【0043】

The decryption device 12D obtains the original information by applying the first private key 2D created by the key pair creation device 2 to the encrypted information received by the information receiving means.

【0044】

The satellite uplink device 13 transmits the first public key 2E created by the key pair creation device 2 to the broadcasting satellite 14 using radio waves as a medium. In this embodiment, the satellite uplink device 13 includes a public key multiplexing device 3 that multiplexes a plurality of public keys.

【0045】

The information receiving device (not shown) is connected to the Internet 1 and receives information from the Internet 1. However, as described above, this information receiving device (information receiving means) is a program deployed on an information terminal such as a server, and can also transmit information on the Internet 1.

【0046】

The public key receiving device 42 includes an encryption device (encrypting means) 12E, a satellite radio wave receiving device (radio wave receiving means) 15, and an information transmitting device (information transmitting means). However, in this embodiment, the public key receiving device 42 is composed of a satellite radio wave receiving device 15 and an information terminal such as a personal computer (not shown). That is, in this embodiment, the encryption means and the information transmission means are programs deployed in the information terminal.

【0047】

The encryption device 12E applies the first public key 2E transmitted from the public key transmission device 40 to the original information to obtain the encryption information.

【0048】

The satellite radio wave receiving device 15 receives the first public key 2E transmitted from the broadcasting satellite 14. The satellite radio wave receiving device 15 is provided with a public key storage device 4 that stores the received first public key 2E.

【0049】

The information transmitting device (not shown) is connected to the Internet 1 and transmits information to the Internet 1. However, as described above, this information transmitting device (information transmitting means) is a program deployed in an information terminal such as a personal computer, and can also receive information on the Internet 1.

【0050】

Next, the operation will be described. In FIG. 1, the information receiver 10R sets a pair of a private key (first private key) 2D that is not disclosed to others and a public key (first public key) 2E that is disclosed to others as a key pair creation device (key pair). Creation means) Create by 2. The created public key 2E is input to the public key multiplexing device 3. The public key multiplexing device 3 is a device that multiplexes the public key 2E and the public key 2E'created by another person, and is not necessarily essential for realizing the present invention. Considering the amount of information that can be transmitted by the broadcasting satellite described later, a plurality of public keys can be distributed by one broadcasting satellite. Therefore, in practice, a plurality of public keys are distributed using the public key multiplexing device 3. It is good to do.

【0051】

The plurality of multiplexed public keys are transmitted to the broadcasting satellite 14 in the form of radio waves 14up by the satellite uplink transmission device (radio wave transmission means) 13. The broadcasting satellite 14 receives the radio wave 14up and transmits it as a radio wave 14dn. The public key information included at this time does not change. The satellite receiving device (radio wave receiving means) 15 that has received the radio wave 14dn separates the plurality of multiplexed public keys into each public key before multiplexing, and the public keys are separated by the public key storage device 4. Be remembered.

【0052】

On the other hand, the information sender (information sender) 10S acquires the public key 4E corresponding to the information receiver (information receiver) 10R from the public key storage device 4. Here, since there is no room for a third party to intervene from the time when the public key 2E is created by the information receiver 10R to the encryption device (encryption means) 12E, the public key used by the encryption device 12E is used. 4E is the same as public key 2E. Therefore, the original information 11a is encrypted using this public key 4E (2E). The obtained encrypted information 11b is transmitted to the information receiver 10R via the Internet 1 using this information transmission device (information transmission means). The information receiver 10R receives the encrypted information 11b transmitted from the information sender 10S by using the information receiving device (information receiving means).

【0053】

Since the encryption information 11b can be decrypted only by those who know the private key 2D corresponding to the public key 2E, it is possible that the original original information 11a is known to a third party from the encryption information 11b on the Internet 1. Absent.

【0054】

The information receiver 10R holds the private key 2D, and the decryption device (decryption means) 12D can decrypt the encrypted information 11b using the private key 2D, and the decrypted information 11c is the original source. Equal to information 11a.

【0055】

As described above, according to the embodiment of the present invention shown in FIG. 1, since there is no room for a third party to intervene in the route to which the public key 2E is distributed, the public key 2E can be distributed without being tampered with. Furthermore, the public key can be obtained anywhere within the broadcasting area of the broadcasting satellite 14 (in the case of Japanese broadcasting satellites, all over Japan).

【0056】

Next, a modified example of the first embodiment shown in FIG. 2 will be described. Here, the object to be encrypted in the first embodiment is a common key of another encryption, and the credit card number is secretly transmitted by using the common key. Of the configurations of the present modification, the same parts as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

【0057】

In the modification of the first embodiment, the public key transmission device 40A is provided with the key pair creation device 2, the decryption device 12D, the satellite uplink device 13, and the decryption device 23CR. Further, the public key receiving device 42A is provided with the encryption device 12E, the satellite receiving device 15, and the encryption device 23CS.

【0058】

What the encryption device 12E encrypts is the common key 21a of the common key cryptosystem, and this common key 21a is created by the information sender 10S. In the same way that the original information 11a (11c) is secretly transmitted to the information receiver 10R in the first embodiment (Fig. 1), the common key 21a (21c) is secretly transmitted to the information receiver 10R in this modified example. It is transmitted to the recipient 10R. Since the common key 21a (21c) could be secretly shared between the sender 10S and the receiver 10R of the information, the communication contents can be shared with a third party by performing the subsequent communication between the two using the common key cryptosystem. Not known.

【0059】

For example, the encryption 22b obtained by encrypting the credit card number 22a of the information sender 10S with the encryption device 23CS of the common key encryption method is transmitted via the Internet 1, and the information receiver 10R shares the received encryption 22b. Decrypt with the key encryption decryption device 23CR to obtain information 22c. Information 22c is nothing but the original information (card number 22a). Since the third party cannot know the common key 21a (21c), the card number 22a cannot be decrypted.

【0060】

The confidentiality of the common key is guaranteed by the public key cryptosystem using the public key 2E. Then, as long as the public key 2E is distributed by the method of the present invention, it is guaranteed that the public key 2E will not be tampered with on the way.

【0061】

Next, the second embodiment of the present invention will be described with reference to FIG. Here, the information sender (information sender) 30S publishes the homepage on the Internet 1, and the information receiver (information receiver) 30R can view this homepage without being tampered with on the way. , Teletext broadcasting of terrestrial television shall be used for distribution of public keys.

【0062】

In FIG. 3, the information sender 30S is the side that distributes the public key and includes the public key transmitting device 40B. In addition, the information receiver 30R is the side that receives the public key, and is equipped with the public key receiving device 42B.

【0063】

The public key transmission device 40B includes a key pair creation device (key pair creation means) 2, a terrestrial television transmission device (radio wave transmission means) 33, a conversion device (conversion means) 32D, and an information transmission device (information transmission means). It is configured with and. However, in this embodiment, the public key transmission device 40B is composed of an information terminal such as a terrestrial television transmission device 33 and a server device (not shown). That is, in this embodiment, the key pair creation means 2, the conversion means 32D, and the information transmission means are programs deployed in the information terminal.

【0064】

The key pair creation device 2 creates a second private key 2D that converts information into encrypted information, and a second public key that reversely converts the converted encrypted information in response to this second private key 2D. It creates 2E.

【0065】

The terrestrial television transmission device 33 transmits radio waves used for terrestrial television broadcasting. The terrestrial television transmission device 33 includes a public key multiplexing device 3 that multiplexes the second public key to be transmitted.

【0066】

The conversion device 32D applies the second private key created by the key pair creation device 2 to the original information to obtain an authenticator.

【0067】

The information transmitting device (not shown) is connected to the Internet 1 and transmits information to the Internet 1. However, as described above, this information transmitting device (information transmitting means) is a program deployed in an information terminal such as a personal computer, and can also receive information on the Internet 1.

【0068】

The public key receiving device 42B includes a television receiving device (radio wave receiving means) 35 and an information terminal 38. The information terminal 38 includes an information receiving device (information receiving means), an inverse conversion device (inverse conversion means) 32E, a comparison device (comparison means) 36, and a switching device 37. However, in this embodiment, the public key receiving device 42B is composed of a television receiving device 35 and an information terminal 38 such as a personal computer (not shown). That is, in this embodiment, the information receiving means, the inverse conversion means, and the comparing means are programs developed in the information terminal 38.

【0069】

The television receiver 35 receives radio waves used for terrestrial television broadcasting. The television receiver 35 includes a public key storage device 4 that stores the transmitted second public key 2E.

【0070】

The information receiving device is connected to the Internet 1 and receives information from the Internet 1. However, as described above, this information receiving device (information receiving means) is a program deployed on an information terminal such as a server, and can also transmit information on the Internet 1.

【0071】

The inverse conversion device 32E applies the second public key received by the television receiving device 35 to the authenticator converted into the encrypted information received by the information receiving device, and applies the inversely converted original information (inverse conversion original information). What you get.

【0072】

The comparison device 36 compares the inverse conversion original information obtained from the inverse conversion device 32E with the original information obtained from the information receiving means. Further, in this embodiment, as a result of comparing the inverse conversion original information and the original information, if they are equal, the original information is transmitted to the information receiver 30R (information receiving side) as it is, and if they are not equal, an error statement is sent to the information. A switching device 37 for transmitting information to the receiver 30R (information receiving side) is added.

【0073】

Next, the operation will be described. Specifically, first, the operator of the homepage (information sender 30S) has a private key (second private key) 2D that is not disclosed to others and a public key (second public key) 2E that is disclosed to others. The pair of is created by the key pair creation device 2. The created public key 2E is input to the public key multiplexing device 3. The public key multiplexing device 3 is a device that multiplexes the public key 2E and the public key 2E'created by another person, and is not necessarily essential for realizing the present invention. Considering the amount of information that can be transmitted by teletext broadcasting, a plurality of public keys can be distributed in one broadcast wave. Therefore, in practice, when a plurality of public keys are distributed using the public key multiplexing device 3. Good.

【0074】

The plurality of multiplexed public keys are transmitted in the form of radio waves 34 by the terrestrial television transmission device (radio wave transmission means) 33. The television receiving device (radio wave receiving means) 35 that has received the radio wave 34 separates the public key information, and the public key is stored by the public key storage device 4.

【0075】

The information receiver (information receiving side) 30R operates the information terminal 38 to obtain information 31a of the homepage operated by the information sender 30S via the Internet 1. At this time, the information sender 30S side operates the information transmission device (information transmission means) to transmit the information 31a (desired information) of the homepage to the Internet 1 as it is, and the information 31a is transmitted by the private key 2D. The converter 31b obtained by conversion is also transmitted. As shown in FIG. 6 described in the conventional technique, the hash value by the hash processing device 61 may be converted into an authenticator, but here, it is assumed that the hash processing device 61 is not inserted.

【0076】

In Figure 3, information 31a and authenticator 31b can be tampered with while traveling through Internet 1. Therefore, the information 31a and the authenticator 31b received on the information receiver 30R side are represented by the codes 31a # and 31b #, respectively. The information receiver 30R acquires the public key 4E corresponding to the information sender 30S from the public key storage device 4. Here, since there is no room for a third party to intervene from the time when the public key 2E is created by the information sender 30S to the reverse conversion device 32E, the public key 4E used in the reverse conversion device 32 is the public key. It is the same as 2E. The received authenticator 31b # is inversely converted using the public key 4E (2E). If the authenticator 31b # has not been tampered with, the information obtained after the reverse conversion is equal to the information 31a on the homepage, but since there is no guarantee that it has not been tampered with, the code of the information after the reverse conversion is represented by 31a ##. ..

【0077】

Next, the comparison device 36 compares the information 31a ## after the inverse conversion with the received information 31a #. As described in the description of the prior art, if the comparison results by the comparison device 36 are equal, the information 31a # has not been tampered with and is equal to the original information 31a. In this case, the switching device 37 is controlled to transmit the information 31a to the information receiver 30R as it is. If the comparison results of the comparison device 36 are not equal, the switching device 37 is controlled to transmit an error sentence 3e indicating that the information has been tampered with to the information receiver 30R. By controlling as described above, it is possible to prevent the falsified information from being transmitted to the information receiver 30R.

【0078】

As described above, according to the present embodiment, since there is no room for a third party to intervene in the propagation path, the public key can be distributed without being tampered with. Furthermore, this public key can be obtained anywhere within the broadcasting area of television broadcasting. The detection of tampering with information 31a # and authenticator 31b # is guaranteed by digital signature using public key 2E. Then, as long as the public key 2E is distributed by the method of the present invention, it is guaranteed that the public key 2E will not be tampered with on the way.

【0079】

In the first and second embodiments described above, the devices 15 and 35 and the public key storage device 4 that receive the radio waves including the public key information are not required for each of the encryption device 12E and the inverse conversion device 32E. .. If the encryption device 12E or inverse conversion device 32E and the public key storage device 4 are connected by a communication path that makes it difficult to falsify information on the way, they are stored in one public key storage device. The public key information may be modified so that it can be used by a plurality of encryption devices 12E and inverse conversion devices 32E.

【0080】

A modified example of the second embodiment is shown in FIG. Here, in addition to the configuration of the second embodiment shown in FIG. 3, the public key information stored in one public key storage device 4 is converted into inverse conversion devices 32E, 32E'without going through the Internet 1. It is equipped with a router 41 that delivers information to the Internet and communication paths 42 and 42'that are difficult to falsify information on the way. In the figure, the one with a dash and the one with a dash have the same function as the one without a dash. Further, FIG. 4 shows a simplified internal configuration of the information terminal 38 shown in FIG.

【0081】

The public keys 2E and 2E'created by the information senders 30S and 30S'are sent to the public key storage device 4 without the intervention of a third party and without being tampered with, as in the second embodiment. Then, since the information receivers 30R and 30R'are transmitted from the public key storage device 4 through the communication paths 42 and 42', there is no possibility of falsification of the information. As described above, the plurality of information receivers 30R and 30R'can use the public key storage device 4 to obtain a public key that has not been tampered with. In this modification, the information receiver must connect to the public key storage device 4 separately from the Internet 1, but the connection is not complicated considering the following specific example.

【0082】

In the first specific example, the information terminal 38 is a computer for dial-up connection to the Internet, the communication path 42 is a wired or mobile phone line used for dial-up connection, and the router 41 and the public key storage device 4 are dial-up. This is the case when the equipment of the ISP (Internet Service Provider) to which the connection is made.

【0083】

In the second specific example, the information terminal 38 is a mobile phone having an Internet connection function, the communication path 42 is a mobile phone line, and the router 41 and the public key storage device 4 are facilities of a mobile phone company. Is.

【0084】

In common with the above two specific examples, since the information terminal 38 and the ISP or the mobile phone company occupy the communication path 42, there is no possibility of information falsification, and the ISP or the mobile phone company , The router 41 may be used to switch between connecting the information terminal 38 to the Internet and connecting to the public key storage device 4.

【0085】

In the first and second embodiments described above, it is not preferable to use the same private key 2D and public key 2E pair for a long period of time. This is because, in the public key cryptosystem shown in FIG. 1, the public key 2E, the information 11a before conversion, and the encryption 11b are used, and in the digital signature method shown in FIG. 3, the public key 2E, the information 31a before conversion, and the authenticator 31b are used. Therefore, the private key 2D may be analyzed.

【0086】

Therefore, if the secret key 2D is changed to a new pair of the private key 2D and the public key 2E before the private key 2D is derived by the analysis, the confidentiality of the private key 2D is improved. In particular, if the private key 2D and the public key 2E are computer programs that describe the calculation method in the process of performing an operation on the input data and outputting it, the cryptographic algorithm can be changed by changing the computer program. It can be changed, further increasing confidentiality.

【0087】

In the public key distribution method of the present invention, since the public key is distributed using radio waves as a medium, immediate distribution is completed to an unspecified and extremely large number of people who use the public key.

【0088】

[Effect of the invention]

As described above, according to the present invention, since the public key is distributed using terrestrial broadcast radio waves or communication or broadcasting satellite radio waves as a medium, the first public key that cannot be tampered with by a third party. And the second public key can be distributed. By using these public keys, it is possible to prevent the information to be transmitted from being leaked or falsified. The radio waves used in the public key distribution method of the present invention, particularly radio waves of communication satellites or broadcast radio waves, are suitable for immediately sending the same information to many people as compared with distribution on the Internet or physical media. In addition, among radio waves, broadcast radio waves have a larger transmission power than other wireless communications, so they are less susceptible to disturbing radio waves, and radio waves from communications or broadcasting satellites do not transmit fake radio waves from satellites. Since it is not disturbed as long as possible, it is possible to provide a public key transmitting device and a public key receiving device that are not easily affected by disturbed radio waves. Further, according to the public key distribution method of the present invention, the first public key and the second public key paired with the first private key and the second private key are changed periodically or irregularly. That is, by changing to a new private key before these private keys are decrypted, the strength of protection against decryption of the private key can be substantially strengthened. In particular, if the private key and the public key are computer programs and the programs are changed regularly or irregularly, the cryptographic algorithm is changed, so that the confidentiality of the private key is further enhanced.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the 1st Embodiment of this invention.

[Figure 2]

It is a block diagram which shows the modification of the 1st Embodiment in this invention.

[Fig. 3]

It is a block diagram which shows the 2nd Embodiment of this invention.

[Fig. 4]

It is a block diagram which shows the modification of the 2nd Embodiment in this invention.

[Fig. 5]

It is a block diagram quoted for demonstrating the conventional public key cryptosystem.

[Fig. 6]

It is a block diagram quoted for demonstrating the conventional digital signature system.

[Fig. 7]

It is a block diagram quoted for explaining "spoofing" by a third party in the public key cryptosystem shown in FIG.

[Explanation of symbols]

1 internet 2 Key pair creation device (key pair creation means) 3 Public key multiplier 4 Public key storage device 10S Information sender (information sender) 10R Information receiver (information receiver) 12E Cryptographic device (encryption means) 12D decoding device (decoding means) 13 Satellite uplink device (radio wave transmission means) 14 Broadcast satellite 15 Satellite radio wave receiver (radio wave receiving means) 23 Decoding device (decoding means) 32D converter (conversion means) 32E Inverse conversion device (inverse conversion means) 34 radio waves 38 Information terminal