JPH0916678A - Cipher communication equipment and its system - Google Patents

Abstract

PURPOSE: To suitably charge a user executing cipher communication. CONSTITUTION: Each of an information presenting side communication terminal 10 and a user side communication terminal 10 is provided with plural ciphering devices 11 having respectively different cipher systems and a selection means 14 for selecting one of the devices 11. A key corresponding to the selected cipher system is generated by a key generating/selecting means 13. An amount corresponding to a cipher system selected by a charging means included in an information presenting center is charged to the user. Thus a proper cipher system is selected in accordance with ciphering processing speeds included in plural cipher systems or the sort of information for ciphering cipher intensity and charge corresponding to the selected cipher system can be properly executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryptographic communication used in a multimedia network or the like, and more particularly to a cryptographic communication device and a cryptographic communication system for charging a communication service of encrypted secret information. is there.

[0002]

2. Description of the Related Art In recent years, with the development of optical fiber networks in trunk communication networks, the spread of cable television systems, the practical use of satellite communication, the spread of local area networks, etc., various information has been provided using such communication networks. Then
The so-called information service industry, which collects fees according to the content and amount of the information, is increasing. In addition, it is considered to provide multimedia information such as moving image data, still image data, audio data, computer data as the information. In such a service that provides multimedia information, it is important to properly charge the provided information. However, the conventional billing system is a monthly billing system that is unrelated to the frequency of use such as a cable television system or satellite broadcasting, or a frequency of use that is unrelated to the type and quality of information such as a computer usage service (or In many cases, it was a billing method in which only the usage time) was counted.

On the other hand, in such a communication network, it is important to safely transmit information, and a technique for encrypting and transmitting the information is known as a means therefor. Ciphers are roughly classified into two encryption methods, common key encryption and public key encryption, and various methods are considered for each classification.

First, cryptographic communication using the common key cryptosystem will be described. As shown in FIG. 18, the cryptographic communication network that realizes the information providing service includes an information providing center and users. The information providing center and the user share a unique and secret key in advance. A,
B, ..., M are users of the network, K _A , K _B ,
,, K _M is a key shared between the information providing center and the user A, a key shared between the information providing center and the user B, ..., is shared between the information providing center and the user M. Showing the key that is. Further, the information providing center and each user have a communication terminal including an encryption device that performs encryption (and decryption) according to an algorithm determined by the network and a communication interface, as shown in FIG. . The communication interface exchanges data between the communication terminal and the communication path.

For example, the conventional information providing service using the common key cryptosystem when the user A receives information from the information providing center is performed by the following procedure. 1. The user A requests the information providing center to provide the information required by the user A through the communication interface. 2. The information providing center sets the secret key K _A shared with the user _A in the encryption device in advance, encrypts the information provided by the encryption device, and sends the encrypted information to A via the communication interface. To do. 3. The user A receives the ciphertext from the information providing center via the communication interface, sets the secret key K _A shared with the information providing center in advance in the encryptor, and the encryptor sends the secret key K _A from the information providing center. Decrypt the received sentence and obtain the provided information.

Next, cryptographic communication using the public key cryptosystem will be described. When providing the information providing service, the information providing center has the public key of each user in the database because the information providing center only performs the encryption. In FIG. 19, the public keys of users A, B, ..., M are indicated by K ^p _A , K ^p _B , ..., K ^p _M , and the private keys are K.
^{, s} _A , K ^s _B , ..., K ^s _M. In the public key cryptographic communication network of FIG. 19, each user secretly holds a private key corresponding to his public key. Further, the information providing center and the respective users are as shown in FIG.
It has a communication terminal equipped with an encryption device that performs encryption (and decryption) according to an algorithm determined by the network. 20 shows a common key / public key cryptographic communication network using the common key cryptographic communication network of FIG. 18 and the public key cryptographic communication network of FIG.

Next, in FIG. 19, the conventional information providing service using the public key cryptosystem in the case where the user A is provided with information from the information providing center is performed by the following procedure. 1. The user A requests the information providing center to provide the information that he or she needs through the communication interface. 2. The information providing center sets the public key K ^p _A of the user _A in the encryptor, encrypts the information provided by the encryptor, and sends the encrypted information to A via the communication interface. 3. The user A receives the ciphertext from the information providing center via the communication interface, sets his own secret key K ^s _A in the encryptor, decrypts the received text from the information providing center by the encryptor, and provides it. Get the information given.

According to the above procedure, the information providing service is provided between the information providing center and the authorized user. Further, by providing the information according to the above procedure, the information providing center can provide the information secretly to the users other than the user who wants to send the information. Therefore, the user who sent the information is charged for the information providing service. be able to. However, when the information providing center charges a fee for the information providing service by such a procedure, conventionally, the information providing center simply charges the communication time regardless of the type or quality of the information, or charges each time the information is provided. There were many different methods.

Regarding the encryption technology, which is an important technology for the information providing service, various methods are conceivable even if it is limited to the typical encryption method known at present. In addition, various usage modes are considered even with the same encryption method, and various measures are being considered to further increase the strength against decryption in order to realize reliable communication.

Here, the DES encryption will be briefly described as a conventional encryption method. In the DES encryption, encryption and decryption are performed in units of 64-bit data blocks, and the key length is 56 bits (64 bits including 8 parity bits). The cryptographic algorithm is basically based on transposition and substitution. By appropriately repeating the transposition and substitution with 16 steps, the bit patterns of plaintexts are mixed and converted into ciphertexts that do not make sense. When decrypting, the original plaintext is restored by stirring in reverse.

The parameter of this stirring method is designated by a 56-bit key. The number of key candidates is 2 56 (about 10
(17 to the power of 17), which means that if the decryption is performed by changing the key for each pair of the obtained ciphertext and plaintext and checking it, 500ns per check.
In this case (processing speed of 128 Mbps), it takes about 1000 years as a whole.

In the DES encryption processing, transposition (initial transposition IP) is first performed on 64-bit plaintext. This initial transposition is fixed. The output of this transposition process is subjected to a transposition (final transposition IP ⁻¹ ) at the end after a complicated 16-stage encryption process on the way. This final transposition is also fixed.

The 64-bit data subjected to the initial transposition is divided into left and right by 32 bits, and the left half is L ₀ and the right half is R ₀ . The process shown in FIG. 22 is performed over 16 stages from L ₀ and R ₀ to L ₁₆ and R ₁₆ . That is, assuming that the left and right 32 bits at the end of the processing of the n-th stage are L _n and R _n , respectively, L _n and R _n are expressed by the following equation. L _n = R _n-1 R _n = L _n-1 #f (R _n-1 , K _n )

Here, # is exclusive of mod2 for each bit.
Means disjunction, K_nIs the 48 bits input to the nth stage
The key of L_n-1And R_n-1Is the output of the (n-1) th stage, f
Is R _n-1And K_nTo output 32-bit data
Function.

[0015]

However, in the conventional cipher communication, which cipher system is used to provide information between the information providing center and the user, and which use mode and how to decrypt. No consideration was given to the adjustment as to whether or not the encrypted communication should be performed using a method with various measures. In particular, no consideration was given to adjusting the encryption strength according to the type of information to be exchanged. For example, in the case of large-capacity data such as video that requires high-speed real-time processing, information is provided using an encryption method with a high encryption processing speed.
On the other hand, in the case of small-capacity, non-real-time, highly confidential data as represented by documents, on the other hand, it is possible to provide information using a highly secure encryption method, although the load on the encryption device is high. There wasn't.

Therefore, it has been difficult to set the fee system for the information providing service to a system corresponding to the transmission speed at the time of providing information and the security required for communication. The conventional cryptographic communication methods have the above problems.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fee system according to transmission speed and security for providing encrypted information.

[0018]

According to a first aspect of the present invention, there is provided an encryption transmission means for encrypting and transmitting data by a plurality of encryption methods, and a selection means for selecting one encryption method from the plurality of encryption methods. , And charging means for charging according to the encryption method selected by the selecting means.

According to a sixth aspect of the present invention, there is provided an encryption communication system in which encrypted data is communicated via a network and an encryption method can be selected, wherein the data transmission side is a data reception side. On the other hand, the fee is charged according to the selected encryption method.

[0020]

According to the present invention, by selecting the encryption method, the encrypted communication with a high degree of freedom is realized, and the fee system according to the encryption strength, the transmission speed, and the security of the selected encryption method is realized. The information providing service having the following is realized.

[0021]

EXAMPLES Examples 1 to 8 of the present invention will be described below, but each example has the following viewpoints. [Example 1] Setting an encryption method from a plurality of encryptions,
The fee for the information providing service is charged according to the set encryption method. [Second Embodiment] An encryption method is set from common key encryption and public key encryption, and the fee for the information providing service is charged according to the set encryption method.

[Third Embodiment] An encryption method is set from among a plurality of block ciphers, and the fee for the information providing service is charged according to the set encryption method. [Fourth Embodiment] A plurality of f-functions are prepared for the DES type encryption, and by selecting them, the encryption method is set, and the fee for the information providing service is charged according to the set encryption method.

[Embodiment 5] For the block cipher, an encryption method is set from a plurality of usage modes, and the fee for the information providing service is charged according to the set encryption method. [Embodiment 6] "Perform encryption while updating key" An encryption method is set from among a plurality of encryption methods, and the fee for the information providing service is charged according to the set encryption method.

[Embodiment 7] For the block cipher, an encryption method is set from the encryption method "encrypt using a fixed key" and the encryption method "encrypt while updating the key". , The fee for the information providing service is charged according to the set encryption method. [Embodiment 8] The internal variables of the key generation / selection device of the encryption method "encrypting while updating the key" of Embodiment 7 are made readable.

However, the essence of the present invention is to provide an information providing service by using an information providing server and a communication terminal equipped with a selecting means for selecting a plurality of encryption methods so that a user can execute a specific encryption method. In addition to the above, there is a charging means for charging the information providing service according to the encryption method set in the communication terminal. Therefore, by using the above communication terminal, the encryption strength can be selected, and the fee for the information providing service can be charged according to the security and processing speed realized by the set encryption method.

The selected encryption methods are:
It is not limited to the encryption method shown in the embodiment. As described in the section of the prior art, it is difficult to describe all the encryption methods in the embodiments because there are many encryption methods currently proposed. Further, an encryption method in which a plurality of encryption methods are combined is also included as an encryption method selected by the present invention.

[Embodiment 1] In this embodiment, as shown in FIG. 1, a plurality of encryption devices 11 for performing encryption (and decryption).
, Communication interface 12, and key generation / selection device 13
And cryptographic communication is performed using the communication terminal 10 including the selection unit 14 that selects one of the outputs of the plurality of encryption devices 11.

Each encryption device 11 realizes a different encryption method process. In the present embodiment, the encryption methods are: encryption method 1 encryption method 2 ... Encryption method t, and t types of encryption methods are used for each encryption device 11 of encryption device 1, encryption device 2 ,. It is assumed that the processing is realized. Further, which encryption device 11 to use can be set by an encryption method setting signal. In the following description, the cryptographic device 11 will be referred to as the cryptographic device 1 ... T when necessary.

The selecting means 14 is controlled by the encryption method setting signal and can select one of the outputs of the plurality of encryption devices 11. For example, when encryption processing of encryption method 1 is desired, the selection means 14 may be set to select the output from the encryption device 1 by the encryption method setting signal. Similarly, if encryption processing of encryption method 2 is desired, the selection means 14 may be set to select the output from the encryption device 2 by the encryption method setting signal.

The communication interface 12 sends the information indicating the encryption method and the transmission text encrypted by the encryption device 11 to the transmission path, and the information indicating the encryption method from the communication partner and the encryption device 11 encrypts the information. It is a communication interface for receiving the transmitted message and the transmitted message from the transmission line.

Further, since the key length is generally different for each encryption method, there is a key generation / selection device 13 as means for generating or selecting a key corresponding to the encryption method selected by the encryption method setting signal. . Key generation / selection device 13
Then, a key corresponding to the encryption method selected from one key having a certain length is generated. Alternatively, the keys corresponding to the number of encryption methods that can be realized by the encryption device are prepared in advance, and the key corresponding to the selected encryption method is selected.

FIG. 2 shows a key generation / selection device 13 according to the present invention.
An example is shown below. The key generation / selection device 13 generates a key according to the following algorithm. One key having a certain length which is input to the key generation / selection device 13 is used as an initial value (x ₀ ) in the following algorithm. x _{i + 1} = f (x _i ) (i = 0,1, ...) (1) b _{i + 1} = g (x _{i + 1} ) (i = 0,1, ...) 2)

As shown in FIG. 2, the key generation / selection device 13 has a processing circuit 13 for performing the feedback calculation of the equation (1).
a, the processing circuit 13b for performing the calculation of the equation (2), and the output of the length required for the key corresponding to the cryptosystem selected by the cryptosystem setting signal are output from the processing circuit for performing the calculation of the formula (2). It is composed of an arithmetic unit 13c for converting it into a key when issued.

In the arithmetic unit 13c, b ₁ , b ₂ , ..., B _i output from the processing circuit 13b for performing the operation of the equation (2) have a length corresponding to the encryption method selected by the encryption method setting signal. Convert to a key. The key is the selected cipher system bit string length of which is determined by algorithm, generates the arithmetic unit 13c, for example, by b _1, b _2, ..., by arranging as the b _i, or by rearranging their order To be done.

Therefore, the operation of the key generation / selection device 13 is as follows.
It looks like below. 1. X as initial value₀To the key generation / selection device 13
I do. 2. From equation (2), x₁, X_Two, ..., x_iGenerate
You. 3. The generated x₁, X_Two, ..., x_iFor equation (2)
And obtained b ₁, B_Two, ..., b_iIs output. 4. B by the computing unit 13c₁, B_Two, ..., b_iThe encryption method
Output as a key corresponding to the encryption method selected by the formula setting signal.
Power.

The key generation / selection unit 13 determines how many times the formulas (1) and (2) are calculated according to the encryption method setting signal, and how long the key is output from the calculator 13c. Is controlled, thereby generating a key having a length corresponding to the encryption method selected by the encryption method setting signal.

Further, the key generation / selection device 13 can be configured as shown in FIG. The key generation / selection device 13 of FIG. 3 is composed of t keys (k ₁ , k ₂ , ..., K _t ) and key selection means 13d. The keys k ₁ , k ₂ , ..., K _t are input to the key selection means 13d, and one of them is selected by the encryption method setting signal. As a result, a key having a length corresponding to the encryption method selected by the encryption method setting signal is selected.

Here, it is assumed that the key generation / selection device 13 is the one shown in FIG. 2, and as described above, a key corresponding to the encryption method selected from one key having a certain length is generated. .

As shown in FIG. 18, the encryption communication network for realizing the information providing service is composed of an information providing center and users A, B, ..., M. Between the information center and each user, a unique and secret key K _A ,
Share K _B , ..., K _M. Sharing of the key can be realized by setting the key in advance by the information providing center. Also, it can be realized by a known key sharing system as shown in, for example, "Cryptography and Information Security" (Tsujii, Kasahara, 1990, Shokosha Co., Ltd., 72-73, 97-104). .

Each user of the encrypted communication network realizing the information providing service has a portable storage device 30 as shown in FIG. The portable storage device 30 stores the secret key of the owner of each portable storage device 30 required for cryptographic communication. If the secret key is known to anyone other than the owner, confidential communication cannot be performed and a highly reliable information providing service cannot be realized.Therefore, keep the secret key secure so that only the owner knows it. In consideration of this, each user has a portable storage device 30 separately from the communication terminal 10. The portable storage device 30 may be a part of the communication terminal 10 as long as a physically safe area can be secured for each user, but in that case, a communication terminal that can be used for encrypted communication for each user. 10 will be limited. The communication terminal 10 and the portable storage device 30 are separated from each other,
By not storing the confidential information of each user in the communication terminal 10, the user can exchange the confidential information of the user in any communication terminal 10 through his / her own portable storage device 30. It is convenient because it can be used for encrypted communication.

The portable storage device 30 is the communication terminal 1 described above.
It is possible to exchange information with 0 through a secure communication path, and has a physically secure area as the holding means 30a. Only the legitimate owner can operate the portable storage device 30 normally, and it is determined whether or not the legitimate owner by the authentication procedure such as the password. still,
The portable storage device 30 can be realized by an IC card or the like.

FIG. 5 shows the structure of the information providing center 40.
The information providing center 40 includes the communication terminal 10 described above, a database 41 in which information to be provided is stored, a billing device 42 that bills according to the provided information and conditions at the time of providing, and encrypted communication. It has at least one storage device 43 in which information of all required secret keys and usage amounts of users is stored. In FIG. 5, a plurality of communication terminals 10 are provided in order to be able to simultaneously provide information to a plurality of users. When building a larger-scale information providing system, there may be a plurality of databases 41, billing devices 42, and storage devices 43.

The database 41 is configured as shown in FIG. 6, and stores information to be provided to the user and fee information for the service providing the information in association with each other. The charge information is divided into charges depending on which encryption method is used to provide the information. For example, the encryption method is set to C by the encryption method setting signal.
_{If it is possible to set 1} , C ₂ , ..., C _t , the charge when the information i is provided by the encryption method C _j is set as P _{i, j} . Such a database 41 can be easily configured with an existing database.

Further, if it is desired to charge in consideration of the communication time required to provide information, the charge is set as the charge of the information providing service per unit communication time in the price setting of P _{i, j} above, and the information is provided. It measures how many times the required communication time is longer than the unit communication time and multiplies the value by the charge of the information providing service per unit communication time, and charges the charge as the information providing service charge.

The storage device 43 is configured as shown in FIG. 7, and for each user who subscribes to the information providing network,
There are a key storage area in which a secret key required for cryptographic communication is stored, and a cumulative amount storage area in which an accumulated amount of usage charges for a certain period is stored. This period will be referred to as a usage fee collection period. The usage fee collection period is set to, for example, one month. The information providing center 40 calculates the fee for the information providing service for each user within the usage fee total period based on the accumulated amount of money for each user in the accumulated amount storage area, and charges each user. After a certain usage charge tabulation period, it is stored in the accumulated amount storage area,
The usage amount for each user during the usage fee collection period is moved to another storage unit as backup information, and the usage amount for each user in the accumulated amount storage area is reset. However, the accumulated amount storage area is not necessary if the information is settled each time information is provided.

The charging device 42 is constructed as shown in FIG. The billing device 42 performs billing calculation according to the encryption speed used at the time of providing information currently provided. Further, the charging device 42 can retrieve the charge information from the database 41. In addition, a new cumulative amount of money is calculated by adding the current information charge to the cumulative amount of money of the user who provided the information, which is held in the storage device 43, and newly stored in the cumulative amount storage area of the user of the storage device 43. Write the cumulative amount of money. However, it is not necessary to calculate the cumulative amount of money and write it when clearing each time information is provided. The information providing network according to the present invention is configured by the above respective devices.

Next, the user A requests the information providing center to provide certain information, the information providing center 40 sends the information to the user A, and the information providing center 40 charges the user A for the information providing service. The procedure according to the present invention for charging is performed as follows. Here, the user A has already been provided with information from the information provision center several times within the current usage fee collection period, and as a result, the user A's current usage fee collection period in the accumulated amount storage area of the storage device 43. The cumulative amount of money is Ch
It is assumed that it is in the area _A. Further, the name of the information requested by the user A to be provided is Info. Further, it is assumed that the user A wants to provide Info with the encryption method C _j . Further, it is assumed that the fee for the Info information providing service with the encryption method C _j is P _{Info, j} according to the amount of information and the encryption speed. Further, it is assumed that the name Info of the user A and the charge P _{Info, j} are known in advance.

In the following description, the authorized user A is authenticated by his / her own portable storage device 30, and the portable storage device 3 is confirmed.
It is assumed that 0 is set so that it can communicate with the communication terminal 10 in an operable state. Further, it is assumed that the user A has been authenticated by the information providing center 40 as a legitimate user and is certainly A. These two authentications can be sufficiently realized by a known authentication technique.

[Pre-Procedure for Providing Information According to the Present Invention] 1. The user A requests the information providing center 40 to provide Info. At the same time, let us know that you want to use the encryption method C _j . 2. In response to a request from the user A to provide Info, the information providing center 40 sends a charge P _{Info, j} for the information providing service using the encryption method C _j . 3. If the user A receives the charge information and is satisfied with the charge for providing Info, the information providing center 4
0 to request Info provision. If not satisfied, the information providing center 40 is notified that the Info providing request has been canceled, and this procedure ends.

Next, the user A informs the information providing center Inf.
The procedure is continued in case of requesting provision of o. [Procedure of Information Providing According to the Present Invention (Regarding Information Providing Center)] The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. A secret key K _A held in the key storage area of the user A of the storage device 43 is set as an initial value in the key generation / selection device 13, and a key corresponding to the encryption method selected by the encryption method setting signal is set. To generate. The generated key is set in the encryption device 11. 3. The data is encrypted by the encryption device 11, and the selection unit 1
The ciphertext output from the encryption device 11 determined in the previous procedure is selected by 4 and transmitted to the user A via the communication interface 12.

[Procedure for providing information according to the present invention (user A
Regarding)] 1. The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. The secret key K _A held in the portable storage device 30 is set in the key generation / selection device 13 as an initial value, and a key corresponding to the encryption method selected by the encryption method setting signal is generated. The generated key is set in the encryption device. 3. The encrypted data is received from the transmission path via the communication interface 12, and the encryption device 11 causes the information providing center 4 to receive the encrypted data.
0 is used to decrypt the encrypted data sent from
In step 4, the plaintext output from the encryption device 11 determined in the previous procedure is selected.

It is also possible to use the one shown in FIG. 3 as the key generation / selection device 13. In that case, FIG.
The key shown in means a combination of a plurality of keys.
That is, the key K _A between the information providing center 40 and the user _A
Is composed of a key K _A1 when using the encryption method 1, a key K _A2 when using the encryption method 2, ..., And a key K _At when using the encryption method t. In this case, the information providing service from the information providing center 40 to the user A according to the present invention is performed by the following procedure.
However, the pre-procedure is the same as above, so it is omitted.

[Procedure of Information Providing According to the Present Invention (Regarding Information Providing Center)] The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. The secret key K _A (consisting of K _A1 , K _A2 , ..., K _At ) held in the key storage area of the user A of the storage device 43 is set in the key generation / selection device 13, and the encryption method is set. A key corresponding to the encryption method selected from the plurality of keys K _A1 , K _A2 , ..., K _{At is} selected by the setting signal. The selected key is set in the encryption device 11. 3. The data is encrypted by the encryption device 11, and the selection unit 1
The ciphertext output from the encryption device 11 determined in the previous procedure is selected by 4 and transmitted to the user A via the communication interface 12.

[Procedure for providing information according to the present invention (user A
Regarding)] 1. The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. Secret key K held in the portable storage device 30
Key generation for _A (consisting of K _A1 , K _A2 , ..., K _At )
A key corresponding to the selected encryption method is selected from the plurality of keys K _A1 , K _A2 , ..., K _At by setting the selection device 13 and the encryption method setting signal. The selected key is set in the encryption device 11. 3. The encrypted data is received from the transmission path via the communication interface 12, and the encryption device 11 causes the information providing center 4 to receive the encrypted data.
0 is used to decrypt the encrypted data sent from
In step 4, the plaintext output from the encryption device 11 determined in the previous procedure is selected.

Next, a charging procedure after the Info providing center 40 has finished providing Info. This charging procedure is
The key generation / selection device 13 is common to those shown in FIGS. [Billing procedure according to the present invention] 1. Charging device 42, rates of information providing services of an Info from the database 41 at cryptosystem C _j is P _{Info, j}
Take out the information that is. 2. The charging device 42 calculates a fee for providing information. In this case, the charge is P _{Info , j} . 3. The charging device 42 adds the charge P _{Info, j} to the accumulated amount Charge _A of the user A held in the storage device 43 to calculate a new accumulated amount Charge _A + P _{Info, j} ,
The new accumulated amount Charge _A + P _{Info, j} is written in the accumulated amount storage area of the user A of the storage device 43. However,
When clearing each time, it is not necessary to calculate the cumulative amount.

The information providing center 40 charges a charge to each user based on the accumulated amount of money for each user every time the above-mentioned charge collection period ends. Further, when the usage fee total period ends, the amount is stored in the accumulated amount storage area.
The usage amount for each user during the usage fee collection period is moved to another storage unit as backup information, and the usage amount for each user in the accumulated amount storage area is reset.

According to the procedure described above, the encryption method can be selected with a high degree of freedom. Therefore, for example, when it is desired to select an encryption method having a high encryption security but a heavy processing load, the information providing service When it is desired to set a high fee and select an encryption method in which the security of encryption is low but the processing load is small, it is possible to set a high fee for the information providing service. That is, in this embodiment, it is possible to perform the encrypted communication between the information providing center 40 and the user, in which the encryption strength of the communication terminal 10 and the information providing fee can be selected.

The above [pre-procedure for providing information according to the present invention] does not have to be performed every communication. For example, it is not necessary when the encryption method is previously discussed between the information providing center 40 and the user and the encrypted communication is performed by the encryption method.

[Embodiment 2] In this embodiment, a plurality of encryption devices 15 for performing encryption (and decryption), as shown in FIG.
The communication terminal 10 includes a communication interface 16, a communication interface 12, a key generation / selection device 13, and a selection unit 14 that selects one of the outputs of the plurality of encryption devices 15 and 16.

In this embodiment, the encryption method is 1. DES encryption method (or FEAL encryption method) as a representative of the common key encryption method. As a representative of public key cryptosystems, there are two types of cryptosystems of RSA cryptosystem (or ElGamal cryptosystem), and a DES cryptosystem (or FEAL cryptosystem) 15 and an RSA cryptosystem (or ElGamal cryptosystem) 16 respectively. It is assumed that the processing is realized. However, the DES encryption exemplified here,
The FEAL cipher, the RSA cipher, and the ElGamal cipher are listed as typical examples of the common key cipher or the public key cipher, and the present invention is not limited to these and can be applied to other cipher algorithms.

When the communication terminal 10 shown in FIG. 9 is used in the DES encryption system, the selecting means 14 selects the DES encryption device 1
Select the output from 5. Further, when the RSA encryption method is used, the selection means 14 may select the output from the RSA encryption device 16.

The same key generation / selection device 13, communication interface 12, and selection means 14 as those in the first embodiment are used. However, the key generation / selection device 13 uses the one shown in FIG. 3, and selects the key corresponding to the encryption method selected by the encryption method setting signal. That is, when the DES encryption method is selected, the key distributed in advance for the DES encryption is selected, and when the RSA encryption method is selected, the RS
Select a public key published for A encryption.

In this embodiment, the encryption communication network shown in FIG. 20 is used. The common key / encryption key encryption communication network of FIG. 20 is configured by adding the public key encryption communication network of FIG. 19 to the common key encryption communication network of FIG. When providing the information providing service, encryption is limited to the information providing center 40. Therefore, the information providing center 40 has the database 41 having the public key of each user.

In the encrypted communication network shown in FIG. 20, each subscriber secretly holds a secret key corresponding to his public key and a key shared with the information providing center. Further, in FIG. 20, the public keys of the users A, B, ..., M are K ^p _A , K ^p.
_{, B} , ..., K ^p _M , and the private key is K ^s _A , K ^s _B ,.
It is indicated by K ^s _{M. Also, K A, K B, ...} , the common key shared K _M common key shared between the respective information providing center 40 user A, and the information providing center 40 between users B, ..., A common key shared between the information providing center 40 and the user M is shown. Therefore, the user j secretly holds his own secret key K ^s _j and the common key K _j of the information providing center 40.

In this case, the information providing service from the information providing center to the user A according to the present invention is performed by the following procedure. However, the pre-procedure and the charging procedure are the same as those in the first embodiment. [Procedure of Information Providing by the Present Invention (Regarding Information Providing Center)] The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. A key corresponding to the encryption method selected from the common key K _A and the public key K ^p _A held in the key storage area of the user A of the storage device 43 is selected. The selected key is the encryption device 15,
It is set to 16. 3. The encryption devices 15 and 16 encrypt the data, the selection means 14 selects the ciphertext output from the encryption device determined in the previous procedure, and sends it to the user A via the communication interface 12.

[Procedure for providing information according to the present invention (user A
Regarding)] 1. The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. _A key corresponding to the selected encryption method is selected from the common key K _A and the secret key K ^s _A held in the portable storage device 30 by the encryption method setting signal. The selected key is set in the encryption devices 15 and 16. 3. The encrypted data is received from the transmission path via the communication interface 12, the encrypted data sent from the information providing center 40 is decrypted by the encryption devices 15 and 16, and the encryption device determined by the selecting means 14 from the encryption device in the previous procedure. Select the plain text to be output.

By the above procedure, the encryption method can be selected according to the confidentiality of the information provided. For example, it is possible to select the public key encryption method in the case of particularly confidential data and to select the common key encryption method to simplify the processing otherwise. Therefore, the fee system of the information providing service according to the selected encryption method can be realized.

[Embodiment 3] In this embodiment, a plurality of encryption devices 1 for performing encryption (and decryption) as shown in FIG.
Communication terminal 11 provided with 7, 18 and communication interface 12, key generation / selection device 13, and selection means 14 for selecting one of the outputs of a plurality of encryption devices 17, 18.
Is used.

In this embodiment, the encryption method is 1. DES encryption 2. Two types of block ciphers, FEAL cipher, are used, and the processing is realized by the DES cipher device 17 and the FEAL cipher device 18, respectively. However, the DES encryption and the FEAL encryption exemplified here are only listed as typical examples of the common key encryption, and the present invention is not limited to these and can be applied to other encryption algorithms.

When it is desired to perform the DES encryption processing using the communication terminal 10 shown in FIG.
Select the output of the S encryption device. When the FEAL encryption process is desired, the selection means 14 always selects the output from the FEAL encryption device.

The key generation / selection device, communication interface, and selection means are the same as those in the first embodiment, and the encryption communication network shown in FIG. 18 is used. Also in this embodiment, the procedure of communication and billing between the information providing center 40 and the user A is the same as the procedure shown in the first embodiment.

[Embodiment 4] In this embodiment, an encryption device 19 for performing encryption (and decryption) as shown in FIG.
, Communication interface 12, and key generation / selection device 13
The communication terminal 11 including and is used. In addition, the selection unit 14 shown in the above embodiments is included in the encryption device in this embodiment. In this embodiment, DES type (involution type) encryption is considered as the encryption method. By preparing a plurality of f-functions that are the constituents and selecting a certain f-function from among them, a plurality of encryption methods can be set.

Since the DES type encryption is an algorithm for repeating the same processing as described above with reference to FIG. 22, it is possible to repeat the processing in the same circuit. For example, FIG.
If the processing for one stage of the DES encryption shown in 2 is made into a circuit as one processing unit, the encryption processing can be realized by repeatedly using the circuit.

The encryption device 19 in this case is as shown in FIG.
Be composed. The encryption device 19 of FIG.
a, 19b, the exclusive OR circuit 19c, and a plurality of f functions.
Number (f ₁, F_Two, ..., f_t) And the output of multiple f-functions?
The selection means 19d for selecting one of them. Selection
The selecting means 19d is controlled by the encryption method setting signal.
I have. The configuration of a plurality of f-functions is, for example, the same number as the f-functions.
This can be achieved by preparing a set of Sboxes.
You. In this case, f function f₁For S_11,S₁₂,
…, S₁₈Using Sbox of f function f_TwoFor
S_{twenty one}, S_{twenty two}, ..., S₂₈Using Sbox of ...
You can do it. Also, f function f₁Against DES dark
Number f function, f function f_TwoFor FEAL encryption
Using the f function of, f ...
It can also be realized by preparing a function.

The same key generation / selection device 13 and communication interface 12 as in the first embodiment are used, and the encryption communication network shown in FIG. 18 is used. Also in this embodiment, the procedure of communication and billing between the information providing center 40 and the user is the same as the procedure shown in the first embodiment.

[Embodiment 5] In this embodiment, a communication terminal 10 having the same structure as the communication terminal 10 shown in FIG. 11 is used.
However, instead of the encryption device 19, the encryption device 20 shown in FIG.
Is used. Further, the selecting means is also provided in the encryption device 2 in this embodiment.
It is included in 0. Further, in the present embodiment, the bit length of the key does not change depending on the encryption method, so the key generation / selection device 13
Is not always necessary.

In this embodiment, a block cipher is used as the encryption method. In addition, the block cipher ECB (Electric Codebook) mode 1. CBC (Cipher Block Chaini
ng) mode, it can be set by the encryption method setting signal.

The CBC mode will be described later, but here
But let me briefly explain. Plaintext is M _iCiphertext C_iinitial value
Is IV and the encryption using the encryption key K is E_K, Decrypt the D
_KThen, the CBC mode is expressed by the following equation. C₁= E_K(M₁+ IV) ……… (3) C_i= E_K(M_i+ C_i-1) (I = 2, 3, ...) (4) M₁= D_K(C₁) + IV ………… (5) M_i= D_K(C_i) + C_i-1(I = 2, 3, ...) (6)

The encryption device 20 in this case is configured as shown in FIG. The encryption device 20 of FIG. 13 includes a block cipher 20a and selection means 20 for selecting one from two inputs.
b and an exclusive OR circuit 20c that performs an exclusive OR operation for each bit. The selection means 20b is controlled by the encryption method setting signal.

When the encryption device 20 of FIG. 13 is used in the ECB mode, the input initial value IV is a bit string of all 0s, and the selecting means 20b always selects the initial value IV. When using in the CBC mode, an arbitrary bit string is set as the input initial value IV, and the selecting means 20b uses the initial value I when encrypting the first block.
V is selected, and thereafter, the output from the encryption device 20 is selected. The initial value IV does not need to be kept secret between correspondents.

The same key generation / selection device 13 and communication interface 12 as those in the first embodiment are used, and the encryption communication network shown in FIG. 18 is used.

Also in this embodiment, the procedure of communication and billing between the information providing center 40 and the user is the same as the procedure shown in the first embodiment. However, in the previous procedure,
When the CBC mode is selected, a procedure for sharing the initial value IV is required. For example, a procedure for sharing the initial value IV between the information providing center 40 and the user A is required before performing encrypted communication. The initial value IV is the information provision center 40
Since it does not need to be kept secret between the user and user A, it does not need to be encrypted. In addition to the secret key K _A , the shared initial value IV must be set in the encryption device 20 in the communication terminal 10.

[Embodiment 6] This embodiment is an improvement of the encryption system based on Embodiment 1. In this embodiment, as in the first embodiment, as shown in FIG. 1, a plurality of encryption devices 11 for performing encryption (and decryption), a communication interface 12, a key generation / selection device 13, and a plurality of encryption devices. Device 1
A communication terminal 10 having a selecting means 14 for selecting one of the outputs of 1 is used.

The present embodiment is different from the first embodiment in the following points. Although there are a plurality of encryption devices 11 in the first embodiment,
The key for each encryption device 11 is fixed during one encrypted communication. That is, the key is not changed at any time during the encrypted communication, and the same key is used from the beginning to the end of the encrypted communication. On the other hand, in this embodiment, the key is changed at any time during the encrypted communication in order to improve the security against the decryption by the third party. In order to update the key at any time during the cryptographic communication, the key generation / selection device 13 also generates the key during the cryptographic communication, and every time a key having a length corresponding to the cryptosystem selected by the cryptosystem setting signal is generated. Then, the key of the encryption device 11 is updated. However, it is necessary to update the key in synchronization with the sender and the receiver of the encrypted communication.

The key generation / selection device 13 of this embodiment is
As in the case of the first embodiment, the configuration is as shown in FIG. However, as described above, the key generation / selection device 13 of the present exemplary embodiment also performs key generation during encrypted communication, and each time a key having a length corresponding to the encryption method selected by the encryption method setting signal is generated. Since the key of the encryption device is updated, the operation is different from that of the first embodiment.

Key generation / selection device 13 in the case of the first embodiment
Does not need to operate any more if a key having a length corresponding to the encryption method selected by the encryption method setting signal is generated. On the other hand, in the key generation / selection device 13 of this embodiment, it is necessary to successively generate keys having a length corresponding to the encryption method selected by the encryption method setting signal. That is, the key generation / selection device 13 in the present embodiment repeatedly performs the operation of the key generation / selection device 13 in the first embodiment.

The key generation algorithm of the key generation / selection device 13 used in this embodiment is not particularly limited, and a general one as shown in the first embodiment can be used. In the present embodiment, a description will be given of a case where a computationally secure pseudo-random number sequence generation algorithm is used as a key generation algorithm, and in particular, a square pseudo-random number sequence is used among them.

The square-type pseudo random number sequence is a pseudo random number sequence b ₁ , b ₂ , ... Generated by the following procedure. [Square type pseudo-random number sequence] p, q is p≡q≡3 (mod
4) is a prime number, N = p · q, and an initial value x
₀ (integer of 1 <x ₀ <N−1) and recursive expression x _{i + 1} = x _i ² modN (i = 0, 1, 2, ...) ... (7) b _i = lsb _j (x _i ) (I = 1, 2, ...) ... The bit sequence b ₁ , b ₂ , ... Obtained by (8) is called a square type pseudo-random number sequence. However, lsb _j (x _i ) represents the lower j bits of x _i , where j is the number of bits of N.
= O (log ₂ n).

The square type pseudo-random number sequence is a computationally secure pseudo-random number sequence under the assumption that the square residue property determination problem in the modulus N is computationally difficult. In order to make the square type pseudo random number sufficiently safe, it is desirable that the number of bits n of the modulus N of the square arithmetic expression (7) is about 512 bits. Furthermore, keys (initial values of the key generation / selection device 13) K _AB , K _AC , which are secretly shared in advance among the subscribers,
Is 1 <K _AB , K _AC , ... <N-1.

Key generation using this square type pseudo-random number sequence
The selection device 13 is shown in FIG. The key generation / selection device 13 shown in FIG. 14 is composed of a processing circuit 13e for performing the feedback calculation of the equation (7), a processing circuit 13f for performing the calculation of the equation (8), and a calculator 13g. This key generation / selection device 1
The operation of No. 3 is as follows. 1. The initial value x ₀ is input to the processing circuit 13a. 2. By the formula (7), x ₁ , x ₂ , ... Are generated. 3. Processing circuit 13f for the generated x ₁ , x ₂ , ...
Equation (8) is executed in step (1) to output the obtained b ₁ , b ₂ , ... 4. The arithmetic unit 13g converts b ₁ , b ₂ , ... To key strings k ₁ , k ₂ , ... Of keys having a length corresponding to the encryption method selected by the encryption method setting signal.

FIG. 15 shows the procedure of encrypted communication when the key is updated at any time. Consider a block cipher as an encryption method.
In FIG. 15, M _uv (u = 1, 2, ... t; v = 1,
2, ..., S) is a plaintext block, and k _u (u = 1, 2,
, T) is the block cipher key, k _u (M _uv ) (u =
, 1, t; v = 1, 2, ..., s) represent ciphertext blocks obtained by encrypting the plaintext block M _uv with the key k _u . Here, s blocks from M _u1 to M _us are encrypted with the same key k _u . The plaintext block in FIG. 15 is encrypted by a plurality of encryption keys by sequentially using the key sequences k ₁ , k ₂ , ... Updated by the key generation / selection device 13 as the keys of the block cipher. By thus updating the key as needed, the number of plaintext blocks encrypted with the same key becomes s, which makes it difficult to analyze the key.

The encryption device 11 and the communication interface 1
2. The same selection means 14 as that used in the first embodiment is used, and the encryption communication network shown in FIG. 18 is used.

The information providing service from the information providing center 40 to the user A according to this embodiment is performed by the following procedure.
However, the pre-procedure and the charging procedure are the same as in the first embodiment. [Procedure of Information Providing According to the Present Invention (Regarding Information Providing Center)] The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. A secret key K _A held in the key storage area of the user A of the storage device 43 is set in the key generation / selection device 13 as an initial value, and a key string corresponding to the encryption method selected by the encryption method setting signal. To generate. 3. The key sequence output from the key generation / selection device 13 is used as a key of the encryption device 11 while being updated at any time to encrypt the data, and the selection device 14 determines the encryption device 11 in the previous procedure.
Select the ciphertext output from the communication interface 1
2 to the user A.

[Procedure for providing information according to the present invention (user A
Regarding)] 1. The selection unit 14 is set so that the output from the encryption method determined in the previous procedure is selected by the encryption method setting signal. 2. The secret key K _A held in the portable storage device 30 is set in the key generation / selection device 13 as an initial value, and a key string corresponding to the encryption method selected by the encryption method setting signal is generated. 3. The encrypted data is received from the transmission path via the communication interface 12, and the key string output from the key generation / selection device 14 is used as the key of the encryption device 11 while being updated at any time,
The transmitted encrypted data is decrypted, and the selection means 14 selects the plaintext output from the encryption device 11 determined in the previous procedure.

Although the square pseudo random number is used as the computationally secure pseudo-random number generation algorithm, any computationally secure pseudo random number generation algorithm can be used. For example, as shown in the document "Cryptography and Information Security" (Tsujii, Kasahara, 1990, Shokosha Co., Ltd., Paragraph 86), the present invention also employs RSA cryptography, discrete logarithm, and reciprocal cryptography. Can be used for the pseudo-random number generation algorithm of. The method of updating the key described in the present embodiment as needed is described based on the first embodiment, but it can be applied not only to the first embodiment but also to the third, fourth, and fifth embodiments.

[Embodiment 7] In Embodiment 1, a certain encryption method is selected from a plurality of fixed key encryption methods, and in Embodiment 6, a key is an encryption method selected from among the updated encryption methods (plural). The method is to select the method. As a variation of the above two embodiments, in this embodiment, the encryption method can be selected between a fixed encryption method for the key and an updated encryption method for the key.

In this embodiment, as shown in FIG.
A communication terminal 10 that includes an encryption device 11 that performs encryption (and decryption), a communication interface 12, and a key generation / selection device 13 is used. Here, for simplicity of explanation, it is assumed that there is one encryption device.

In this embodiment, a block cipher is considered as an encryption method. In addition, the block cipher 1. Perform encryption using a fixed key. The encryption method setting signal can be used to set which method is to be used for encryption while updating the key.

The key generation / selection device 13 is controlled by the encryption method setting signal and "performs encryption using a fixed key".
In the case of using the encryption method, the key generation / selection device stops the process when a fixed key (one key) is generated. Also,
In the case of using the encryption method of "encrypting while updating the key", the key generation / selection device 14 operates so as to repeat the process for generating the key string (a plurality of keys).

When the communication terminal 10 of FIG. 16 is used in the "encrypt using a fixed key" encryption method, the key generation / selection device 14 generates a fixed key by the encryption method setting signal. Then, the encryption device 11 may use the fixed key for encryption. When the communication terminal 10 is used with the encryption method “encrypt while updating the key”, the key generation / selection device 14 generates a key string by the encryption method setting signal, and the encryption device 11 Then, encryption may be performed while sequentially updating the key with the key sequence.

The key generation / selection device 13 is the same as that of the sixth embodiment, and the encryption device 11 and the communication interface 12 are the same as those of the first embodiment. Further, the one shown in FIG. 18 is used as the encryption communication network.

Also in this embodiment, the procedure of communication and billing between the information providing center 40 and the user is the same as the procedure shown in the first embodiment. However, when encryption is selected while updating the key, the procedure for providing information is performed in the same manner as in the sixth embodiment. With the above procedure, the encryption method can be selected according to the confidentiality of the data to be transmitted. For example, especially for highly sensitive data,
Select the "encrypt while updating the key" encryption method,
If not, it is possible to select an encryption method "encrypt using a fixed key" to simplify the process. Therefore, the fee system of the information providing service according to the selected encryption method can be realized.

In this embodiment, one encryption device 11 is used for the sake of simplicity of explanation, but the case of using a plurality of encryption devices 11 is also included in the present invention. When a plurality of encryption devices 11 are used, selection means 14 for selecting the output from the plurality of encryption devices 11 is required.

[Embodiment 8] In this embodiment, Embodiments 6 and 7 are used.
A case will be described in which the configuration of the key generation / selection device 13 used in the above is slightly changed. In the sixth and seventh embodiments, since the key shared between the subscribers is fixed, the key generation / selection device 13 is used when the users are the same even in the encryption method of “encrypting while updating the key”. There is a problem that the initial value of is always the same value and the same key string is generated.

Therefore, in the present embodiment, even if the user is the same, the initial value of the key generation / selection device 13 is changed every time it is used, and the security can be improved. Expressions (7) and (8), which are the procedures for key sequence generation shown in the sixth embodiment.
X is updated one after another by feedback calculation in
_{i + 1} will be called an internal variable of the key generation / selection device 13.

The key generation / selection device 13 of this embodiment is shown in FIG.
As shown in FIG. 7, the processing circuit 13h that performs the feedback calculation of the formula (7) and the processing circuit 13 that performs the calculation of the formula (8).
i and an arithmetic unit 13j, and is configured to read an internal variable updated by the calculation of the equation (7). In the communication terminal 10 on the user side, the read internal variables are stored in the holding means 30a of the portable storage device 30 connected to the communication terminal 10 according to the first embodiment. Further, in the communication terminal 10 on the information providing center 40 side, it is stored in the key storage area of the storage device 43 in the first embodiment.

In the sixth and seventh embodiments, the key generation / selection device 13
Although the data movement is in one direction only by setting the initial value to, in the present embodiment, the internal variables of the key generation / selection device 13 can be read in the opposite direction. The read internal variable is replaced with the common key used for the current encrypted communication as the common key used for the next encrypted communication. This key generation / selection device 13
By replacing with the selection device 13, the communication terminal 1 can be changed each time the initial value of the key generation / selection device 13 is used.
0 can be configured.

Also in this embodiment, the encryption communication network shown in FIG. 18 is used. In addition, the information providing center 40
The procedure of communication and billing between the user and the user is the same as the procedure shown in the first embodiment. However, in the procedure of providing information, the information providing center 40 side says, “The value of the internal variable of the pseudo random number generator when the encryption of the information to be provided is completed is set as a new initial value for cryptographic communication with A next time. The procedure "Keep secretly in the key storage area of 43" is required at the end, and the user side will provide the value of the internal variable of the pseudo-random number generator when the decryption of the encrypted information is completed next time. Holding means 30 of portable storage device 30 as a new initial value for encrypted communication when asked
The procedure "Keep secret in a" is finally required.

[0109]

As described above, according to the present invention, since the encryption method can be selected, it has not been conventionally considered depending on the encryption strength and the encryption processing speed of the selected encryption method. It is possible to realize a highly flexible fee system for the information providing service by making it possible to select the security of encryption at the time of providing information and the service fee thereof, or the speed of encryption and the service fee thereof.

[Brief description of the drawings]

FIG. 1 is a block diagram of a communication terminal according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a key generation / selection device according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a key generation / selection device according to the first embodiment of the present invention.

FIG. 4 is a block diagram of a portable storage device according to the first embodiment of the present invention.

FIG. 5 is a block diagram of an information providing center according to the first embodiment of the present invention.

FIG. 6 is a block diagram of a database according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a storage device according to a first embodiment of the present invention.

FIG. 8 is a block diagram of a charging device according to the first embodiment of the present invention.

FIG. 9 is a block diagram of a communication terminal according to a second embodiment of the present invention.

FIG. 10 is a block diagram of a communication terminal according to a third embodiment of the present invention.

FIG. 11 is a block diagram of a communication terminal according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram of an encryption device according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram of an encryption device according to a fifth embodiment of the present invention.

FIG. 14 is a block diagram of a key generation / selection device using a squared pseudo random number according to a sixth embodiment of the present invention.

FIG. 15 is a configuration diagram showing a procedure of encrypted communication when performing a key update according to the sixth embodiment of the present invention.

FIG. 16 is a block diagram of a communication terminal according to a seventh embodiment of the present invention.

FIG. 17 is a block diagram of a key generation / selection device using a squared pseudo random number according to a seventh embodiment of the present invention.

FIG. 18 is a configuration diagram of a common key encryption communication network.

FIG. 19 is a configuration diagram of a public key cryptographic communication network.

FIG. 20 is a configuration diagram of a common key / public key cryptographic communication network.

FIG. 21 is a block diagram of a conventional communication terminal.

FIG. 22 is a block diagram showing processing for one stage of DES encryption.

[Explanation of symbols]

 10 communication terminal 11, 15-20 encryption device 13 key generation / selection device 14 selection means 41 database 42 billing device 43 storage device

Claims (6)

[Claims] 1. An encryption transmission means for encrypting and transmitting data by a plurality of encryption methods, a selection means for selecting one encryption method from the plurality of encryption methods, and an encryption method selected by the selection means. A cryptographic communication device having a charging means for charging. 2. Decryption receiving means for receiving and decrypting encrypted data is provided, and key generating means for generating a key according to the selected encryption method is provided in the encryption transmitting means and the decryption receiving means. The cryptographic communication device according to claim 1, which is provided. 3. The cryptographic communication device according to claim 2, further comprising an updating unit that updates the key generated by the key generating unit at any time when the data is encrypted. 4. The cryptographic communication apparatus according to claim 2, wherein a pseudo-random number generation algorithm that is secure in terms of computational complexity is used as the algorithm used by the key generation means. 5. The cryptographic communication device according to claim 4, wherein a square pseudo random number generation algorithm is used as the computationally secure pseudo random number generation algorithm. 6. An encryption communication system capable of communicating encrypted data via a network and selecting an encryption method, wherein the data transmission side is selected with respect to the data reception side. An encryption communication system characterized by charging according to an encryption method.