JP2001156765A - Encryption display method, encryption communication method and encryption communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encryption communication method and an encryption communication system that can conduct encryption communication between entities with high convenience. SOLUTION: Display section 17, 27 of entities a, b display common keys Kab, Kba, a plain text M and an encrypted text C. The display sections 17, 27 display the plain text and/or the encrypted text that are binary data by using character conversion software such as the base 64 so as to visualize the data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryptographic display method for displaying plaintext and ciphertext, and a cryptographic communication method and cryptographic communication system for performing cryptographic communication between entities.

[0002]

2. Description of the Related Art In a modern society called an advanced information society, important documents and image information in business are transmitted, communicated, and processed in the form of electronic information based on a computer network. Such electronic information has a property that it can be easily copied and it is difficult to distinguish a copy from an original, and thus the importance of information security is emphasized. In particular, "sharing of computer resources",
The realization of a computer network that satisfies the elements of “multi-access” and “wide area” is indispensable for the establishment of an advanced information society, but this includes elements inconsistent with the problem of information security between the parties. As an effective method for resolving such inconsistency, cryptographic technology that has been used mainly in military and diplomatic aspects in the past history of humankind has attracted attention.

[0003] Encryption means exchanging information so that the meaning of the information cannot be understood by anyone other than the parties. In encryption, it is encryption to convert an original sentence (plaintext) that anyone can understand into a sentence (ciphertext) whose meaning is unknown to a third party, and decryption is to return the ciphertext to plaintext. The entire process of encryption and decryption is collectively called an encryption system. In the encryption process and the decryption process, secret information called an encryption key and a decryption key are used, respectively. Since a secret decryption key is required at the time of decryption, only a person who knows the decryption key can decrypt the ciphertext, and the encryption can maintain the confidentiality of the information.

[0004] The encryption key and the decryption key may be the same or different. An encryption method in which both keys are equal is called a common key encryption method, and DES (Data Encryption Standards) adopted by the United States Department of Commerce Standard Bureau is a typical example. Conventional examples of such a common key cryptosystem can be classified into the following three methods.

[0005] A first method is to secretly store all common keys with a partner who may perform encrypted communication. Second method A method in which keys are shared by preliminary communication each time cryptographic communication is performed (a key sharing method using Diffie-Hellman, a key distribution method using a public key method, etc.). Third method Using public specific information (ID (Identity) information) for specifying an individual, such as the name and address of each user (entity), the entity on the transmitting side and the receiving side without performing preliminary communication. In which the same entity independently generates the same common key (KPS (Key Predistribution System), I
D-NIKS (ID-based Non-Interactive Key Sharing
Schemes) etc.).

[0006]

The above three conventional methods have the following problems. In the first method, since all common keys are stored, the method is not suitable for a network society in which an unspecified number of users act as entities and perform cryptographic communication. Also, the second method has a problem in that preliminary communication for key sharing is required.

[0007] The third method does not require preliminary communication, and can generate a common key with an arbitrary partner by using the ID information of the disclosed partner and a unique secret parameter distributed in advance from the center. So it is a convenient way. FIG. 6 is a diagram showing the principle of the ID-NIKS system. Assuming the existence of a reliable center, the common key generation system is configured around this center. In FIG.
ID information such as the name, address, and telephone number of the entity X, which is the specific information of the entity X, is stored in a hash function h
It is represented by h (ID _X ) using (·). The center calculates a secret key S _Xi for an arbitrary entity X based on center public information {PC _i }, center secret information {SC _i }, and ID information h (ID _X ) of entity X as follows. And secretly distributes it to entity X. S _Xi = F _i ({SC _i }, {PC _i }, h (ID _X ))

The entity X exchanges a common key K _XY for encryption and decryption with another arbitrary entity Y by using its own secret key {S _Xi } and the center public information {P
C _i ＩＤ and the ID information h (ID
_Y ) is generated as follows. K _XY = f ({S _Xi }, {PC _i }, h (ID _Y )) Similarly, the entity Y also generates a common key K _YX as a key to the entity X. If the relationship of K _XY = K _YX always holds, the keys K _XY and K _YX can be used as the encryption key and the decryption key between the entities X and Y.

The present inventors have proposed such an ID-NIKS.
Has proposed various encryption methods and encryption communication methods, and has a configuration in which ID information of each entity is divided into a plurality of parts and a secret key based on the divided ID information is distributed to the entities from a plurality of centers. Also, an encryption method and an encryption communication method using ID-NIKS for improving security have been proposed. Furthermore, such an I
Various devices for realizing a cryptographic communication system using various encryption methods such as D-NIKS are also being studied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a cryptographic display method capable of displaying plaintext and ciphertext with good convenience for an entity, and a cryptographic communication method and a cryptographic communication system using this display method. The purpose is to provide.

[0011]

According to a first aspect of the present invention, there is provided a method for displaying plaintext and ciphertext in cipher communication, wherein the plaintext and / or the ciphertext which is binary data is converted to character conversion software. And visualized and displayed.

According to a second aspect of the present invention, there is provided an encryption display method according to the first aspect.
In the character conversion software, base64
It is characterized by being.

According to a third aspect of the present invention, in one of the entities, a plaintext is converted into a ciphertext by using a common key generated from a secret key unique to the entity, and transmitted to the other entity of the communication partner. The other entity uses the same common key as the common key, which is generated from a secret key unique to the entity, to decrypt the ciphertext into plaintext, thereby performing information communication between the entities. In the communication method, the plaintext and / or the ciphertext, which are binary data, are visualized and displayed using character conversion software.

[0014] According to a fourth aspect of the present invention, there is provided an encrypted communication method.
In the character conversion software, base64
It is characterized by being.

According to a fifth aspect of the present invention, there is provided an encrypted communication method according to the third aspect.
Wherein the cipher communication is performed by e-mail, the cipher text which is binary data is converted into text data, and the converted text data is attached and transmitted.

According to a sixth aspect of the present invention, there is provided an encrypted communication method according to the third aspect.
In any one of the first to fifth aspects, a secret key unique to each entity is created using specific information of each entity.

According to a seventh aspect of the present invention, there is provided an encrypted communication method according to the sixth aspect.
, A secret key unique to each entity is generated by using divided specific information obtained by dividing specific information of each entity.

[0018] The cryptographic communication system according to claim 8, wherein the encrypting process for encrypting the plaintext, which is the information to be transmitted, into ciphertext and the decrypting process for decrypting the transmitted ciphertext into plaintext are performed by a plurality of entities. In a cryptographic communication system that performs mutual communication between each other, means for generating a common key common to the entities to be used for the encryption and decryption processes using a secret key unique to each entity, It is characterized by comprising means for converting the plaintext and / or the ciphertext as data into text data using character conversion software, and means for visualizing and displaying the converted text data.

A ninth aspect of the present invention provides the cryptographic communication system according to the eighth aspect, wherein a secret key unique to each entity is created using the specific information of each entity.

A cryptographic communication system according to a tenth aspect is characterized in that, in the ninth aspect, a secret key unique to each entity is generated by using division specific information obtained by dividing specific information of each entity.

In the present invention, plain text and / or cipher text as binary data are visualized and displayed using character conversion software such as base64. Therefore, the correspondence between the plaintext and the ciphertext can be easily recognized in the entity. In the case of performing the encrypted communication by e-mail, if the mail software does not have the pasting file function, it is possible to paste the cipher text, which is binary data, as text data in the body.

Specific information (ID information) of each entity,
Alternatively, by generating a secret key unique to each entity using the division information of the specific information, it is possible to construct a cryptographic communication system capable of performing cryptographic communication between entities using ID-NIKS with high convenience of the entities.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. FIG. 1 is a schematic diagram showing the configuration of the cryptographic communication system of the present invention. A plurality (K) of centers 1 that can reliably conceal information are set as servers for creating secret keys. The centers 1 may be, for example, public institutions of society.

Each of these centers 1 and a plurality of entities a, b,..., Z as users who use this cryptographic communication system are connected to communication paths 2 _a1 ,..., 2 _aK , 2 _b1 ,
, 2 _bK ,..., 2 _z1 ,..., 2 _zK , and each entity a, b,
, Z are requested to each center 1 to create a secret key, and each center 1 creates a secret key unique to each entity for each entity a, b,. Also, communication paths 3ab, 3az, 3bz,... By e-mail are provided between the two entities, so that cipher text obtained by encrypting communication information is transmitted and received between the two entities by e-mail. Has become.

FIG. 2 is a schematic diagram showing a communication state of information between two entities a and b. The example in FIG.
The figure shows a case where an entity a encrypts a plaintext (message) M into a ciphertext C and transmits it to the entity b, and the entity b decrypts the ciphertext C into the original plaintext (message) M.

In each of the K centers 1, a selected one for each of the entities a and b is encrypted based on its own secret information (symmetric matrix) based on the password of each of the entities, and each center 1 has its own unique information. A secret key generator 2 for generating a secret key is provided. As shown in FIG. 3 showing the internal configuration, the secret key creator 2 stores a secret information storage unit 3 for storing encrypted secret information and an encrypted secret information stored in the secret information storage unit 3. A secret information decryption unit 4 for reading and decrypting, a secret key unique to each of the entities a and b from the secret information of the center 1 itself, specific information (ID information) of each of the entities a and b, and an input password of each of the entities a and b. And a secret information updating unit 6 that encrypts the secret information of the center 1 that is updated at predetermined intervals and writes the encrypted secret information into the secret information storage unit 3.

On the entity a side, each of the K centers 1
A first private key decryption unit 11 for decrypting a private key unique to the entity a itself in a private key scheme sent from the private key system, and a private key encryption unit 1 for encrypting the K decrypted private private keys
2 and a secret key storage unit 13 for storing an encrypted secret key.
A second secret key decryption unit 14 for reading and decrypting an encrypted secret key stored in a secret key storage unit 13; and an entity based on a secret key unique to itself and identification information (ID information) of entity b. A common key generation unit 15 for generating a common key _Kab with the entity b required by a, and a plaintext (message) M is encrypted into a ciphertext C using the common key _Kab and output to the communication path 30 by e-mail. Plaintext encryption unit 16
And a display unit 17 for displaying a common key, plaintext, ciphertext and the like.

On the entity b side, a first secret key decryption unit 21 for decrypting a private key unique to the entity b itself in a secret key system sent from each of the K centers 1, and K decrypted The secret key encrypting unit 22 for encrypting a secret key unique to itself, a secret key storing unit 23 for storing an encrypted secret key, and an encrypted secret key stored in the secret key storing unit 23 are read out. A second secret key decryption unit 24 for decryption, and a common key generation unit 25 for generating a common key K _ba for the entity a determined by the entity b based on the secret key unique to the unit and the identification information (ID information) of the entity a. And a ciphertext decryption unit 26 that decrypts the ciphertext C input from the communication channel 30 into a plaintext (message) M using the common key _Kba and outputs the plaintext (message) M.
And a display unit 27 for displaying a common key, plaintext, ciphertext and the like.

Next, the processing operation of the cryptographic communication in the cryptographic communication system having such a configuration will be described.

(Preliminary processing) Specific information (ID information) for specifying each entity, for example, an ID vector (L-bit binary vector) representing the mail address of the entity
, As shown in FIG.
Divide into blocks. For example, an ID vector (vector _Ia ) indicating the mail address of the entity a is divided as in Expression (1). Each vector I _aj (j = 1, 2,..., K), which is division specifying information, is called an ID division vector. The mail address of the entity is converted into an L-bit ID vector by a hash function.

[0031]

(Equation 1)

(Secret key creation process (entity registration process)) An entity that wants to participate in this cryptographic communication system, that is, an entity that wishes to create a secret key unique to itself, accesses the home page and sends it via the server.
A public key method (S
SL, etc.). In the secret key creator 2 of each center 1, the secret information (a symmetric matrix described later) obtained by decrypting the encrypted secret information stored in the secret information storage unit 3 by the secret information decryption unit 4 is transmitted to the secret key generation unit 5. Then, a part corresponding to the entity is selected, and the selected secret key (a secret key vector described later) is encrypted based on the password input on the entity side, that is, the secret obtained by incorporating the password in the selected secret key. In a key scheme, a private key unique to the entity is issued to the entity via email. In this case, the secret key method is DE
S is available. In addition, the mail address of the entity may be encrypted and sent.

Note that, more simply, by e-mail,
It is also possible to perform a secret key creation request process and a secret key issuance process. In this case, an entity desiring to create its own private key sends its password directly to each center 1 by e-mail using the public key method. In each center 1, as in the above case, the secret key unique to the entity is determined by a secret key method (DES or the like) in which a password input on the entity side is incorporated into a secret key selected corresponding to the entity from the secret information. , Publish to that entity via email.

In the above-described example, the secret key is issued by e-mail. However, the secret key unique to the entity is written in a portable recording medium such as an IC card.
It is also possible to send the recording medium to the entity.

Here, the secret information (symmetric matrix) at each center 1 and the specific contents of the secret key (secret key vector) unique to each entity will be described. j (j = 1,
(2,..., K) -th center 1
Symmetric matrix H _j (2 ^M × 2 ^M ) with random numbers as elements
have. Then, for each entity, a row vector corresponding to the split ID vector of the entity of the symmetric matrix _Hj is created as a secret key (secret key vector). That is, H _j [vector I _aj ] is created for entity a. This H _j [vector I _aj ] represents a vector obtained by extracting one row corresponding to the vector I _aj from the symmetric matrix H _j .

The secret information (symmetric matrix H _j ) in each center 1 is periodically updated. That is, the secret information (symmetric matrix H _j ) that is encrypted and stored in the secret information storage unit 3 is updated at predetermined intervals by the processing of the secret information update unit 6.

Here, an example of inputting a password on the entity side will be described. Regarding the password input process, the following two examples are particularly suitable for an entity that is not used to inputting a password.

In one example, each entity inputs a character string, and the input data encoded by base64 is used as a password. In this case, 6-bit data can be represented by inputting each of the 64 types of characters, so if the password is 64 bits, it is sufficient to input 11 characters.

In the other example, 16 types of characters 0 to 9 and A to F are input in principle.
If a character other than six types is entered, the character is
9. Replace with any of A to F characters.

(Generation of Common Key Between Entities) Entity a (entity b) is composed of K centers 1
The first private key decryption unit 11 (21) decrypts a private key (private vector) unique to the entity a (entity b) in the private key scheme sent from the first private key decryption unit 11 (21). The decrypted secret key (secret vector) is once encrypted by the secret key encryption unit 12 (22) and stored in the secret key storage unit 13 (23).
Then, when generating a common key K _ab (K _ba ) with the entity b (entity a) as the communication partner, the encrypted secret key is read from the secret key storage unit 13 (23) and the second secret key is read. The secret key (secret vector) is decrypted again by the key decryption unit 14 (24).

The entity a (entity b) extracts the element corresponding to the entity b (entity a) from the secret vector (secret key) received from each center 1 by the common key generation unit 15 (25). By combining these K elements, entity a (entity b)
Key K for entity b (entity a)
_ab (K _ba ) is generated. Here, the two common keys _Kab and _Kba match based on the symmetric surname of the secret information (matrix) possessed by each of the K centers.

As described above, the secret information (symmetric matrix) in each center 1 is updated periodically in consideration of security. Therefore, the secret key (secret vector) distributed to each entity is also changed periodically. Therefore, in the present invention, the encryption secret keys stored in the secret key storage units 13 and 23 are sequentially updated in synchronization with the update cycle of the secret information (symmetric matrix) in each center 1, or A new encrypted secret key is additionally stored in the secret key storage units 13 and 23.

In the latter case of additional storage, the receiving entity
Email from entity a in email b
When you receive a sentence, check the sent date of the email
The secret key that matches the transmission date.
23 and selectively decrypted by the second secret key decryption unit 24.
Using the secret key (secret vector)
Common key K at 25_baIs generated, each center 1
If the secret information (symmetric matrix) in is updated
Is the common key K used by the entity a at the time of encryption. _abWhen
Same common key K_baCan always be generated.

(Ciphertext Creation at Entity a, Ciphertext Decryption at Entity b) In the entity a, the plaintext encryption unit 16 uses the common key K _ab generated by the common key generation unit 15 The plaintext (message) M is encrypted into a ciphertext C, and the ciphertext C is transmitted to the communication path 30 by electronic mail. In the entity b, the ciphertext C is decrypted by the ciphertext decryption unit 26 into the original plaintext (message) M using the common key _Kba generated by the common key generation unit 25.

At the time of such encryption / decryption processing,
On the display units 17 and 27, the common key, the plaintext, and the ciphertext are displayed in the respective display areas. However, the ciphertext C to be transmitted is binary data and is invisible to the entities a and b. Therefore, in the present invention, binary data is converted into character data by base64 and then visually displayed.

For example, when the plaintext M is text data, the text data is directly displayed on the display units 17 and 2.
7 is displayed in the plain text display area. Since the ciphertext C obtained by encrypting the encrypted data is binary data, base64
Are displayed in the ciphertext display area of the display units 17 and 27. On the other hand, when the plaintext M is binary data, the binary data converted to character data by base64 is displayed in the plaintext display area of the display units 17 and 27. And the ciphertext C which encrypted it
Is binary data, and converted into character data by base64 is plaintext in the ciphertext display areas of the display units 17 and 27.

According to the present invention, a mail address that can be recognized by an entity at the time of encrypted communication by electronic mail is used as identification information (ID information) of the entity.
When the receiving entity b receives the encrypted mail,
It is possible to generate a common key using the mail address in the from field of the mail as specific information (ID information). In addition to the mail address, other information that can identify the other party at the time of encrypted communication, for example, a source telephone number, a facsimile TSI signal, and the like can be used as the identification information (ID information).

By the way, the longer the length of the secret key (secret vector) created from each center 1 for each entity, the higher the security as a cryptographic communication system. on the other hand,
When the length of the secret key (secret vector) is short, there is an advantage that a simple system can be constructed although the security is low.
Therefore, in the present invention, a plurality of cryptographic communication systems having different secret key (secret vector) lengths are considered.

For example, a system for creating a 64-bit and 128-bit secret key (secret vector) for each entity is constructed. A system for creating a 64-bit secret key (secret vector) is a system for general use that anyone can arbitrarily participate in, and is free of charge for gathering a large number of participants. On the other hand, a system that creates a 128-bit secret key (secret vector) is a system in which only members of a specific company, organization, or organization can participate as an entity, and is charged for reasons of achieving high security. I do. In the latter case, since the entities are limited, they are resistant to collusion attacks by multiple entities.

Next, an example in which a session key is used for encrypting plaintext and decrypting ciphertext will be described. The following two examples will be described as modes using the session key. In any case, the security of the encrypted communication can be improved by introducing the session key.

In the first example, the transmitting entity a
Then, a session key K for converting the plaintext M into the ciphertext C
_S is encrypted by, for example, DES using the common key K _ab generated as described above, and the encrypted information DESK _ab (K _S )
Create The cipher information DESK _ab (K _S ) is arranged before the cipher text C in which the plaintext M is encrypted with the session key K _S , and is transmitted to the entity b by e-mail together with the cipher text C. In the receiving entity b,
First, the encryption information DESK _ab (K _S ) is obtained using the common key K _ba.
By decoding the calculated session key K _S, it decrypts the ciphertext C received by the obtained session key K _S to the original plaintext M.

In the second example, the transmitting entity a,
Using the shared information that can be shared by the receiving-side entity b and the common key generated as described above, the session key K is used by both entities a and b as f (shared key, shared information) = K _{S. Ask} for _S. Since the shared information and the common key obtained by the two entities a and b are the same, the same session key K _S is required. Plaintext M by the session key K _S obtained by the entity a side is sent encrypted into ciphertext C from the entity a to entity b, the ciphertext C is the session key K _S obtained by the entity b side To the original plaintext M.

FIG. 5 is a diagram showing the configuration of an embodiment of the recording medium of the present invention. The program exemplified here is a secret key creation process as described above for creating a private key unique to each entity at each center based on a request from the entity, and a secret key created by a secret key method from each center is transmitted to each entity. , A secret key decryption process as described above, a common key generation process as described above for generating a common key with a communication partner using a secret key unique to itself, secret information of a center (a symmetric matrix), As described above, the secret information for storing and periodically updating the secret key (secret vector) of the entity and storing or updating the secret key, and displaying the common key, plaintext, and ciphertext as described above. And / or plain text encryption / cipher text decryption processing, etc., and are recorded on a recording medium described below. The computer 40 is provided on each host side or each entity side.

In FIG. 5, a recording medium 41 that is connected online to a computer 40 is, for example, a WWW (World Wide) that is installed separately from the installation location of the computer 40.
(Web) server computer, and the recording medium 41
Stores the program 41a as described above. The program 41 a read from the recording medium 41 controls the computer 40 to execute at least one of the above processes.

The recording medium 42 provided inside the computer 40 uses a built-in hard disk drive or ROM, for example, and the recording medium 42 stores the program 42a as described above. The program 42a read from the recording medium 42 controls the computer 40 to execute at least one of the above processes.

The recording medium 43 used by being loaded into the disk drive 40a provided in the computer 40 is a transportable medium such as a magneto-optical disk, a CD-ROM, or a flexible disk. Is recorded. The program 43a read from the recording medium 43 controls the computer 40 to execute at least one of the above processes.

In the above-described embodiment, a plurality of centers are provided and identification information (ID information) of each entity is provided.
The secret key (secret vector) unique to each entity is created using the division identification information (division ID information) obtained by dividing the above. However, based on the identification information (ID information) of each entity from one center, A private key (secret vector) unique to the entity may be created.

[0058]

As described above in detail, in the present invention, a plaintext and / or a ciphertext which is binary data is converted into a base text.
Since it is visualized and displayed using character conversion software such as 64, character correspondence between plaintext and ciphertext can be easily recognized in the entity. In the case of performing the encrypted communication by e-mail, if the mail software does not have the pasting file function, it is possible to paste the cipher text, which is binary data, as text data in the body.

Furthermore, since the secret key unique to each entity is created by using the specific information (ID information) of each entity or the division information of the specific information, the ID-code having high convenience of the display function is provided. An NIKS cryptographic communication system can be constructed.

(Supplementary Note) The following items are further disclosed with respect to the above description. (1) A cipher display for displaying plain text and cipher text in cipher communication, means for converting the plain text and / or the cipher text, which is binary data, to text data using character conversion software, Means for displaying text data. (2) In a computer-readable recording medium on which a program for causing a computer to display plain text and cipher text in cipher communication is stored, the plain text and / or cipher text as binary data is converted to text data. A recording medium in which a program including program code means for causing a computer to perform conversion into a program and program code means for causing a computer to display the converted text data is recorded.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a cryptographic communication system of the present invention.

FIG. 2 is a schematic diagram illustrating a communication state of information between two entities.

FIG. 3 is a diagram showing an internal configuration of a secret key generator.

FIG. 4 is a schematic diagram showing an example of division of an ID vector (specific information) of an entity.

FIG. 5 is a diagram illustrating a configuration of an embodiment of a recording medium.

FIG. 6 is a diagram illustrating the principle configuration of an ID-NIKS system.

[Explanation of symbols]

 Reference Signs List 1 center 2 secret key generator 5 secret key generator 15, 25 common key generator 17, 27 display unit 16 plaintext encryption unit 26 ciphertext decryption unit 30 communication path 40 computer 41, 42, 43 recording media a, b, z entity

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasumichi Murakami 136 Takeda Mukoshirocho, Fushimi-ku, Kyoto-shi, Kyoto Inside Murata Machinery Co., Ltd. (72) Inventor Shinya Saito 4-30-6 Midorigaoka, Yao-shi, Osaka (72) Inventor Masao Kasahara 4-15-3 Ao Gaien, Minoh-shi, Osaka (72) Inventor Shigeo Tsujii 4-2-1-19 Jingumae, Shibuya-ku, Tokyo F-term (reference) 5B017 AA08 BA05 BA07 BB02 CA07 CA16 5J104 AA01 AA16 EA04 EA26 JA03 NA02 NA05 PA07

Claims (10)

[Claims] 1. A method for displaying plaintext and ciphertext in cipher communication, wherein the plaintext and / or the ciphertext which is binary data is visualized and displayed using character conversion software. Method. 2. The character conversion software includes a base
The cipher display method according to claim 1, wherein the number is 64. 3. An entity converts a plaintext into a ciphertext using a common key generated from a secret key unique to the entity, and transmits the ciphertext to the other entity of the communication partner.
On the other entity side, using the same common key as the common key, generated from the private key unique to the entity,
In a cryptographic communication method for communicating information between entities by decrypting the ciphertext into plaintext, the plaintext and / or the ciphertext that are binary data are visualized and displayed using character conversion software. An encryption communication method characterized by the above-mentioned. 4. The character conversion software includes a base
The encryption communication method according to claim 3, wherein the number is 64. 5. The cipher communication method according to claim 3, wherein the cipher communication is performed by electronic mail, the cipher text being binary data is converted into text data, and the converted text data is attached and transmitted. 6. The cryptographic communication method according to claim 3, wherein a secret key unique to each entity is created using specific information of each entity. 7. The cryptographic communication method according to claim 6, wherein a secret key unique to each entity is generated by using division specific information obtained by dividing specific information of each entity. 8. A cryptographic communication system in which a plurality of entities mutually perform an encryption process of encrypting a plaintext, which is information to be transmitted, into a ciphertext, and a decryption process of decrypting the transmitted ciphertext into a plaintext. A means for generating, on each entity side, a common key common to an entity to be used for the encryption processing and the decryption processing using a secret key unique to the entity, and the plaintext and / or binary data which is binary data. A cryptographic communication system comprising: means for converting the cipher text into text data using character conversion software; and means for visualizing and displaying the converted text data. 9. The cryptographic communication system according to claim 8, wherein a secret key unique to each entity is created using specific information of each entity. 10. The cryptographic communication system according to claim 9, wherein a secret key unique to each entity is generated by using divided specific information obtained by dividing specific information of each entity.