JP2001086109A - Cipher communication method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a cipher strength by preparing display information including choice corresponding to each kind of information and transmitting a plurality kind of ciphered information together with display information. SOLUTION: A cipher key creating part 3 creates respectively different random number bit strings concerning each group. A normal sentence data stored in a storage part 2 is enciphered in a normal sentence data enciphering part 4 through the use of the random number bit string which is created by the part 3 and enciphered normal sentence data (cipher data) is created. A preservation page to be displayed in a client is described by a page data describing part 5. The page data is transmitted to the client 10 by way of Internet 20 via a transmitting/receiving part 7 together with cipher data. Then the plurality kind of information are enciphered, display information including choice corresponding to each kind of information is prepared in order to select a specified kind of information from the respective groups by an information receiver and the plurality of ciphered information are transmitted to the receiver together with display information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption communication method and apparatus for concealing communication data in network communication.

[0002]

2. Description of the Related Art Today, data communication is widely performed on open computer networks such as the Internet. In such a network environment, there is a data communication format in which a data receiver selects a specific one from a plurality of options included in data from a sender and answers the sender. For example, there is a case where a member looks at a schedule table transmitted from an organizer, selects a specific time from the schedule table, and makes a time reservation at a driving school or an English conversation classroom with a membership system. When performing data communication on such a public network, it is necessary to ensure the security of the data transmitted.
As a method for ensuring confidentiality of data on the network, a data encryption technique is widely used. The encryption is performed, for example, by generating a random number bit string serving as an encryption key, and performing an exclusive OR operation on the random number bit string and the bit string of the data (plaintext data) to be encrypted for each bit by a stream encryption method. Done. In a communication system in which the receiver (client) has no encryption function, the encryption is performed by the sender (server).

For example, a description will be given of a car training reservation system using the Internet. For example, a server at a driving school side responds to a request from a client at a member side.
It encrypts plaintext data and transmits it. The plaintext data to be encrypted is data corresponding to a reservable date and time, training contents, and the like, which are selectively selected by the member. At the time of such plaintext data encryption, the server cannot know in advance which plaintext data among the plurality of plaintext data is the data selected by the member. It is encrypted with a key. That is, one random number bit string is generated, the exclusive OR of the random number bit string and each plaintext data is calculated, and the calculation result is transmitted to the client as encrypted data.
When the member selects a time slot to be reserved, the encrypted data corresponding to the selected content is returned to the server, and the encrypted data is exclusive-ORed with the random number bit string used in the previous encryption. Is decrypted. Then, the reservation data is updated based on the decrypted plaintext data, and the reservation is established.

[0004]

In such conventional cryptographic communication, since a plurality of plaintext data are simply encrypted with the same encryption key, a plurality of encrypted data encrypted with the same encryption key are illegally transmitted. May be intercepted. When such a plurality of encrypted data are obtained, the original plaintext data can be easily inferred by calculating the exclusive OR of the plurality of encrypted data. Also, it becomes easy to infer plaintext data from the number of transmitted encrypted data. Therefore, in the conventional encryption communication in which a plurality of plaintext data is encrypted with the same encryption key, there is a problem that the encryption strength is reduced.

An object of the present invention is to provide an encryption communication method and apparatus which do not reduce the encryption strength when a plurality of data arbitrarily selected on the receiver side are encrypted on the sender side. .

[0006]

In order to achieve the above object, an encryption communication method according to the present invention prepares a plurality of information sets which are selectively selected, and uses a different encryption method for each of the sets. A step of encrypting the plurality of pieces of information; a step of preparing display information including options corresponding to the pieces of information so as to allow a receiver of the information to select specific information from each of the sets; Transmitting the plurality of information together with the display information to the receiver.

Further, the present invention provides a procedure for receiving a plurality of pieces of information selected by the above-mentioned recipient, and decoding the plurality of pieces of received information by a decryption method corresponding to an encryption method to which each set belongs. And a step of performing the operation.

In this case, the encryption method and the decryption method may be based on a stream encryption method that performs an exclusive OR operation on a bit string of information and a random number bit string for each bit.

[0009] The encryption communication device of the present invention prepares a plurality of sets of a plurality of information that are alternatively selected, and encrypts the plurality of pieces of information by a different encryption method for each of the sets. A display information generating unit that prepares display information including options corresponding to the respective information in order to allow the information receiver to select specific information from the respective sets; and And transmission means for transmitting the display information to the receiver.

Further, the present invention provides a receiving means for receiving a plurality of pieces of information selected by the receiver, and a decryption method for each of the plurality of pieces of received information by a decryption method corresponding to an encryption method to which each set belongs. And decoding means for decoding.

In this case, the encryption method and the decryption method may be based on a stream encryption method that performs an exclusive OR operation on a bit string of information and a random number bit string for each bit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on one embodiment shown in the drawings. In the following, a description will be given of a car training reservation system using the Internet as an example. However, the present invention can be used for data communication of arbitrary contents via any type of communication network. Further, the encryption method used for realizing the present invention may be any method in which at least the data sender holds an encryption key kept secret by a third party, for example, a secret method in which the encryption key is not disclosed to a third party. In key encryption, stream encryption for encrypting information in bit units, DES encryption or FEA
Any of block ciphers, such as the L cipher, that performs encryption for each block composed of a plurality of bits may be employed.

FIG. 1 is a block diagram showing the overall configuration of a cryptographic communication system according to the present embodiment, FIG. 2 is a sequence chart showing a communication procedure in the system shown in FIG. 1, and FIG. FIG. 4 is a diagram showing a flow, and FIG. 4 is a diagram showing a flow of each data in the decryption processing on the server side. In the present embodiment, when a plurality of data are encrypted on the server side, encryption is performed by a different encryption method for each data set.

In FIG. 1, a server 1 as an encryption communication device arranged at a training school (sender) side and a client 10 provided at a member (recipient) side are communicably connected via the Internet 20. ing. The server 1 includes a storage unit 2 for storing plaintext data, reservation data, and an encryption key, an encryption key generation unit 3 for generating an encryption key used for encrypting the plaintext data, and a plaintext data encryption for encrypting the plaintext data. A section 4, a page data description section 5 for describing page data, a transmission / reception section 6 for transmitting / receiving various data, and a plaintext data decryption section 7 for decrypting encrypted plaintext data are provided. The client 10 includes a transmission / reception unit 11 for transmitting / receiving various data, and a display unit 12 for displaying page data. These servers 1
The client 10 can be configured by a general-purpose or dedicated computer, and each of the above-described components realized therein can be configured by a CPU and a program operating on the CPU.

Next, a procedure when the client 10 makes a reservation for a car training in such a system will be described with reference to FIG. 1 and FIG. First, the client 10 opens the initial screen of the reservation system on the browser displayed on the display unit 12 and sets the ID assigned in advance.
To log in (step S1). This ID
When the ID is valid, the server 1 approves the login (step S2) and encrypts data to be transmitted to the client 10 (step S2).
4-S6).

The data to be encrypted here is the client
Associated with the description of the training reservation page displayed on the
Data that is available for reservation and selected by the member
This is a plurality of data corresponding to time, training content, and the like. Below
This data before encryption is called plaintext data. Multiple flats
Sentence data consists of a plurality of data items that can be selected by the member.
Multiple sets of data. For example, Sunday to Saturday
Multiple lessons for each day (this corresponds to each group)
Interzone (this is the description corresponding to the data in each group) is set
One lesson for each day.
If you choose, the plaintext data corresponding to each training time slot is
Grouped by each day of the week, maintaining the state of its data structure
It is stored in the storage unit 2 as it is. In FIG.
The six plaintext data are "r₀₁"," R₁₁, R₁₂"," R
_{twenty one}"," R₃₁, R ₃₂4 sets combined as
Is configured. The plaintext data that composes each set in this way
In the data, the plaintext data is alternatively selected by the members for each group.
If necessary, include plaintext data of "No selection"
Can be

Prior to the encryption of the plaintext data configured as described above, the encryption key generation unit 3 generates a different random number bit string for each set (step S3). In the present embodiment, a stream encryption method using a random number bit string is employed for encryption. The generation of the plurality of types of random number bit strings is performed by setting different encryption keys as initial values of the feedback shift register. In FIG. 3, different random number bit strings “x ₀ ”, “x ₁ ”, “x ₂ ”, and “x ₃ ” are assigned to each set. However, when implementing the present invention, using an encryption method other than the stream encryption method,
Data encryption can be performed. In the plaintext data encryption unit 4, the plaintext data stored in the storage unit 2 is encrypted using the random number bit string generated by the encryption key generation unit 3, and the encrypted plaintext data ( (Encrypted data) is created (step S4). In the stream cipher used here, the bit string of each set of plaintext data and the random number bit string assigned to each set are subjected to exclusive OR operation in bit units. Here, the same set of plaintext data is encrypted using a random number bit string assigned to this set (see encrypted data in FIG. 3). The plurality of random number bit strings used for the encryption are stored in the storage unit 2.

Next, a page for reservation to be displayed on the client is described in the page data description section 5 (step S5). The page data includes a description or a mechanism corresponding to each of the above cipher data. The description or mechanism enables the member to select one of a plurality of training time zones on a daily basis. It will be apparent to those skilled in the art that such a description or mechanism can be realized by a program module such as a pull-down menu, a radio button, or the like, or a code according to an HTML (Hyper Text Markup Language) description. The data of this page is transmitted to the client 10 via the Internet 20 via the transmission / reception unit 7 together with the encrypted data.
(Step S6).

On the client 10 side, when the page data is received via the transmission / reception unit 11 (step S7),
This page data is displayed on the display unit 1 as a page for training reservation.
2 is displayed (step S8). Then, the member selects the date and time or the like to make a reservation by viewing the displayed training reservation page (step S9). This selection is performed so as to always select one data for each set as described above.
When this selection is made, the encrypted data corresponding to the selected data is transmitted to the server 1 via the transmission / reception unit 11 (step S10). FIG. 4 shows a state in which one set of encrypted data is returned from each of the above six sets of encrypted data.

In the server 1, when the encrypted data is received by the transmission / reception unit 6 (step S11), the encrypted data is decrypted using the encryption key stored in the storage unit 2 (step S12). ). That is, a plurality of random number bit strings that are encryption keys are called from the storage unit 2, and an exclusive OR of the plurality of random number bit strings and the returned encrypted data is obtained. Here, since one plaintext data is always selected and returned by the member for each group, the number of returned encrypted data corresponds to the random number bit string at the time of encryption, and decryption is performed without excess or shortage. It can be carried out. FIG. 4 conceptually shows a state in which exclusive OR operation is performed between each of the four encrypted data and the corresponding random number bit string used for the encryption, and the plaintext data is decrypted. ing. Then, the reservation data in the storage unit 2 is updated based on the plaintext data (step S1).
3), the reservation is established.

According to such encrypted communication, since each set of information is encrypted by a different method, it is difficult to infer plaintext data even if encrypted data is intercepted. Further, since the number of encrypted data returned from the receiver is constant, it is difficult for an eavesdropper to guess the contents from the number of data.

The embodiment of the present invention has been described with reference to the drawings. However, it is apparent that the present invention is not limited to the matters described in the above embodiments, and that changes, improvements, and the like can be made based on the description in the claims. The encryption only needs to be performed by a different encryption method for each set, and an encryption method other than the stream encryption method using a different random bit string as described above may be employed.

[0023]

As described above, according to the present invention, since a plurality of encrypted data to be transmitted and received are encrypted by different encryption methods, it becomes difficult to estimate plaintext data and the encryption strength is not reduced. . Further, since the number of data returned from the receiver is constant, it is difficult to infer plaintext data from the number.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a cryptographic communication system according to an embodiment of the present invention.

FIG. 2 is a sequence chart showing a communication procedure in the system of FIG.

FIG. 3 is a conceptual diagram showing a flow of each data in an encryption process on a server side.

FIG. 4 is a conceptual diagram showing a flow of each data in a decoding process on a server side.

[Explanation of symbols]

 Reference Signs List 1 server 2 storage unit 3 encryption key generation unit 4 plaintext data encryption unit 5 page data description unit 6, 11 transmission / reception unit 7 plaintext data decryption unit 10 client 12 display unit 20 Internet

Claims (6)

[Claims] A step of preparing a plurality of alternatively selected information sets and encrypting the plurality of information by a different encryption method for each of the sets; A procedure for preparing display information including options corresponding to the information in order to select specific information from the set, and the plurality of encrypted information, together with the display information,
Transmitting the message to the recipient. 2. a step of receiving a plurality of pieces of information selected by the receiver; a step of respectively decoding the plurality of pieces of received information by a decryption method corresponding to an encryption method to which each set belongs; The encryption communication method according to claim 1, further comprising: 3. The stream encryption method according to claim 1, wherein the encryption method and the decryption method are based on an exclusive OR operation of a bit string of information and a random number bit string for each bit.
Or the encrypted communication method according to 2. 4. An encrypting means for preparing a plurality of alternatively selected information sets, encrypting the plurality of pieces of information by a different encryption method for each of the sets, Display information generating means for preparing display information including options corresponding to the respective information, in order to select specific information from the respective sets, and the plurality of encrypted information, together with the display information,
And a transmitting means for transmitting to the receiver. 5. A receiving means for receiving a plurality of pieces of information selected by the receiver, and a decryption means for decrypting the plurality of pieces of received information by a decryption method corresponding to an encryption method to which each set belongs. The encryption communication device according to claim 4, further comprising: means. 6. The method according to claim 4, wherein the encryption method and the decryption method are based on a stream encryption method that performs an exclusive OR operation on a bit string of information and a random number bit string for each bit.
Or the encryption communication device according to 5.