JP4294938B2 - File transfer system, key server device, file transmission device, file storage device, file reception device, and program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
An object of the present invention is to provide a file transfer system, a key server device, a file transmission device, a file storage device, a file reception device, and a program for realizing them by a computer, which are suitable for safely transferring files. And
[0002]
[Prior art]
Conventionally, various techniques have been proposed in order to ensure the security of a communication path for transferring various information using the Internet. For example, HTTPS (Hyper Text Transfer Protocol over SSL) using SSL (Secure Socket Layer) protocol is an example.
[0003]
On the other hand, even when a file is transferred using the SSL protocol or the HTTPS service, an Internet provider business that provides a service for transferring a file from a file transmission side to a reception side is also popular.
[0004]
In this case, the file is transmitted from the file transmission side to the file server of the provider company using HTTPS. The provider company's file server stores the transmitted files. The file receiving side acquires the file stored in the file server of the provider company. In this way, file transmission is performed.
[0005]
Therefore, the contents of the file transmitted to the malicious provider may be leaked.
[0006]
[Problems to be solved by the invention]
Therefore, there is a strong demand for a technique for easily improving security from a third party that can be interposed during file transmission via a computer communication network.
[0007]
The present invention has been made in order to solve the above-described problems, and is preferably a file transfer system, a key server device, a file transmission device, a file storage device, a file reception device, which are suitable for safely transferring a file, It is another object of the present invention to provide a program for realizing these by a computer.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the following invention is disclosed in accordance with the principle of the present invention.
[0009]
A file transfer system according to a first aspect of the present invention includes a key server device, a file transmission device, a file storage device, and a file reception device, and is configured as follows.
[0010]
That is, the key server device generates seeds, generates a random number by applying a predetermined random number generation function to the generated seeds, and transmits the generated seeds and the generated random numbers to the file transmission device. .
[0011]
On the other hand, the file transmission device receives the seed and random number transmitted from the key server device, encrypts the file to be transferred with the received random number, generates an encrypted file, and receives the received seed. And the generated encrypted file are transmitted to the file storage device.
[0012]
Further, the file storage device receives the seed transmitted from the file transmission device and the encrypted file, and stores the received seed and the encrypted file.
[0013]
Then, the file reception device acquires the seed stored in the file storage device and the encrypted file, and applies the predetermined random number generation function to the acquired seed to generate a random number. The obtained encrypted file is decrypted with the random number obtained to obtain a file to be transferred.
[0014]
The file transfer system of the present invention can be configured as follows.
[0015]
That is, the key server device stores a program for a predetermined random number generation function in association with each of the plurality of file reception devices.
[0016]
On the other hand, the file transmission apparatus transmits the destination of the file to be transferred to the key server apparatus before receiving the seed and the random number.
[0017]
Further, the key server device is generated by receiving the destination of the file to be transferred transmitted from the file transmitting device, obtaining a program stored in association with the received destination, and executing the program. The random number is generated by applying the predetermined random number generation function to the seed.
[0018]
In the file transfer system of the present invention, the communication path used for transmitting the encrypted file from the file transmission apparatus to the file storage apparatus can be configured to be encrypted.
[0019]
A file transfer system according to another aspect of the present invention includes a file transmission device, a file storage device, and a file reception device, and is configured as follows.
[0020]
That is, the file receiving device generates a seed, applies a predetermined random number generation function to the generated seed, generates a random number, and transmits the generated seed and the generated random number to the file transmission device. .
[0021]
On the other hand, the file transmission device receives the seed and the random number transmitted from the file reception device, encrypts the file to be transferred with the received random number, generates an encrypted file, and receives the received seed. And the generated encrypted file are transmitted to the file storage device.
[0022]
Further, the file storage device receives the seed transmitted from the file transmission device and the encrypted file, and stores the received seed and the encrypted file.
[0023]
Then, the file reception device acquires the seed stored in the file storage device and the encrypted file, and applies the predetermined random number generation function to the acquired seed to generate a random number. The obtained encrypted file is decrypted with the random number obtained to obtain a file to be transferred.
[0024]
In the file transfer system of the present invention, the communication path used for transmitting the encrypted file from the file transmission apparatus to the file storage apparatus can be configured to be encrypted.
[0025]
A key server device according to another aspect of the present invention is a key server device in the above file transfer system.
[0026]
A file transmission apparatus according to another aspect of the present invention is a file transmission apparatus in the above file transfer system.
[0027]
A file receiving apparatus according to another aspect of the present invention is a file receiving apparatus in the above file transfer system.
[0028]
A program according to another aspect of the present invention is configured to function as any one of the key server device, the file transmission device, or the file reception device.
[0029]
The program can be recorded and distributed and sold on various computer-readable information recording media such as a flexible disk, CD-ROM (Compact Disk Read Only Memory), and DVD-ROM (Digital Versatile Disk ROM). It can be distributed and sold via a computer communication network such as the Internet.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below. The embodiments described below are for explanation, and do not limit the scope of the present invention. Therefore, those skilled in the art can employ embodiments in which each of these elements or all of the elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention.
[0031]
(First embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of a file transfer system according to the first embodiment of the present invention. Hereinafter, a description will be given with reference to FIG.
[0032]
The file transfer system 101 includes a key server device 111, a file transmission device 121, a file storage device 131, and a file reception device 141.
[0033]
To transfer a file from the file transmission device 121 to the file reception device 141, first, information is uploaded from the file transmission device 121 to the file storage device 131, and the file storage device 131 stores this, and then the file storage device 131. Is performed by downloading the stored information to the file receiving device 141.
[0034]
At this time, the following configuration is adopted so that the third party operating the file storage device 131 does not know the contents of the file to be transferred.
[0035]
FIG. 2 is a flowchart showing a procedure of processing executed in the file transmission apparatus 121. FIG. 3 is a flowchart showing a procedure of processing executed in the key server device 111. FIG. 4 is a flowchart showing a procedure of processing executed in the file storage device 131. FIG. 5 is a flowchart illustrating a procedure of processing executed in the file reception device 141. FIG. 6 is a response diagram of various messages exchanged between them. Hereinafter, description will be made with reference to these drawings as appropriate.
[0036]
First, the file transmission device 121 transmits the destination of the file to be transferred to the key server device 111 (step S201). In the present embodiment, an identifier associated with the file receiving apparatus 141 (providing an operator name, an IP (Internet Protocol) address, or the like that allows the operator of the file receiving apparatus 141 to be identified) may be a file. Will be sent as the destination.
[0037]
On the other hand, the key server device 111 stores a program for a predetermined random number generation function in advance in association with the identifier. "Program" is a binary / script format that can be actually executed, a parameter indicating which of a plurality of random number generation programs prepared in advance, various parameters given to the random number generation program, or a combination thereof It may be.
[0038]
As the random number generation function, any function can be adopted as long as it generates “random numbers” when “seed” is given. For example, the following can be employed.
(1) Joint law. In the simplest congruential method, a random number is obtained by multiplying a certain number by another number of times, but any one of “some number”, “other number”, and “some number of times” is used as a parameter, By doing so, it is possible to avoid duplication between the file receiving apparatuses 141 as much as possible.
(2) MT (Mersenne Trister) method. By using either of the seed for random number generation or the repetitively generated random number as a parameter and using either as a seed, duplication between the file receiving apparatuses 141 is avoided as much as possible. be able to.
[0039]
Note that the number of random numbers generated by such an algorithm may be one, or a sequence of random numbers may be generated and used as a “random number”.
[0040]
The “program” needs to be shared by the key server device 111 and the file receiving device 141. Typically, the key server device 111 provides “programs” that do not overlap each other to the file reception devices 141 of each business operator, and stores them in advance in association with identifiers.
[0041]
For example, when the MT method is employed, since “seed” is selected from a seed space of 4096 bytes (about 30,000 bits), if the length of the output random number sequence is shorter than 4096 bytes (for example, If it is 1024 bytes), since the number of bytes is reduced, information is lost, so it is impossible to calculate the “seed” from the random number sequence. In the calculation based on brute force, since a test of the number of times of 2 to 30,000 is necessary, it is possible to ensure security higher than the key length of the existing public key / private key.
[0042]
When the key server device 111 receives the identifier of the destination of the file to be transferred transmitted from the file transmission device 121 (step S301), the key server device 111 acquires a program stored in association with the identifier (step S302).
[0043]
Next, the key server device 111 generates seeds (step S303). For generation of the seed, the above algorithm may be used. The identifier transmission / reception time, the generation time of the seed, the process ID (Identifier) of the program used for generation of the seed, the identifier of the destination, and the file transmission device 121 An assigned identifier, or a combination of these pieces of information may be used. For example, when these pieces of information are viewed as byte sequences, various hash functions applied to them, their checksums, their MD (Message Digest) 5 values, their CRC (Cyclic Redundancy Check) values, etc. Can be adopted.
[0044]
Then, by executing the program acquired in step S302, a predetermined random number generation function is applied to the generated seed to generate a random number used for file encryption (step S304).
[0045]
Then, the generated seed and the generated random number are transmitted to the file transmitting apparatus 121 (step S305).
[0046]
On the other hand, the file transmission device 121 receives the seed and random number transmitted from the key server device 111 (step S202).
[0047]
Then, the file to be transferred is encrypted by the received random number to generate an encrypted file (step S203). Various techniques such as those used in various block ciphers can be used as a method for encrypting files with random numbers.
[0048]
Then, the received seed and the generated encrypted file are transmitted to the file storage device 131 (step S204). The communication between the file transmission device 121 and the file storage device 131 is preferably performed through an encrypted communication path. For example, a communication path using the HTTPS protocol can be adopted. Thereby, it is possible to prevent the encrypted file from leaking to a third party.
[0049]
Further, the file storage device 131 receives the seed transmitted from the file transmission device 121 and the encrypted file (step S401). Then, the received seed and the encrypted file are accumulated (step S402).
[0050]
When the file reception device 141 transmits an acquisition request to the file storage device 131 (step S501), the file storage device 131 receives the request (step S403), and stores the stored seed and the encrypted file as a file. It transmits to the receiver 141 and responds to this (step S404).
[0051]
On the other hand, the file receiving device 141 receives this response and acquires the seed and the encrypted file (step S502). The communication between the file reception device 141 and the file storage device 131 is also preferably performed using an encrypted communication path such as a communication path based on the HTTPS protocol.
[0052]
Then, the predetermined random number generation function is prepared using a program prepared in advance (typically a program provided in advance for the file reception device 141 from the key server device 111) as the acquired seed. Is applied to generate a random number (step S503). This random number should be the same as that generated by the key server device 111 in step S304 or the one used when the file transmission device 121 generates the encrypted file in step S203.
[0053]
Next, the obtained encrypted file is decrypted with the generated random number to obtain a file to be transferred (step S504).
[0054]
In the present embodiment, the seeds and random numbers generated by the key server device 111 are temporary, and the possibility of overlapping each other is extremely low. Even if a seed or encrypted file is leaked to a third party (including the business operator of the file storage device 131), it is difficult to obtain a random number. Since a random number different from is used, security can be improved.
[0055]
Further, since the transfer of the encrypted file between the file device 121 and the file storage device 131 is performed through the encrypted communication path, leakage to a third party can be prevented as much as possible.
[0056]
Furthermore, if the communication path for requesting random numbers to the key server device 111 and the communication path for transferring files to the file storage device 131 are different, security can be further improved.
[0057]
In the following, the method of the present embodiment is compared with other existing technologies.
[0058]
First, in the public key method, “encryption cannot be performed in units of files” “even if a set of public / private keys is created in units of files, it is necessary to manage key sets as many as the number of files” There is a problem such as “If a file is addressed to a person, a file must be created for each address”. However, according to the present technology, encryption in units of files is easy, and management of keys for each file is unnecessary.
[0059]
In the common key method for each file, it is necessary to generate as many keys as the number of files. If the management of this is left to the key server device, in order to restore the file by the file receiving device, the key server device must Communication is necessary, and speeding up is difficult. However, according to the present technology, such a drawback does not occur.
[0060]
As a modification of the present embodiment, when the file receiving apparatus 141 transmits a seed after logging in to the key server apparatus 111 so as to satisfy a predetermined security condition, a random number sequence corresponding to the seed is generated from the key server apparatus 111. It is also possible to adopt the method of being available. Even in this case, if the key server device 111 holds the random number generation algorithm for each file receiving device 141, it is not necessary to manage a common key for each file.
[0061]
(Other embodiments)
In the above embodiment, the key server device 111 is used to outsource management of the random number generation function and processing such as seed and random number generation from the business of the file reception device 141 to the business of the key server device 111. However, in the present embodiment, the file receiving apparatus 141 itself performs these processes.
[0062]
FIG. 7 is a schematic diagram showing a schematic configuration of the file transfer system according to the present embodiment. The file transfer system 101 according to the present embodiment includes a file transmission device 121, a file storage device 131, and a file reception device 141. FIG. 8 is a response diagram of messages exchanged between them.
[0063]
First, the file transmission device 121 and the file reception device 141 ensure a communication path that does not involve the file storage device 131 or a communication method that is extremely unlikely to leak the contents to the file storage device 131. For example, a technique such as HTTPS communication can be used.
[0064]
Then, the file reception device 141 generates seeds, applies a predetermined random number generation function to the generated seeds, generates random numbers, and generates the generated seeds and the generated random numbers using this communication method. , To the file transmission device 121.
[0065]
On the other hand, the file transmission apparatus 121 receives the seed and random number transmitted from the file reception apparatus 141 by this communication method, encrypts the file to be transferred by the received random number, and converts the encrypted file into the encrypted file. The generated and received seed and the generated encrypted file are transmitted to the file storage device 131.
[0066]
Further, the file storage device 131 receives the seed transmitted from the file transmission device 121 and the encrypted file, and stores the received seed and the encrypted file.
[0067]
Then, the file reception device 141 acquires the seed stored in the file storage device 131 and the encrypted file, and applies the predetermined random number generation function to the acquired seed to generate a random number, The obtained encrypted file is decrypted with the generated random number to obtain a file to be transferred.
[0068]
【The invention's effect】
As described above, according to the present invention, the file transfer system 101, the key server device 111, the file transmission device 121, the file storage device 131, the file reception device 141, and the file reception system suitable for safely transferring files, A program for realizing these by a computer can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a file transfer system according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of processing executed in the file transmission device of the file transfer system according to the first embodiment of the present invention.
FIG. 3 is a flowchart showing a flow of processing executed in the key server device of the file transfer system according to the first embodiment of the present invention.
FIG. 4 is a flowchart showing a flow of processing executed in the file storage device of the file transfer system according to the first embodiment of the present invention.
FIG. 5 is a flowchart showing a flow of processing executed in the file receiving apparatus of the file transfer system according to the first embodiment of the present invention.
FIG. 6 is a message response diagram in the file transfer system according to the first embodiment of the present invention;
FIG. 7 is a schematic diagram showing a schematic configuration of a file transfer system according to another embodiment of the present invention.
FIG. 8 is a message response diagram in the file transfer system according to another embodiment of the present invention;
[Explanation of symbols]
101 File Transfer System 111 Key Server Device 121 File Transmission Device 131 File Storage Device 141 File Reception Device

Claims (9)

A file transfer system comprising a key server device, a file transmission device, a file storage device, and a file reception device,
(A) The key server device
Generate seeds,
Applying a predetermined random number generation function to the generated seed to generate a random number;
Transmitting the generated seed and the generated random number to the file transmission device;
(B) The file transmission device
Receiving a seed and a random number transmitted from the key server device;
Encrypt the file to be transferred with the received random number to generate an encrypted file,
Sending the received seed and the generated encrypted file to the file storage device;
(C) The file storage device
Receiving the seed transmitted from the file transmission device and the encrypted file;
Storing the received seed and the encrypted file;
(D) The file receiving device
Obtaining the seed stored in the file storage device and the encrypted file;
Applying the predetermined random number generation function to the obtained seed to generate a random number,
The obtained encrypted file is decrypted with the generated random number to obtain a file to be transferred. The file transfer system according to claim 1,
(D) The key server device
A program for a predetermined random number generation function is stored in association with each of a plurality of file reception devices,
(E) The file transmission device
Prior to receiving the seed and the random number, the destination of the file to be transferred is transmitted to the key server device,
(F) The key server device
Receiving the destination of the file to be transferred sent from the file sending device;
Obtaining a program stored in association with the received destination;
By executing the program, a random number is generated by applying the predetermined random number generation function to the generated seed. The file transfer system according to claim 1 or 2,
A communication path used for transmitting an encrypted file from the file transmission device to the file storage device is encrypted. A file transfer system comprising a file transmission device, a file storage device, and a file reception device,
(A) The file receiving device
Generate seeds,
Applying a predetermined random number generation function to the generated seed to generate a random number;
Transmitting the generated seed and the generated random number to the file transmission device;
(B) The file transmission device
Receiving a seed and a random number transmitted from the file receiving device;
Encrypt the file to be transferred with the received random number to generate an encrypted file,
Sending the received seed and the generated encrypted file to the file storage device;
(C) The file storage device
Receiving the seed transmitted from the file transmission device and the encrypted file;
Storing the received seed and the encrypted file;
(D) The file receiving device
Obtaining the seed stored in the file storage device and the encrypted file;
Applying the predetermined random number generation function to the obtained seed to generate a random number,
The obtained encrypted file is decrypted with the generated random number to obtain a file to be transferred. The file transfer system according to claim 4, wherein
A communication path used for transmitting an encrypted file from the file transmission device to the file storage device is encrypted. The key server apparatus in the file transfer system of any one of Claim 1 to 3. The file transmission apparatus in the file transfer system of any one of Claim 1 to 5. The file receiving apparatus in the file transfer system of any one of Claim 1 to 5. A program that causes a computer to function as any one of the key server device according to claim 6, the file transmission device according to claim 7, or the file reception device according to claim 8.

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