JPH10268762A - Method for delivering cryptographic key - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the needs of previously notifying both transmitter and receiver of assignment of a cryptographic key (a secret key) when they communicate with each other by using a secret key, and further to make it physically difficult for a tapping person to calculate the cryptographic key. SOLUTION: A method of delivering cryptographic key in a network system which sends and receives data through a cryptographic communication between a first device and a second device which are connected via the network, wherein preparatory communication is carried out by using two or more communication routes between the above-mentioned first device and the second device, and a cryptographic key necessary for the cryptographic communication is generated based on the information determined in the process of this preliminary communication. The information determined in the process of the above-mentioned preliminary communication contains information on transmitting order and receiving order at a time of transmitting numeric data for the cryptographic key generation by arbitrary number of times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryptographic key distribution method for securely sharing information between a transmitting party and a transmitting party against eavesdropping for performing cryptographic communication.

[0002]

2. Description of the Related Art In a distributed system for use in a limited area such as in a company, for example, when confidential information is communicated between a server computer and a client computer, it is indispensable to protect it by encryption. .

[0003] In this encryption communication, it is necessary to share an encryption key required for encryption processing and decryption processing by both the transmitting side and the receiving side. In addition, this encryption key must be safely delivered to eavesdroppers and the like.

Conventional encryption communication methods are roughly classified into two types: (1) a secret key encryption communication method, and (2) a public key encryption communication method.

[0005] The secret key cryptographic communication method is based on the premise that the transmitting device and the receiving device have a common key, and both decide an encryption key in advance and store it, or secure the security separately. There is a need for a means of delivering in a manner.

[0006] In other words, in the secret key cryptographic communication method, it is necessary to prepare another means for delivering and storing a secure cryptographic key in order to transmit and receive information safely. For example, as disclosed in Japanese Patent Application Laid-Open No. 2-203377, it is necessary to set a center for managing encryption keys in a network environment. In addition, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 5 (1993), an IC card storing a secret key needs to be distributed to a transmitting side and a receiving side in advance.

[0007] On the other hand, the public key cryptographic communication method is to disclose one of complementary key information and use it for encrypted transmission, and to use the other for decryption on the receiving side. ,
It is based on the difficulty in solving mathematical problems of (a) a prime factorization problem and (b) a discrete logarithm problem.

All of these problems are security based on the empirical fact that it is only expected to be difficult and there is no report that an algorithm that solves fast has been found so far. That is, a person who eavesdrops on the encrypted data has all the information necessary for decryption. However, since it is used based on the expectation that the amount of calculation for decoding it should be enormous, an algorithm that can solve the above difficult problem at least partially even at high speed should be used If found, the method will need to be fundamentally reviewed.

[0009]

As described above, in the secret key cryptographic communication method, it is necessary to prepare another means for delivering and storing a secure cryptographic key in order to transmit and receive information safely. is there.

In addition, the public key cryptographic communication method has a problem that if the difficulty in solving a mathematical problem is solved by finding a high-speed algorithm for solving the mathematical problem or the like, data can be eavesdropped.

[0011] An object of the present invention is to provide an encryption key (secret key) that is not required to be distributed to both the transmitting and receiving parties in advance when performing cryptographic communication using a secret key. An object of the present invention is to provide a physically difficult encryption key distribution method.

[0012]

To achieve the above object, the present invention provides a network system for transmitting and receiving data between a first device and a second device connected via a network by cryptographic communication. In the encryption key distribution method according to the above, preliminary communication is performed using a plurality of communication routes between the first device and the second device, and necessary for encryption communication based on information determined in the process of the preliminary communication. It is characterized by generating a simple encryption key.

Here, the information determined in the process of the preliminary communication is, for example, information such as a data transmission / reception order.

Thus, as long as the eavesdropper does not eavesdrop on all the paths between the first device and the second device, even if the eavesdropper knows the key generation algorithm, the eavesdropper can identify the encryption key itself. , It becomes impossible to calculate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a system configuration diagram showing an embodiment of a network system to which the present invention is applied. This embodiment is, for example, in a company, a personnel information management server 5, a personnel time management server 6, which manages a personnel time management information database 2, an inventory management information database 3, an accounting information database 4, etc. A management server 7 and an accounting information management server 8 are arranged, and a number of client computers such as a personal computer (PC) 9 and a network computer (NC) 10 are arranged in each department, and these are connected by a network 11 such as a corporate LAN. By operating each client computer, each database 1, 2, 3, 4
FIG. 1 shows an example of a network system in which necessary information is acquired from the Internet and browsed.

In this embodiment, a server 5 to 8 (sending device) for managing information of each database and a personal computer (PC) 9 and a network computer (NC) 10 (receiving device) as client computers. In order to perform encryption communication by generating an encryption key on both sides, preliminary communication is performed as a previous stage. At this time, the preliminary communication is performed via the plurality of servers by using the cooperation of the plurality of servers 5 to 8 connected to the network environment, and the data for generating the encryption key is transmitted from the transmitting side a plurality of times in the process of the preliminary communication. . In this case, the number of transmissions of the data for generating the encryption key is an arbitrary number of times until the transmitting side sends the preliminary communication end command.

When data for generating an encryption key is transmitted a plurality of times via a plurality of servers, information that can be known only by the transmitting side and the receiving side is the transmission order and the receiving order. In other words, the transmitting side does not transmit any information on the transmission order, but the transmitting side has a clear transmission order of the data for generating the encryption key, and one receiving side does not receive the information on the receiving order. Nevertheless, the information on the receiving order is obvious. On the other hand, the eavesdropper cannot know the information of the transmission order and the reception order unless the data for generating the encryption key is eavesdropped on all routes.

FIG. 2 is a diagram showing a situation in which a large number of data transmission paths exist when performing cryptographic communication between the server X (for example, the personnel information management server 5) and the client Y (for example, the personal computer 9). is there. In FIG. 2, there is a server that manages subsystems A, B, C, D, E, and F between the sender and the receiver. For example, as a data transmission path, (1) server X → A → B → client Y ( 2) Server X->C->D->A->E-> Client Y (3) Server X->A->D->F-> Client Y indicates that there are multiple physical path options.

In the preliminary communication, the server X, which provides information, specifies a communication path with the client Y, who receives the information, by ordering a plurality of other server names.

FIG. 3A is a diagram showing an example of the structure of key generation data transmitted / received between the server X and the client Y in the preliminary communication, and includes a destination pointer 31, path data 32, an encryption key The path data 32 is composed of numerical data 33 for generation, and the path data 32 is constructed by arranging the names (or unique information such as network addresses) of a plurality of relay servers between the transmission source and the final destination in the order of relay.

The server in the middle of the communication path supports the preliminary communication by relaying the key generation data. The server at each relay point advances the destination pointer (arrow in the figure) pointing to the next relay server or the receiver in the key generation data. For example, when the key generation data shown in FIG. 3A is relayed by the server A, the destination pointer is advanced by one and changed to point to the server E.

The key generation data transmitted from the server X in the preliminary communication reaches the client Y on the receiving side via the relay servers C, D, A, and E on the way. The arriving key generation data is sent from the client Y to the server X via the reverse route to confirm that the data has arrived.

FIG. 3B is a diagram showing the structure of key generation data sent in reverse order.
The return route relay processing in A, D, and C is the same as the outward route.

The preliminary communication mainly consists of performing the round trip communication of the key generation data a plurality of times. The end user selects a certain client, and performs the preliminary communication with the server managing the information to be obtained. start.

FIG. 4 is a diagram showing a procedure of preliminary communication between the server X and the client Y.

Step S1 (Preliminary Communication Start Request) First, a request for starting preliminary communication is sent from the client Y to the server X.

Step S2 (transmission of key generation data 1) The server X generates numerical data 33 for key generation, selects an arbitrary number of relay servers, determines a transmission path, and
The first “encryption key generation data 1” having the configuration shown in FIG. 9A is created and transmitted to the client Y that has made the request.

Step S3 (Echo back of key generation data 1) The client Y that has received the "key generation data 1"
The numerical data 33 and the number of the received data are stored.

Next, the client Y returns to the server X “key generation data 1” in which the transmission route is reversed.

Step S4 (transmission of key generation data 2) The server X to which "key generation data 1" has been sent back creates "key generation data 2" on the second floor in the same manner as in step S2. And sends it to client Y.

In this case, it is desirable that the route data 32 and the numerical data 33 are different from the first time from the viewpoint of security.

Step S5 (Echo back of key generation data 2) The client Y that has received the "key generation data 2"
The numerical data 33 and the number of the received data are stored.

Next, the client Y returns to the server X “key generation data 2” in which the transmission route is reversed.

The above process is repeated an arbitrary number of times K.

Step S6 (Preliminary communication end request) Finally, a preliminary communication end request is sent from the server X to the client Y.

Step S7 (preliminary communication end echo back) The client Y transmits an echo back indicating the end of the preliminary communication to the server X, and ends the preliminary communication.

After the completion of such preliminary communication, an arbitrary number of key generation data m {i} (i = 1, 2,..., K) ordered in both the server X and the client Y. Is in a known state.

From these numerical data, an encryption key can be generated by the following algorithm, for example.

(A) Sum of m {i} (b) All products of m {i} (c) Sum of m {i} to the power of i (d) Product of odd-numbered m {i} Difference from the product of even-numbered m {i} (e) When the i-th prime number is written as p {i}, the sum of m {i} raised to the power of p {i} is (f) m {i} The sum of all quotients when divided by p {i}. For eavesdroppers, if eavesdropping on some routes, m {i}
First, information for calculating the encryption key cannot be physically collected because only some of the information can be obtained. Although the possibility of mathematically estimating the encryption key from the partial information remains, the eavesdropper can determine the order in which each m {i} was transmitted and received, , It is impossible to determine how many are transmitted and received, so that estimation becomes almost impossible.

Here, for example, considering the case where the above algorithm is already known to an eavesdropper by disclosure or eavesdropping, an algorithm that does not use the arrival order of m {i} such as (a) and (b) is used. If there is a possibility to calculate the encryption key only if a method for efficiently estimating the remaining information that cannot be eavesdropped is found, the arrival order information of m {i} such as (c) to (f) may be calculated. According to the algorithm used, each e
It is not clear from the preliminary communication what the {i} has arrived at or how many in total. For this reason, it is very difficult to estimate the encryption key. Further, by including the arrival order information in the encryption key generation algorithm, the key estimation calculation can be made almost impossible.

Therefore, the present embodiment employs an algorithm that uses the arrival order information of m {i} represented by (c) to (f).

After the encryption key is generated by both the server X and the client Y, the secret key cryptographic communication is performed in the usual manner conventionally used. In this case, login to each information management server and access control to confidential data
Since the encrypted communication is performed after the start of the encrypted communication, for example, the account name and the like are transmitted in an encrypted form, security against eavesdroppers can be ensured.

As described above, according to the present embodiment, (1) it is not necessary to distribute an encryption key for encrypted communication to both the transmitting and receiving apparatuses in advance, and as a result, the user or the machine stores the key in advance. There is no need to provide any means for doing so.

(2) Since the network environment itself for distributing the encrypted data is used for generating the encryption key, a distribution means such as a special secure route is not required.

(3) The generated encryption key is physically difficult for an eavesdropper to calculate. Thus, finding a fast algorithm for solving a mathematical problem does not affect the difficulty of its calculation.

Therefore, for example, it is very effective when constructing a distributed network system in which many inexpensive clients (for example, network computers) are introduced in a company.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be applied to all network configurations in which a plurality of communication paths can be selected.

[0049]

As is apparent from the above description, according to the present invention, when performing cryptographic communication using a secret key, it is necessary to distribute the encryption key (secret key) to both the transmitting and receiving parties in advance. In addition, the calculation of the encryption key can be made physically difficult for an eavesdropper.

Therefore, the present invention is extremely effective when constructing a distributed network system in which a large number of clients such as network computers are installed as inexpensively as possible in a company.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a network system to which an encryption key distribution method of the present invention is applied.

FIG. 2 is a diagram illustrating a situation in which a large number of data transmission paths exist when performing cryptographic communication between a server X and a client Y;

FIG. 3 is a diagram illustrating an example of a structure of key generation data transmitted and received between a server X and a client Y in preliminary communication.

FIG. 4 is a diagram illustrating a procedure of preliminary communication between a server X and a client Y.

[Description of sign]

DESCRIPTION OF SYMBOLS 1 ... Personnel information database, 2 ... Work absence management information database, 3 ... Inventory management information database, 4 ... Accounting information database, 5 ... Personnel information management server, 6 ... Work absence management information server, 7 ... Inventory management server, 8 ... Accounting information management server, 9 personal computer (client), 1
0: Network computer (client).

Claims (2)

[Claims] 1. A cryptographic key distribution method in a network system for transmitting and receiving data by cryptographic communication between a first device and a second device connected via a network, the method comprising the steps of: And performing a preliminary communication using a plurality of communication routes with the second device and generating an encryption key required for the cryptographic communication based on information determined in the process of the preliminary communication. Method. 2. The information determined in the course of the preliminary communication includes information on a transmission order and a reception order when numerical data for generating an encryption key is transmitted an arbitrary number of times. The described encryption key distribution method.