JPH11355858A - Information distribution method in mobile communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To encrypt distributed information and to distribute the encrypted information with an encryption method with high security, where management of an encryption key is easy. SOLUTION: An information server 5 encrypts distributed information by an encryption key and encrypts the encryption key, by using an authentication key different by every mobile station. The encrypted encryption key and the distributed information are transferred to a mobile station 1 at the same time or at different times. The mobile station 1 uses the authentication key possessed by itself to interpret the encrypted encryption key and uses the interpreted encryption key to decode the distributed information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information distribution method in a mobile communication network for setting a secret key in a mobile station when encrypting information for information distribution in the mobile communication network.

[0002]

2. Description of the Related Art Information distribution services are also provided in mobile communication networks. An information server is installed in the mobile communication network, and at a predetermined time, the distribution information stored in the information server is distributed to a predetermined mobile device. Since such distribution information is distributed only to a specific mobile device, users are often demanding confidentiality of the information. In the field of communication, encryption is performed to keep communication information secret. A common method of encryption is to use a secret key (also called a secret key, such as a specific numerical value) and an arithmetic expression for encryption to transmit information, for example, a character code string, to another source. Convert to character code string. At the destination receiving the encrypted information (character code string), the encrypted information is decrypted (also referred to as decryption) by using the same secret key as the above-mentioned secret key and an arithmetic expression opposite to the encryption. I do.

When using such an encryption method, the following points are important in mobile communication.

[0004] 1. Since the information content is transmitted wirelessly, there is a high risk of eavesdropping, and it is desired that no one knows the secret key.

[0005] 2. Since there are many mobile stations that receive the distribution information service, it is desirable to make the secret key different for each mobile station.

[0006]

In order to satisfy the first point, two methods are known. In the first method, the secret key is stored in a ROM or the like, and the secret key is confined in the ROM so that the secret key cannot be read by a human instruction. This method has the disadvantage that the stored contents of the ROM are read out when the ROM is removed and the ROM reader is used, and that once the secret key is determined, it is difficult to change the secret key.

In the second method, the information transmission source changes the secret key at regular time intervals, and transmits the secret key used at the time of encryption together with the ciphertext from the source to the destination. The transmission destination decrypts the ciphertext using the received secret key. In this method, there is a danger of eavesdropping on the secret key itself.

[0008] In order to satisfy the above second point, the secret key must be stored for each mobile station, for example, for each subscriber number, at the source of the information, so that information management becomes a great effort. . Considering the case where the secret key is to be changed at regular time intervals, a heavy load is imposed on the computer system that performs the process of changing the stored secret key.

[0009] Therefore, the present invention facilitates the management of the secret key on the mobile communication network side, and enables the secret key to be changed and the secret key to be used when the distribution information is encrypted and distributed using the secret key. An object of the present invention is to provide an information distribution method in a mobile communication network in which the confidentiality of a key and distribution information is high.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, distribution information stored in an information server installed in a mobile communication network is encrypted and transmitted to a mobile station. In the information distribution method in a mobile communication network for distribution, the information server side encrypts the distribution information using a secret key, and encrypts the secret key using an authentication key used for authentication of a target mobile station. And transmits the encrypted confidential key and the distribution information to the mobile device to be distributed, and the mobile device to be distributed uses the authentication key that the encrypted and transmitted confidential key owns. And decrypts the encrypted and transmitted distribution information using the decrypted secret key.

According to a second aspect of the present invention, in the information distribution method in the mobile communication network according to the first aspect, the encrypted secret key and the encrypted distribution information are transmitted from the information server to the distribution target at different times. Transfer to the mobile device.

According to a third aspect of the present invention, in the information distribution method in the mobile communication network according to the first aspect, the encrypted secret key and the encrypted distribution information are simultaneously transmitted from the information server to the distribution target. Transfer to the mobile device.

According to a fourth aspect of the present invention, in the information distribution method in the mobile communication network according to the first aspect, the secret key is changed at a predetermined timing.

According to a fifth aspect of the present invention, in the information distribution method in the mobile communication network according to the first aspect, a home memory for storing the authentication key and the secret key is installed in the mobile communication network. The authentication key and the secret key are transferred from a home memory to the information server.

[0015]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a system configuration and information flow in a mobile communication network. In FIG. 1, 1 is a mobile device,
The distribution information is received, and the distribution information is displayed on the display of the mobile device 1. The circuit configuration of the mobile device 1 can be the same as the conventional one, but the secret key related to the decryption of the distribution information is encrypted, and the processing procedure for decrypting the encrypted secret key is executed. Is different from the past. Such a processing procedure is stored, for example, in a ROM or the like in the mobile device 1 and executed by a CPU or a digital processor in the mobile device 1.

Reference numeral 2 denotes a base station, which exchanges information with the mobile device 1 by radio. Reference numeral 3 denotes a subscriber exchange. The subscriber exchange 3 exchanges information with the base station 2, the other exchanges, the home memory 4, and the information server 5 in the mobile communication network 10.

Since the base station 3 and the local exchange 4 can be the same as those of the prior art, detailed description will not be required. Reference numeral 4 denotes a home memory. The home memory 4 is installed in the mobile communication network 10, and includes a subscriber number (so-called telephone number) of the mobile device 1, a communication packet address, an authentication key and a concealment key, and various other information related to the subscriber. Store and manage information. Although the authentication key itself is well known, it is related to the present invention, and will be briefly described. The authentication key is a code used for authentication of the mobile device 1. When a communication contract is concluded between a user (subscriber) and a mobile communication service company, the authentication key is determined. The authentication key differs for each mobile device, and is written and stored in the non-volatile memory directly from the viewpoint of the operator instead of transmitting the wireless section at the time of the first communication for security.

The mobile communication network 10 generates a random number at the time of authentication (procedure performed before location registration and communication start), and transfers the random number to the mobile device 1.

The network performs a calculation using a random number and a secret key based on a certain user's authentication key stored in a home memory.

The mobile station 1 also performs an operation based on the transferred random number using its own secret key, and returns the operation result to the mobile communication network 10.

The mobile communication network 10 collates its own calculation result with the calculation result returned by the mobile station, and if they match, the location registration and communication start procedure are continued with the authentication okay.

When they match, it is authenticated that the mobile device 1 has contracted with the mobile communication service company.

The inventor of the present invention pays attention to the fact that the authentication key used for this authentication is stored in the home memory 4, and performs the first encryption and transfer of the above-mentioned secret key using the above-mentioned authentication key. The second embodiment is characterized in that distribution information is secondly encrypted and transferred using a secret key. For this reason, since the secret key is encrypted with an authentication key that differs for each user, even if the secret key is single, the encrypted secret key is different for each user. Therefore, the home memory 4 only needs to manage a single secret key. In the present embodiment, the home memory 4 changes the secret key randomly (at random) at regular time intervals, but this change process can also be easily performed. Further, since the secret key and the distribution information are encrypted with different keys, even if a single encryption algorithm is used, the confidentiality of the secret key and the distribution information is high. In the present embodiment, the encryption algorithm (arithmetic expression) of the secret key is different from the encryption algorithm of the distribution information.

Returning to FIG. 1, reference numeral 5 denotes an information server, which stores information such as information to be distributed, a subscriber number relating to a mobile device of a distribution destination, a communication packet address for mobile communication, and the like.

A plurality of base stations 1, a plurality of local exchanges 1,
A plurality of home memories 4 and one or more information servers 5 are connected by wired signal lines, and transfer control information, call information, and distribution information relating to mobile communication between related parties.

A distribution process of distribution information performed in such a system configuration will be described with reference to FIGS.
FIG. 2 shows the contents of the communication basic sequence related to the distribution processing.

FIG. 3 shows a processing procedure related to the distribution of the information server 5. FIG. 4 shows a processing procedure related to the distribution of the home memory 4. FIG. 4 shows a processing procedure of the mobile device 1 that receives distribution information.

The information server 5 determines whether there is distribution information to be distributed at the current time according to the distribution schedule stored therein (step S10 in FIG. 3).
0). If there is distribution information to be distributed at the current time, the information server 5 calls the registered mobile device 1. This call may take the form of calling with a subscriber number, similarly to a normal call, or may transmit a communication packet indicating a call with an identifier for distributing distribution information to the subscriber exchange 3 and the base station 1. A configuration may be adopted in which the data is transmitted to the mobile device 1 via the mobile terminal 1. When the mobile device 1 receives this call (step S300 in FIG. 5), the mobile device 1 responds to the call and then waits for an authentication request (step S310 → S320 in FIG. 5).

In the home memory 4 receiving the response from the mobile station 1 via the base station 2 and the local exchange 3, the registration authentication key corresponding to the mobile station 1 is transmitted to the local exchange 3.
The local exchange 3 transmits an authentication request to the mobile station 1 via the base station 2 in the same manner as in the prior art (step S2 in FIG. 4).
00 → S210).

The mobile station 1 that has received the authentication request performs an operation using the secret key stored therein and transmits the operation result to the base station 2 (steps S320 → S33 in FIG. 5).
0). In this embodiment, the local exchange 3 compares the operation result on the mobile communication network side with the operation result from the mobile station 1 side. In this collation, if a match is determined, that is, a successful authentication is determined, a wireless section between the mobile device 1 and the base station 2 is set, the local exchange 3, the home memory 4,
A relay section between the information servers 5 is set, and the mobile device 1 and the information server 5 are connected. The processing procedure up to the above is the same as the conventional one.

After the authentication using the authentication key, the information server 5 transmits a request for transmitting the secret key and the authentication key to the home memory 4 to the home memory 4 and receives the authentication key and the secret key from the home memory 4 ( Step S120 in FIG. 3). The information server 5 encrypts the secret key using the received authentication key (step S130 in FIG. 3).
Since the encryption algorithm itself cannot be disclosed due to security problems in implementing the present invention, a temporary encryption method will be described. As an example, a numerical value (for example, 5 in decimal) indicated by the authentication key is multiplied by a numerical value (for example, 3 in decimal) indicated by the secret key. The multiplication result (numerical value 1
5) is the value of the encrypted secret key. It should be noted that if the authentication key of a different mobile device 1 is numerical value 4, the value of the encrypted secret key is 4 × 3 = 12, which is different from the above value 15. It goes without saying that the secret key value 3 is also different.

Next, the information server 5 uses the secret key to encrypt the secret key by a second encryption method different from the encryption method of the secret key. If the distribution information to be transmitted is a character code string, an encrypted character code string is created by adding the value of the secret key (3 in this case) to the numerical value indicated by each character code in the character code string (step S140 in FIG. 3). ).

In this manner, the secret key encrypted by the first encryption method and the distribution information encrypted by the second encryption method are transmitted to the designated mobile station (delivery target mobile station) 1. (Step S15 in FIG. 3).
0).

After the authentication procedure, the encrypted secret key and the distribution information are received (step S340 in FIG. 5), and the secret key is decrypted first (step S350 in FIG. 5).
Since the value of the encrypted confidential key is 15 (5 × 3), the inverse of the multiplication using the authentication key (numerical value 5) stored by itself for verification, that is, the encrypted value 15 is used for verification. Of the secret key to obtain the value of the secret key.

Next, the mobile device 1 decrypts the received distribution information using the value of the secret key. In this example, since the encryption is performed by adding the secret key, the distribution information is decrypted by subtracting the secret key value 3 from the value of each character code of the encrypted character code string (see FIG. 5). Step S3
60). The decrypted (decoded) distribution information is displayed on the display of the mobile device 1 (step S370 in FIG. 5).

After transmitting the authentication key and the confidential key in response to the request from the information server 5 in the home memory 4 (after step S230 in FIG. 4), steps S200 → S2 in FIG.
The procedure from 40 to S260 is repeated until the secret key change time is reached. For example, when the home memory 1 detects that one hour has elapsed since the last change of the secret key and the change time has been reached (YES in step S240 in FIG. 4).
Judgment), the home memory 4 generates a new secret key using, for example, a random number device. The created secret key is stored in an internal storage device and used for encryption on the information server 5 side until the next change. Hereinafter, the secret key is changed every time a fixed time elapses.

In the above distribution process, the mobile device 1 receives the encrypted secret key which differs depending on the time, so that the same arithmetic expression (algorithm) for decryption uses the same one as the other mobile device 1. can do. Further, even if the distribution information is wirelessly transmitted between the base station 2 and the plurality of mobile devices 1, the value of the encrypted secret key transmitted differs for each mobile device. Even so, it would not be possible to identify even that the secret key is included in the eavesdropping information.

Further, in the home memory 4, it is only necessary to change a single confidential code at predetermined time intervals (the interval does not need to be constant), so that the confidential code management (save and change) is very easy.

The following embodiment can be carried out in addition to the above embodiment.

1) In the above embodiment, since the secret key is changed, the encrypted secret key and the distribution information are encrypted by different encryption methods and distributed to the mobile device 1, but the secret key is fixed. If it is desired, the secret key and the distribution information may be distributed from the information server at different timings. In this case, the encryption method can be shared. The transmission timing of the encrypted confidential key can be the time when there is a location registration request from the mobile device 1 or the time when there is a call.

2) In the above-described embodiment, the confidential key is managed by the home memory 4 and the distribution information is managed by the information server 5, but the confidential key may be managed by the information server 5.

3) Any method can be used for encrypting the secret key and the distribution information.

4) In the above-described embodiment, the form in which the distribution information is displayed on the display of the mobile device 1 has been described.
The distribution information may be displayed by a terminal connected to the terminal, for example, an information processing device called an electronic organizer or a mobile computer.

5) In the above-described embodiment, a mode in which a single type of confidential code is used has been described. However, this confidential code is used when transmitting distribution information to a plurality of broadcasters, such as broadcast communication. Good to do. It goes without saying that if the information distribution service contractor is different, the secret code may be different.

6) The distribution information is not limited to characters, but may be an image,
Various types of information such as voice, document information described in the HTML language, information in which these information are mixed, and software programs (also called application programs) executed on the terminal side can be handled.

[0047]

As described above, according to the first aspect of the present invention, since the secret key used for encrypting the distribution information is also encrypted and transferred to the mobile station, the mobile station holds the secret key. Therefore, the secret key can be freely changed on the transmission information transmitting side. Furthermore, since the content of the encrypted secret key differs by each mobile device by encrypting the secret key using the authentication key, even if the encrypted secret key is eavesdropped, the security of the secret key itself is maintained. Nature is achieved. Furthermore, since the secret key itself does not need to be set for each authentication number, that is, for each mobile device, the type of the secret key can be reduced, and the management of the secret key becomes easy.

According to the second aspect of the present invention, the transmission timing of the encrypted confidential key and the distribution information is made different so that the confidentiality is not impaired even if encryption is performed by a common encryption method. .

According to the third aspect of the present invention, even if the secret key is changed by transmitting the encrypted secret key and the distribution information at the same time, the receiving mobile station only needs to use the received secret key. There is no restriction on the transmission timing of the distribution information or the update timing of the secret information.

According to the fourth aspect of the present invention, by changing the secret key, the security and confidentiality of the secret key and thus the distribution information are improved.

According to the fifth aspect of the present invention, information relating to confidentiality such as an authentication key and a confidential key is stored in a home memory separate from an information server storing distribution information.
It is difficult to obtain the distribution information and all the keys related to decryption of the authentication key and the secret key.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a distribution processing procedure according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a system configuration and a flow of information according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a processing procedure of the information server 5 of FIG.

FIG. 4 is a flowchart illustrating a processing procedure of a home memory in FIG. 1;

FIG. 5 is a flowchart illustrating a processing procedure of the mobile device in FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 mobile station 2 base station 3 local exchange 4 home memory 5 information server

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Motoi Tamura 2- 10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd. (72) Inventor Daisuke Akiyama 2-chome Toranomon, Minato-ku, Tokyo No. 10 in NTT Mobile Communication Network Co., Ltd.

Claims (5)

[Claims] An information delivery method in a mobile communication network for encrypting delivery information stored in an information server installed in a mobile communication network and delivering the encrypted information to a mobile device, wherein the information server uses a secret key. Encrypts the distribution information, encrypts the secret key using an authentication key used for authentication of the mobile station to be distributed, and transmits the encrypted secret key and the distribution information to the mobile station to be distributed. However, the mobile device to be delivered decrypts the encrypted and transmitted confidential key using its own authentication key, and is encrypted and transmitted using the decrypted confidential key. An information distribution method in a mobile communication network, characterized by decoding distribution information. 2. The information distribution method in a mobile communication network according to claim 1, wherein the encrypted secret key and the encrypted distribution information are transmitted from the information server to the distribution target mobile device at different points in time. An information distribution method in a mobile communication network, characterized in that the information is transferred in a mobile communication network. 3. The information distribution method in a mobile communication network according to claim 1, wherein the encrypted secret key and the encrypted distribution information are simultaneously transmitted from the information server to the distribution target mobile device. An information distribution method in a mobile communication network, characterized in that the information is transferred in a mobile communication network. 4. The information distribution method in a mobile communication network according to claim 1, wherein the secret key is changed at a predetermined timing. 5. The information distribution method in a mobile communication network according to claim 1, wherein a home memory for storing the authentication key and the secret key is provided in the mobile communication network.
An information distribution method in a mobile communication network, wherein the authentication key and the secret key are delivered from the home memory to the information server.