JP3640237B2 - Information distribution method in mobile communication network - Google Patents

Description

[0001]
BACKGROUND 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 device when information is encrypted for information distribution in a mobile communication network.
[0002]
[Prior art]
Information distribution services are also provided in mobile communication networks. An information server is installed in the mobile communication network, and distribution information stored in the information server is distributed to a predetermined mobile device at a predetermined time. Since such distribution information is distributed only to a specific mobile device, there is an increasing demand for confidentiality of information from users. In the field of communication, encryption is performed in order to keep communication information secret. The general method of encryption is that the information source uses a secret key (also called a secret key, such as a specific numerical value) and an arithmetic expression for encryption to transfer information such as a character code string to another Convert to character code string. At the destination that received the encrypted information (character code string), the encrypted information is decrypted (also called decryption) by using the same secret key as the above-mentioned secret key and an operation formula opposite to encryption. To do.
[0003]
When such an encryption method is used, 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 desirable to prevent anyone from knowing the secret key.
[0005]
2. Since there are many mobile devices that receive the distribution information service, it is desirable to use a different secret key for each mobile device.
[0006]
[Problems to be solved by the invention]
Two methods are known for satisfying the first point. In the first method, the secret key is stored in the 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 a drawback that when the ROM is removed and the ROM reader is used, the stored contents of the ROM are read, and once the secret key is determined, it is difficult to change the secret key.
[0007]
In the second method, the information transmission source changes the secret key at fixed time intervals, and transmits the secret key used when the information is encrypted together with the ciphertext from the transmission source to the transmission destination. The destination decrypts the ciphertext with the received secret key. In this method, the secret key itself has a risk of eavesdropping.
[0008]
In order to satisfy the second point, since the information transmission source must store a secret key for each mobile device, for example, for each subscriber number, the information management becomes a great effort. Considering the case where it is desired to change the secret key at regular time intervals, a large burden is imposed on the computer system that performs the process of changing the stored secret key.
[0009]
Accordingly, the present invention provides a secret key and a distribution method in which the secret key on the mobile communication network side can be easily managed and the secret key can be changed 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 with high confidentiality of information.
[0010]
[Means for Solving the Problems]
In order to achieve such an object, the invention according to claim 1 is an information distribution method in a mobile communication network in which distribution information stored in an information server installed in the mobile communication network is encrypted and distributed to a mobile device. The information server side encrypts the distribution information using a secret key, encrypts the secret key using an authentication key used for authentication of a mobile device to be distributed, and the encrypted secret key And the distribution information is transmitted to the mobile device to be distributed, and the mobile device to be distributed decrypts the encrypted secret key using an authentication key held by itself, and the decrypted secret together to decrypt the distribution information transmitted is encrypted using a key, the confidentiality key change at a predetermined timing, the authentication key and the storing confidential key home memory within the mobile communication network Installed, characterized in that delivering the authentication key and said secret key to said information server from the home memory.
[0011]
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 transferred from the information server to the mobile device to be distributed at different time points. It is characterized by transferring to.
[0012]
The invention according to claim 3 is the information delivery method in the mobile communication network according to claim 1, wherein the encrypted secret key and the encrypted delivery information are simultaneously sent from the information server to the delivery target mobile device. It is characterized by transferring to.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 shows a system configuration and information flow in a mobile communication network. In FIG. 1, reference numeral 1 denotes a mobile device that receives distribution information and displays the distribution information on a display device 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. This is different from the conventional method. 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.
[0017]
Reference numeral 2 denotes a base station that exchanges information with the mobile device 1 by radio. Reference numeral 3 denotes a subscriber exchange. The subscriber exchange 3 exchanges information with other exchanges, the home memory 4 and the information server 5 in the base station 2 and the mobile communication network 10.
[0018]
Since the base station 3 and the subscriber exchange 4 can be similar to the conventional one, 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. The subscriber number (so-called telephone number) and communication packet address of the mobile device 1, an authentication key and a secret key, and other various types of subscribers Store and manage information. Although the authentication key itself is well known, it relates to the present invention and will be described briefly. The authentication key is a code used for authentication of the mobile device 1, and is determined when a communication contract is concluded between the user (subscriber) and the mobile communication service company. The authentication key is different for each mobile device. For security, the wireless key is not directly transmitted in the first communication, but is directly written and stored in the nonvolatile memory from the operator's viewpoint.
[0019]
The mobile communication network 10 generates a random number at the time of authentication (procedure performed prior to location registration and communication start), and transfers the random number to the mobile device 1.
[0020]
The network performs a calculation using a random number and a secret key based on an authentication key of a user stored in a home memory.
[0021]
The mobile device 1 also performs calculations using the secret key that it has based on the transferred random numbers, and returns the calculation results to the mobile communication network 10.
[0022]
The mobile communication network 10 collates its own calculation result with the calculation result returned by the mobile device, and if they match, the location registration and communication start procedure is continued with the authentication OK.
[0023]
When the two match, it is authenticated that the mobile device 1 is contracted with the mobile communication service company.
[0024]
The inventor of the present application 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-described secret key using the above-mentioned authentication key. The feature of this embodiment is that the distribution information is second-encrypted and transferred using the. For this reason, since the secret key is encrypted with a different authentication key for each user, the encrypted secret key is different for each user even if the secret key is single. Therefore, the home memory 4 may manage a single secret key. In this embodiment, the home memory 4 further changes the secret key randomly (randomly) at regular time intervals, but this change process can be easily performed. Furthermore, since the secret key and the distribution information are encrypted with different keys, the confidentiality of the secret key and the distribution information is high even if a single encryption algorithm is used. In the present embodiment, the secret key encryption algorithm (calculation formula) and the distribution information encryption algorithm are different.
[0025]
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 as a distribution destination, and a communication packet address for mobile communication.
[0026]
A plurality of base stations 1, a plurality of subscriber exchanges 1, a plurality of home memories 4, and one or more information servers 5 are connected by wired signal lines, and control information, call information, and distribution information related to mobile communication are exchanged between related parties. Forward.
[0027]
Distribution information distribution processing performed in such a system configuration will be described with reference to FIGS. FIG. 2 shows the contents of a basic communication sequence related to the distribution process.
[0028]
FIG. 3 shows a processing procedure related to distribution of the information server 5. FIG. 4 shows a processing procedure related to distribution of the home memory 4. FIG. 4 shows a processing procedure of the mobile device 1 that receives distribution information.
[0029]
The information server 5 determines whether or not there is distribution information to be distributed at the current time according to the distribution schedule stored therein (step S100 in FIG. 3). When 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 by the subscriber number as in a normal call, or a communication packet indicating a call with an identifier for distributing distribution information is sent to the subscriber switch 3 and the base station 1. It may take the form of transmitting to the mobile device 1 via 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 (steps S310 → S320 in FIG. 5).
[0030]
The home memory 4 that has received the response from the mobile device 1 via the base station 2 and the subscriber switch 3 transmits a registration authentication key corresponding to the mobile device 1 to the subscriber switch 3. The subscriber exchange 3 transmits an authentication request to the mobile device 1 through the base station 2 in the same manner as before (steps S200 → S210 in FIG. 4).
[0031]
The mobile device 1 that has received the authentication request performs a calculation using a secret key stored therein and transmits the calculation result to the base station 2 (steps S320 → S330 in FIG. 5). In this embodiment, the subscriber exchange 3 compares the calculation result on the mobile communication network side with the calculation result from the mobile station 1 side. In this collation, when a match is determined, that is, a successful authentication is determined, setting of a wireless section between the mobile device 1 and the base station 2, relay between the subscriber switch 3, the home memory 4, and the information server 5 is performed. The section is set and the mobile device 1 and the information server 5 are connected. The processing procedure up to this point is the same as the conventional one.
[0032]
After authentication by the authentication key, the information server 5 transmits a secret key and a request for transmitting the authentication key to the home memory 4 and receives the authentication key and the secret key from the home memory 4 (FIG. 3). Step S120). 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 provisional encryption method will be described. As an example, a numerical value (for example, 5 in decimal number) indicated by the authentication key is multiplied by a numerical value (for example, 3 in decimal system) indicated by the secret key. The multiplication result (numerical value 15) becomes the value of the encrypted secret key. Note that for a different mobile device 1, if the authentication key is a numerical value 4, the value of the encrypted secret key is 4 × 3 = 12, which is different from the value 15 described above. Needless to say, the secret key value 3 is also different.
[0033]
Next, the information server 5 uses the secret key to encrypt the secret key by a second encryption method different from the secret key encryption method. If the distribution information to be transmitted is a character code string, an encrypted character code string is created by adding the secret key value (3 in this case) to the numerical value indicated by each character code in the character code string (step S140 in FIG. 3). ).
[0034]
The secret key encrypted by the first encryption method and the distribution information encrypted by the second encryption method are distributed to the mobile device (distribution target mobile device) 1 designated for distribution. (Step S150 in FIG. 3).
[0035]
After the authentication procedure is completed, the encrypted secret key and distribution information are received (step S340 in FIG. 5), and the secret key is first decrypted (step S350 in FIG. 5). Since the value of the encrypted secret key is 15 (5 × 3), the reverse of multiplication using the verification authentication key (numerical value 5) stored by itself, that is, the encrypted value 15 is used for verification. The secret key value is obtained by dividing by the authentication key value 5.
[0036]
Next, the mobile device 1 decrypts the received distribution information using the secret key value. In this example, since encryption is performed by adding a secret key, the distribution information is decrypted by subtracting the secret key value 3 from each character code value of the encrypted character code string (FIG. 5). Step S360). The decrypted (decrypted) distribution information is displayed on the display of the mobile device 1 (step S370 in FIG. 5).
[0037]
After sending the authentication key and the secret key in response to the request from the information server 5 (after step S230 in FIG. 4), the home memory 4 changes the secret key by repeating the steps S200 → S240 → S260 in FIG. Wait for the time. 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 determination in step S240 in FIG. 4), the home memory 4 uses, for example, a random number machine. Generate a new secret key. 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 certain time elapses.
[0038]
In the above distribution processing, since the mobile device 1 receives a secret key that is encrypted and differs depending on the time, the same calculation formula (algorithm) for decryption may be used as the other mobile device 1. it can. Even if distribution information is transmitted wirelessly 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. However, it cannot be identified that the wiretapping information includes a secret key.
[0039]
Furthermore, since it is only necessary to change a single secret code every predetermined time (the interval does not need to be constant) in the home memory 4, it is very easy to manage (save and change) the secret code.
[0040]
In addition to the above embodiment, the following embodiment can be implemented.
[0041]
1) Since the secret key is changed in the above-described embodiment, 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 to be fixed. 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 secret key can be the time when a location registration request is made from the mobile device 1 or the time when a transmission is made.
[0042]
2) In the above-described embodiment, the secret key is managed by the home memory 4 and the distribution information is managed by the information server 5, but the secret key may be managed by the information server 5.
[0043]
3) As an encryption method for encrypting the secret key and the distribution information, any method can be used.
[0044]
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. However, the distribution information is distributed by a terminal connected to the mobile device 1, for example, an electronic notebook or an information processing device called a mobile computer. Information may be displayed.
[0045]
5) In the above-described embodiment, a single type of secret code is used. However, this secret code may be used when the distribution information is communicated to a plurality of broadcasters like broadcast communication. Needless to say, if the information delivery service contractors are different, the secret code may be different.
[0046]
6) Distribution information is not limited to text, but includes various information such as images, audio, document information written in HTML language, mixed information, software programs (also called application programs) executed on the terminal side, etc. It can be handled.
[0047]
【The invention's effect】
As described above, in the invention of claim 1, since the secret key used for encrypting the distribution information is also encrypted and transferred to the mobile device side, it is not necessary to hold the secret key on the mobile device side. The secret key can be freely changed on the transmission side of the distribution information. Furthermore, since the contents of the encrypted secret key differ by each mobile device by encrypting the secret key using the authentication key, even if the encrypted secret key is wiretapped, the security of the secret key itself is safe. Sex is planned. Furthermore, since the secret key itself does not need to be set for each authentication number, that is, for each mobile device, the types of the secret key can be reduced, and the secret key can be easily managed.
In the first aspect of the invention, by changing the secret key, the security of the secret key and thus the distribution information is improved.
In the first aspect of the invention, the distribution information and the information related to the confidentiality such as the authentication key and the secret key are stored in a home memory different from the information server storing the distribution information. It is difficult to obtain all the keys related to the decryption of the authentication key and the secret key.
[0048]
In the invention of claim 2, by making the transmission timing of the encrypted secret key and the distribution information different, even if encryption is performed by a common encryption method, the confidentiality is not impaired.
[0049]
In the invention of claim 3, even if the secret key is changed by transmitting the encrypted secret key and the distribution information at the same time, the reception-side mobile device may use the reception secret key. There is no restriction on the transmission timing or the update timing of the confidential information.
[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 an information flow according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a processing procedure of the information server 5 of FIG. 1;
4 is a flowchart showing a processing procedure of the home memory of FIG. 1. FIG.
FIG. 5 is a flowchart showing a processing procedure of the mobile device of FIG. 1;
[Explanation of symbols]
1 Mobile equipment 2 Base station 3 Subscriber exchange 4 Home memory 5 Information server

Claims (3)

In an information distribution method in a mobile communication network that encrypts distribution information stored in an information server installed in a mobile communication network and distributes it to a mobile device.
The information server side encrypts the distribution information using a secret key,
Encrypt the secret key using an authentication key used to authenticate the mobile device to be delivered,
Transmitting the encrypted secret key and distribution information to the mobile device to be distributed;
In the mobile device to be distributed, the secret key transmitted after being encrypted is decrypted using the authentication key held by itself,
Decrypting the delivery information encrypted and transmitted using the decrypted secret key ,
Changing the secret key at a predetermined timing;
In the mobile communication network, wherein a home memory for storing the authentication key and the secret key is installed in the mobile communication network, and the authentication key and the secret key are delivered from the home memory to the information server . Information distribution method.   2. The information delivery method in the mobile communication network according to claim 1, wherein the encrypted secret key and the encrypted delivery information are transferred from the information server to the delivery target mobile device at different points in time. An information distribution method in a mobile communication network.   2. The information delivery method in the mobile communication network according to claim 1, wherein the encrypted secret key and the encrypted delivery information are transferred from the information server to the delivery target mobile device at the same time. An information distribution method in a mobile communication network.

Images