JP2007281892A - Device and method of forming secret key - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for forming a secret key through which IMSI can be encrypted using a secret key whose security is ensured. <P>SOLUTION: A secret key forming unit 112 forms a secret key periodically at a predetermined interval using time information that indicates the time, and a secret key managing table 111 stores them successively. A WLAN control unit 110 encrypts poly ID (IMSI) which is transmitted from a mobile terminal to indicate a subscriber, using the latest secret key stored in the secret key managing table 111 forms Pseudonym, and transmits it to the mobile terminal. By this setup, IMSIs of mobile terminals can be encrypted using the same secret key in each AAA server so that security can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a secret key generation apparatus and a secret key generation method.

  The mobile device connects to an AAA (Authentication, Authorization and Accounting) server via PDG (Packet Data Gateway) using IPsec, so that the AAA server can perform authentication processing in the mobile device. Here, when the PDG that has received the IPsec connection request from the mobile device accesses the AAA server, the PDG does not grasp the accommodation form such as which subscriber information is stored in the AAA server. For this reason, the PDG randomly selects an AAA server. With respect to the operation at this time, an outline of the operation in the conventional WLAN Registration will be described with reference to FIG.

  FIG. 9 is a schematic diagram showing an operation of WLAN Registration in a communication system using WLAN. The communication system includes a mobile terminal 200, a PDG 201, and AAA servers 202 to 204. Upon receiving the IPsec connection request from the mobile terminal 200, the PDG 201 randomly selects one AAA server from the AAA servers 201-204. Here, the AAA server 203 is selected.

  The selected AAA server 203 needs to identify the user based on the key notified from the mobile terminal 200 via the PDG 201. When IMSI (International Mobile Station Identity) is used as a key, whether or not the subscriber information indicated by the corresponding IMSI is held as a subscriber profile. The AAA server 203 performs a check.

  When the AAA server 203 does not hold the subscriber information as the subscriber profile, the AAA server 203 stores the subscriber information of the user of the mobile terminal 200 from the IMSI notified from the mobile terminal 200. The server address is expanded to instruct the PDG 201 to perform rerouting. The PDG 201 performs WLAN Registration again for the address of the notified AAA server (in the figure, the AAA server 204). The AAA server 204 generates Padded-IMSI from the user's IMSI using the secret key, encrypts the Padded-IMSI, and generates Encrypted-IMSI. Further, a Tag and a secret key index are added to the generated Encrypted-IMSI to generate Pseudonym indicating a temporary identifier, and the PDG 201 is transmitted. The PDG 201 transmits the received Pseudonym to the mobile terminal 200.

  Here, a method of generating Encrypted-IMSI will be described. FIG. 10 is a schematic diagram showing an encrypted-IMSI generation process. IMSI is a numerical value of 15 or less, and Compressed-IMSI in which each digit is expressed by 4 bits and the shortage is supplemented with “1” so as to be 16 digits is generated in the AAA server. By combining this Compressed-IMSI and a 64-bit random value, a 128-bit Padded-IMSI is generated. In the AAA server, a predetermined encryption algorithm can generate Encrypted-IMSI by encrypting Padded-IMSI using a secret key.

  Next, the configuration of Pseudonym will be described. FIG. 11 is a schematic diagram showing the configuration of Pseudonym. Pseudonym is 138-bit binary data, and is composed of a 6-bit Tag, a 4-bit secret key index, and a 128-bit Encrypted-IMSI. Tag is used as information for identifying Pseudonym and IMSI, and the secret key index is an index (index) representing a key used at the time of encryption when performing decryption processing from Pseudonym to IMSI in the AAA server. .

  When Pseudonym is generated by the process shown in FIG. 9, the mobile terminal can next request an AAA server for authentication processing using this Pseudonym. Hereinafter, the operation will be described with reference to FIG. FIG. 12 is an explanatory diagram showing an outline of WLAN registration when the key notified from the mobile terminal 200 is Pseudonym. The AAA server 203 selected at random from the PDG 200 extracts the Encrypted-IMSI from Pseudonym included in the request from the mobile terminal 200, and decrypts the Encrypted-IMSI using the secret key indicated by the secret key index.

  The AAA server 203 decrypts the Encrypted-IMSI to derive the Padded-IMSI, and expands the address of the AAA server 204 that accommodates the subscriber information of the user according to the Compressed-IMSI included in the Padded-IMSI. Each AAA server stores which AAA server stores which IMSI subscriber information.

  The AAA server 203 returns to the PDG 201 the IP address of the AAA server 204 that accommodates user subscriber information. The PDG 201 performs WLAN Registration again for the notified address of the AAA server 204.

  The AAA server 204 extracts the Encrypted-IMSI from the Pseudonym included in the request from the mobile terminal 200, decrypts the Encrypted-IMSI using the secret key indicated by the secret key index, and obtains the user's Padded-IMSI. derive. Then, the AAA server 204 encrypts the user's Padded-IMSI using the secret key, creates Pseudonym, and sends it to the PDG 201. The PDG 201 transfers the sent Pseudonym to the mobile terminal 200. The above processing is described in Non-Patent Document 1 and Non-Patent Document 2.

As described above, by adopting a configuration in which authentication processing can be performed using Pseudonym, authentication processing with improved security can be performed.
3GPP TS 33.234V6.5.0 (2005-06), 3rd Generation Partnership Project; Technical Specification Group Service and System; Aspects; 3G Security; Wireless Local Area Network (WLAN) interworking security (Release 6) 3GPP TS 29.234 V6.4.0 (2005-09), 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; 3GPP system to Wireless Local Area Network (WLAN) interworking; Stage 3 (Release 6)

  However, since the AAA server for encryption and the AAA server for decryption are not necessarily the same, the secret key for encrypting / decrypting Padded-IMSI is the same for all AAA servers (AAA servers 202 to 204). There was a need to do. Therefore, a secret key that uses a fixed value is required, and the security for the secret key is low. This Non-Patent Document 1 describes a procedure in which the periodic key generator updates the secret key to the AAA server through the O & M Interface as a key configuration. The builder needs to clearly indicate the update timing and update procedure of the private key to the maintainer. Moreover, there is a problem that it is necessary to regularly update the secret key as a system maintainer, which is very troublesome.

  Therefore, in order to solve the above-described problems, the present invention has an object to provide a secret key generation apparatus and a secret key generation method capable of performing IMSI encryption using a secret key that ensures security. To do.

  In order to solve the above-described problem, a secret key generation apparatus according to the present invention generates a secret key using time information indicating time for each predetermined period, and the generation unit generates the secret key. A predetermined number of secret keys are sequentially stored as secret keys, and if the number of secret keys generated by the generating means is generated more than the predetermined number, the oldest secret key is generated. Secret key storage means for overwriting and storing sequentially, and encryption means for encrypting an identifier indicating a subscriber transmitted from a mobile terminal using one of the secret keys stored in the secret key storage means And a temporary identifier transmitting means for generating a temporary identifier including index information indicating the identifier encrypted by the encryption means and the secret key used for the encryption, and transmitting the temporary identifier to the mobile terminal. Have

  In addition, the secret key generation method of the present invention has a generation step of generating a secret key using time information indicating a time and a secret key generated by the generation step are determined in advance at predetermined intervals. The number of secret keys is sequentially stored in the secret key storage means, and when the number of secret keys generated by the generating step is generated more than the predetermined number, the oldest generated secret key is overwritten. Then, the identifier indicating the subscriber transmitted from the mobile terminal is encrypted using the secret key storing step to be sequentially stored in the secret key storing means and one of the secret keys stored in the secret key storing means. A temporary identifier including an encryption step and an index encrypted indicating the identifier encrypted by the encryption step and the secret key used for the encryption is generated and transmitted to the mobile terminal. And it includes a temporary identifier transmitting step of, a.

  According to the present invention, a secret key is generated using time information indicating time for each predetermined period, and a predetermined number of secret keys are sequentially stored and generated. When more than the predetermined number of secret keys are generated, the oldest generated secret keys are overwritten and sequentially stored. Then, using one of the stored secret keys, the identifier indicating the subscriber transmitted from the mobile terminal is encrypted, and the encrypted identifier and index information indicating the secret key used for the encryption are obtained. The included temporary identifier can be generated and transmitted to the mobile terminal. As a result, it is possible to increase the commonality of secret keys and generate a secret key with improved security.

  Further, the secret key generation apparatus of the present invention is acquired by the acquisition unit that acquires the secret key indicated by the index information included in the temporary identifier transmitted from the mobile terminal from the secret key storage unit, and is acquired by the acquisition unit. A decryption unit that decrypts the temporary identifier using the private key and obtains the identifier, and an address of the authentication device that holds the authentication data of the subscriber indicated by the identifier based on the identifier obtained by the decryption unit. It is preferable to include an address acquisition unit to acquire and an address transmission unit to transmit the address acquired by the address acquisition unit to the mobile terminal.

  According to the present invention, the secret key indicated by the index information included in the temporary identifier transmitted from the mobile terminal is acquired from the secret key storage unit, and the temporary identifier is decrypted using the acquired secret key. To get. And based on the acquired identifier, the address of the authentication apparatus holding the authentication data of the subscriber indicated by the identifier can be acquired, and the acquired address can be transmitted to the mobile terminal. Accordingly, it is possible to perform a decryption process using the secret key generated based on the time, and it is possible to increase the commonality of the secret key and generate a secret key with improved security.

  Further, the secret key generation apparatus according to the present invention is configured such that the secret key acquired by the acquiring unit is valid, and the determination unit determines that the secret key is not valid. When it is determined, it is preferable to include requesting means for requesting the identifier again from the mobile terminal.

  According to the present invention, it is determined whether or not the acquired secret key is valid. If it is determined that the secret key is not valid, the mobile terminal again requests an identifier. It can be performed. Thus, efficient communication can be performed without causing a call loss during communication connection.

  The present invention can increase the commonality of secret keys and generate a secret key with improved security.

  The present invention can be readily understood by considering the following detailed description with reference to the accompanying drawings shown for the embodiments. Subsequently, embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  A network configuration using an AAA server which is a secret key generation apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a system configuration diagram showing a network system of a secret key generation apparatus. This network system includes a PDG 101, AAA servers 102 a to 102 c (hereinafter, an arbitrary AAA server is abbreviated as AAA server 102), and an NTP (Network Time Protocol) server 103. Each configuration will be described below.

  The PDG 101 is a gateway device that functions as an interface with a wireless network in a wired network, and is a gateway device that terminates IPsec. When the PDG 101 receives a connection request to the AAA server 102 from the mobile terminal side, the PDG 101 transmits and receives signals between the mobile terminal and the AAA server 102.

  The AAA server 102 is a server that holds subscriber information, performs authentication processing on the mobile terminal using the subscriber information, and enables network connection to the mobile terminal. This is a secret key generation device that periodically generates a secret key. Each AAA server 102 can connect to the same NTP server 103 in the network and share time information indicating the time. Thereby, each AAA server 102 can acquire substantially the same time information, and the effectiveness can be enhanced with respect to the commonality of the secret key using the same time information.

  As described later, the AAA server 102 can decrypt Encrypted-IMSI using a secret key to derive IMSI, and issue the address of the AAA server, but the Encrypted-IMSI issued by another AAA server 102 can be used. If the IMSI cannot be decrypted, the IMSI can be acquired using a procedure for requesting the IMSI defined in the IETF (Internet Engineering Task Force), and call loss can be avoided. That is, the AAA server 102 can request the IMSI for the mobile terminal again, and the mobile terminal that has received the request can transmit the IMSI to the PDG 101 and perform the process again. The IETF specifically specifies draft-arkko-pppext-eap-aka-15.txt (see http://ietfreport.isoc.org/idref/draft-arkko-pppext-eap-aka/ ).

  The NTP server 103 is a server that provides correct Japanese standard time, and each AAA server 102 can adjust the Japanese standard time by referring to the NTP server 103.

  The AAA server 102 that functions as a secret key generation device in the network system configured as described above will be described. FIG. 2 is a block diagram of the AAA server 102. The AAA server 102 includes a WLAN control unit 110, a secret key management table 111 (secret key storage unit), a secret key generation unit 112 (generation unit), and a subscriber profile storage unit 113. The AAA server 102 includes hardware as shown in FIG.

  FIG. 3 is a hardware configuration diagram of the AAA server 102. As shown in FIG. 3, the AAA server 102 physically includes a CPU 11, a RAM 12 and a ROM 13 that are main storage devices, a communication module 14 that is a data transmission / reception device such as a network card, an auxiliary storage device 15 such as a hard disk, and the like. It is configured as a computer system including. Each function described in FIG. 3 operates the communication module 14 under the control of the CPU 11 by loading predetermined computer software on the hardware such as the CPU 11 and the RAM 12 shown in FIG. This is realized by reading and writing data in the storage device 15. Hereinafter, each functional block will be described based on the functional blocks shown in FIG.

  The WLAN control unit 110 has a function of including a secret key (that is, a hash value of time information) in Padded-IMSI used for encryption, in addition to functions as an AAA server such as authentication and IMSI encryption and decryption. (See FIG. 4). Then, the WLAN control unit 110 includes the secret key (the hash value of the time information) in the Padded-IMSI used at the time of encryption, so that the hash value of the time information included in the Padded-IMSI at the time of decryption Based on the above, it can be determined whether or not the expiration date has passed, and IMSI guarantee can be realized. Detailed processing for determining whether or not the expiration date has expired will be described later.

  More specifically, the WLAN controller 110 will be described. The WLAN control unit 110 includes a transmission unit 110a (temporary identifier transmission unit), a reception unit 110b, an authentication processing unit 110c, a determination / request unit 110d (determination unit and request unit), and a decryption processing unit 110e (acquisition unit and decryption unit). And an encryption processing unit 110f (encryption unit) and an address acquisition unit 110g (address acquisition unit).

  The transmission unit 110a and the reception unit 110b are parts for performing pseudonym or IMSI transmission / reception with respect to the mobile terminal. The authentication processing unit 110c is a part for performing authentication processing of the mobile terminal as an AAA server. The determination / request unit 110d determines whether or not the IMSI obtained by decryption by the decryption processing unit 110e is valid. If the IMSI is invalid, the determination / request unit 110d requests the mobile terminal again for the IMSI. This is the part that performs processing.

  The encryption processing unit 110f performs IMSI encryption processing by using the secret key stored in the secret key management table 111 to generate pseudonym, and the decryption processing unit 110e analyzes the pseudonym to obtain the secret management key. This is a part for performing a decryption process using a secret key stored in the table 111. The address acquisition unit 110g is a part that acquires the address of the AAA server that stores the profile of the mobile terminal specified by the IMSI based on the IMSI.

  Here, the processing procedure when the Padded-IMSI of the WLAN control unit 110 is generated will be described with reference to FIG. FIG. 4 is a schematic diagram showing the procedure. As shown in FIG. 4, the WLAN control unit 110 obtains the latest secret key from the secret key management table 111 and combines the latest secret key, that is, the hash value of time information and Compressed-IMSI. , Padded-IMSI is generated. Then, the WLAN control unit 110 may generate Encrypted-IMSI, which is the encrypted IMSI, by encrypting the generated Padded-IMSI using the latest secret key. it can.

  The secret key generation unit 112 is a part that generates a secret key using time information obtained from the NTP server 103, generates a secret key at a predetermined cycle, and is stored in the secret key management table 111. Update the list of existing private keys with the newly generated private key. In consideration of the confidentiality of information, different secret keys are used in a certain period, and the old secret key is also retained for a certain period so that the old secret key can be decrypted.

  Further, a secret key is generated based on the time information generated by the NTP server 103 so that the Pseudonym indicating the temporary identifier becomes the same in each AAA server 102. Here, since only the time information is not confidential, the hash value of the time information is used as the secret key. In addition, the secret key generation unit 112 is synchronized with the operation of acquiring the optimum secret key from the secret key management table when the key generation cycle and the IMSI encryption or decryption are performed by the WLAN control unit. Absent.

  The secret key management table 111 stores a secret key and a secret key index in association with each other. The secret key management table 111 can hold a plurality of secret keys in accordance with standard specifications, and can hold a maximum of 16 secret keys. Therefore, when a new secret key is generated as the 17th one with a fixed payment cycle, the area where the oldest secret key stored in the secret key management table 111 is stored is the latest secret key. Overwritten.

  Here, a specific configuration of the secret key management table 111 will be described. FIG. 5 is a schematic diagram showing the configuration of the secret key management table 111. According to FIG. 5, the secret key management table 111 stores a secret key index and a secret key in association with each other. Here, the secret key is a hash value of time information. For example, as shown in FIG. 6, the secret key generated from time information one time before the payout period from the current time is stored in the secret key management table 111 corresponding to the index [0]. It is assumed that the secret key generated from the current time information is stored, and the secret key generated from the time information 15 times before the payout period from the current time is stored in the index [2]. At this time, when a new secret key is generated, the new secret key is overwritten on the secret key associated with the index [2].

  The subscriber profile storage unit 113 is a part that stores subscriber information of each mobile terminal. Based on the subscriber information stored in the subscriber profile storage unit 113, the WLAN control unit 110 can perform an authentication process.

  Next, the operation of the AAA server 102 configured as described above will be described. FIG. 7 is a sequence diagram showing the operation of the AAA server 102 when paying out the secret key. Here, operations of the AAA server 102b and the AAA server 102c are shown. It is assumed that the AAA server 102b is a server selected randomly by the PDG 101, and the AAA 102c is a server designated by the AAA server 102b that holds subscriber information.

  Both the AAA server 102b and the AAA server 102c hold secret key management tables 111b and 111c, and the secret key management tables 111b and 111c store the latest issued secret key 1 in association with the index [0]. As described above, the secret key 1 stored in each of the secret key management tables 111b and 111c is generated using the same time information, and constitutes the same secret key. The index [15] stores the secret key 16 that has been issued one cycle before.

  At this time, the WLAN controller 110 of the AAA server 102c receives the WLAN Registration request from the external mobile terminal and receives IMSI (IMSI-A) (S101). Then, the WLAN control unit 110 refers to the secret key management table 111 and acquires the latest secret key 1 and the secret key index [0] of the secret key 1 (S102). Then, the WLAN control unit 110 generates Compressed-IMSI from IMSI (IMSI-A), acquires the acquired secret key (that is, the hash value of time information), and converts the acquired hash value of time information into Compressed-IMSI. Add to generate Padded-IMSI.

  Then, the WLAN control unit 110 encrypts the Padded-IMSI including the hash value of the time information and the acquired secret key 1 according to the encryption algorithm, and generates Encrypted-IMSI (S103). Then, the WLAN control unit 110 generates Pseudonym-A in which the encrypted Encrypted-IMSI, the secret key index [0], and Tag are combined (S104). The WLAN control unit 110 transmits the generated Pseudonym-A to the mobile terminal (S105).

  Thereafter, when the secret key payout period elapses, the secret key is updated. That is, in the secret key generation unit 112 in the AAA server 102b and the AAA server 102c, the same secret key is generated using the same time given from the NTP server 103, and the generated secret key is stored in each secret key management table. 111b and the private key management table 111c (S201, S202). Here, the secret key corresponding to the oldest updated index [1] is updated, and the secret key 2 is newly registered.

  Thereafter, when the WLAN control unit 110 of the AAA server 102c receives an authentication request from an external mobile terminal and receives the IMSI (IMSI-B), the latest secret key 2 and secret are referenced with reference to the secret key management table 111c. The private key index [1] corresponding to the key 2 is acquired (S111).

  Then, the WLAN control unit 110 generates Compressed-IMSI from the received IMSI (IMSI-B), further generates Padded-IMSI, and the generated Padded-IMSI and the acquired secret key 2 are encrypted. Encryption is performed according to the algorithm, and Encrypted-IMSI (IMSI-B) is generated (S112). Thereafter, the WLAN controller 110 combines the generated Encrypted-IMSI, the secret key index [1], and Tag to generate Pseudonym-B (S113) and returns it to the mobile terminal (S114).

  As described above, the AAA server 102b and the AAA server 102c periodically update the secret key by generating the secret key using the same (or including some error) time information from the NTP server 103. Can improve security.

  Next, an operation when deriving IMSI using Pseudonym paid out from the AAA server 102c will be described. FIG. 8 is a sequence diagram showing an operation when deriving IMSI using Pseudonym.

  In the WLAN control unit 110, a WLAN Registration request is received from the mobile terminal (S301), and Pseudonym-A included in the request is extracted and analyzed. Then, the WLAN control unit 110 acquires the private key index and the encrypted Encrypted-IMSI included in Pseudonym-A (S302). Here, for example, the secret key index [0] and IMSI-A are acquired.

  In the WLAN control unit 110, based on the acquired secret key index [0], the secret key stored in the secret key management table 111 corresponding to this index is acquired (S303). Then, the Encrypted-IMSI encrypted with the obtained secret key 1 is decrypted, and Padded-IMSI is generated. It is checked whether or not the generated Padded-IMSI has been decrypted with the expired secret key (S304). Specifically, the hash value (ie, secret key) of the time information included in the Padded-IMSI obtained by decryption is the hash value (secret key) of the time information stored in the secret key management table 111. It is determined whether or not it matches any one. When the WLAN control unit 110 determines that they are matched, it is determined that the expiration date has not expired, and when they do not match, it is determined that the expiration date has expired. .

  If it is determined that the IMSI has been generated because the validity period has not expired, the address of the AAA server 102 that stores the subscriber information corresponding to the IMSI is expanded (S305), and the address is transmitted to the mobile terminal. (S306). If it is determined in S304 that the expiration date has expired and no IMSI is generated, an IMSI key is requested from the mobile terminal (S307). Upon receiving this request, the mobile terminal transmits the IMSI again to the AAA server, and acquires Pseudonym by an authentication process based on the IMSI.

  With the above operation, the address of the AAA server can be paid out from Pseudonym to the mobile terminal, and authentication processing with security can be performed.

  Next, operational effects of the AAA server 102 of the present embodiment will be described. The AAA server 102 of the present embodiment generates a secret key using time information indicating the time for each predetermined period by the secret key generation unit 112, and the secret key management table 111 stores the generated secret key. A predetermined number of secret keys are sequentially stored, and if more than the predetermined number of generated secret keys are generated, the oldest generated secret key is overwritten and sequentially stored. . The WLAN control unit 110 encrypts an identifier (Padded-IMSI) indicating the subscriber transmitted from the mobile terminal, using the latest secret key stored in the secret key management table 111. The WLAN control unit 110 transmits an encrypted Encrypted-IMSI and Pseudonym, which is a temporary identifier including index information indicating the secret key used for the encryption, to the mobile terminal. As a result, the IMSI of the mobile terminal can be encrypted using the same secret key in each AAA server, thereby improving security.

  In addition, the AAA server 102, the WLAN control unit 110 acquires the secret key indicated by the index information included in the Pseudonym transmitted from the mobile terminal from the secret key management table 111, and uses the acquired secret key to obtain the Pseudonym To obtain IMSI. Then, based on the acquired IMSI, the WLAN control unit 110 acquires the address of another AAA server that holds the authentication data of the subscriber indicated by this IMSI. Then, the WLAN control unit 110 transmits the acquired address to the mobile terminal. Thereby, it is possible to cause the mobile terminal to appropriately perform the authentication process using the identifier encrypted using the time.

  Further, the AAA server 102 determines whether or not the secret key acquired by the WLAN control unit 110 is legitimate, and if it determines that the secret key is not legitimate, The IMSI request can be made again. That is, Pseudonym is decrypted based on the acquired secret key to generate Padded-IMSI, and the same hash value is stored in the secret key management table 111 based on the hash value of the time information included in the Padded-IMSI. It is determined whether it is included. If the same hash value is included, it can be determined that the secret key is valid. If the same hash value is not included, it can be determined that the secret key is not valid. Thereby, even when IMSI cannot be decoded, call loss does not occur and communication connection processing can be performed appropriately.

1 is a system configuration diagram showing a network system of a secret key generation apparatus. 2 is a block configuration diagram of an AAA server 102. FIG. 2 is a hardware configuration diagram of an AAA server 102. FIG. It is a schematic diagram which shows the process sequence when Padded-IMSI is produced | generated. 3 is a schematic diagram showing a configuration of a secret key management table 111. FIG. FIG. 4 is a schematic diagram showing a relationship between secret keys stored in a secret key management table 111. It is a sequence diagram which shows the operation | movement of the AAA server 102 when paying out a secret key. It is a sequence diagram which shows operation | movement when deriving IMSI using Pseudonym. It is a schematic diagram which shows the operation | movement of WLAN Registration in the communication system using WLAN. It is a schematic diagram which shows the production | generation process of Encrypted-IMSI. It is a schematic diagram which shows the structure of Pseudonym. It is explanatory drawing which shows the outline | summary of WLAN registration in case the key notified from the mobile terminal 200 is Pseudonym.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 ... WLAN control part, 111 ... Secret key management table, 112 ... Secret key generation part, 113 ... Subscriber profile memory | storage part, 101 ... PDG, 102 ... AAA server, 103 ... NTP server.

Claims (4)

Generating means for generating a secret key using time information indicating a time for each predetermined period;
When a predetermined number of secret keys are sequentially stored as the secret key generated by the generating means, and the secret key generated by the generating means is generated more than the predetermined number, A secret key storage means for overwriting an old secret key and sequentially storing it,
Encryption means for encrypting an identifier indicating a subscriber transmitted from a mobile terminal, using one of the secret keys stored in the secret key storage means;
A temporary identifier transmitting means for generating a temporary identifier including index information indicating the identifier encrypted by the encryption means and the secret key used for the encryption, and transmitting the temporary identifier to the mobile terminal;
A secret key generation apparatus comprising: Obtaining means for obtaining, from the secret key storage means, a secret key indicated by index information included in the temporary identifier transmitted from the mobile terminal;
Decryption means for decrypting the temporary identifier using the secret key obtained by the obtaining means to obtain the identifier;
Based on the identifier acquired by the decryption means, an address acquisition means for acquiring the address of the authentication device that holds the authentication data of the subscriber indicated by the identifier;
Address transmitting means for transmitting the address acquired by the address acquiring means to the mobile terminal;
The secret key generation device according to claim 1. Determining means for determining whether the secret key acquired by the acquiring means is valid;
When the determination means determines that the secret key is not valid, the request means for requesting the identifier again to the mobile terminal;
The secret key generation apparatus according to claim 2, comprising: A generating step for generating a secret key using time information indicating time for each predetermined period;
When the predetermined number of secret keys generated by the generating step are sequentially stored in the secret key storage means, and the number of secret keys generated by the generating step is generated more than the predetermined number Includes a secret key storage step of overwriting the oldest generated secret key and sequentially storing it in the secret key storage means;
An encryption step of encrypting an identifier indicating a subscriber transmitted from a mobile terminal using one of the secret keys stored in the secret key storage means;
A temporary identifier transmitting step of generating a temporary identifier including index information indicating the identifier encrypted by the encryption step and the secret key used for the encryption, and transmitting the temporary identifier to the mobile terminal;
A secret key generation method comprising:

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