Certification method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an authentication method when accessing a home network while seamlessly moving between different types of networks.

【0002】

[Conventional technology]

In recent years, with the progress of mobile computing, VPN (Virtual Private Network) technology that accesses the office network that one normally accesses from the outside beyond the firewall is developing. The basis of VPN is the establishment of an authentication and encrypted tunnel by a tunnel server inside a firewall.

【0003】

FIG. 3 is an explanatory diagram showing an outline example of a system in which a mobile terminal accesses home network A from the outside via access networks (premises networks) B and C while opening a VPN. In this figure, the firewall is set to pass only the authentication packet with the tunnel server and the packet passing through the encrypted tunnel with the tunnel server.

【0004】

To open an encrypted tunnel, follow the procedure below (see Fig. 4). The mobile terminal and the tunnel server authenticate (2-a). Negotiate the encryption key (2-b). Open an encrypted tunnel (2-c).

【0005】

Further, in general, the time required for decryption is determined by the number of encryption trials per unit time, so that a cipher having a faster encryption trial speed tends to be easily decrypted in a short time. FIG. 5 is a chart showing the relationship between the characteristics (strength / speed) of the encryption algorithm and the network. As shown in this table, in the case of connection via a dedicated line and in the case of connection via a premises network, high security is not required, but the high transmission speed of the leased line and the premises network can be achieved. A high-speed encryption algorithm is required so as not to reduce it. On the other hand, in the case of connection via the Internet, since the transmission speed of the transmission line (Internet) itself is considered to be low, a high-speed encryption algorithm is not required, but high security is required.

【0006】

Actually, the VPN systems currently on the market are (1) systems that use simple encryption, keeping in mind that they are mainly used in the premises network, and (2) are used in commercial Internet services such as OCN. With that in mind, some systems use strong ciphers. As an example of the above (1), there is Logical Office (Tanimoto et al., "Logical Office Service", NTT R & D, Vol.45 No.10 1996). Further, as an example of the above (2), there is an Altavista tunnel manufactured by DEC, NTT-AT.

【0007】

[Problems to be Solved by the Invention]

By the way, as a new usage form of wireless LAN whose standardization has been remarkably progressed in recent years, a communication form in which continuous communication is performed while moving across different types of networks has become a reality. As an example of the usage pattern, as shown in FIG. 3, it is conceivable to change the access network via communication from the access network C to the access network B as the mobile terminal moves. In such a usage pattern, an encrypted tunnel between the mobile terminal and the home network goes through various communication paths.

【0008】

Therefore, in a conventional system (a system in which only a single encryption algorithm is prepared), the prepared encryption algorithm is required to be more secure than necessary for the communication path currently being passed. Even if the processing speed is not met, or if it is faster than necessary but does not meet the required security, the prepared encryption algorithm must be used. There was a problem that there was no such thing.

【0009】

This invention was made against such a background, and even if the access to the home network is continued while seamlessly moving between different networks, the required strength and speed of the encryption algorithm are appropriately selected. The purpose is to provide an authentication method that can be used.

【0010】

[Means for solving problems]

The invention according to claim 1 is composed of a mobile terminal, an access network, a relay network, a home network, and a tunnel server in the home network, and the mobile terminal is connected to the tunnel server via the access network and the relay network. In the authentication method of the communication system that authenticates with, and opens an encrypted tunnel between the mobile terminal and the tunnel server to communicate, the mobile terminal authenticates when connecting to the access network and authenticates with the access network. Occasionally, based on the network information notified by the access network, the required encryption strength is determined, the encryption algorithm is selected, and when authenticating with the tunnel server, the selected encryption algorithm type and this session The information that can identify this session is signed and sent with its own signature key, the tunnel server verifies the signature, and the information that can identify this session notified from the mobile terminal and the tunnel server manages it. Based on the collation result with the information that can identify this session, the legitimacy of the mobile terminal is judged, and when the legitimacy is recognized, the encrypted VPN communication by the selected encryption algorithm is started. It is characterized by that. The invention according to claim 2 is characterized in that, in the authentication method according to claim 1, the number of accesses from the outside of the mobile terminal is used as the information that can identify the current session. The invention according to claim 3 is characterized in that, in the authentication method according to claim 1, the time information at which the session was performed is used as the information that can identify the current session. The invention according to claim 4 is composed of a mobile terminal, an access network, a relay network, a home network, and a tunnel server in the home network, and the mobile terminal is connected to the tunnel server via the access network and the relay network. In the authentication method of the communication system that authenticates with the mobile terminal and opens an encrypted tunnel between the mobile terminal and the tunnel server to communicate, the mobile terminal authenticates when connecting to the access network and performs the tunnel. At the time of authentication with the server, the information that can identify this session and the network information notified from the access network at the time of authentication with the access network are signed and sent with their own signature key, and the tunnel server signs the signature. After verification, the validity of the mobile terminal is judged based on the collation result of the information that can identify this session notified from the mobile terminal and the information that can identify this session managed by the tunnel server. When the legitimacy is recognized, the required encryption strength is determined based on the network information notified from the mobile terminal, the encryption algorithm is selected, and the encrypted VPN communication by the selected encryption algorithm is performed. It is characterized by starting. The invention according to claim 5 is characterized in that, in the authentication method according to claim 4, the number of accesses from the outside of the mobile terminal is used as the information that can identify the current session. The invention according to claim 6 is characterized in that, in the authentication method according to claim 4, the time information at which the session was performed is used as the information that can identify the current session.

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

§1. Overview In the present invention, when connecting to an access network, the mobile terminal and the access network perform mutual authentication, obtain information about the access network (network address, information of the operating organization), and based on the information, the required strength. -Selecting a speed encryption algorithm is the most important feature. It differs from the prior art in that a mobile terminal can move across dissimilar networks while selecting and communicating with the most appropriate encryption algorithm at each point in time. According to the present invention, it is possible to determine the required security and speed according to the network to be connected and select an appropriate encryption algorithm, and in particular, in an advanced mobile communication system such as a wireless LAN, it is always possible. It has the effect of allowing you to continue to access your office environment.

【0012】

§2. First embodiment Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. Although the present embodiment corresponds to claim 2, in the following description, the explanation corresponds to claim 3 by replacing the "number of times information" with the "time information", and the "number of times information" is referred to as "this time". The explanation corresponds to claim 1 by replacing it with "information that can identify the session of."

【0013】

FIG. 1 is a sequence diagram showing an example of an authentication method according to the first embodiment of the present invention. In this figure, as an initial state, as shown in FIG. 3, a case where "a mobile terminal establishes a VPN encrypted tunnel with home network A via access network C and communicates with each other" is considered.

【0014】

In this initial state, when the mobile terminal moves as shown in FIG. 3, the access network used for communication is switched from the access network C to the access network B. When switching to access network B, the mobile terminal and access network B mutually authenticate the public key certificate.

【0015】

At the time of mutual authentication with access network B, the mobile terminal selects an encryption algorithm suitable for access network B based on the network information in the certificate of access network B.

【0016】

The mobile terminal signs the encryption algorithm selection message indicating the type of the selected encryption algorithm with the signature key unique to the mobile terminal, and sends the signed encryption algorithm selection message to the VPN of the home network A. Send to the terminal node (tunnel server).

【0017】

At this time, the mobile terminal must prevent the signature key (obtained by analyzing this signed encryption algorithm selection message) from being diverted by the access network B. Therefore, the mobile terminal incorporates the number of times information indicating the number of times the home network A is accessed from the outside into the signed statement (that is, the encryption algorithm selection message), and the mobile terminal incorporates the number of times information into the encryption algorithm selection message. To sign. According to this, since the access network B cannot forge the number-of-times information, it is also impossible to analyze and divert the signature key.

【0018】

Upon receiving the encrypted encryption algorithm selection message signed after the number of times information is incorporated, the home network A receives the number of times information (that is, the number of times information managed by the mobile terminal, hereinafter, "the number of times on the mobile terminal side" from the received contents. Information) is taken out, and the number-of-times information on the mobile terminal side is referred to as the number-of-times information managed by the home network A regarding the access from the mobile terminal to the home network A (hereinafter referred to as "home network-side number-of-times information"). Match.

【0019】

If the number-of-times information on the mobile terminal side and the number-of-times information on the home network side do not match, the home network A refuses the connection with the mobile terminal, and the process ends. On the other hand, if the mobile terminal side count information and the home network side count information match, the home network A increments the home network side count information (the number indicated by) by 1.

【0020】

The home network A extracts the encryption algorithm selection message from the encryption algorithm selection message signed after the number information is incorporated, and selects the encryption algorithm of the type indicated by the encryption algorithm selection message (that is, selected by the mobile terminal). Establish a VPN encryption tunnel based on the encryption algorithm). Finally, the mobile terminal increments the mobile terminal side count information (the number indicated by) by 1. This completes the process.

【0021】

According to the above authentication method, even if access to the home network is continued while seamlessly moving between different networks, the required strength and speed encryption algorithm can be appropriately selected.

【0022】

§3. Second embodiment Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. Although the present embodiment corresponds to claim 5, in the following description, the explanation corresponds to claim 6 by replacing the "number of times information" with the "time information", and the "number of times information" is referred to as "this time". The explanation corresponds to claim 4 by replacing with "information that can identify the session of."

【0023】

FIG. 2 is a sequence diagram showing an example of the authentication method according to the second embodiment of the present invention. Also in this figure, as an initial state, consider the case where "a mobile terminal establishes a VPN encrypted tunnel with home network A via access network C and communicates" as shown in FIG.

【0024】

In this initial state, when the mobile terminal moves as shown in FIG. 3, the access network used for communication is switched from the access network C to the access network B. When switching to access network B, the mobile terminal and access network B mutually authenticate the public key certificate.

【0025】

At the time of mutual authentication with access network B, the mobile terminal signs the network information in the certificate of access network B with the signature key unique to the mobile terminal, and the signed network information is used as the VPN of home network A. Send to the terminal node (tunnel server) of.

【0026】

At this time, the mobile terminal must prevent the signature key (obtained by analyzing the signed network information) from being diverted by the access network B. Therefore, the mobile terminal incorporates the number of times information indicating the number of times the home network A is accessed from the outside into the signed statement (that is, the network information), and signs the network information in which the number of times information is incorporated. According to this, since the access network B cannot forge the number-of-times information, it is also impossible to analyze and divert the signature key.

【0027】

Upon receiving the signed network information after the number-of-times information is incorporated, the home network A extracts the number-of-times information (that is, the number-of-times information on the mobile terminal side) from the received contents, and obtains the number-of-times information on the mobile terminal side from the mobile terminal. The access to the home network A is collated with the number-of-times information managed by the home network A (that is, the number-of-times information on the home network side).

【0028】

If the number-of-times information on the mobile terminal side and the number-of-times information on the home network side do not match, the home network A refuses the connection with the mobile terminal, and the process ends. On the other hand, if the mobile terminal side count information and the home network side count information match, the home network A increments the home network side count information (the number indicated by) by 1.

【0029】

The home network A extracts the network information from the network information signed after the number-of-times information is incorporated, and selects an encryption algorithm suitable for the access network B based on the network information. Home network A opens a VPN encryption tunnel based on the selected encryption algorithm. Finally, the mobile terminal increments the mobile terminal side count information (the number indicated by) by 1. This completes the process.

【0030】

According to the above authentication method, even if access to the home network is continued while seamlessly moving between different networks, the required strength and speed encryption algorithm can be appropriately selected.

【0031】

§4. Capture Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within a range that does not deviate from the gist of the present invention. Is also included in this invention.

【0032】

[Effect of the invention]

As described above, according to the present invention, the encryption algorithm can be selected based on the network information about the access network, so that the encryption algorithm having the required security and processing speed is appropriately selected. be able to. In particular, in mobile computing using a wireless LAN, the present invention makes it possible to seamlessly move between different types of networks. In addition, as a system vender, you can enjoy economies of scale because it is not necessary for users to purchase two systems (systems for premises networks and systems for commercial Internets) as explained in the section of "conventional technology". ..

[Simple explanation of drawings]

[Figure 1]

It is a sequence diagram which shows an example of the authentication method by 1st Embodiment of this invention.

[Figure 2]

It is a sequence diagram which shows an example of the authentication method by 2nd Embodiment of this invention.

[Fig. 3]

It is explanatory drawing which shows the outline example of the system which establishes a VPN and performs communication.

[Fig. 4]

It is a sequence diagram which shows an example of the procedure of opening an encrypted tunnel.

[Fig. 5]

It is a chart which shows the relationship between the characteristic (strength / speed) of an encryption algorithm and a network.

[Explanation of symbols]

A ...... Home network B, C ...... Access network