Abstract:
Due to the mobility of mobile node devices including for example a laptop computer used on a work network and also on a home network with different home addresses, a mobile node (MN) home address and HA (home agent) address may need to be dynamically changed when using prefix communication functions and HA address discovery functions so methods for manually setting the IPsec SA security for encryption between the MN and HA are not practical in this environment. The current Mobile IPv6 protocol also has no function allowing recognition of the MN itself.  
     In the present invention may perform the following. Information on whether a prefix is distributable to a MN is held by a CA (certification authority). The server section of the HA allots prefix information to a MN approved by the CA. When the server section of the HA receives an IKE packet from the MN, the server section generates an IPsec SA after checking the prefix information in the server section. The server section allows an MN location registration request to fulfill the IPsec SA. The CA approves distribution of a prefix to the MN and verifies that the MN is genuine by generating an IPsec SA with the HA by utilizing the prefix distributed by the MN.

Description:
PRIORITY CLAIM  
         [0001]    This application claims priority under 35 USC 119 to Japanese patent application P2003-064329 filed Mar. 11, 2003, the entire disclosure of which is hereby incorporated by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a server, mobile control device, and terminal authentication method. The present invention relates in particular to a server, home agent device and terminal authentication method for guaranteeing and issuing public key certifications in communication systems using mobile IP protocol.  
         BACKGROUND OF THE INVENTION  
         [0003]    The IETF (Internet Engineering Task Force) is evaluating specifications for Mobile IPv6 (Ref. Mobility Support in IPv6 &lt;draft-ietf-mobileip-ipv6-19.txt&gt;, Work in Progress).  
           [0004]    The elements comprising the Mobile IPv6 network are a mobile node (MN), a home agent (HA), and correspondent node (CN).  
           [0005]    The MN is assigned an IP address (home address) that does not change even if the MN moves. A link possessing a prefix identical to the home address is called a home link. The HA manages MN location information (binding cache) in locations other than the home link.  
           [0006]    The MN acquires a Care of Address (hereafter CoA) for links other than the home link. The MN that is not within the home link receives router reports (advertisements) sent periodically by a router within the visited link. The MN senses movement by detecting a prefix different from the home address and generates a CoA. The MN registers (stores) information linking the CoA and home address within the HA.  
           [0007]    The MN contains a home agent address discovery function (function for finding the HA address) and may actively search for the IP address of the HA. The MN first of all creates a Mobile IPv6 Home-Agents Anycast Address from the prefix of the home link. The MN sends an ICMP Home Agent Address Discovery Request to the address destination. This signal is received by one of the home link HA. The HA that received the signal sends an ICMP Home Agent Address Discovery Reply containing information on the HA to the MN. The MN extracts the HA information from this signal and acquires the HA address. The MN sends a binding update for that HA address.  
           [0008]    The HA receives the binding update and stores the MN location information in the binding cache.  
           [0009]    In order to function as a proxy for the MN, the HA sends a neighbor advertisement addressed to all-nodes multicast addresses of the home link. The node that received that neighbor advertisement, stores information linking the MN home address and HA link layer address, in the neighbor. cache. The HA captures the packet addressed to the home address of the MN.  
           [0010]    Mobile IPv6 contains a function to notify MN outside the home link, of home network prefix information. For example, if the prefix of the home network has been changed, the HA refers (searches) the binding cache and reports the prefix information (makes a mobile prefix advertisement) to the MN among the registered positions. The MN may also make a request to the HA for prefix information (mobile prefix solicitation).  
           [0011]    The IP Security Protocol (IPsec) is the focus of attention as a technology for achieving security on the IP network. This IPsec is a technology for safely conveying IP packets by utilizing encryption technology and certification technology. Mobile IPv6 is applying this IPsec technology in the sending of location registration signals (binding updates) from the MN to the HA (Ref. draft-ietf-mobileip-mipv6-ha-ipsec-01.txt, Work in Progress).  
           [0012]    This IPsec technology provides a security function by creating an SA (security association) among the devices using IPsec. The devices utilizing IPsec contain a SPD (security policy database) and an SAD (security association database).  
           [0013]    The security policy database (SPD) specifies the method for processing the packets. The security association database (SAD) is a list of SA (security associations) held in the devices using IPsec. The SA is identified by a SPI (Security Parameters Index).  
           [0014]    The method for creating the SA includes a manual setting method and an automatic creation method. The IKE (Internet Key Exchange) is a protocol for automatically creating and managing these SA. The IKE automatically generates the SA by making use of a proposal exchange function, a function to generate a secret key, and a certification function for IKE correspondent nodes.  
           [0015]    Certification methods specified for IKE correspondent nodes are the Pre-shared key authentication method, public key certification method, digital signature authentication method, etc. The digital signature authentication method is highly flexible since it need not share key information beforehand with the other communication party (or correspondent node). The digital signature certification method is used by the CA (Certification Authority) for issuing public key certifications. The format for public key certification is the specified in X. 509.  
           [0016]    The CMP (Certificate Management Protocol) is a protocol for issuing and managing electronic certifications. The CMP is specified in IETF RFC2510. The CMP is utilized in transport protocols in HTTP (HyperText Transfer Protocol) and TCP (Transmission Control Protocol).  
           [0017]    One technology proposed for localized mobility management based on Mobile IPv6 is Hierarchial Mobile IPv6 mobility management (HMIPv6) (Ref. draft-ietf-mobileip-hmipv6-07.txt, Work in Progress). This HMIPv6 contains a MAP (Mobile Anchor Point) between the HA and MN. The MN receives a router advertisement containing MAP options from the AR (Access Router), acquires the MAP IP address, and generates a RCOA (Regional Care of Address) and LCoA (On-link CoA). The MN compatible with HMIPv6 registers location information in the MAP and HA. The MAP manages the binding information of the MN RCoA and LCoA. The HA manages the binding information of the MN home address and RCoA. The MN only rewrites (updates) the MAP location information when the MN has moved within the MAP.  
           [0018]    The IETF is currently evaluating IPv6 Prefix Delegation Options for DHCPv6 (hereafter, DHCP-PD) (draft-ietf-dhc-dhcpv6-opt-prefix-delegation-01.txt, Work in Progress). The DHCP-PD is a function making use of DHCP (Dynamic Host Configuration Protocol) to assign IPv6 prefixes (group) to sites from the address assignment side.  
           [0019]    The elements comprising the DHCP-PD are the delegating router and the requesting router. The requesting router asks the delegating router to assign an IPv6 prefix (group). The delegating router selects an IPv6 prefix (group) and sends that to the requesting router. The DHCP-PD for example, is utilized by the ISP (Internet Service Provider) when assigning prefixes to subscribers.  
           [0020]    In a communication system mutually connected to both a zone A and zone B, when a mobile node (MN) belonging to zone A has moved to zone B, that MN registers its location in the HA of zone A. The location registration signal (binding update signal) is then subjected to IPsec processing.  
           [0021]    The related art has the problem that security cannot be maintained when manually setting the SA (security association) for the HA and MN, and information about the key used in encryption has leaked out. Also, using the Mobile IPv6 prefix report (advertise) function and HA address discovery function will change the home address of the MN or HA address. The method for manually setting the SA between the MN and HA is therefore not practical during system operation. There is also no means for currently verifying on Mobile IP if the MN is genuine.  
         SUMMARY OF THE INVENTION  
         [0022]    The present invention may provide a terminal authentication method that utilizes Mobile IP technology. In particular, this invention may provide a procedure for authenticating terminals by linking a digital signature authentication method with a Mobile IP location registration procedure, and by creating and holding a SA (security association) for a home address linked to the HA issuing public key certifications.  
           [0023]    The present invention may also to provide a system for authenticating genuine terminals by linking a DHCP-PD delegating router and CA, and by linking a DHCP-PD delegating router and HA, when the MN is dynamically acquiring a home address.  
           [0024]    The present invention in particular may have the following features when a terminal x of a home network with an HA belonging to zone A, utilizes a DHCP-PD section in zone B to acquire a home network prefix.  
           [0025]    1) The DHCP-PD delegating router may allot prefix information to a terminal approved by CA.  
           [0026]    2) The HA creates an SA for an IP address possessing a prefix allocated by that delegating router, and approves location registration to satisfy the SA.  
           [0027]    The present invention may also to provide an authentication method for a DHCP delegating router to allot prefix information to terminals approved by the CA, when a communication device belonging to zone B possesses a HMIPv6 compatible MAP, and that communication device receives a binding update from the MN and starts the DHCP-PD section.  
           [0028]    The present invention may also provide a communication method for the HA to report prefix information to a terminal approved by CA.  
           [0029]    More specifically:  
           [0030]    (1) The CA may be comprised of a system for communicating with a DHCP-PD delegating router section  16  as show in FIGS. 2, 20, and  23 . The CA issues a public key certification to the terminal and allows reporting prefix information.  
           [0031]    (2) The terminal is comprised of a Mobile IPv6 function, an IPsec function, and a function to hold information required for a digital signature name. Information required for authenticating a digital signature name may be received from an external storage device. The terminal need not be a mobile terminal.  
           [0032]    (3) The terminal control device contains a delegating router function for a DHCPv6 Prefix delegation option (hereafter, DHCP-PD). The delegating router function is comprised of a system for communicating with CA, and a system for reporting prefix information to a terminal approved by CA.  
           [0033]    (4) The terminal control device inquires about prefix information to the DHCP-PD delegating router function when a request to create an SA is received from the terminal. The terminal control device comprises a system to create an SA among terminals if the terminals utilize prefixes allotted by the delegating router function.  
           [0034]    (5) The terminal control device may contain a storage device or system to hold the public key certification for a terminal. Prefix information may be conveyed to terminals approved by the CA. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0035]    [0035]FIG. 1 is a concept drawing showing the structure of the communication network of the present invention;  
         [0036]    [0036]FIG. 2 is block diagram of the home agent HA1;  
         [0037]    [0037]FIG. 3 is a binding cache management table contained in HA1:  
         [0038]    [0038]FIG. 4 is a prefix control table contained in HA1;  
         [0039]    [0039]FIG. 5 is a flow chart of the prefix delegation processing routine contained in the DHCP-PD section of HA1:  
         [0040]    [0040]FIG. 6 is a flow chart of the IPsec processing routine contained in the IPsec of HA1;  
         [0041]    [0041]FIG. 7 is a block diagram of the certification authority CA 3 ;  
         [0042]    [0042]FIG. 8 is a drawing of a prefix allocation control table contained in CA 3 ;  
         [0043]    [0043]FIG. 9 is a flow chart of the public key certification issue routine contained in A 3 ;  
         [0044]    [0044]FIG. 10 is drawing showing the format of the IPv6 packet;  
         [0045]    [0045]FIG. 11 is a drawing showing an example of a CMP message;  
         [0046]    [0046]FIG. 12 is drawing showing the format of the DHCPv6 packet;  
         [0047]    [0047]FIG. 13 is a drawing showing the format of an ISAKMP packet;  
         [0048]    [0048]FIG. 14 is a drawing showing the format of an ISAKMP packet when confirming an identity of IKE phase  1 ;  
         [0049]    [0049]FIG. 15 is an example of a binding update message;  
         [0050]    [0050]FIG. 16 is an example of a binding acknowledgement message;  
         [0051]    [0051]FIG. 17 is a sequence drawing  1  for location registration (binding update) and authentication in the present invention;  
         [0052]    [0052]FIG. 18 is a sequence drawing  2  for location registration (binding update) and authentication in the present invention;  
         [0053]    [0053]FIG. 19 is a concept drawing showing the structure of the communication network of the second embodiment;  
         [0054]    [0054]FIG. 20 is a block diagram of the communication device  2  of the second embodiment;  
         [0055]    [0055]FIG. 21 is a sequence drawing for location registration (binding update) and authentication in the second embodiment;  
         [0056]    [0056]FIG. 22 is a concept diagram showing the structure of the communication network of the third embodiment;  
         [0057]    [0057]FIG. 23 is a block diagram of the communication device  2  of the third embodiment;  
         [0058]    [0058]FIG. 24 is a sequence drawing for location registration (binding update) and authentication in the third embodiment;  
         [0059]    [0059]FIG. 25 is a sequence drawing  1  for location registration (binding update) and authentication in the fourth embodiment;  
         [0060]    [0060]FIG. 26 is a sequence drawing  2  for location registration (binding update) and authentication in the fourth embodiment; and  
         [0061]    [0061]FIG. 27 is a sequence drawing  3  for location registration (binding update) and authentication in the fourth embodiment.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0062]    The first embodiment of the present invention is described next while referring to the accompanying drawings. In this embodiment, the HA is equivalent to a terminal control device.  
         [0063]    The MN authentication method and location registration method used when the Mobile IPv6 compatible mobile node (MN) is in a network (hereafter, visited network) other than the home link (hereafter, home network) is described in detail.  
         [0064]    [0064]FIG. 1 shows the structure of the communication network of the present invention. The communication network is comprised of a home network  8  for MN 4 , an IP network  7  and a visited network  5  ( 5   a ,  5   b ). In this embodiment, the home network  8 , the IP network  7  and the visited network  5  are IPv6 networks. The MN 4  is a mobile node (MN) compatible with Mobile IPv 6 . The information appliance terminal  9  contains MN functions compatible with Mobile IPv6. The visited network  5  and IP network  7 , and the IP network  7  and home network  8  are connected by router or a gateway device. The visited network  5  and home network  8  may also be directly connected by a router or a gateway device.  
         [0065]    The home network  8  contains a home agent HA1. The HA1 is a home agent (HA) compatible with Mobile IPv6. The HA1 manages MN location information other than in the home network  8 .  
         [0066]    The visited network  5  ( 5   a ,  5   b ) is comprised of a communication device  2  ( 2   a ,  2   b ) and a router  6  ( 6   a ,  6   b ,  6   c ,  6   d ). The communication device  2  is comprised of an interface with a router  6 , and an interface with an IP network  7 . The router  6  contains a device authentication function.  
         [0067]    Instead of the device authentication function, the router  6  may utilize a system for communicating with a server possessing a device authentication function.  
         [0068]    The IP network  7  contains the CA 3 . The home network  8  or the visited network  5  may also contain the CA 3 .  
         [0069]    [0069]FIG. 2 shows the structure of the HA1 installed in the home network  8  of MN 4 . The HA1 is comprised of a server section  11 , ( 11   a ,  11   b ) , a server section  12 , and an interface section (IF)  19  ( 19   a ,  19   b ,  19   m ,  19   n ) containing a line  18  ( 18   a ,  18   b ,  18   m ,  18   n ) and, a switch section  17  ( 17   a ,  17   b )  
         [0070]    The server section  11  mainly contains a packet transmit-receive processor  13 , an IPsec processor  14 , and a mobile IP processor  15 . The packet transmit-receive processor  13  contains a function to transmit or receive data packets. The IPsec processor  14  contains mainly an SPD, SAD and an IPsec processing routine  70 . The IPsec processor  14  authenticates packets and performs encoding. The IPsec processor  14  acquires server section  11  public key certification from the CA 3 . The mobile IP processor  15  contains a Mobile IPv6 for the home agent (HA) function. The mobile IP processor  15  contains a binding cache management table  310 .  
         [0071]    [0071]FIG. 3 shows the table structure of the binding cache management table  310 . The binding cache management table  310  stores at least a Care of Address (CoA)  312  acquired by the MN in the visited network for the MN home address  311 , and a Lifetime  313  showing the effective period of the binding cache.  
         [0072]    The server section  12  contains a packet transmit-receive processor  13  and a DHCP PD section  16 .  
         [0073]    The DHCP PD section  16  contains a DHCP-PD delegating router function. It also contains mainly a prefix control table  320 , a prefix delegation processing routine  60 , and a table linking the IA_PD for identifying the DHCP-PD and an MN identifier.  
         [0074]    [0074]FIG. 4 shows the structure of the prefix control table  320 . This prefix control table  320  in DHCP PD Section  16  stores at least an IAID 322  showing the prefix (group), an allocated prefix  323 , and a lifetime  324  of the prefix, and shows the corresponding relation with the DHCP Client identifier  321 . The DHCP-PD section of the server  12  is mounted in HA1, however a DHCP-PD section may be mounted in a server separate from the HA1.  
         [0075]    [0075]FIG. 7 shows the structure of the certification authority (CA)  3  installed in the IP network  7 . The CA 3  is comprised a CPU 31 , a memory  32 , and an interface section (IF)  33  containing the line  34 , and a bus  35  connecting these components.  
         [0076]    The memory  32  is comprised of at least a prefix allocation control table  330  and, a public key certification issue routine  80 , and a certifying information storage table.  
         [0077]    [0077]FIG. 8 shows the table structure of the prefix allocation control table  330 . The prefix allocation control table  330  stores a Prefix issue OK flag  332  showing whether or not permission to issue a prefix was issued to the identifier (ID)  331  of the terminal.  
         [0078]    The sequence for location registration and authentication of MN 4  in the network  5   b  shown in FIG. 1, is described according to the sequence shown in FIG. 17 and FIG. 18. In this embodiment, the MN 4  contains a system to load the identifier and secret key and public key from a storage device typically a Secure Multimedia Card (SMMC), etc. The MN 4  further contains a DHCP-PD requesting router function.  
         [0079]    When power is turned on, the MN 4  receives ( 101 ) a router advertisement from the router  6   c  belonging to the network  5   b . The MN 4  searches the M bit of the router advertisement and decides on a method for acquiring the CoA (Care of Address). If the M bit is 1, then MN acquires the CoA using the automated structure of the IPv6 statefull address. If the Mbit has not been set, then the Mbit creates a CoA ( 102 ) utilizing the automated structure of the IPv6 stateless address.  
         [0080]    The MN 4  next sends a device authentication request to the router  6   c  ( 103 ). The router  6   c  authenticates the device, using the device ID as a search (or retrieval) key. The router  6   c  sends ( 104 ) a device authentication response including the authentication results to MN 4 . A MAC address for example is utilized as the device ID.  
         [0081]    When device authentication ends correctly, the MN 4  loads the MN 4  identifier and secret key and public key from a storage device such as the SMMC. The MN 4  identifier specifies for example, a FQDN (fully qualified domain name) or a distinguished name of X.500.  
         [0082]    The MN 4  sends a public key certification issue request containing an MN 4  public key and identifier to the CA 3  ( 105 ). A CMP (Certificate Management Protocol) is utilized for sending and receiving the public key certification.  
         [0083]    [0083]FIG. 11 shows a packet format S 1  containing a CMP message.  
         [0084]    [0084]FIG. 10 shows the format of an IPv6 packet.  
         [0085]    The CMP message S 1  is stored in data section  43 B within the payload  43  of the IPv6 packet.  
         [0086]    The CA 3  receives the request and starts the public key certification issue routine  80 .  
         [0087]    [0087]FIG. 9 shows the public key certification issue routine  80 . The CA 3  confirms whether a certification can be issued to MN 4  using the MN 4  identifier ( 81 ). If a certification can be issued then the CA 3  issues a public key certification for MN 4 . The CA 3  next creates a new entry for MN 4  in the prefix allocation control table  330 , and sets up a prefix issue OK flag ( 82 ,  106 ). The CA 3  sends a public key issue request response containing a public key certification for MN 4  and a public key for CN 3 , and ends this routine ( 83 ,  107 ).  
         [0088]    When the certification cannot be issued in step  81 , or in step  82  when the certification cannot be issued for a public key for MN 4 , the CA 3  issues a certification issue request response ( 84 ) to notify the MN 4  of the error and ends this routine.  
         [0089]    The server section  11  of HA1 holds an identifier ,a HA secret key and a HA public key. This procedure is similar to the procedure used by the MN which has its own MN secret and MN public key. The server section  11  acquires the public key certification from the CA 3  (for server section  11 ) ( 183 ).  
         [0090]    After acquiring the MN&#39;s public key certification, the MN 4  starts the prefix request process and acquires a home prefix.  
         [0091]    To find a DHCP server with a prefix that can be allocated, the MN 4  sends a DHCP solicit message to the All_DHCP_Relay_Agents_and_Servers address ( 108 ). This solicit message includes a DHCP client identifier (client identifier option) and IA_PD option. An IAID showing a group (IA_PD) applying a prefix within the MN is set in the IA_PD options.  
         [0092]    [0092]FIG. 12 shows an S 2  packet format containing a DHCPv6 message. The DHCPv6 is an application protocol using UDP/IP in the transport layer. The DHCP message S 2  is stored in the data section  43 B of payload  43  of the IPv6 packet. The DHCP message specifies the value in the message-type field  51 . The option parameter of the DHCP message is set in the Options field  53 .  
         [0093]    Here, the server section  12  for HA1 receives the DHCP solicit message ( 108 ). The server section  12  for HA1 then starts up the prefix delegation processing routine  60 .  
         [0094]    [0094]FIG. 5 shows the prefix delegation processing routine  60 .  
         [0095]    The server section  12  loads the IAID from the IA_PD options of the DHCP solicit message, and decides ( 61 ) if a prefix can be allocated to the IAID. If a prefix can be allocated then the server section  12  designates an IA_PD from the IAID containing that DHCP solicit message. The server section  12  searches the table linking the MN 4  identifier and IA_PD, using the IA_PD as a search (retrieval) key, and decides the MN 4  identifier. The server section  12  sends a request ( 62 ,  109 ) containing MN 4  identifiers to the CA 3 .  
         [0096]    When an inquiry is received, the CA 3  searches the prefix allocation control table  330  using the NN 4  identifier as a search key ( 110 ).  
         [0097]    The CA 3  searches for the MN 4  entry generated in step  106 . The CA 3  confirms that a prefix issue OK flag is set for the applicable entry, and sends a response showing prefix allocation is allowed, to the server  12  ( 63 ,  111 ).  
         [0098]    When a response is received, the server section  12  searches the DHCP client identifier with the IAID contained in that DHCP solicit message, and the prefix control table  320 . When the applicable entry is not present in the prefix control table  320 , the server section  12  generates a new entry in the prefix control table  320 , and stores an IAID 322  and DHCP client identifier  321  that are contained in that DHCP solicit message. The server section  12  then sends a DHCP advertise message to the MN 4  ( 64 ,  112 ). This advertise message contains an identifier for server section  12  (server identifier option), an identifier for MN 4  (client identifier option), and the IA_PD options received in step  108 . The advertise message from the server section  12  may also include IPv6 prefix information for allocation.  
         [0099]    When the server  12  cannot allocate the IPv6 prefix to the IAID instep  61 , or when the CA 3  does not allow allocation of the prefix in step  63 , then the-server  12  sends an advertise message containing a status code option to the MN 4  showing the prefix cannot be allocated and ends this routine ( 67 ).  
         [0100]    When allocation (or distribution) of the prefix is approved, the MN 4  sends a DHCP request message containing IA_PD options to the server section  12  and requests IPv6 prefix information ( 113 ).  
         [0101]    When the advertise message received in step  112  contains an IPv6 prefix message, the request message contains the prefix that the MN 4  needs to use.  
         [0102]    Here, returning to FIG. 5, the description of the prefix delegation processing routine  60  continues.  
         [0103]    When the DHCP request message is received ( 65 ), the server section  12  loads the IAID and specifies the IPv6 prefix for allocation. When the request message contains IPv6 prefix information, then the prefix needed for use by MN 4  is approved.  
         [0104]    The server section  12  next searches the prefix control table  320  with the IAID and DHCP client identifier contained in the DHCP request message. The server section  12  detects and entry generated in step  64 , and stores the IPv6 prefix for distribution and the prefix lifetime in the applicable entries. The server section  12  sends a DHCP reply message containing the prefix information to MN 4  ( 66 ,  114 ), and ends this routine.  
         [0105]    When a prefix for allocation to MN 4  could not be specified in step  65 , or when there was no applicable entry in the prefix control table  320  in step  66 , then the server section  12  sends a DHCP reply message ( 68 ) to MN 4  to report the error and ends this routine.  
         [0106]    The MN 4  extracts IPv6 prefix information from that DHCP reply message. The MN 4  creates a home address from the prefix information and the MN 4  interface identifier.  
         [0107]    The MN 4  next specifies the HA address using the HA (home agent) address discovery function. The MN 4  sends the Home Agent Address Discovery Request ( 116 ) to the Mobile IPv6 Home-Agents Anycast Address set in the home network prefix received in step  114 .  
         [0108]    One of the HAs which process the same prefix as the Mobile IPv6 Home-Agents Anycast Address may receive the Home Agent Address Discovery Request.  
         [0109]    The server section  11   a  of HA1 receives the Home Agent Address Discovery Request. The server section  11   a  sends the Home Agent Address Discovery Reply to the MN 4  ( 117 ).  
         [0110]    The MN 4  receives the Home Agent Address Discovery Reply and acquires the HA address (address of server section  11   a ) ( 118 ).  
         [0111]    The MN 4  next utilizes an IKE to create an IPsec SA for use between the server section  11   a  and MN 4 .  
         [0112]    In IKE phase 1 , an ISAKMP SA is established between the MN 4  and server section  11   a . The ISAKMP SA is a control channel for the IKE. The MN 4  proposes ISAKMP SA parameters ( 121 ) utilizing the SA payload in the server section  11   a.    
         [0113]    [0113]FIG. 13 shows the ISAKMP packet format S 3 . The packet format used by IKE is specified in the ISAKMP protocol. The IKE transport protocol is UDP/IP.  
         [0114]    The ISAKMP packet S 3  is stored in the data section  43 B of payload  43  of the IPv6 packet. The ISAKMP packet S 3  is comprised of an ISAKMP header  55  and one or more payloads  56 . The payload  56  contains for example, an SA payload to transport the proposed SA, an identification payload to exchange the ID information, and a signature payload to send the digital signature, etc.  
         [0115]    The server section  11   a  selects an acceptable proposal from the SA payload received in step  121  and returns it to the MN 4  ( 122 ).  
         [0116]    The MN 4  and server section  11   a  next exchange Diffe-Hellman public values and random numbers obtained per Nonce ( 123 ,  124 ) and generate a secret key.  
         [0117]    The MN 4  and server section  11   a  next exchange ID information for verifying a personal identity. In this embodiment, the signal sent when confirming if the identity attribute is the actual person is defined as the personal identity check signal. FIG. 14 shows the ISAKMP packet format S 4  utilized in checking the personal identity for IKE phase  1 . The ISAKMP packet S 4  contains the identification payload  56 A, signature payload  56 B and the certificate payload  56 C.  
         [0118]    The MN 4  sends ( 125 ) the ISAKMP packet utilized in the personal identity check to the server section  11   a . The identification payload  56 A of this ISAKMP packet  125  includes the home address generated by MN 4  in step  115 . The MN 4  calculates the hash value, executes the digital signature utilizing the MN 4  public key in that hash value, and sets it in the signature payload  56 B. The certificate payload  56 C includes MN 4  public key certification that CA 3  issued.  
         [0119]    The server section  11   a  extracts the MN 4  digital signature from the signature payload  56 B of packet  125 . The server section  11   a  then decodes the digital signature using the MN 4  public key. The MN 4  public key is acquired from the certificate payload  56 C of packet  125 .  
         [0120]    The server section  11   a  confirms the personal identity of the packet sender MN 4  by comparing the hash value calculated from the received packet  125  and the decoded value of that digital signature.  
         [0121]    The server section  11   a  next extracts the MN 4  home address from the identification payload of packet  125 . The server section  11   a  sends an inquiry containing the home prefix to the server section  12  ( 126 ). The server section  12  searches the prefix control table  320  using the prefix contained in that request  126  as a search key. If an applicable entry is present in the prefix control table  320 , then assigning of the prefix is complete ( 127 ). The server section  12  sends a reply to the server section  11   a  notifying that prefix allocation is complete ( 128 ).  
         [0122]    If allocating of the prefix is complete, the server section  11   a  continues the processing of IKE phase  1 . The server section  11   a  executes the digital signature using the public key of server section  11   a  in the hash value. The server section  11   a  sends the ISAKMP packet containing the digital signature to MN 4  ( 129 ). The IP address of server section  11   a  is set in the identification payload of the ISAKMP packet  129 . This ISAKMP packet may be included in the public key certification of server section  11   a . The public key certification of server section  11   a  was issued in step  183 . Alternatively the public key certification of server section  11   a  may be issued in step  181  and  182  of FIG.29, and in this case the step  183  is needless (FIG. 28). The MN 4  receives the packet  129  and confirms if the other party in the IKE communication using the public key of server section  11   a  is genuine. The MN 4  acquires the server section  11   a  public key from the public key certification in packet  129  or acquires it from CA 3 .  
         [0123]    The ISAKMP SA has now been established between MN 4  and the server section  11   a.    
         [0124]    The IPsec SA is next created in IKE phase  2 , for MN 4  and server section  11   a . This IPsec SA is utilized when IPsec processing and forwarding the packets between the MN 4  and server section  11   a . The payload for ISAKMP packets sent and received in IKE phase  2  is encoded using the ISAKMP SA established in IKE phase  1 .  
         [0125]    The MN 4  sends an ISAKMP packet to the server section  111   a . An SA payload containing the IPsec SA proposal, a Nonce payload, and a hash payload were set in this ISAKMP packet ( 130 ). The server section  11   a  then sends to the MN 4 , the ISAKMP packet in which are set the IPsec SA payload containing the accepted IPsec proposal, the Nonce payload, and the hash payload ( 131 ).  
         [0126]    The MN 4  sends the ISAKMP packet containing the hash payload to the server section  11   a  ( 132 ). The server section  11   a  receives this packet ( 132 ) and confirms that MN 4  has received the packet  131 . The above process generates two IPsec SA (the IPsec to the server section  11   a  from MN 4 , and the IPsec SA to the MN 4  from the server section  11   a ). The server section  11   a  and the MN 4  store the IPsec SA (SPI, MN 4  home address, and server section  11   a  address, etc.) in the respective SAD.  
         [0127]    The MN 4  sends a binding update adapted for the SA generated in IKE phase  2  to the server section  11   a  ( 133 ). The MN 4  temporarily stores the address of server section  11   a  in the binding update list control table ( 134 ).  
         [0128]    [0128]FIG. 15 shows the binding update message format S 11  compatible with IPsec. The IPv6 destination options header  401 , IPsec header (AH header or ESP header)  402 , and the IPv6 mobility header  403  are stored in the IPv6 packet extension header  42 .  
         [0129]    The MN 4  stores the following values in the binding update sent to the server section  11   a . The CoA of the MN 4  is set in the source address  41 a of the IPv6 packet header. The home address that the MN 4  generated in step  115  is set in the home address field of the IPv6 Destination Options Header  401 .  
         [0130]    The server section  11   a  receives this binding update  133  and starts the IPsec processing routine.  
         [0131]    [0131]FIG. 6 shows the IPsec processing routine  70 . The IPv6 Destination Options Header  401  is processed first ( 71 ). More specifically, the Destination Options Header value (home address) and the source address value (CoA) are exchanged with each other.  
         [0132]    The server section  11   a  next searches the SAD for the type of IPsec (AH or ESP), SPI value, and destination address, and specifies the IPsec SA. When the received packet has been encoded, the server section  11   a  first decodes the received packet and checks that it matches the specified IPsec SA ( 72 ). The server section  11   a  next searches the SPD, and checks whether the (now) reconstructed packet can be accepted ( 73 ).  
         [0133]    If the packet can be accepted, then the IPsec processor  14  of server section  11   a  sends the reconstructed packet to the mobile IP processor  15 .  
         [0134]    The mobile IP processor  15  registers the MN 4  location (makes a binding update) ( 74 ).  
         [0135]    The mobile IP processor  15  searches the binding cache management table  310  using the MN 4  home address as a search (retrieval) key. If there is no MN 4  entry in that binding cache management table  310 , then an MN 4  entry is added to the binding cache management table  310  ( 135 ). The MN 4  sets the CoA acquired in the visited network  5   b , into the Care of Address  312  entry.  
         [0136]    If the processing in step  72  and step  73  did not end correctly, then the server section  11   a  discards the received packet and ends this routine ( 78 ).  
         [0137]    The mobile IP processor  15  sends the packet to the IPsec processor  14  for sending a binding acknowledgement adapted to IPsec, to the MN 4 . The IPsec processor  14  searches the SPD and investigates the packet security policy ( 75 ). When found that the packet is usable with IPsec, a matching SA is detected from the SAD. The IPsec processor  14  adds a routing header  404  to this packet and applies IPsec ( 76 ). The server section  11   a  next interchanges the routing header value and the destination address value. The server section  11  sends a binding acknowledgement subjected to IPsec processing, to MN 4  ( 77 ,  136 ) and then ends this routine.  
         [0138]    [0138]FIG. 16 shows the format S 12  of a binding acknowledgement message subjected to IPsec. The IPv6 routing header  404 , the IPsec header (AH Header or ESP header)  402 , and the IPv6 mobility header  403  are stored in the IPv6 packet extension header  42 . The server section  11   a  stores the following values in the binding acknowledgment sent to the MN 4 . The CoA of MN 4  is stored in the destination address  41 b of the IPv6 packet header. The MN 4  home address is stored in the home address field of the IPv6 routing header  404 .  
         [0139]    When the binding acknowledgement is received, the MN 4  searches the SAD and specifies an SA. When the received packet has been encoded, the received packet is checked after decoding, to find if it matches the SA. The SPD is also searched and a check made to determine if the reconstructed packet can be accepted. If acceptable, the MN 4  registers the entry temporarily stored in step  134 , into the binding update list control table ( 137 ).  
         [0140]    Here, the MN 4  may register the identification information (for example FQDN) and information matching the home address acquired in step  115 , into the home network  8 , the visited network  5 , or the location information control device (for example a DNS server device) belonging to the IP network  7 .  
         [0141]    The information appliance terminal  9  is comprised of a Mobile IPv6 function and a DHCP-PD requesting router function. An authentication method can be used with the information appliance terminal  9  if a public key certification is acquired from the CA 3 .  
         [0142]    The first embodiment of the present invention can therefore provide an authentication method for verifying the authenticity of the IPv6 terminal, by linking a digital signature authentication method with a Mobile IP location registration (binding update) procedure, and by the HA creating and holding an SA for the home address linked to the public key certification.  
         [0143]    The MN 4  and HA1 server section  11  hold a public key certification issued by the CA 3 . The HA1 server section  12  and the MN 4  contain a DHCP-PD section. By linking the CA 3  and the HA1 server section  12 , the HA1 can give a prefix notification to the MN 4  to whom prefix allocation was approved by CA 3 . The HA1 server section  11  can further provide an authentication method for verifying the MN is genuine by generating an IPsec SA among the MN 4  home prefix for the prefix that has been allocated by the server section  12  already.  
       Second Embodiment  
       [0144]    The second embodiment of the present invention is described next while referring to the accompanying drawings.  
         [0145]    [0145]FIG. 19 shows the structure of the communication network of the second embodiment of the present invention. The second embodiment is characterized in that the communication device  2  contains a DHCP-PD requesting router function. In the example of the second embodiment, the IP network  7  contains an authentication server  10 . The authentication server  10  controls information (ID, passwords, etc,) required for authorizing access to the home network.  
         [0146]    [0146]FIG. 20 shows the structure of the communication device  2  of the second embodiment of the present invention. The communication device  2  is comprised of a CPU 21 , a memory  22 , and an interface section (IF)  23  ( 23   a ,  23   b ) containing a line  24  ( 24   a ,  24   b ), and a bus  25  connecting these components.  
         [0147]    The memory  22  is comprised mainly of a DHCP-PD section  26  containing a DHCP-PD requesting router function, and an authentication processor  27  for authorizing access to the home network  8 .  
         [0148]    [0148]FIG. 21 shows the sequence for location registration (binding update) and authentication of MN 4  in the second embodiment of the present invention.  
         [0149]    The first embodiment and the second embodiment differ in the installation locations for the DHCP-PD requesting router function. The communication device  2  (GW 2 ) of the second embodiment contains a DHCP-PD requesting router function, and sends and receives DHCP-PD messages.  
         [0150]    The process from step  101  to step  107  is the same as the first embodiment.  
         [0151]    Hereafter, the process from step  141  onwards is described.  
         [0152]    When a packet is received from the MN 4 , the GW 2  requests that the MN 4  send authentication information ( 141 ). The MN 4  sends an authentication request containing an ID and password ( 142 ). The GW 2   b  sends a DHCP solicit containing an IAID ( 143 ).  
         [0153]    The server section  12  receives that DHCP solicit and specifies an IA_PD from the IAID. The server section  12  searches the table of corresponding MN 4  identifiers and IA_PD using the IA_PD as a search (retrieval) key, and decides on an MN 4  identifier.  
         [0154]    The process from step  144  to step  146  is the same as steps  109  to step  111  in the first embodiment.  
         [0155]    When the reply  146  is received, the server section  12  sends a DHCP Advertise (notification) to the GW 2   b  ( 147 ). Hereafter, the processing from step  148  to step  149  for the server section  12  is the same as in the first embodiment.  
         [0156]    When the DHCP reply  149  containing the prefix information is received, the GW 2   b  sends an authentication reply containing prefix information to the MN 4  ( 150 ). Hereafter, the MN authentication processing and the location registration (binding update) processing is the same as from step  115  to step  137  in the first embodiment.  
         [0157]    The second embodiment of the present invention can therefore provide an authentication method for verifying the authenticity of IPv6 terminals not containing a DHCP-PD section, by linking a digital signature authentication method with a mobile IP location registration (binding update) procedure, even in cases where the communication device  2  is equipped with a DHCP-PD requesting router function.  
         [0158]    The second embodiment can also provide a highly safe communication service by providing a function for authorizing access to HA from the communication device  2 .  
       Third Embodiment  
       [0159]    The third embodiment of the present invention is described next while referring to the accompanying drawings.  
         [0160]    [0160]FIG. 22 shows the structure of the communication network of the third embodiment of the present invention. In addition to the functions of the second embodiment, the third embodiment is characterized by possessing HMIPv6 MAP functions. In the third embodiment, the MN 4  is a mobile terminal compatible with HMIPv6.  
         [0161]    [0161]FIG. 23 shows the structure of the communication device  2  of the third embodiment. The memory  22  of the communication device  2  contains an HMIPv6 processor  29  in addition to the functions shown in the second embodiment. The HMIPv6 processor  29  provides the HMIPv6 compatible MAP functions. The HMIPv6 processor  29  contains a binding cache management table for holding information linking the RCoA and LCoA.  
         [0162]    The sequence for location registration (binding update) and authorization for MN 4  in the network  5  shown in FIG. 22 are described according to the sequence shown in FIG. 24.  
         [0163]    The MN 4  receives a router notification (router advertisement) containing MAP options from the router (AR: Access Router)  6   c  belonging to the network  5   b  ( 161 ). The MN 4  specifies the communication device (hereafter MAP) using the router advertisement information  161  and generates an RCoA and LCoA ( 162 ).  
         [0164]    The process from step  103  to step  107  is the same as in the first embodiment.  
         [0165]    When the MN 4  receives the public key certification from the CA 3 , it sends a binding update (location registration signal) to the MAP 2   b  ( 163 ).  
         [0166]    In the third embodiment, the MAP 2   b  utilizes the receiving of the binding update (location registration signal) to initiate authentication processing. The process hereafter from step  141  to step  150  is the same as the second embodiment.  
         [0167]    When the processing up to step  150  ends correctly, the MAP 2   b  stores information linking the RCoA and LCoA of MN 4 , into the binding cache management table of the HMIPv6 processor  29 . The MAP 2   b  sends the binding acknowledgement to the MN 4  ( 164 ).  
         [0168]    The MN authorization process and location registration (binding update) process hereafter are the same as from step  115  to step  137  of the first embodiment. The third embodiment of the present invention can therefore provide an authentication method for verifying the authenticity of IPv6 terminals not containing a DHCP-PD section, by linking a digital signature authentication method with a mobile IP location registration (binding update) procedure, even in cases where the communication device  2  is equipped with a HMIPv6 function.  
         [0169]    The third embodiment can also provide a communication service with higher safety by the communication device initiating the access authentication processing for the home network when the HMIPv6 control signal is received.  
       Fourth Embodiment  
       [0170]    The fourth embodiment of the present invention is described next while referring to the accompanying drawings. The structure of the communication network in the fourth embodiment is the same as in the first embodiment.  
         [0171]    The fourth embodiment is characterized in that the server section  11  of the HA1 comprises a system to allocate the prefix to MN approved by the CA 3 , and in containing a MN 4  public key certification control table. Information on the identification payload contained in the ISAKMP packet of IPsec phase  1  and information linked to the public key certifications are stored in the public key certification control table.  
         [0172]    In the fourth embodiment, the HA1 and the MN need not contain a DHCP-PD section. The HA of the MN 4  is the server section  11   a.    
         [0173]    After the MN 4  in the network  5   b  shown in FIG. 1, has completed location registration (binding update) in the server section  11   a , the sequence from the HA1 server section  11   a  notifying the MN 4  of the prefix, to the MN 4  once again completing location registration (binding update) is described while following the sequence shown from FIG. 25 through FIG. 27.  
         [0174]    The sequence from step  101  to step  107  is the same as in the first embodiment.  
         [0175]    The MN 4  next creates an IPsec SA in the server section  11   a.    
         [0176]    The sequence from step  121  through step  125  is the same as in the first embodiment. The MN 4  sends to the server section  11   a , an ISAKMP packet  125  containing an identification payload set with the M 4  home address, and with a certificate payload set with the MN 4  public key certification.  
         [0177]    The server section  11   a  loads the certificate payload and identification payload information from the packet  125 , and adds the MN 4  entry to the public key certification control table ( 171 ). If an MN 4  entry is already present, then the applicable entry is rewritten (updated).  
         [0178]    The sequence from step  129  to step  132  is the same as in the first embodiment.  
         [0179]    The MN 4  carries out location registration (binding update) utilizing an IPsec SA generated by MN 4  and the server section  11   a . The location registration (binding update) is the same as the first embodiment (from step  133  to  137 ).  
         [0180]    When the server section  11   a  is for example changing its own prefix, the MN 4  current performing the binding update is notified of the prefix by the server section  11   a.    
         [0181]    The server section  11   a  first searches the binding cache management table  310  and then detects the MN 4  entry generated in step  135 . The server section  11   a  next searches the public key certification control table using the MN 4  home address as a search (retrieval) key and loads the MN 4  public key certification made in step  171 .  
         [0182]    The server section  11   a  specifies the MN 4  identifier from the public key certification, and sends an inquiry along with this MN 4  identifier to the CA 3  ( 172 ,  173 ).  
         [0183]    When this inquiry is received, the CA 3  searches the prefix allocation control table  330  using the MN 4  identifier as a search (retrieval) key.  
         [0184]    The CA 3  detects the MN 4  entry created in step  106 . The CA 3  confirms that an applicable entry is set in the prefix issue OK flag ( 174 ). The CA 3  sends a reply to the server section  11   a  showing a prefix can be allocated ( 175 ).  
         [0185]    When the reply is received, the server section  11   a  sends a mobile prefix advertisement to report the prefix information to the MN 4  ( 176 ). The server section  11   a  applies the IPsec SA generated in steps  130  to  132 , in the mobile prefix advertisement message.  
         [0186]    The MN 4  loads the prefix from the mobile prefix advertisement. The MN 4  detects changes in the home prefix, and generates a home address. The process from creating the home address to completion of location registration (binding update) is the same as step  115  through  125  in the first embodiment (step  129  through step  137 ).  
         [0187]    The fourth embodiment of the present invention is therefore capable of notifying the MN 4  of the prefix information, by linking HA1 and CA 3  after confirming the MN is genuine.  
         [0188]    As clearly shown by the above embodiments, the present invention provides an authentication method for verifying that the IPv6 terminal is genuine by linking a digital signature authentication method with a Mobile IP location registration (binding update) procedure.  
         [0189]    In particular, an authentication method can be provided for verifying the terminal x is genuine when performing Mobile IP binding updates (location registration) with a terminal x an HA belonging to zone A as a home network in zone B, with the method comprising a system for a DHCP-PD delegating router function belonging to zone A to distribute a prefix to the terminal X belonging to zone B; and further comprising: 1) a system for inquiring whether a DHCP-PD delegating router function can allocate a prefix to CA, 2) a system for inquiring whether the HA contains prefix information in the DHCP-PD delegating router function, 3) a system for acquiring a terminal x public key from CA or terminal x when the HA is creating IPsec SA with the terminal x, 4) a system for the HA to approve only location registration (binding update) subjected to the IPsec generated above in 3).  
         [0190]    The above described authentication method for verifying a terminal x not comprising a DHCP-PD section, can be provided if a communication device mutually connected to both zone A and zone B contains a DHCP-PD requesting router function and a function authorizing zone A access. Further, a communication service with a high degree of safety can be provided since the communication device allows only authenticated terminals x to have access to the HA.  
         [0191]    Also, if the communication device mutually connected to both zone A and zone B contains a MAP function for HMIPv6, then the communication device can use the HMIPv6 control signal as a trigger to initiate access authorization processing for zone A.  
         [0192]    Further, if the HA1 contains a system for communicating with CA 3  and a system for holding MN 4  public key certification, then prefix information can be reported to the MN 4 , after the HA1 verifies the MN 4  is authentic and reports this to CA 3 .