Abstract:
The present invention relates to a security access control method and system for wired local area network, the method includes the following steps: 1) a requester (REQ) negotiates the security policy with an authentication access controller (AAC); 2) the requester (REQ) and the authentication access controller (AAC) authenticate the identity; 3) the requester (REQ) negotiates the key with the authentication access controller (AAC). The direct identity authentication between the user and the network access control device is realized by the present invention; the negotiation and the dynamic update of the session key for the link layer data protection are realized; a variety of network architectures such as the enterprise network, the telecommunication network are supported; the scalability is good, the multiple authentication methods are supported; the authentication protocols with different security levels are supported, the requirements of the various subscribers are satisfied; the sub-modules of the protocol are independent, flexible, and easy to be accepted or rejected.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application of PCT/CN2009/075895 filed on Dec. 23, 2009, which claims the benefit of Chinese patent application No. 200910023628.2 titled “SECURITY ACCESS CONTROL METHOD FOR WIRED LOCAL AREA NETWORK AND SYSTEM THEREOF” and filed with the State Intellectual Property Office on Aug. 19, 2009. Both the international application and the Chinese application are incorporated herein by reference in their entireties. 
     FIELD OF THE INVENTION 
     The present invention relates to a security access control method for a wired local area network and a system thereof, and in particular to a Tri-element Peer Authentication (TePA) based security access control method for accessing a wired Local Area Network (LAN), also known as Tri-element LAN Access Control (TLAC), and a system thereof. 
     BACKGROUND OF THE INVENTION 
     TePA is a technological idea and framework for peer authentication between a terminal and a network originally developed by China. This technology defines a tri-element entity authentication architecture, which realizes mutual authentication between a user and a network based on a peer authentication idea. 
     Currently, in a wired local area network, IEEE uses security-enhanced IEEE 802.3 to realize the security of the link layer, including the typical security access protocol IEEE 802.1x and IEEE 802.1x authentication based key management protocols. The basic method of IEEE 802.1x authentication includes an additional authentication server to the terminal and the access point device, and the access point device using the authentication server to authenticate the identity of the terminal, thereby realizing security access control of the terminal. The access point device forwards directly authentication information between the terminal and the authentication server, without participating in the identity authentication process as an independent entity. This method can only achieve validity authentication of the identity of the terminal by the network, but cannot meet the requirement of validity authentication of the identity of the access network by the terminal, thereby failing to realize mutual authentication between the terminal and the network. The terminal cannot verify the identity of the access point device, and even if security vulnerabilities are remedied by such measures as adding security patches to this type of security architecture subsequently, security problems such as man-in-the-middle attacks and the terminal accessing an invalid network cannot be avoided. This type of security access protocol is still in use, and presents a serious obstacle to the development of the industry. 
     SUMMARY OF THE INVENTION 
     In order to solve the above technical problems in the background of the invention, it is provided according to the present invention a security access control method for a wired local area network and a system thereof, which can realize mutual (unilateral) authentication between a user and a network and also realize key negotiation for the secret communication between a terminal and a network device. 
     The technical solution of the present invention includes a security access control method for a wired local area network, characterized in that the method includes the following steps: 
     step 1, performing security policy negotiation between a requester (REQ) and an authentication access controller (AAC); and 
     step 2, performing identity authentication between the REQ and the AAC. 
     The method may further include: 
     step 3, performing key negotiation between the REQ and the AAC. 
     Specifically, step 1 may include: 
     step 11, security policy negotiation requesting: 
     when the REQ accesses the AAC, the AAC sends a security policy negotiation request message to the REQ, the security policy negotiation request message including TIE AAC , 
     wherein, 
     the TIE AAC  field indicates an information element of tri-element peer authentication (TePA) supported by the AAC, including an authentication and key management suite and a cryptography suite supported by the AAC; 
     step 12, security policy negotiation responding: 
     on receipt of the security policy negotiation request message, the REQ performs the following: 
     selecting an authentication and key management suite and a cryptography suite that are commonly owned by the REQ and the AAC according to the authentication and key management suite and the cryptography suite supported by the AAC indicated by the TIE AAC  field in the security policy negotiation request message in conjunction with a local policy, and forming a security policy negotiation response message and sending it to the AAC; discarding the security policy negotiation request message according to a local policy if the REQ does not support any of the authentication and key management suite and the cryptography suite supported by the AAC in the security policy negotiation request message, 
     the security policy negotiation response message including TIE REQ , 
     wherein, 
     the TIE REQ  field indicates a TePA information element selected by the REQ, including the authentication and key management suite and the cryptography suite selected by the REQ; 
     step 13, on receipt of the security policy negotiation response message, the AAC performs the following: 
     step 131, determining whether the AAC supports the authentication and key management suite and the cryptography suite selected by the REQ; if not, discarding the security policy negotiation response message, and if so, go to step 132; 
     step 132, starting a corresponding identity authentication process according to the authentication and key management suite selected by the REQ. 
     In step 13, if the authentication and key management suite selected by the REQ is a certificate-based authentication and key management suite, the identify authentication process may use a certificate-based authentication protocol Triple-element Authentication Extensible Protocol Certificate-based 1 An Authentication Protocol (TAEP-CAAP). 
     Specifically, step 2 may include: 
     step 21, authentication activation: 
     the AAC sends an authentication activation message to the REQ to activate the REQ to perform certificate authentication, the authentication activation message including SNonce, IDA AS-AAC , Cert AAC , Para ECDH , TIE AAC  and SIG AAC ; 
     wherein, 
     the SNonce field indicates an authentication identifier, and is a random number generated by the AAC if the identify authentication process is performed for the first time; or an authentication identifier value generated from negotiation during the last identify authentication process if the current identify authentication process is an updating process; 
     the ID AS-AAC  field indicates an identity ID of an authentication server (AS) trusted by the AAC, which is an ID of the AS who issued a certificate of the AAC (Cert AAC ); 
     the Cert AAC  field indicates the certificate of the AAC; 
     the Para ECDH  field indicates an elliptic curve cryptography parameter of an elliptic curve cryptography mechanism, which is an elliptic curve cryptography parameter used during calculation of Elliptic Curve Diffie-Hellman (ECDH) by the REQ and the AAC; 
     the TIE AAC  field indicates an authentication and key management suite and a cryptography suite supported by the AAC, and has a value the same as the value of the TIE AAC  field in the security policy negotiation request message; 
     the SIG AAC  field indicates a signature by the AAC, which is a signature signed by the AAC using a private key on all the other fields except the SIG AAC  field in the authentication activation message; the SIG AAC  field is an optional field; 
     step 22, access authentication request: 
     on receipt of the authentication activation message, the REQ performs the following: 
     step 221, if the current identity authentication process is an updating process, the REQ checks whether the authentication identifier field value in the authentication activation message is in accordance with the authentication identifier saved during the last identity authentication process, if not, discards the authentication activation message, otherwise, go to step 222; if the current identity authentication process is not an updating process but an identity authentication process for the first time, go to step 222 directly; 
     step 222, the REQ verifies whether the TIE AAC  field value is in accordance with the TIE AAC  field value in the security policy negotiation request message received during the security policy negotiation; if not, discards the authentication activation message, if so, go to step 223; 
     step 223, if the SIG AAC  field is included in the received authentication activation message, the REQ verifies correctness of the SIG AAC  field; if the SIG AAC  field is incorrect, discards the received authentication activation message, if the SIG AAC  field is correct, go to step 224; if no SIG AAC  field is included in the received authentication activation message, go directly to step 224; 
     step 224, the REQ selects a certificate of the REQ issued by the AS (Cert REQ ) according to the ID AS-AAC  field in the authentication activation message or selects a certificate of the REQ (Cert REQ ) according to a local policy; generates REQ key data x·P and a REQ challenge (N REQ ) for ECDH exchange; generates an access authentication request message and sends it to the AAC, the access authentication request message including SNonce, N REQ , x·P, ID AAC , Cert REQ , Para ECDH , List AS-REQ , TIE REQ  and Sig REQ ; 
     wherein, 
     the SNonce field indicates an authentication identifier and has a value the same as the value of the SNonce field in the authentication activation message; if the identify authentication process is performed for the first time, the value of the SNonce field is determined directly by the value of the SNonce field in the authentication activation message; if the current identify authentication process is an updating process, the value of the SNonce field is the authentication identifier value calculated during the last identity authentication process; 
     the N REQ  field indicates a REQ challenge, which is a random number generated by the REQ; 
     the x·P field indicates key data of the REQ, which is a temporary public key generated by the REQ for ECDH exchange; 
     the ID AAC  field indicates an identity ID of the AAC, and is obtained according to the Cert AAC  field in the authentication activation message; 
     the Cert REQ  field indicates a certificate of the REQ; 
     the Para ECDH  field indicates an ECDH parameter, which is an elliptic curve cryptography parameter used during ECDH calculation by the REQ and the AAC; and has a value the same as the value of the Para ECDH  field in the authentication activation message; 
     the List AS-REQ  field indicates a list of ASs trusted by the REQ, not including an issuer of the certificate of the REQ (Cert REQ ); the AAC is notified of by the REQ using the List AS-REQ  field when the REQ trusts an entity other than the issuer of its certificate; the List AS-REQ  field is an optional field; 
     the TIE REQ  field indicates an authentication and key management suite and a cryptography suite selected by the REQ, and has a value the same as the value of the TIE REQ  field in the security policy negotiation response message; 
     the Sig REQ  field indicates a signature by the REQ, which is a signature signed by the REQ using a private key on all the other fields except the Sig REQ  field in the access authentication request message; 
     step 23, certificate authentication requesting: 
     on receipt of the access authentication request message, the AAC performs the following: 
     step 231, if the AAC has sent the authentication activation message, the AAC checks whether the SNonce field value and the Para ECDH  field value in the received access authentication request message are in accordance with the corresponding field values in the authentication activation message, if any of the SNonce field value and the Para ECDH  field value is not, discards the access authentication request message, otherwise, got to step 232; if the AAC has not sent the authentication activation message, the AAC checks whether the SNonce field value is in accordance with the authentication identifier calculated during the last certificate authentication process and whether the Para ECDH  field is in accordance with the Para ECDH  field in the last authentication activation message, if any of the SNonce field value and the Para ECDH  field is not, discards the access authentication request message, otherwise, go to step 232; 
     step 232, the AAC checks whether the ID AAC  is in accordance with the identity of the AAC itself and whether the TIE REQ  field value is in accordance with the TIE REQ  field value in the security policy negotiation response message received during the security policy negotiation; if any of the ID AAC  and the TIE REQ  field value is not, discards the access authentication request message; otherwise, go to step 233; 
     step 233, the AAC verifies correctness of the Sig REQ  field; if the Sig REQ  field is incorrect, discards the access authentication request message; otherwise, go to step 234; 
     step 234, if it is required according to a local policy of the AAC to use the AS to authenticate the certificate of the REQ (Cert REQ ), the AAC generates a certificate authentication request message and sends it to the AS; otherwise, go to step 235; 
     step 235, the AAC authenticates the certificate of the REQ (Cert REQ ) locally, which includes validating a verification result of the certificate of the REQ (Cert REQ ) according to a verification result of the certificate of the REQ (Cert REQ ) cached locally and timeliness defined by a local policy; if the verification result of the Cert REQ  is valid, generates locally key data and an AAC challenge (N AAC ) for ECDH exchange, the key data including a temporary public key y·P of the AAC, performs ECDH calculation according to the temporary public key x·P of the REQ and a temporary private key y of the AAC to obtain a base key (BK) and an authentication identifier for the next identity authentication process and store them, sets an access result to be successful, forms an access authentication response message and sends it to the REQ, and permits a user to access the network; if the verification result of the Cert REQ  is invalid, the AAC sets the access result to be unsuccessful and the AAC challenge (N AAC ) and the key data y·P to be any values, forms an access authentication response message and sends it to the REQ, and removes association with the REQ, 
     the certificate authentication request message includes: N AAC , N REQ , Cert REQ , Cert AAC  and List AS-REQ ; 
     wherein, 
     the N AAC  field indicates an AAC challenge, which is a random number generated by the AAC; 
     the N REQ  field indicates REQ challenge, which is a random number generated by the REQ, and has a value the same as the value of the N REQ  field in the access authentication request message sent by the REQ; 
     the Cert REQ  field indicates a certificate of the REQ and has a value the same as the value of the Cert REQ  field in the access authentication request message; 
     the Cert AAC  field indicates a certificate of the AAC and has a value the same as the value of the Cert AAC  field in the authentication activation message; 
     the List AS-REQ  field indicates a list of ASs trusted by the REQ and has a value the same as the value of the List AS-REQ  field in the access authentication request message sent by the REQ; the List AS-REQ  field is an optional field; 
     step 24, certificate authentication responding: 
     on receipt of the certificate authentication request message, the AS performs the following: 
     step 241, in the case of unilateral authentication, the AS verifies the certificate of the REQ (Cert REQ ); in the case of mutual authentication, the AS verifies both the certificate of the AAC (Cert AAC ) and the certificate of the REQ (Cert REQ ), the verification of the certificates are performed with reference to RFC3280, and if the verification cannot be performed, the AS sets a verification result of a corresponding certificate to be issuer of the certificate undefined, otherwise, the AS verifies the certificate and performs step 242; 
     step 242, the AS forms a certificate authentication response message according to the verification result of the certificate; adds a corresponding signature and sends the certificate authentication response message to the AAC, the certificate authentication response message including RES Cert , SIG AS-REQ  and SIG AS-AAC , 
     wherein 
     the RES Cert  field indicates the verification result of the certificate and includes an AAC challenge value (N AAC ), a REQ challenge value (N REQ ), the verification result of the Cert AAC  and the verification result of the Cert REQ ; in case of unilateral verification, the RES Cert  field does not include the verification result of the certificate of the AAC (Cert AAC ); 
     the SIG AS-REQ  field indicates a signature signed by the AS trusted by the REQ on the verification result of the certificate (RES Cert ) in the certificate authentication response message; 
     the SIG AS-AAC  field indicates a signature signed by the AS trusted by the AAC on all the other fields in the certificate authentication response message except the SIG AS-AAC  field; the SIG AS-AAC  field is an optional field, and is omitted if the AS who signed the verification result of the certificate is the same as the AS trusted by the AAC; 
     step 25. access authentication responding: 
     on receipt of the certificate authentication response message, the AAC performs the following: 
     step 251, the AAC checks whether the AAC challenge (N AAC ) field value in the RES Cert  field is the same as the N AAC  field value in the certificate authentication request message; if not, discards the certificate authentication response message, if so, go to step 252; 
     step 252, if two signature fields are included in the certificate authentication response message, the AAC checks whether the SIG AS-AAC  field is correct, if not, discards the certificate authentication response message, if so, go to step 253; if only one signature field is included in the certificate authentication response message, which indicates that the AS trusted by the REQ is also the AS trusted by the AAC, the AAC checks whether the SIG AS-REQ  field is correct, if not, discards the certificate authentication response message, if so, go to step 253; 
     step 253, the AAC checks whether the verification result of the Cert REQ  in the RES Cert  field is valid; if so, generates locally key data y·P and an AAC challenge (N AAC ) for ECDH exchange, performing ECDH calculation according to the temporary public key x·P of the REQ and a temporary private key y of the AAC to obtain a base key (BK) and an authentication identifier for the next identity authentication process and store them, sets an access result to be successful, forms an access authentication response message and sends it to the REQ, and permits a user to access the network; if the verification result of the Cert REQ  is invalid, the AAC sets the access result to be unsuccessful, the AAC challenge (N AAC ) and the private data y·P to be any value, forms an access authentication response message and sends it to the REQ, and remove association with the REQ, the access authentication response message including N REQ , N AAC , Acc RES , x·P, y·P, ID AAC , ID REQ , MRES Cert  and SIG AAC  or MIC1, 
     wherein, 
     the N REQ  field indicates a REQ challenge, which is a random number generated by the REQ; the N REQ  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; and if the N REQ  field exists, it has a value the same as the value of the N REQ  field in the access authentication request message sent by the REQ; 
     the N AAC  field indicates an AAC challenge, which is a random number generated by the AAC; the N AAC  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; and if the N AAC  field exists, it has a value the value of the N AAC  field in the access authentication request message sent by the AAC; 
     the Acc RES  field indicates an access result, which is access success or access failure and a reason of the failure set by the AAC according to the authentication result; 
     the x·P field indicates key data of the REQ, which is a temporary public key generated by the REQ for ECDH exchange; the x·P field has a value the same as the value of the x·P field in the access authentication request message sent by the REQ; 
     the y·P field indicates key data of the AAC, which is a temporary public key generated by the AAC for ECDH exchange; 
     the ID AAC  field indicates an identity ID of the AAC and is obtained according to the Cert AAC  field; 
     the ID REQ  field indicates an identity ID of the REQ and is obtained according to the Cert REQ  field in the received access authentication request message; 
     the MRES Cert  field indicates a combined certificate verification result; the MRES Cert  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; if the MRES Cert  field exists, it includes the fields in the certificate authentication response message and the same values; 
     the SIG AAC  field indicates a signature of the AAC, which is a signature signed by the AAC using a private key of the AAC on all the other fields except the SIG AAC  field in the access authentication response message; 
     the MIC1 field indicates a message authentication code, which is a hash value of all the other fields except the MIC1 field in the access authentication response message and an authentication identifier for the next certificate authentication process calculated by the AAC using the BK generated from negotiation during the authentication; 
     the access authentication response message includes one or more of the SIG AAC  field and the MIC1 field; if the authentication activation message exists in the current identity authentication process and if the access authentication activation message includes the SIG AAC  field, the authentication response message includes only the MIC1 field; if no authentication activation message exists in the current identity authentication or if the authentication activation message does not include a SIG AAC  field, the access authentication response message includes only the SIG AAC  field; 
     step 26, access authentication confirmation: 
     on receipt of the access authentication response message, the REQ performs the following: 
     step 261, the REQ determines whether the received access authentication response message corresponds to the current access authentication request message according to the ID AAC  field and the ID REQ  field in the access authentication response message; if not, discards the received access authentication response message; if so, go to step 262; 
     step 262, the REQ determines whether the REQ key data field x·P value in the access authentication response message is in accordance with the x·P field value in the access authentication request message sent by the REQ itself; if not, discards the access authentication response message, otherwise, go to step 263; 
     step 263, in the case of unilateral authentication, the REQ determines whether the N REQ  field value is in accordance with the N REQ  field value in the access authentication request message sent previously; if not, discards the access authentication response message, otherwise, go to step 264; in the case of mutual authentication, go directly to step 264; 
     step 264, the REQ checks the Acc RES  field in the access authentication response message; if the access result is unsuccessful, removes association with the AAC, otherwise, go to step 265; 
     step 265, if the received access authentication response message includes the SIG AAC  field, the REQ verifies correctness of the SIG AAC  field, if the SIG AAC  is incorrect, discards the access authentication response message, otherwise, go to step 266; if the received access authentication response message includes the MIC1 field, the REQ verifies correctness of the MIC1 field, if the MIC1 field is incorrect, discards the access authentication response message, otherwise, go to step 266; 
     step 266, in the case of unilateral authentication, go to step 268; otherwise, the REQ verifies whether the N REQ  field value included in the MRES Cert  field is in accordance with the N REQ  field value in the access authentication request message sent by the REQ itself, if not, discards the access authentication response message, if so, verifies whether the SIG AS-REQ  is correct, if not, discards the access authentication response message, if so, go to step 267; 
     step 267, the REQ verifies whether the AAC certificate verification result in the MRES Cert  field is valid; if not, it is determined that the network is invalid and should not be accessed, otherwise, it is determined that the network is valid and can be accessed, and go to step 268; 
     step 268, the REQ performs ECDH calculation according to the temporary public key y·P of the AAC and the temporary private key x of the REQ to obtain a BK and an authentication identifier for the next certificate authentication process, and stores the BK and the authentication identifier; 
     step 269, if the received access authentication response message includes the SIG AAC  field, sending an access authentication confirmation message is optional; if the received access authentication response message includes the MIC1 field, the REQ forms an access authentication confirmation message and sends it to the AAC, the access authentication confirmation message including MIC2, 
     wherein, 
     the MIC2 field indicates a message authentication code, which is a hash value of the AAC challenge value (N AAC ), the REQ challenge value (N REQ ) and an authentication identifier for the next certificate authentication process calculated by the REQ using the BK generated from negotiation during the authentication. 
     In step 26, if the SIG AAC  field is included in the access authentication response message sent by the AAC, the AAC may wait to receive the access authentication confirmation message after sending the access authentication response message to the REQ. 
     In step 26, on receipt of the access authentication confirmation message sent by the REQ, the AAC may verify correctness of the MIC2 field in the access authentication confirmation message, if the MIC2 field is correct, then the REQ has a BK in accordance with the AAC; if the MIC2 field is incorrect, the AAC discards the access authentication response message. 
     In step 3, the key negotiation between the REQ and the AAC may include a unicast key negotiation process and a multicast key notification process, and the unicast key negotiation process in the key negotiation may include: 
     step 31, unicast key negotiation requesting: 
     after the AAC and the REQ complete the identity authentication processes, the AAC sends a unicast key negotiation request message to the REQ to start a unicast key negotiation process with the REQ, the unicast key negotiation request message including N AAC  and MIC3; 
     wherein, 
     the N AAC  field indicates an challenge of the AAC, which is a random number generated by the AAC if the unicast key negotiation process is performed for the first time; or has a value the same as the N AAC  field saved during the last unicast key negotiation process if the current unicast key is an updating process of a unicast key; 
     the MIC3 field indicates a message authentication code, which is a hash value calculated by the AAC by using a BK commonly owned by the AAC and the REQ; 
     step 32, unicast key negotiation responding: 
     on receipt of the unicast key negotiation request message, the REQ performs the following: 
     step 321, if the current key negotiation process is an updating process of a unicast key, the REQ checks whether the N AAC  field in the unicast key negotiation request message is in accordance with the N AAC  saved during the last key negotiation process, if not, discards the unicast key negotiation request message, if so, go to step 322; if the current key negotiation process is not an updating process of a unicast key, go directly to step 322; 
     step 322, the REQ verifies whether the MIC3 field is correct, if not, discards the unicast key negotiation request message, if so, go to step 323; 
     step 323, the REQ generates a REQ challenge (N REQ ), calculates a unicast session key and N AAC  used for the next key negotiation process and stores the unicast session key and the N AAC,  the unicast session key including a protocol data key (PDK) and a unicast data key (UDK); 
     the REQ calculates MIC4 using the PDK, forms a unicast key negotiation response message and sends it to the AAC; 
     the REQ installs the newly negotiated unicast session key, 
     the unicast key negotiation response message including N REQ , N AAC  and MIC4, 
     wherein, 
     the N REQ  field indicates an challenge of the REQ, which is a random number generated by the REQ; 
     the N AAC  field indicates an challenge of the AAC, and has a value the same as the value of the N AAC  field in the unicast key negotiation request message; if the unicast key negotiation process is performed for the first time, the value of the N AAC  field is determined directly by the value of the N AAC  field in the unicast key negotiation request message; if it is an updating process of the unicast key, the value of the N AAC  field is the value of the N AAC  field saved during the last unicast key negotiation process; 
     the MIC4 field indicates a message authentication code, which is a hash value of all the other fields except the MIC4 field in the unicast key negotiation response message calculated by the REQ using the generated PDK; 
     step 33, unicast key negotiation confirmation: 
     on receipt of the unicast key negotiation response message, the AAC performs the following: 
     step 331, if the current key negotiation process is an updating process of a unicast key, the AAC checks whether the N AAC  field in the unicast key negotiation response message is in accordance with the N AAC  saved during the last key negotiation process, if not, discards the unicast key negotiation response message, if so, go to step 332; f the current key negotiation process is not an updating process of a unicast key, the AAC checks whether the N AAC  field value in the unicast key negotiation response message is in accordance with the N AAC  field value in the unicast key negotiation request message; if not, discards the unicast key negotiation response message, if so, go to step 332; 
     step 332, the AAC calculates the unicast session key and the N AAC  used for the next key negotiation according to the N REQ  field and the N AAC  field in the unicast key negotiation response message, stores them, the unicast session key including PDK and UDK; 
     step 333, the AAC verifies whether the MIC4 in the unicast key negotiation response message is correct using the PDK, if not, discards the unicast key negotiation response message, if not, go to step 334; 
     step 334, the AAC calculates MIC5 using the PDK, forms a unicast key negotiation confirmation message, and sends it to the REQ; 
     step 335, the AAC installs the newly negotiated unicast session key by the AAC, and activates sending and receiving functions of the newly installed unicast session key to allow encryption and decryption of unicast data based on the new key; if the current unicast key negotiation process is an updating process, the AAC further deletes the old unicast session key, 
     the unicast key negotiation confirmation message including N REQ  and MIC5, 
     wherein, 
     the N REQ  field indicates challenge of the REQ, which is a random number generated by the REQ; the N REQ  field has a value the same as the value of the N REQ  field in the unicast key negotiation response message; 
     the MIC5 field indicates a message authentication code, which is a hash value of all the other fields except the MIC5 field in the unicast key negotiation confirmation message calculated by the AAC using the generated PDK; 
     step 34, on receipt of the unicast key negotiation confirmation message, the REQ performs the following: 
     step 341, the REQ checks whether the N REQ  field is the same as the N REQ  field in the unicast key negotiation response message sent by the REQ itself; if not, discards the unicast key negotiation confirmation message, if so, go to step 342; 
     step 342, the REQ verifies whether the MIC5 in the unicast key negotiation confirmation message is correct using the PDK; if not, discards the unicast key negotiation confirmation message, if so, go to step 343; 
     step 343, the REQ activates sending and receiving functions of the newly installed unicast session key to allow encryption and sending of unicast data based on the new key; 
     if the current unicast key negotiation process is an updating process, the REQ further deletes the old unicast session key. 
     The multicast key notification process in the key negotiation may include: 
     step 35, multicast key notification, 
     the multicast key notification message including a key notification identifier KN, encrypted key data E MDK  and MIC6; 
     wherein, 
     the KN field indicates a key notification identifier, which is initialized as an integer and added by 1 for every key updating notification; if the notified key is unchanged, the KN field remains unchanged; 
     the E MDK  field indicates encrypted key data, which is multicast data key (MDK) encrypted by the AAC using the PDK; 
     the MIC6 field indicates a message authentication code, which is a hash value of all the other fields except the MIC6 field in the multicast key notification message calculated by the AAC using the PDK generated during the unicast key negotiation; 
     step 36, multicast key responding: 
     on receipt of the multicast key notification message, the REQ performs the following: 
     step 361, the REQ checks whether the KN field is increased monotonically; if not, discards the multicast key notification message, if so, go to step 362; 
     step 362, the REQ verifies whether the MICE field is correct using the PDK generated during the unicast key negotiation; if not, discards the multicast key notification message, if so, go to step 363; 
     step 363, the REQ obtains the MDK by decrypting the E MDK  field using the PDK generated during the unicast key negotiation; 
     step 364, the REQ stores the current value of the KN field, and generates a multicast key response message and sends it to the AAC, 
     the multicast key response message including KN and MIC7; 
     wherein, 
     the KN field indicates a key notification identifier, and has a value the same as the value of the KN field in the multicast key notification message; 
     the MIC7 field indicates a message authentication code, which is a hash value of all the other fields except the MIC7 field in the multicast key confirmation message calculated by the REQ using the PDK generated during the unicast key negotiation; 
     step 37, on receipt of the multicast key response message, the AAC performs the following: 
     step 371, the AAC compares whether the KN field is in accordance with the corresponding field in the multicast key notification message previously sent; if not, discards the multicast key response message, if so, go to step 372; 
     step 372, the AAC verifies whether the MIC7 field is correct using the PDK generated during the unicast key negotiation; if not, discards the multicast key response message, if so, obtains a multicast data key. 
     A security access control system for a wired local area network is also provided according to the present invention, characterized in that the security access control system for a wired local area network includes a requester (REQ), an authentication access controller (AAC) and an authentication server (AS), both the REQ and the AS are connected to the AAC, the AAC provides a service interface for the REQ, and the AS provides authentication service for the REQ and the AAC. 
     The present invention may bring the following advantages: the present invention provides a Tri-element Peer Authentication (TePA) based security access control method for accessing a wired Local Area Network (LAN), Tri-element LAN Access Control (TLAC), and a system thereof; direct identity authentication between the user and the network access control device can be realized; negotiation and dynamic update of the session key for link layer data protection can be achieved; a variety of network architectures such as an enterprise network and a telecommunication network are supported; good scalability and multiple authentication methods are supported; authentication protocols with different security levels are supported, meeting requirements of various users; and sub-modules of the protocol are independent and flexible, making it easy to select. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a security policy negotiation process according to the present invention; 
         FIG. 2  is a schematic diagram of a core authentication process of TAEP-CAAP according to the present invention; 
         FIG. 3  is a schematic diagram of a unicast key negotiation process according to the present invention; and 
         FIG. 4  is a schematic diagram of a multicast key notification process according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1 to 4 , it is according to the present invention provided a security access control method for a wired local area network, which includes a security policy negotiation process, an identity authentication process and a key negotiation process. Specifically, the security access control method may include the following steps. 
     1) As shown in  FIG. 1 , the security policy negotiation process may include the follow steps. 
     1.1) security policy negotiation requesting: when the REQ accesses the AAC, the AAC sends a security policy negotiation request message to the REQ. 
     The security policy negotiation request message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the TIEAAC field indicates an information element of tri-element peer authentication (TePA) supported by the AAC, including an authentication and key management suite and a cryptography suite supported by the AAC; 
     1.2) security policy negotiation responding: on receipt of the security policy negotiation request message, the REQ performs the following: 
     selecting an authentication and key management suite and a cryptography suite that are commonly owned by the REQ and the AAC according to the authentication and key management suite and the cryptography suite supported by the AAC indicated by the TIE AAC  field in the security policy negotiation request message in conjunction with a local policy, and forming a security policy negotiation response message and sending it to the AAC; discarding the security policy negotiation request message according to a local policy if the REQ does not support any of the authentication and key management suite and the cryptography suite supported by the AAC in the security policy negotiation request message. 
     The security policy negotiation response message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the TIE REQ  field indicates a TePA information element selected by the REQ, including the authentication and key management suite and the cryptography suite selected by the REQ. 
     1.3) on receipt of the security policy negotiation response message, the AAC performs the following: 
     1.3.1) determining whether the AAC supports the authentication and key management suite and the cryptography suite selected by the REQ; if not, discarding the security policy negotiation response message, and if so, go to 1.3.2); 
     1.3.2) starting a corresponding identity authentication process according to the authentication and key management suite selected by the REQ. 
     According to the present invention, it is provided a certificate-based authentication protocol TAEP-CAAP (Triple-element Authentication Extensible Protocol-Certificate-based 1 An Authentication Protocol). 
     2) As shown in  FIG. 2 , the certificate-based authentication protocol TAEP-CAAP process may include: 
     2.1) authentication activation: if the authentication and key management suite negotiated by the REQ and the AAC is a certificate-based authentication and key management suite, the AAC sends an authentication activation message to the REQ to activate the REQ to perform certificate authentication, the authentication activation message including mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the SNonce field indicates an authentication identifier, and is a random number generated by the AAC if the identify authentication process is performed for the first time; or an authentication identifier value generated from negotiation during the last identify authentication process if the current identify authentication process is an updating process; 
     the ID AS-AAC  field indicates an identity ID of an authentication server (AS) trusted by the AAC, which is an ID of the AS who issued a certificate of the AAC (Cert AAC ); 
     the Cert AAC  field indicates the certificate of the AAC; 
     the Para ECDH  field indicates an elliptic curve cryptography parameter of an elliptic curve cryptography mechanism, which is an elliptic curve cryptography parameter used during calculation of Elliptic Curve Diffie-Hellman (ECDH) by the REQ and the AAC; 
     the TIE AAC  field indicates an authentication and key management suite and a cryptography suite supported by the AAC, and has a value the same as the value of the TIE AAC  field in the security policy negotiation request packe; 
     the SIG AAC  field indicates a signature by the AAC, which is a signature signed by the AAC using a private key on all the other fields except the SIG AAC  field in the authentication activation message; the SIG AAC  field is an optional field. 
     2.2) access authentication request: on receipt of the authentication activation message, the REQ performs the following: 
     2.2.1) if the current identity authentication process is an updating process, the REQ checks whether the authentication identifier field value in the authentication activation message is in accordance with the authentication identifier saved during the last identity authentication process, if not, discards the authentication activation message, otherwise, go to 2.2.2); if the current identity authentication process is not an updating process but an identity authentication process for the first time, go to 2.2.2) directly; 
     2.2.2) the REQ verifies whether the TIE AAC  field value is in accordance with the TIE AAC  field value in the security policy negotiation request message received during the security policy negotiation; if not, discards the authentication activation message, if so, go to 2.2.3); 
     2.2.3) if the SIG AAC  field is included in the received authentication activation message, the REQ verifies correctness of the SIG AAC  field; if the SIG AAC  field is incorrect, discards the received authentication activation message, if the SIG AAC  field is correct, go to 2.2.4); if no SIG AAC  field is included in the received authentication activation message, go directly to 2.2.4); 
     2.2.4) the REQ selects a certificate of the REQ issued by the AS (Cert REQ ) according to the ID AS-AAC  field in the authentication activation message or selects a certificate of the REQ (Cert REQ ) according to a local policy; generates REQ key data x·P and a REQ challenge (N REQ ) for ECDH exchange; generates an access authentication request message and sends it to the AAC. 
     The access authentication request message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the SNonce field indicates an authentication identifier and has a value the same as the value of the SNonce field in the authentication activation message; if the identify authentication process is performed for the first time, the value of the SNonce field is determined directly by the value of the SNonce field in the authentication activation message; if the current identify authentication process is an updating process, the value of the SNonce field is the authentication identifier value calculated during the last identity authentication process; 
     the N REQ  field indicates a REQ challenge, which is a random number generated by the REQ; 
     the x·P field indicates key data of the REQ, which is a temporary public key generated by the REQ for ECDH exchange; 
     the ID AAC  field indicates an identity ID of the AAC, and is obtained according to the Cert AAC  field in the authentication activation message; 
     the Cert REQ  field indicates a certificate of the REQ; 
     the Para ECDH  field indicates an ECDH parameter, which is an elliptic curve cryptography parameter used during ECDH calculation by the REQ and the AAC; and has a value the same as the value of the Para ECDH  field in the authentication activation message; 
     the List AS-REQ  field indicates a list of ASs trusted by the REQ, not including an issuer of the certificate of the REQ (Cert REQ ); the AAC is notified of by the REQ using the List AS-REQ  field when the REQ trusts an entity other than the issuer of its certificate; the List AS-REQ  field is an optional field; 
     the TIE REQ  field indicates an authentication and key management suite and a cryptography suite selected by the REQ, and has a value the same as the value of the TIE REQ  field in the security policy negotiation response message; 
     the Sig REQ  field indicates a signature by the REQ, which is a signature signed by the REQ using a private key on all the other fields except the Sig REQ  field in the access authentication request message; 
     2.3) certificate authentication requesting: on receipt of the access authentication request message, the AAC performs the following: 
     2.3.1) if the AAC has sent the authentication activation message, the AAC checks whether the SNonce field value and the Para ECDH  field value in the received access authentication request message are in accordance with the corresponding field values in the authentication activation message, if any of the SNonce field value and the Para ECDH  field value is not, discards the access authentication request message, otherwise, got to 2.3.2); if the AAC has not sent the authentication activation message, the AAC checks whether the SNonce field value is in accordance with the authentication identifier calculated during the last certificate authentication process and whether the Para ECDH  field is in accordance with the Para ECDH  field in the last authentication activation message, if any of the SNonce field value and the Para ECDH  field is not, discards the access authentication request message, otherwise, go to 2.3.2); 
     2.3.2) the AAC checks whether the ID AAC  is in accordance with the identity of the AAC itself and whether the TIE REQ  field value is in accordance with the TIE REQ  field value in the security policy negotiation response message received during the security policy negotiation; if any of the ID AAC  and the TIE REQ  field value is not, discards the access authentication request message; otherwise, go to 2.3.3); 
     2.3.3) the AAC verifies correctness of the Sig REQ  field; if the Sig REQ  field is incorrect, discards the access authentication request message; otherwise, go to 2.3.4); 
     2.3.4) if it is required according to a local policy of the AAC to use the AS to authenticate the certificate of the REQ (Cert REQ ), the AAC generates a certificate authentication request message and sends it to the AS; otherwise, go to 2.3.5); 
     2.3.5) the AAC authenticates the certificate of the REQ (Cert REQ ) locally, which includes validating a verification result of the certificate of the REQ (Cert REQ ) according to a verification result of the certificate of the REQ (Cert REQ ) cached locally and timeliness defined by a local policy; if the verification result of the Cert REQ  is valid, generates locally key data and an AAC challenge (N AAC ) for ECDH exchange, the key data including a temporary public key y·P of the AAC, performs ECDH calculation according to the temporary public key x·P of the REQ and a temporary private key y of the AAC to obtain a base key (BK) and an authentication identifier for the next identity authentication process and store them, sets an access result to be successful, forms an access authentication response message and sends it to the REQ, and permits a user to access the network; if the verification result of the Cert REQ  is invalid, the AAC sets the access result to be unsuccessful and the AAC challenge (N AAC ) and the key data y·P to be any values, forms an access authentication response message and sends it to the REQ, and removes association with the REQ. 
     The certificate authentication request message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the N AAC  field indicates an AAC challenge, which is a random number generated by the AAC; 
     the N REQ  field indicates REQ challenge, which is a random number generated by the REQ, and has a value the same as the value of the N REQ  field in the access authentication request message sent by the REQ; 
     the Cert REQ  field indicates a certificate of the REQ and has a value the same as the value of the Cert REQ  field in the access authentication request packe; 
     the Cert AAC  field indicates a certificate of the AAC and has a value the same as the value of the Cert AAC  field in the authentication activation message; 
     the List AS-REQ  field indicates a list of ASs trusted by the REQ and has a value the same as the value of the List AS-REQ  field in the access authentication request message sent by the REQ; the List AS-REQ  field is an optional field; 
     2.4) certificate authentication responding: on receipt of the certificate authentication request message, the AS performs the following: 
     2.4.1) in the case of unilateral authentication, the AS verifies the certificate of the REQ (Cert REQ ); in the case of mutual authentication, the AS verifies both the certificate of the AAC (Cert AAC ) and the certificate of the REQ (Cert REQ ), the verification of the certificates are performed with reference to RFC3280, and if the verification cannot be performed, the AS sets a verification result of a corresponding certificate to be issuer of the certificate undefined, otherwise, the AS verifies the certificate and performs 2.4.2); 
     2.4.2) the AS forms a certificate authentication response message according to the verification result of the certificate; adds a corresponding signature and sends the certificate authentication response message to the AAC. 
     The certificate authentication response message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the RES Cert  field indicates the verification result of the certificate and includes an AAC challenge value (N AAC ), a REQ challenge value (N REQ ), the verification result of the Cert AAC  and the verification result of the Cert REQ ; in case of unilateral verification, the RES Cert  field does not include the verification result of the certificate of the AAC (Cert AAC ); 
     the SIG AS-REQ  field indicates a signature signed by the AS trusted by the REQ on the verification result of the certificate (RES Cert ) in the certificate authentication response message; 
     the SIG AS-AAC  field indicates a signature signed by the AS trusted by the AAC on all the other fields in the certificate authentication response message except the SIG AS-AAC  field; the SIG AS-AAC  field is an optional field, and is omitted if the AS who signed the verification result of the certificate is the same as the AS trusted by the AAC; 
     2.5) access authentication responding: on receipt of the certificate authentication response message, the AAC performs the following: 
     2.5.1) the AAC checks whether the AAC challenge (N AAC ) field value in the RES Cert  field is the same as the N AAC  field value in the certificate authentication request message; if not, discards the certificate authentication response message, if so, go to 2.5.2); 
     2.5.2) if two signature fields are included in the certificate authentication response message, the AAC checks whether the SIG AS-AAC  field is correct, if not, discards the certificate authentication response message, if so, go to 2.5.3); if only one signature field is included in the certificate authentication response message, which indicates that the AS trusted by the REQ is also the AS trusted by the AAC, the AAC checks whether the SIG AS-REQ  field is correct, if not, discards the certificate authentication response message, if so, go to 2.5.3); 
     2.5.3) the AAC checks whether the verification result of the Cert REQ  in the RES Cert  field is valid; if so, generates locally key data y·P and an AAC challenge (N AAC ) for ECDH exchange, performing ECDH calculation according to the temporary public key x·P of the REQ and a temporary private key y of the AAC to obtain a base key (BK) and an authentication identifier for the next identity authentication process and store them, sets an access result to be successful, forms an access authentication response message and sends it to the REQ, and permits a user to access the network; if the verification result of the Cert REQ  is invalid, the AAC sets the access result to be unsuccessful, the AAC challenge (N AAC ) and the private data y·P to be any value, forms an access authentication response message and sends it to the REQ, and remove association with the REQ. 
     The access authentication response message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the N REQ  field indicates a REQ challenge, which is a random number generated by the REQ; the N REQ  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; and if the N REQ  field exists, it has a value the same as the value of the N REQ  field in the access authentication request message sent by the REQ; 
     the N AAC  field indicates an AAC challenge, which is a random number generated by the AAC; the N AAC  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; and if the N AAC  field exists, it has a value the value of the N AAC  field in the access authentication request message sent by the AAC; 
     the Acc RES  field indicates an access result, which is access success or access failure and a reason of the failure set by the AAC according to the authentication result; 
     the x·P field indicates key data of the REQ, which is a temporary public key generated by the REQ for ECDH exchange; the x·P field has a value the same as the value of the x·P field in the access authentication request message sent by the REQ; 
     the y·P field indicates key data of the AAC, which is a temporary public key generated by the AAC for ECDH exchange; 
     the ID AAC  field indicates an identity ID of the AAC and is obtained according to the Cert AAC  field; 
     the ID REQ  field indicates an identity ID of the REQ and is obtained according to the Cert REQ  field in the received access authentication request message; 
     the MRES Cert  field indicates a combined certificate verification result; the MRES Cert  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; if the MRES Cert  field exists, it includes the fields in the certificate authentication response message and the same values; 
     the MRES Cert  field indicates a combined certificate verification result; the MRES Cert  field is an optional field, it is included in the access authentication response message only in the case of unilateral authentication; if the MRES Cert  field exists, it includes the fields in the certificate authentication response message and the same values; 
     the MIC1 field indicates a message authentication code, which is a hash value of all the other fields except the MIC1 field in the access authentication response message and an authentication identifier for the next certificate authentication process calculated by the AAC using the BK generated from negotiation during the authentication; 
     the access authentication response message includes one or more of the SIG AAC  field and the MIC1 field; if the authentication activation message exists in the current identity authentication process and if the access authentication activation message includes the SIG AAC  field, the authentication response message includes only the MIC1 field; if no authentication activation message exists in the current identity authentication or if the authentication activation message does not include a SIG AAC  field, the access authentication response message includes only the SIG AAC  field; 
     2.6) access authentication confirmation: on receipt of the access authentication response message, the REQ performs the following: 
     2.6.1) the REQ determines whether the received access authentication response message corresponds to the current access authentication request message according to the ID AAC  field and the ID REQ  field in the access authentication response message; if not, discards the received access authentication response message; if so, go to 2.6.2); 
     2.6.2) the REQ determines whether the REQ key data field x·P value in the access authentication response message is in accordance with the x·P field value in the access authentication request message sent by the REQ itself; if not, discards the access authentication response message, otherwise, go to 2.6.3); 
     2.6.3) in the case of unilateral authentication, the REQ determines whether the N REQ  field value is in accordance with the N REQ  field value in the access authentication request message sent previously; if not, discards the access authentication response message, otherwise, go to 2.6.4); in the case of mutual authentication, go directly to 2.6.4); 
     2.6.4) the REQ checks the Acc RES  field in the access authentication response message; if the access result is unsuccessful, removes association with the AAC, otherwise, go to 2.6.5); 
     2.6.5) if the received access authentication response message includes the SIG AAC  field, the REQ verifies correctness of the SIG AAC  field, if the SIG AAC  is incorrect, discards the access authentication response message, otherwise, go to 2.6.6); if the received access authentication response message includes the MIC1 field, the REQ verifies correctness of the MIC1 field, if the MIC1 field is incorrect, discards the access authentication response message, otherwise, go to 2.6.6); 
     2.6.6) in the case of unilateral authentication, go to 2.6.8); otherwise, the REQ verifies whether the N REQ  field value included in the MRES Cert  field is in accordance with the N REQ  field value in the access authentication request message sent by the REQ itself, if not, discards the access authentication response message, if so, verifies whether the SIG AS-REQ  is correct, if not, discards the access authentication response message, if so, go to 2.6.7); 
     2.6.7) the REQ verifies whether the AAC certificate verification result in the MRES Cert  field is valid; if not, it is determined that the network is invalid and should not be accessed, otherwise, it is determined that the network is valid and can be accessed, and go to 2.6.8); 
     2.6.8) the REQ performs ECDH calculation according to the temporary public key y·P of the AAC and the temporary private key x of the REQ to obtain a BK and an authentication identifier for the next certificate authentication process, and stores the BK and the authentication identifier; 
     2.6.9) if the received access authentication response message includes the SIG AAC  field, sending an access authentication confirmation message is optional; if the received access authentication response message includes the MIC1 field, the REQ forms an access authentication confirmation message and sends it to the AAC. 
     The access authentication confirmation message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the MIC2 field indicates a message authentication code, which is a hash value of the AAC challenge value (N AAC ), the REQ challenge value (N REQ ) and an authentication identifier for the next certificate authentication process calculated by the REQ using the BK generated from negotiation during the authentication. 
     If the SIG AAC  field is included in the access authentication response message sent by the AAC, the AAC may wait to receive the access authentication confirmation message after sending the access authentication response message to the REQ. 
     on receipt of the access authentication confirmation message sent by the REQ, the AAC may verify correctness of the MIC2 field in the access authentication confirmation message, if the MIC2 field is correct, then the REQ has a BK in accordance with the AAC; if the MIC2 field is incorrect, the AAC discards the access authentication response message. 
     This protocol is highly integrated, can realize both mutual authentication and unilateral authentication, and supports authentication updating and simplified authentication updating. The simplified authentication updating refers to the AAC and the REQ directly performing signature verification without the AS verifying the certificate. That is, with respect of the content of the message, no complex certificate verification result field is included in the access authentication response message. The simplified authentication process can only be used as an authentication updating process but should not be used for authentication for the client connecting to the network for the first time. 
     3) As shown in Figure, a unicast key negotiation process ay include: 
     3.1) unicast key negotiation requesting: after the AAC and the REQ complete the identity authentication processes, the AAC sends a unicast key negotiation request message to the REQ to start a unicast key negotiation process with the REQ, the unicast key negotiation request message including mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the N AAC  field indicates an challenge of the AAC, which is a random number generated by the AAC if the unicast key negotiation process is performed for the first time; or has a value the same as the N AAC  field saved during the last unicast key negotiation process if the current unicast key is an updating process of a unicast key; 
     the MIC3 field indicates a message authentication code, which is a hash value calculated by the AAC by using a BK commonly owned by the AAC and the REQ; 
     3.2) unicast key negotiation responding: 
     on receipt of the unicast key negotiation request message, the REQ performs the following: 
     3.2.1) if the current key negotiation process is an updating process of a unicast key, the REQ checks whether the N AAC  field in the unicast key negotiation request message is in accordance with the N AAC  saved during the last key negotiation process, if not, discards the unicast key negotiation request message, if so, go to 3.2.2); if the current key negotiation process is not an updating process of a unicast key, go directly to 3.2.2); 
     3.2.2) the REQ verifies whether the MIC3 field is correct, if not, discards the unicast key negotiation request message, if so, go to 3.2.3); 
     3.2.3) the REQ generates a REQ challenge (N REQ ), calculates a unicast session key and N AAC  used for the next key negotiation process and stores the unicast session key and the N AAC , the unicast session key including a protocol data key (PDK) and a unicast data key (UDK); 
     the REQ calculates MIC4 using the PDK, forms a unicast key negotiation response message and sends it to the AAC; 
     the REQ installs the newly negotiated unicast session key, 
     the unicast key negotiation response message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the N REQ  field indicates an challenge of the REQ, which is a random number generated by the REQ; 
     the N AAC  field indicates an challenge of the AAC, and has a value the same as the value of the N AAC  field in the unicast key negotiation request message; if the unicast key negotiation process is performed for the first time, the value of the N AAC  field is determined directly by the value of the N AAC  field in the unicast key negotiation request message; if it is an updating process of the unicast key, the value of the N AAC  field is the value of the N AAC  field saved during the last unicast key negotiation process; 
     the MIC4 field indicates a message authentication code, which is a hash value of all the other fields except the MIC4 field in the unicast key negotiation response message calculated by the REQ using the generated PDK. 
     3.3) unicast key negotiation confirmation: on receipt of the unicast key negotiation response message, the AAC performs the following: 
     3.3.1) if the current key negotiation process is an updating process of a unicast key, the AAC checks whether the N AAC  field in the unicast key negotiation response message is in accordance with the N AAC  saved during the last key negotiation process, if not, discards the unicast key negotiation response message, if so, go to 3.3.2); f the current key negotiation process is not an updating process of a unicast key, the AAC checks whether the N AAC  field value in the unicast key negotiation response message is in accordance with the N AAC  field value in the unicast key negotiation request message; if not, discards the unicast key negotiation response message, if so, go to 3.3.2); 
     3.3.2) the AAC calculates the unicast session key and the N AAC  used for the next key negotiation according to the N REQ  field and the N AAC  field in the unicast key negotiation response message, stores them, the unicast session key including PDK and UDK; 
     3.3.3) the AAC verifies whether the MIC4 in the unicast key negotiation response message is correct using the PDK, if not, discards the unicast key negotiation response message, if not, go to 3.3.4); 
     3.3.4) the AAC calculates MIC5 using the PDK, forms a unicast key negotiation confirmation message, and sends it to the REQ; 
     3.3.5) the AAC installs the newly negotiated unicast session key by the AAC, and activates sending and receiving functions of the newly installed unicast session key to allow encryption and decryption of unicast data based on the new key; if the current unicast key negotiation process is an updating process, the AAC further deletes the old unicast session key, 
     the unicast key negotiation confirmation message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the N REQ  field indicates challenge of the REQ, which is a random number generated by the REQ; the N REQ  field has a value the same as the value of the N REQ  field in the unicast key negotiation response message; 
     the MIC5 field indicates a message authentication code, which is a hash value of all the other fields except the MIC5 field in the unicast key negotiation confirmation message calculated by the AAC using the generated PDK; 
     3.4) on receipt of the unicast key negotiation confirmation message, the REQ performs the following: 
     3.4.1) the REQ checks whether the N REQ  field is the same as the N REQ  field in the unicast key negotiation response message sent by the REQ itself; if not, discards the unicast key negotiation confirmation message, if so, go to 3.4.2); 
     3.4.2) the REQ verifies whether the MIC5 in the unicast key negotiation confirmation message is correct using the PDK; if not, discards the unicast key negotiation confirmation message, if so, go to 3.4.3); 
     3.4.3) the REQ activates sending and receiving functions of the newly installed unicast session key to allow encryption and sending of unicast data based on the new key; if the current unicast key negotiation process is an updating process, the REQ further deletes the old unicast session key; 
     4) As shown in  FIG. 4 , the multicast key notification process may include: 
     4.1) Multicast key notification, 
     the multicast key notification message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the KN field indicates a key notification identifier, which is initialized as an integer and added by 1 for every key updating notification; if the notified key is unchanged, the KN field remains unchanged; 
     the E MDK  field indicates encrypted key data, which is multicast data key (MDK) encrypted by the AAC using the PDK; 
     the MIC6 field indicates a message authentication code, which is a hash value of all the other fields except the MIC6 field in the multicast key notification message calculated by the AAC using the PDK generated during the unicast key negotiation; 
     4.2) multicast key responding: 
     on receipt of the multicast key notification message, the REQ performs the following: 
     4.2.1) the REQ checks whether the KN field is increased monotonically; if not, discards the multicast key notification message, if so, go to 4.2.2); 
     4.2.2) the REQ verifies whether the MIC6 field is correct using the PDK generated during the unicast key negotiation; if not, discards the multicast key notification message, if so, go to step 4.2.3); 
     4.2.3) the REQ obtains the MDK by decrypting the E MDK  field using the PDK generated during the unicast key negotiation; 
     4.2.4) the REQ stores the current value of the KN field, and generates a multicast key response message and sends it to the AAC, 
     the multicast key response message includes mainly: 
     
       
                 
         
             
             
         
      
     
     where 
     the KN field indicates a key notification identifier, and has a value the same as the value of the KN field in the multicast key notification message t; 
     the MIC7 field indicates a message authentication code, which is a hash value of all the other fields except the MIC7 field in the multicast key confirmation message calculated by the REQ using the PDK generated during the unicast key negotiation; 
     4.3) on receipt of the multicast key response message, the AAC performs the following: 
     4.3.1) the AAC compares whether the KN field is in accordance with the corresponding field in the multicast key notification message previously sent; if not, discards the multicast key response message, if so, go to 4.3.2); 
     4.3.2) the AAC verifies whether the MIC7 field is correct using the PDK generated during the unicast key negotiation; if not, discards the multicast key response message, if so, obtains a multicast data key; 
     When the AAC completes multicast key notification to the REQ successfully, secret communication of data between the AAC and the REQ will be conducted using the above unicast data key and multicast data key that have been negotiated or notified. 
     In addition to the security access control method for a wired local area network, the present invention also provides a security access control system for a wired local area network, and the system includes: a requester (REQ), an Authentication Access Controller (AAC) and an Authentication Server (AS). Both the REQ and the AS are connected to the AAC, the AAC provides a service interface for the REQ, and the AS provides authentication service for the REQ and the AAC. 
     It is noted that the above embodiments are for illustrative purposes only, which shall not be considered as limiting the scope of the invention. The present invention is described in detail with reference to the above embodiments, however, those skilled in the art shall understand that modifications and equivalents may made to the technical solutions or some technical features of the above embodiments, without deviation from the scope of the the present invention.