CN1564509A - Key consaltation method in radio LAN - Google Patents

Abstract

The invention discloses a method for negotiating a key in a wireless local area network, which includes the following process: in the first step, the access point sends a unicast key negotiation request to the wireless terminal; in the second step, the wireless terminal sends a unicast key negotiation request to the access point Key negotiation response; Step 3, the access point sends a multicast key negotiation request to the wireless terminal; Step 4, the wireless terminal sends a multicast key negotiation confirmation to the access point. By adopting the method of the invention, safe and efficient key negotiation can be realized in the WLAN system, and the multicast communication protection of the WLAN system can be supported, so that the WLAN system developed according to GB15629.11 is more perfect.

Description

A key agreement method in wireless local area network

technical field

The present invention relates to a wireless local area network (WLAN), in particular to a key negotiation method in the wireless local area network.

Background technique

In May 2003, the National Broadband Wireless IP Working Group released the WLAN national standard GB15629.11. In the eighth chapter of GB15629.11, a new WLAN security mechanism—Wireless Local Area Network Authentication and Privacy Infrastructure (WAPI) is proposed. WAPI mainly includes two parts: WLAN Authentication Infrastructure (WAI) and WLAN Privacy Infrastructure (WPI).

WAI is used to realize the authentication and key agreement between the wireless terminal (STA) and the access point (AP) in the wireless local area network (Infrastructure) mode. The WAI authentication process includes certificate authentication and session key negotiation, as shown in Figure 1. The three entities in the WAI authentication process are wireless terminal STA, wireless access point AP and authentication server ASU.

The detailed process of certificate authentication is as follows:

1) Discrimination activation. When a STA associates or re-associates with an AP, the AP sends an authentication activation to the STA to start the entire authentication process.

2) Access authentication request. The STA sends an access authentication request to the AP, that is, sends the STA certificate and the current system time of the STA to the AP, where the system time is called the access authentication request time.

3) Certificate authentication request. After the AP receives the STA access authentication request, it first records the authentication request time, and then sends a certificate authentication request to the ASU, that is, the STA certificate, the access authentication request time, the AP certificate and the private key of the AP form a certificate authentication request with their signatures. to ASU.

4) Certificate authentication response. After receiving the certificate signing request from the AP, the ASU verifies the signature of the AP and the validity of the AP certificate. If it is incorrect, the authentication process fails. Otherwise, the STA certificate is further verified. After the verification is completed, the ASU will combine the STA certificate authentication result information (including STA certificate and authentication result), AP certificate signing result information (including AP certificate and authentication result and access authentication request time) and ASU's signature on them to form a certificate authentication response Send it back to the AP.

5) Access authentication response. The AP performs signature verification on the certificate signature response returned by the ASU, obtains the authentication result of the STA certificate, and performs access control on the STA according to the result. The AP returns the received certificate signing response to the STA. After verifying the signature of the ASU, the STA obtains the authentication result of the AP certificate, and decides whether to access the AP according to the authentication result.

So far, the certificate authentication process between the STA and the AP is completed. If the authentication is successful, the AP allows the STA to access, otherwise it disassociates it.

The session key negotiation process is:

After the STA and the AP certificate authentication are successful, the key agreement is performed.

1) Key agreement request. The AP generates a string of random data, encrypts it with the STA's public key, and sends a key negotiation request to the STA. This request contains all of the requester's alternative session algorithm information.

2) Key agreement response. After receiving the key negotiation request from the AP, the STA negotiates the session algorithm first. If the responder does not support all the candidate session algorithms of the requester, it responds to the requester that the session algorithm negotiation failed. Choose an algorithm that you support in the selection algorithm; then use the local private key to decrypt the negotiation data to get the random data generated by the AP; then generate a string of random data, encrypt it with the AP's public key, and then send it to the AP.

After the key negotiation is successful, the STA and the AP perform modulo 2 sum operation on the random data generated by themselves and the other party respectively to generate a session key, and use the negotiated session algorithm to encrypt and decrypt the communication data.

In order to further improve the confidentiality of communication, after communicating for a period of time or exchanging a certain amount of data, STA and AP can re-negotiate the session key, the process is the same as above.

From the description of the above process in GB15629.11, it can be seen that the key negotiation method in the WAI mechanism can only be used for unicast key negotiation to form a paired unicast communication protection key between STA and AP, and cannot Applied to multicast key negotiation. Because in the same basic service set (BSS), all STAs and APs need to share the same multicast key, so the multicast key negotiation must be performed in the manner of uniform distribution by the AP. However, such a multicast key negotiation mechanism is not designed in GB15629.11, so the WLAN system implemented according to GB15629.11 will not be able to perform dynamic multicast key negotiation, and thus cannot well support broadcast/multicast security communication.

Contents of the invention

The technical problem to be solved by the present invention is to make up for the lack of multicast key negotiation mechanism in GB15629.11, improve the key negotiation process of WLAN system, provide multicast communication key for the system, and realize key negotiation in wireless local area network.

The key negotiation method in the wireless local area network of the present invention includes the following processing steps:

In the basic mode of the WLAN system, after the certificate authentication process described in GB15629.118.3 is completed between the STA accessing the network and the network, the STA and the AP need to initiate the key agreement process of the present invention,

The first step is a unicast key agreement request. The AP generates a string of random numbers, encrypts them with the STA's public key, and sends them to the STA as a unicast key negotiation request. This request also includes all of the requester's alternate session algorithm information and key replay counters. The key replay counter is used to prevent replay attacks on key agreement messages. If the unicast packet sequence number against replay attack is used in unicast communication, this message shall also contain the unicast packet sequence number.

The second step is the unicast key negotiation response. After receiving the unicast key negotiation request from the AP, the STA first negotiates the session algorithm. If the responder does not support all the alternative session algorithms of the requester, it responds to the requester that the session algorithm negotiation failed. Otherwise, the requester provides Choose one of the algorithms that you support; then use the local private key to decrypt the negotiation data, get the random data generated by the AP, install the unicast communication key and unicast packet serial number; and then generate a string of random data , encrypted with the public key of the AP, and then sent to the AP. The Key Replay Counter from the copied Unicast Key Agreement Request shall also be included in this message.

The third step is the multicast key negotiation request. After the unicast key negotiation is completed, the AP encrypts and protects the multicast key and sends it to the STA as a multicast key negotiation request message. The encryption of the multicast key can use the other party's public key or the previously negotiated unicast key. The key replay counter should also be included in the multicast key agreement request. The key replay counter may use the key replay counter in the above unicast key negotiation to maintain the consistency of the key negotiation message, or may use a separate key replay counter. If the sequence number of the multicast packet against replay attack is used in the multicast communication, the message also includes the sequence number of the multicast packet.

The fourth step is to negotiate and confirm the multicast key. After receiving the multicast key negotiation request from the AP, the STA installs the multicast key and the serial number of the multicast packet, and sends a multicast key negotiation confirmation message to the AP. This message contains the key replay counter copied from the multicast key agreement request.

For the above key negotiation message, in addition to encrypting and protecting the key, the message integrity can also be protected to enhance the security of the negotiation process. During the communication process between the STA and the AP, the above process can be used at any time to update the unicast or multicast key.

By adopting the method of the invention, safe and efficient key negotiation can be realized in the WLAN system, and the multicast communication protection of the WLAN system can be supported, so that the WLAN system developed according to GB15629.11 is more perfect.

Description of drawings

Figure 1 is a flow chart of WAI certificate authentication and key agreement described in GB15629.11.

Fig. 2 is a flow chart of complete authentication and key agreement after adopting the key agreement method of the present invention.

Fig. 3 is a detailed flowchart of the key agreement method in the basic mode.

Detailed ways

In the basic mode of the WLAN system, after the STA and the AP perform the WAI certificate authentication process according to GB15629.118.3, they initiate the key negotiation process described in the present invention, as shown in FIG. 2 . Compared with the existing GB15629.11 WAI certificate authentication and key agreement process, the process of key agreement is different, including the following process:

1) The access point sends a unicast key negotiation request to the wireless terminal;

2) The wireless terminal sends a unicast key negotiation response to the access point;

3) The access point sends a multicast key negotiation request to the wireless terminal;

4) The wireless terminal sends a multicast key negotiation confirmation to the access point;

As shown in Figure 3, the detailed process of key agreement is as follows,

1) The first is unicast key negotiation. The AP generates a string of random numbers, encrypts them with the STA's public key, and sends them to the STA as a unicast key negotiation request. This request also includes information about all of the requesting party's alternative session secrecy algorithms and key replay counters. Key replay counters are used to prevent replay attacks on key agreement messages. If the unicast packet sequence number against replay attack is used in unicast communication, this message shall also contain the unicast packet sequence number.

2) After the STA receives the key negotiation request from the AP, it first conducts session algorithm negotiation. If the responder does not support all the alternative session algorithms of the requester, it responds to the requester that the session algorithm negotiation failed, otherwise

3) The STA selects an algorithm supported by itself from the alternative algorithms provided by the AP as the session secrecy algorithm.

4) The STA uses the local private key to decrypt the negotiation data and obtain the random data generated by the AP.

5) The STA generates a string of random data, and performs a modulo 2 sum operation with the random data of the AP as a unicast communication key. STA installs the unicast communication key and unicast packet sequence number.

6) After the STA encrypts the random data generated by itself with the AP's public key, it forms a unicast key negotiation response message and sends it to the AP. The Key Replay Counter from the copied Unicast Key Agreement Request shall also be included in this message.

7) After the AP receives the unicast key negotiation response message, it checks whether the key replay counter inside is correct, that is, whether it is the same as the value in the previous unicast key negotiation request. If different, disassociate; if same, then

8) The AP decrypts the random data of the STA with its own private key, and performs modulo 2 sum operation with the random data generated by itself to obtain the unicast communication key. The AP installs the unicast communication key, and updates the key replay counter, adding 1 to its value.

9) If an error occurs during the unicast key negotiation, both parties can disconnect or re-initiate the unicast key negotiation.

10) After the unicast key negotiation is completed, start the multicast key negotiation.

11) The AP takes out the current multicast key, or temporarily generates a secure random number as the multicast key, and uses the other party's public key or the encryption algorithm and unicast key obtained through the previous unicast key negotiation Protect. The AP forms a multicast key negotiation request message together with the encrypted multicast key, the key replay counter, and the sequence number of the multicast packet (if necessary) and sends it to the STA.

12) After the STA receives the multicast key negotiation request from the AP, it checks whether the key replay counter in the message is correct, that is, whether it is greater than the key replay counter saved by the STA. If the counter value is wrong, the STA needs to disconnect from the AP. If the key replay counter is correct, then

13) The STA decrypts the multicast key from the multicast key negotiation request message, installs the multicast key and updates the serial number of the multicast packet. If the multicast key is successfully installed, then

14) The STA sends a multicast key negotiation confirmation message to the AP, the content of which is the key replay counter. Indicates that the multicast key is installed.

15) After receiving the multicast key negotiation confirmation message, the AP checks the key replay counter in the message. If the key replay counter is the same as the multicast key negotiation request sent by the AP, the AP installs and configures the multicast key, and adds 1 to the value of the key replay counter.

16) If an error occurs in a link during the multicast key negotiation process, both parties can re-initiate the negotiation process or disconnect the association. If everything is completed successfully, the multicast key negotiation is successful.

17) After both the unicast and multicast key negotiations are completed, the communication parties use the negotiated algorithm and key to keep the communication secret. During the communication between the STA and the AP, in order to prevent the leakage of the multicast key, you can set a fixed time interval, and the two parties re-initiate the multicast key negotiation process to update the multicast key.

In addition, if key leaks are suspected during communication, or data integrity check errors are found and management events are triggered, key negotiation can also be performed at any time to generate new unicast and multicast keys.

Claims (5)

1. A method for key agreement in a wireless local area network, characterized in that the method comprises the following processing steps: The first step is the unicast key negotiation request: the AP generates a string of random numbers, encrypts them with the STA’s public key, and sends them to the STA as a unicast key negotiation request; the request also includes all the candidate session algorithm information of the requesting party And the key replay counter, the key replay counter is used to prevent the replay attack on the key agreement message; The second step, unicast key negotiation response: After receiving the unicast key negotiation request from the AP, the STA first negotiates the session algorithm. If the responder does not support all the alternative session algorithms of the requester, it sends Respond to session algorithm negotiation failure, otherwise, select one of the supported algorithms from the alternative algorithms provided by the requester; then use the local private key to decrypt the negotiation data, obtain the random data generated by the AP, and install the unicast communication key; then Generate a string of random data, encrypt it with the public key of the AP, and then send it to the AP; the message also includes the key replay counter in the copied unicast key negotiation request; Step 3: Multicast key negotiation request: After the unicast key negotiation is completed, the AP encrypts and protects the multicast key and sends it to the STA as a multicast key negotiation request message; the multicast key negotiation request also includes key replay counter; The fourth step is the multicast key negotiation confirmation; after receiving the multicast key negotiation request from the AP, the STA installs the multicast key and sends a multicast key negotiation confirmation message to the AP; The key replay counter copied in the key agreement request. 2. The key agreement method in the wireless local area network according to claim 1, wherein in said step 1, if the unicast packet sequence number of anti-replay attack is used in said step 1, said unicast key The negotiation request should also include the unicast packet serial number; and after the STA obtains the random data generated by the AP in step 2, it should also install the unicast packet serial number. 3. according to claim 1 or 2 described key negotiation method in the wireless local area network, it is characterized in that, in described step 3, if use the multicast packet serial number of anti-replay attack in the multicast communication, then the group The multicast key negotiation request also includes the multicast packet serial number; and in step 4, after the STA receives the multicast key negotiation request from the AP, it should also install the multicast packet serial number. 4. The key agreement method in the wireless local area network according to claim 1, characterized in that, in the step 3, the AP encrypts and protects the multicast key and can use the public key of the STA to keep it secret. 5. The key agreement method in the wireless local area network according to claim 1, characterized in that, in the step 3, the AP encrypts and protects the multicast key and can use the STA's unicast key to keep it secret.