CN1780468A - Method for preventing message from repeating and attacking under idle mode - Google Patents

Abstract

The present invention provides a method for preventing replay attacks, which is used for the terminal to initiate a location update process in idle mode. The first paging controller stores the registration information of the terminal, including the following steps: A) The terminal sends a location update request message, the message contains at least one authentication information; B) the first paging controller receives the location update request message, judges whether the authentication information has been used, if so, discards the message, and ends; otherwise accepts the location update request message . Wherein, when the second paging controller is also included, and the terminal is in the area of the second paging controller; the message between the terminal and the first paging controller is transferred through the second paging controller; and Step B further includes: the first paging controller sends the saved registration information of the terminal to the second paging controller. Using this method, the message replay attack in idle mode can be effectively resisted.

Description

Method of Preventing Message Replay Attack in Idle Mode

technical field

The invention relates to the field of wireless access systems, in particular to a method for preventing message replay attacks in idle mode.

Background technique

The 802.16e standard defines the air interface standard of the mobile broadband wireless access system. The 802.16e network is at least composed of a mobile subscriber station (MSS) and a base station (BS). Multiple BSs can form a group, called a paging group (Paging Group). The purpose of the paging group is to form a continuous area. In this area, the MSS in idle mode does not need to send uplink traffic, but can judge whether there is downlink traffic sent to it through the downlink paging channel.

Idle mode is a terminal working mode defined by the IEEE 802.16e standard. Its characteristics are: MSS can move in the area of the paging group, and receive downlink broadcast service messages at regular intervals to know whether there is downlink service to send; Moreover, the MSS does not need to register with the BS of the cell during the roaming process in this area; when the MSS roams to a different cell in the area, it does not need to perform normal operation procedures such as handover, so as to help the MSS save power and air interface resources.

During normal operation with a serving base station (Serving BS), the MSS can request to enter the idle mode by sending a message. Similarly, the Serving BS can also actively request the MSS to enter the idle mode by sending a message. When the MSS is interrupted and the normal operation process of the Serving BS enters the idle mode, the paging controller (Serving BS or other network entities that control the activities of the MSS idle mode) needs to save some MSS service information. Here, it is called the MSS saved by the paging controller. Service information is MSS registration information.

In idle mode, the MSS will periodically initiate a location update request to the paging controller. After receiving the location update request message sent by the MSS, the paging controller sends a response message, indicating the success or failure of the MSS location update request. The significance of location update is that MSS can regularly notify the paging controller that it is still within the control range of this paging group. If only roaming within a paging group, the location update request will not cause any action between the MSS and the paging controller. When the MSS roams across paging groups, the new paging group controller finds that the paging controller ID (Paging Controller ID) in the location update request message is not its own PagingController ID when it receives the location update request from the MSS, so it A response message will be sent to inform the MSS that the location update is successful, and at the same time notify the original paging group that the MSS has moved to a new paging group through the backbone network, and the original paging group controller will send the stored registration information of the MSS to the new paging group. The paging controller for the paging group.

In the 802.16 system, HMAC-Digest is used to authenticate messages. HMAC-Digest is a message authentication code obtained by digesting the message body based on the shared key between the communicating parties. Before sending the message, the sender uses the shared key exchanged by both parties during the authentication process and the message body (including the message header) to calculate together to obtain an encrypted message digest, that is, HMAC-Digest, and the receiver performs the same process after receiving the message. By calculating an HMAC-Digest and comparing it with the HMAC-Digest sent with the message, the sender of the message can be authenticated.

The location update request of MSS in idle mode includes HMAC-Digest. Since MSS roams to different BSs in idle mode, it does not need to perform a handover process, so it will not authenticate with the new BS. How to authenticate the HMAC-Digest in these management messages, the existing mechanism is to store the MSS registration information on the paging controller as described above, which includes the key information of the MSS and the BS where it enters the idle mode. The location update request initiated for the first time indicates the current paging controller where the key information is located, and the key information can be used to perform HMAC-Digest authentication on the management message in the idle mode. The content of the location update request in the prior art also includes: the paging controller ID of the paging group, the target BSID of the message and other related information.

Replay attack is a common network attack method. The attacker intercepts the message sent by A (or B) during a certain interaction between the two parties (A, B), and at a suitable time in the future, sends a message to B ( Or A) resends the message it intercepts, if the message interaction process is the same every time, and the message does not contain enough information to enable B (or A) to determine whether the message was initiated for the first time or replayed. Attackers can pretend to be one party in the communication to deceive the other party, so as to achieve the purpose of attacking the network.

The existing technology guarantees the authentication of messages, but does not provide a mechanism to resist replay attacks. Combining with Figure 1, through the following analysis process, we will introduce how attackers implement replay attacks:

Step 101: MSS enters idle mode on a certain BS in paging group A. This process is completed by MSS request or BS proactively notifies MSS. ) to save relevant registration information (such as key information) of MSS;

Step 102: MSS roams from paging group A to paging group B;

Step 103: MSS initiates the first location update request in the new paging group B, the current BS BSID=2, so the information contained in the location update request is: Paging Controller ID=1, Target BSID=2, CID= 0 etc. After the message is authenticated (at this moment, the authentication of the message should be sent to the paging controller A to complete), the original MSS reservation information stored on the paging controller A (ID=1) is transferred to the paging controller through the backbone network. on device B (ID=2);

Step 104: The attacker (Attacker) intercepts the location update request message initiated by the MSS at the location, and saves it;

Step 105: The MSS roams in the paging group, and finally roams to the cell with BSID=3, and may initiate multiple location update requests in the middle, and the information contained in the request message includes: Paging ControllerID=2, Target BSID (according to the location update request initiated It depends on the BS at the time), CID=0, etc.;

Step 106: MSS roams from paging group B back to paging group A;

Step 107: The MSS initiates a location update request in the paging group A, and the information contained in the request message includes: Paging Controller ID=2, Target BSID=4, CID=0, etc. After the message is authenticated, the MSS reservation information originally stored on the paging controller B (ID=2) is transferred to the paging controller A (ID=1) through the backbone network;

Step 108: The attacker replays the intercepted location update request at the location where the MSS roams to paging group B and initiates the first location update request. The information contained in the replayed request message is: Paging Controller ID=1, Taget BSID=2, CID=0, etc. Since the MSS has roamed back to the paging group A at this time, the reserved information of the MSS is just stored in the paging controller of the paging group A, so the replay attack succeeds, and the message is saved in the paging controller after being authenticated. The MSS reserved information on A (ID=1) is transferred to the paging controller B (ID=2) through the backbone network, and at this time the actual location of the MSS is in the paging group A, but the system will consider that the MSS has roamed to In paging group B, the MSS may not be paged.

From the above analysis, we can know that in the idle mode, when the MSS initiates a location update message, it can be intercepted by the attacker for replay attacks, which will cause the terminal to be unable to be paged.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for preventing message replay attacks in the idle mode of the 802.16e system.

The present invention provides a method for preventing replay attacks, which is used for the terminal to initiate a location update process in idle mode. The first paging controller stores the registration information of the terminal. The method includes the following steps:

A. The terminal sends a location update request message, which contains at least one piece of authentication information;

B. The first paging controller receives the location update request message, and judges whether the authentication information has been used, and if so, discards the message and ends; otherwise, responds to the location update operation.

Wherein, the terminal is in the area of the first paging controller, and the operation of responding to the location update in step B is: accepting the location update request message.

Wherein, it further includes a second paging controller, the terminal is in the area of the second paging controller; the message between the terminal and the first paging controller is transferred through the second paging controller; described in step B The location update operation in response is: accepting the location update request message, and the first paging controller sends the saved registration information of the terminal to the second paging controller.

Wherein, the serial number is saved on the terminal, and the terminal registration information saved by the first paging controller contains the same serial number; the authentication information in step A is obtained by performing an increment operation on the serial number saved by the terminal new serial number; the step of step B judging whether the authentication information has been used is: judging whether the new serial number is not greater than the serial number contained in the terminal registration information saved by the paging controller; The step of responding to the location update operation further includes: updating the serial number contained in the saved terminal registration information to the new serial number in the received location update request message.

Wherein, the authentication information in step A is: the time stamp when the terminal sends the location update request message; the step of judging whether the authentication information has been used in step B is: judging whether the time stamp is within the current time of the paging controller The allowable error value is outside.

Wherein, before the terminal in step A sends the location update request message, it further includes: using an algorithm to generate an authentication code for the location update request message containing authentication information, and carrying it in the location update request message; After receiving the location update request message, it further includes: using the same algorithm to generate an authentication code for the received location update request message, and comparing and authenticating with the authentication code in the location update request message; if the authentication fails, then end, otherwise continue to follow step. Said certain algorithm may be HMAC-Digest algorithm.

Wherein, after the operation of responding to the location update in step B, it further includes: D. the first paging controller sends a response message to the terminal, and the response message contains the received authentication information; E. the terminal receives the response message and judges the Whether the authentication information in the message is the same as the authentication information in the location update request message sent, if yes, then receive the response message, otherwise discard the message.

As can be seen from the above method, the present invention adds parameters that change according to certain rules in the location update request message, such as increasing serial numbers and time stamps, and the paging controller judges whether the parameters have occurred to identify the replay message , and discard it when it is judged to be a replay message, so as to resist the replay attack.

Description of drawings

FIG. 1 is a schematic diagram of location updating of a terminal.

Fig. 2 is a flow chart of updating the location of the serial number.

Figure 3 is a flowchart of location update using timestamps.

Detailed ways

The replay attack is to replay the previously intercepted message without modification at a suitable time in the future, so as to achieve the purpose of the attack. In order to effectively prevent message replay attacks, it is an effective method to ensure that the sent messages are not repeated for a long enough time.

In fact, the time for an MSS in idle mode to remain in idle mode is limited, so as long as a continuous change is added to the message and the unique authentication information is kept for a long enough period of time, the attacker can effectively prevent the message from being processed. replay. Because the attacker intercepts the location update request message sent by the MSS in a certain interaction, if it is replayed within a certain period of time, it will be recognized as a replayed message, and this message cannot be used to carry out a replay attack. When the MSS ends the idle mode and enters the normal operation mode, the MSS will re-connect and authenticate with the network. At this time, due to the change of the key information, the messages intercepted by the attacker will completely lose the replay value.

Taking an increasing numerical value as continuously changing authentication information as an example, and referring to FIG. 2 , the method for preventing replay attacks of the present invention will be described in detail.

It is necessary to set a value of n bits on the MSS in advance (n is required to be large enough to ensure that it does not repeat within a long enough time, and the initial value is 0) as the location update sequence number. When the MSS requests to enter the idle mode, the sequence number is initialized to 0 on the paging control of the current paging group. When the MSS initiates a location update in the idle state, the following steps are included:

Step 201: MSS adds 1 to the sequence number maintained by itself, puts the new sequence number in the location update request message (RNG-REQ), calculates the HMAC-Digest for the RNG-REQ, and puts the HMAC-Digest in the location update request message (RNG-REQ). In the RNG-REQ message, it is also sent to paging controller B.

Step 202: Paging controller B receives the RNG-REQ message, reads the paging controller ID (Paging Controller ID) recorded in the RNG-REQ, and judges whether it is the same as its own paging controller ID, if so, then Indicates that the MSS is in the paging group, go directly to step 205; otherwise, forward the request message to the original paging controller A corresponding to the paging controller ID recorded in the RNG-REQ, and execute the next step.

Step 203: The original paging controller A receives the RNG-REQ, reads the location update sequence number in the message, compares it with the location update sequence number in the registration information of the MSS saved by itself, if the read If the sequence number in the RNG-REQ is less than or equal to the saved sequence number, then consider that the RNG-REQ is a replay message and discard it, and end the current location update process;

If the sequence number in the read RNG-REQ is greater than the saved sequence number, then it is considered that the RNG-REQ is a new location update request message, and the paging controller A uses the key in the saved registration information of the MSS The RNG-REQ message is authenticated, and after the authentication is passed, a response message of successful location update is generated, and the sequence number in the received RNG-REQ is included in the response message and HMAC-Digest is calculated. At the same time, paging controller A replaces the original saved sequence number with the sequence number in the received RNG-REQ.

Step 204: Paging controller A transmits the saved registration information of the MSS and the location update response message to paging controller B, and paging controller B receives and saves the registration information of the MSS, and forwards the location to the MSS The response message is updated, and at the same time, the original paging controller A deletes the MSS registration information saved by it, and then goes to step 206 .

Step 205: The paging controller B receives the RNG-REQ message, judges whether it is a message replay attack, if so, discards it, and ends the current location update process; otherwise, generates corresponding response information after authentication, and the paging controller B and replace and update the original saved serial number with the new serial number. This step is the same as the process described in step 203, so it is not described in detail.

Step 206: After receiving the response message, the MSS judges whether the sequence number in the message is the same as that in the sent request message. If the same, it is a correct response, otherwise, it is discarded.

When the MSS ends the idle mode and successfully re-connects with a certain BS, it notifies the current paging controller to delete the stored sequence number. The above is an example of an incremented serial number. It is not difficult to understand that the increment range is not limited to the above-mentioned 1, and when the increment range is a negative value, it is equivalent to a decrement.

Through the above process, since the sequence number record of the replayed message must not be greater than the sequence number recorded on the paging controller, the replayed message can be identified to defend against this replay attack.

Next, taking the time stamp as the continuously changing authentication information as an example, and referring to FIG. 3 , the method for preventing replay attacks of the present invention is further described in detail.

The premise of adopting this method is that all the paging controllers in the 802.16e system are required to be synchronized on the clock, which can be realized in reality. For example, when the MSS roams to a new paging group, it will receive The broadcast message of the paging group, and the clock synchronization with the new paging controller can be obtained according to the clock in the message.

Using this method, it is necessary to modify the format of the location update request (RNG-REQ) and response (RNG-RSP) messages in 802.16e, and add the TLV (Type Length Value) code of the time stamp to the message. The TLV encoding (Timestamp Encoding) of the timestamp is added to the 802.16 protocol, and the format of the timestamp can be shown in Table 1 below: TypeType LengthLength value 4 The format is year-month-day hour:minute:second, or the number of seconds counted from 0:00 on the first day of the year, etc. (The time information such as yy-mm-dd hh:mm:ss or the number of seconds from the 00:00:00 of the first day of this year etc.)

Table 1

When the MSS initiates a location update in the idle state, the following steps are included:

Step 301: When MSS sends a location update request message (RNG-REQ), MSS adds Timestamp (Timestamp) information to the message, performs HMAC-Digest calculation on the entire message body, and sends it to paging controller B together.

Step 302: Paging controller B judges whether the MSS is in the paging group (see step 202 for the judging method), if yes, then directly go to step 305; otherwise, forward the request message to the paging controller recorded in the RNG-REQ For the original paging controller A corresponding to the ID, go to the next step.

Step 303: The original paging controller A receives the RNG-REQ, reads the time stamp in the message, and compares it with its own clock. If it is outside the limited time difference range, the RNG-REQ is considered to be a Replay the message and discard it, and end the current location update process;

If it is within the limited time difference range (such as within tens of seconds), then it is considered that the RNG-REQ is a new message, and the paging controller A pairs the RNG-REQ with the key in the registered information of the MSS saved. The message is authenticated, and after the authentication is passed, a response message of successful location update is generated, and the received timestamp is included in the response message and HMAC-Digest is calculated.

Step 304: Paging controller A transmits the saved registration information of the MSS and the location update response message to paging controller B, and paging controller B receives and saves the registration information of the MSS, and forwards the location to the MSS The response message is updated, and at the same time, the original paging controller A deletes the MSS registration information saved by it, and goes to step 306 .

Step 305: The paging controller B judges whether it is a replay message, and the judging method is the same as step 303. And when it is judged to be a replay message, it ends; when it is judged not to be a replay message, a response message is generated and sent to the MSS.

Step 306: After receiving the response message, the MSS judges whether the time stamp in the message is the same as the time stamp in the sent request message. If the same, it is a correct response, otherwise, it is discarded.

Regarding steps 206 and 306, the judgment of the MSS on the response message will not have any impact on the location update process. But the MSS can decide the behavior in the idle mode (such as when to wake up to receive the paging message, etc.) according to other information in the message. These processes have little to do with this patent, so they will not be described in detail here.

Through the above process, since the time recorded by the time stamp of the replayed message will not be the same as the time on the paging controller (within the range of time difference), the replayed message can be identified to defend against this attack.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (8)

1. A method for preventing replay attacks, which is used for the terminal to initiate a location update process in idle mode, the first paging controller saves the registration information of the terminal, and it is characterized in that the method includes the following steps: A. The terminal sends a location update request message, which contains at least one piece of authentication information; B. The first paging controller receives the location update request message, and judges whether the authentication information has been used, and if so, discards the message and ends; otherwise, responds to the location update operation. 2. The method according to claim 1, wherein the terminal is in the area of the first paging controller, and the operation of responding to location updating in step B is: accepting the location updating request message. 3. The method according to claim 1, further comprising a second paging controller, the terminal is in the area of the second paging controller; messages between the terminal and the first paging controller pass through the The second paging controller performs relay; The operation of responding to location update in step B is: accepting the location update request message, and the first paging controller sends the stored terminal registration information to the second paging controller. 4. The method according to claim 1, wherein the terminal stores a serial number, and the terminal registration information stored by the first paging controller contains the same serial number; The authentication information described in step A is: a new serial number obtained by performing an incremental operation on the serial number stored in the terminal; The step of step B judging whether the authentication information has been used is: judging whether the new serial number is not greater than the serial number contained in the terminal registration information saved by the paging controller; The step of responding to the location update operation in step B further includes: updating the serial number contained in the stored terminal registration information to the new serial number in the received location update request message. 5. The method of claim 1, wherein: The authentication information described in step A is: the timestamp when the terminal sends the location update request message; Step B: The step of judging whether the authentication information has been used is: judging whether the time stamp is outside the allowable error value of the current time of the paging controller. 6. A method according to claim 1, 4 or 5, characterized in that, Before the terminal in step A sends the location update request message, it further includes: using an algorithm to generate an authentication code for the location update request message containing authentication information, and carry it in the location update request message; After receiving the location update request message in step B, it further includes: using the same algorithm to generate an authentication code for the received location update request message, and comparing and authenticating with the authentication code in the location update request message; if the authentication fails, then end , otherwise continue to the next step. 7. The method according to claim 6, characterized in that said certain algorithm is an HMAC-Digest algorithm. 8. The method according to claim 1, further comprising: D. The first paging controller sends a response message to the terminal, and the response message includes the received authentication information; E. The terminal receives the response message, and judges whether the authentication information in the message is the same as the authentication information in the location update request message sent, if yes, then receives the response message, otherwise discards the message.

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