CN1964253B - A way to regenerate keys after key contamination - Google Patents

Abstract

The invention discloses a method for regenerating a key after the key is polluted. The key is generated from the initial key through multi-level operations, and the key of each level is generated according to the key of the previous level; When the key of the current level is polluted, re-apply for the key from the previous level of the current level, and then regenerate the new key of the current level according to the applied key. When the intermediate level key is polluted, the present invention generates the key by rekeying the key by applying for the key at the previous level, thereby reducing the time for regenerating the key and reducing the time delay; especially in WLAN, it can reduce the number of STAs The number of interactions with the authentication server, thereby reducing packet loss.

Description

A way to regenerate keys after key contamination

technical field

The invention relates to the field of communication and computer, in particular to a method for regenerating a key after the key is polluted.

Background technique

Currently, in the authentication process of a wireless local area network (WLAN), the key generation process is divided into several levels. When a certain level key is attacked, the lower level keys generated by this key will be polluted, and the resulting sessions will be deleted.

As shown in Figure 1, when the wireless station (STA) performs 802.1X authentication with the authentication server, a master session key (MSK) will be generated (if PSK is used, the PSK should be pre-configured on the STA and the network side device) , at this time there are MSKs on both the network side and the STA. The holder of the paired master key R0 (PMK-R0) on the network side obtains this MSK, and generates PMK-R0 through a certain algorithm together with some other parameters. Similarly, the R1 key holder on the network side obtains PMK-R0 from the R0 key holder on the network side, and generates PMK-R1 through a certain algorithm together with some other parameters. Finally, the wireless access point (AP) gets PMK-R1. On the terminal, STA generates PMK-R0 through the same algorithm from MSK and some parameters, and then generates PMK-R1. Then STA and PMK-R1 perform a four-way handshake, from which PMK-R1 and some parameters generate the same new key PTK on the STA and AP. If the two have the same PMK-R1, then the four-way handshake can be performed , if the PMK-R1 of the two is not the same, the four-way handshake will not be possible.

During the generation process of this key hierarchy, if a key in the middle level is attacked and a polluted key is generated, the resulting lower-level keys will be polluted. In this case, STA and authentication The server needs to re-authenticate to generate the MSK (or reconfigure the PSK). Re-authentication not only has a relatively long delay, but also makes the STA unable to perform data communication with the AP, resulting in data loss.

Contents of the invention

The present invention provides a method for regenerating a key after the key is polluted, so as to solve the problem of increased communication delay and the need for re-authentication when a certain level key is polluted in the process of multi-level key generation in the prior art. Problem with lost data.

The invention provides the following technical solutions:

A method for regenerating a key after key pollution, the key is generated from the initial key through multi-level operations, and the key of each level is generated according to the key of the previous level; after determining the key of the current level If the key is contaminated, perform the following steps:

A. Re-apply for the key from the previous level of the current level;

B. Regenerate a new key at the current level according to the applied key.

After step B, further include steps:

C. Determine whether the new key is the same as the original key of the current level. If it is the same, determine that the key of the previous level is polluted, and use the previous level as the current level and proceed to step A; if different, determine the new key The key is not tainted.

If the unpolluted new key is a key at an intermediate level, keys of subsequent levels are sequentially generated according to the new key.

In step A, before applying for a key, first judge whether the current level is the initial level, if so, regenerate the initial key and use the initial key to generate the keys of subsequent levels in sequence, otherwise, regenerate the keys of the previous level Request key.

Each level also adds the parameters of this level when generating the key.

A method for regenerating a key after key pollution in the authentication process of a wireless local area network (WLAN), in which a paired master key is generated from a master session key (MSK) or a pre-shared key (PSK) through multi-level operations R1, the paired master key R1 is PMK-R1, and the key of each level is generated by the key of the previous level and the parameters of this level; the method includes the following steps:

A. The handshake between the wireless station (STA) and the access point (AP) fails, and it is determined that the PMK-R1 on the network side is polluted;

B. The layer that generates PMK-R1 on the network side applies for a key to the layer that generates PMK-R0; the layer that generates PMK-R0 is the upper level of the layer that generates PMK-R1;

C. The generated PMK-R1 level uses the applied PMK-R0 and parameters to generate a new PMK-R1;

D. Compare the new PMK-R1 with the original PMK-R1. If the two are the same, it is determined that the PMK-R0 is contaminated, and then proceed to step E. If not, the AP uses the PMK-R1;

E. The layer that generates PMK-R0 applies for MSK or PSK from the holder of MSK or PSK, and generates a new PMK-R0 with parameters;

F. Determine whether the new PMK-R0 is the same as the original PMK-R0. If so, generate MSK or reconfigure PSK through re-authentication, and use the MSK or PSK to generate keys for subsequent levels in sequence; if not, use PMK -R0 with parameter generate new PMK-R1.

During the rekeying process on the network side, the STA can communicate with other APs on the network side.

When the intermediate level key is polluted, the present invention generates the key by rekeying the key by applying for the key at the previous level, thereby reducing the time for regenerating the key and reducing the time delay; especially in WLAN, it can reduce the number of STAs The number of interactions with the authentication server, thereby reducing packet loss.

Description of drawings

Fig. 1 is the key generation level in 802.11r in the prior art;

Fig. 2 is the processing flow when the key in the multi-level key is polluted in the present invention;

FIG. 3A and FIG. 3B are respectively a schematic diagram and a flow chart of processing when the key is polluted in the WLAN system in the present invention.

Detailed ways

In order to avoid regenerating a new initial key directly through authentication due to the pollution of a certain level key in the middle of the process of generating the final key after the initial key is multi-level operation, resulting in increased communication delay and data loss , when the intermediate key is polluted, the present invention applies for a key to the previous level that has not been polluted, and regenerates the correct key of the lower level.

For the key of the current level, after applying for the key from the previous level and generating a new key of this level, in order to determine whether the key of the previous level is polluted, compare the new key with the key of this level, if both same, it means that the key of the previous level is polluted, so the previous level needs to apply for a key from its previous level to regenerate a new key, and so on, until the previous level is not polluted. key. If it is determined that the initial key has been contaminated, re-authentication is required to generate a new initial key.

Referring to Figure 2, during the communication process, the processing flow when the key is polluted is as follows:

Step 200, the user equipment interacts with the network-side device, and generates an initial key on the user equipment and the network-side device; or configures an initial key on the user equipment and the network-side device.

Step 210, the user equipment and the network side equipment respectively use the initial key to generate the key of the last level through multi-level operations; wherein the key of each level is generated by the key of the previous level and the parameters of this level.

In step 220, the user equipment and the network side device use the last-level key to verify that the verification fails, that is, the terminal device and the network-side final key are different, and it is determined that the network-side final-level key is polluted.

Step 230: Apply for and obtain a key from the current level to the previous level.

Step 240, generate a new key through calculation by using the applied key and the parameters of the current level.

Step 250 , judging whether the new key is the same as the original key of the current level, if they are the same, go to step 260 , otherwise, go to step 300 .

Step 260 , indicating that the key of the previous level has been polluted, and judging whether the previous level is the initial level, if so, go to steps 280 and 290 , otherwise, go to step 270 .

Step 270 , take the previous level as the current level, and proceed to step 230 .

Step 280, the user equipment interacts with the authentication server to generate an initial key on the user equipment and the network-side device; or reconfigure the initial key on the user equipment and the network-side device.

In step 290, the user equipment and the network side equipment respectively use the initial key to generate a final-level key through multi-level operations.

Step 295: If the current level is the last level, use the key of the level; if the current level is the middle level, then generate the keys of the subsequent levels according to the level according to the new key.

The above-mentioned level may be the authentication key generation level of any communication network, such as the key level of WLAN.

The following takes the hierarchical key in WLAN as an example to further explain:

According to the key generation algorithm defined in the existing 802.11r draft, the generation parameters of PMK-R0 and PMK-R1 are not random. In the case of constant parameters, through the key generation algorithm, the result is generated The new key of is also unchanged, that is, the input does not change, and the output does not change.

According to the prior art, when the four-way handshake is carried out between the wireless station (STA) and the wireless access point (AP), when the two PMK-R1s are not the same, it is generally determined that the PMD-R1 on the network side is polluted, and it is necessary to The STA and the authentication server re-authenticate to generate the MSK; or reconfigure the PSK. However, in the present invention, when the PMK-R1 is polluted, the key is obtained directly from the upper layer that is not polluted to generate the lower correct key. As shown in Figure 3A and Figure 3B, the implementation process is as follows:

In step 300, when the STA and the AP perform the four-way handshake, they find that their PMK-R1s are different, and the four-way handshake fails. It is determined that the key on the AP network side may be polluted.

Step 310: The R1 key holder reapplies for the key PMK-R0 to the upper-level R0 key holder.

Step 320, the R1 key holder regenerates PMK-R1 using the key PMK-R0 and other parameters issued by the R0 key holder.

Step 330 , judging whether the new PMK-R1 is the same as the original PMK-R1 , if they are the same, determine that the PMK-R0 may be polluted, go to step 340 , if not, go to step 400 .

Step 340, the R1 key holder notifies the R0 key holder that the key has been polluted, and the R0 key holder re-requests the MSK or PSK from the MSK or PSK holder.

Step 350, after the R0 key holder successfully obtains the MSK or PSK, use this key to generate a new PMK-R0.

Step 360 , judging whether the generated new PMK-R0 is the same as the original PMK-R0 , if they are the same, the MSK or PSK may be polluted, go to step 370 , otherwise go to step 390 .

Step 370, re-initiate authentication to generate MSK; or reconfigure PSK.

Step 380, the R0 key holder uses the newly generated MSK or PSK to generate a new PMK-R0.

Step 390, the R1 key holder uses the new PMK-R0 to generate a new PMK-R1.

In step 400, the AP uses the newly generated PMK-R1.

During the process from step 310 to step 400, the STA can communicate with other APs.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (6)

1. one kind is polluted the method for back regenerating key at key, and described key is generated after through the computing of multilayer level by initial key, and the key of every level generates according to the key of last level; It is characterized in that, when the key of determining current level is subjected to polluting, carry out following step:

A, apply for key again to the last level of current level;

B, according to the new key of the newly-generated current level of key reconsul of applying for.

C, determine whether new key identical with the original cipher key of current level,, determine that then the key of last level is contaminated if identical, with described last level as current level and carry out steps A; If different, determine that then new key is not comtaminated.

2. the method for claim 1 is characterized in that, if unpolluted new key is the key of intermediate level, then generates the key of follow-up each level successively by level according to this new key.

3. method as claimed in claim 1 or 2, it is characterized in that, in the steps A, before the application key, judge whether current level is initial level earlier, if, then produce initial key again and utilize this initial key to generate the key of follow-up each level successively, otherwise a level is applied for key again forward by level.

4. the method for claim 1 is characterized in that, each level also adds the parameter of this level when generating key.

5. the method for regenerating key after a kind key pollutes in the verification process of WLAN (wireless local area network) WLAN, by generating pairwise master key R1 after master session key MSK or the computing of wildcard PSK process multilayer level, this pairwise master key R1 is PMK-R1, and the key of every level is by the key and the generation of this level parameter of last level; It is characterized in that, comprise the steps:

A, wireless site STA and the access point AP failure of shaking hands determines that the PMK-R1 of network side is contaminated;

B, network side generate the level of PMK-R1 to the level application key that generates PMK-R0; The level of described generation PMK-R0 is the upper level of the level of described generation PMK-R1;

PMK-R0 and parameter that C, the utilization of described generation PMK-R1 level are applied for generate new PMK-R1;

D, with new PMK-R1 and former PMK-R1 relatively if both are identical, determines that then PMK-R0 is contaminated, then carries out step e, if inequality, AP then uses this PMK-R1;

E, apply for MSK or PSK to the holder of MSK or PSK, and itself and parameter are generated new PMK-R0 by the level that generates PMK-R0;

F, judge whether new PMK-R0 is identical with former PMK-R0, if then generate MSK or reconfigure PSK, and utilize this MSK or PSK to generate the key of follow-up each level successively by level by authentication again; If not, utilize PMK-R0 and parameter to generate new PMK-R1.

6. method as claimed in claim 5 is characterized in that, in network side regenerating key process, STA can communicate with other AP of network side.

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