JP2006311394A - Radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform calculation processing for alteration detection at each originating station when fragment packets from different originating stations are mixed and received. <P>SOLUTION: A head decoder 2 decodes a header of a received fragment packet and transmits an originating station address to a calculation value storage part 3. An MIC calculation part 1 stores MIC calculation results in registers 32a-32m corresponding to the originating stations and performs the MIC calculation of the following fragment packets transmitted from each station using MIC calculation values stored in the registers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus having a function of detecting falsification of a received packet.

Conventionally, a high-speed wireless LAN system that performs bidirectional communication between wireless communication devices has been provided. In this field, standardization based on the IEEE 802.11 standard is progressing.
In the IEEE802.11i standard (see Non-Patent Document 1), it is considered to make it difficult to decrypt an encryption key while using RC4 as TKIP (Temporal Key Integrity Protocol). Further, in the IEEE802.11i standard, in order to verify packet tampering, a field called MIC (Message Integrity Check) is provided in addition to the conventional CRC32 code (ICV) for falsification detection.

Here, a process of sequentially receiving fragment packets and detecting falsification by a conventional wireless communication apparatus will be described.
FIG. 3 is a diagram showing the configuration of the fragment packet. FIG. 3A shows the configuration of the last fragment packet, which is based on the MAC header, the frame body, the MIC field storing the MIC calculation result, and the FCS. Composed. FIG. 3B shows the configuration of a fragment packet other than the last fragment packet, which is composed of a MAC header, a frame body, and an FCS.

  The fragment packets configured as described above are sequentially received by the wireless communication device. When the first fragment packet is received, the MIC calculation is performed by setting the MIC key sent in advance as the initial value of the MIC calculation value. Then, the MIC calculation result is stored in a memory in the MIC calculator.

  When the next fragment packet is received, the MIC calculation result stored in the memory of the MIC calculator is set as the initial value of the MIC calculation value, the MIC calculation is performed, and the MIC calculation result is the MIC calculation result of the first fragment packet. Instead, it is stored in a memory in the MIC calculator.

  Thereafter, for the received fragment packet, the MIC calculation value stored in the memory in the MIC calculator is set as an initial value, the MIC calculation is performed, and the MIC calculation result is stored in the memory in the MIC calculator. When the MIC calculation result of the last fragment packet is stored in the memory in the MIC calculator, the MIC calculation result stored in the memory in the MIC calculator and the MIC calculation result stored in the MIC field are obtained. It is determined whether or not they match, and it is determined whether or not tampering has been performed.

Note that a wireless LAN compliant with the IEEE 802.11 standard requires a high communication speed, and therefore, the calculation processing of the MIC field is also implemented in hardware to increase the speed.
"Revised 802.11 High-Speed Wireless LAN Textbook" (pp. 307-308) Supervision: Masahiro Morikura, Shuji Kubota Publication: Impress Corporation

  However, in the wireless LAN conforming to the IEEE802.11i standard described in the above background art, it is necessary to comply with the requirement that fragment packets from three or more stations can be received at the same time. There is a problem that it is difficult to perform the calculation processing.

  That is, since the conventional wireless communication apparatus is configured to store the calculation result of the MIC calculation in the memory in the MIC calculator, the fragment packets sequentially transmitted from one source station may be received continuously. For example, the first fragment packet transmitted from the first source station is received, and the first fragment transmitted from the second source station while receiving the next second fragment packet is received. When receiving the packet, when the MIC calculation result of the first fragment packet transmitted from the second transmission station is calculated, the MIC calculation result of the first fragment packet transmitted from the first transmission station is calculated. MIC meter for the second fragment packet transmitted from the first source station for storage in the memory in the MIC calculator instead of the result When performing, it can not be set as an initial value the MIC calculation results of the first fragmented packet is transmitted from the same source station (the first transmitting station). That is, when fragmentary packets sequentially transmitted from a plurality of transmission stations are mixedly received in the conventional wireless communication apparatus, the MIC calculation result of each transmission station is not carried over, and the calculation starts again from the initial value, so that the MIC There was a problem that the calculation could not be performed correctly.

  An object of the present invention is to enable falsification detection calculation processing for each transmitting station when fragmented packets from different transmitting stations are received together.

  The present invention is a wireless communication apparatus that receives a mixture of fragment packets sequentially transmitted from a first source station and fragment packets sequentially transmitted from a second source station, wherein the fragment packet is altered. A calculation unit that performs a calculation process for detection; a first storage unit that stores a calculation result calculated as a result of performing the calculation process on a fragment packet transmitted from the first source station; And a second storage unit for storing a calculation result calculated as a result of performing the calculation process on the fragment packet transmitted from the second transmission station.

According to the present invention, even when fragment packets from different transmission stations are received together, falsification detection calculation processing can be performed for each transmission station.
In addition, the wireless communication device includes a header decoding unit that determines continuation presence / absence information and a source station address from the header part of the fragment packet, and determines whether to store the continuation presence / absence information in the storage unit based on the continuation presence / absence information. When it is determined that the data is stored in the storage unit, the calculation result is stored in the storage unit corresponding to the source station address.

With this configuration, even when a fragment packet transmitted from the same source station is sent later, the calculation result can be left in the storage unit.
Further, the wireless communication device determines whether or not it is the first fragment packet based on the fragment number determined from the header part of the fragment packet by the header decoding unit. The calculation process is performed using the calculation result stored in the storage unit corresponding to the station address as an initial value.

  By configuring in this way, it is possible to perform a calculation for falsification detection based on a calculation result for a fragment packet previously transmitted from the same source station.

  According to the present invention, even when fragment packets transmitted from different transmitting stations are mixedly received, calculation processing for detecting falsification can be performed for each transmitting station.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a wireless communication device according to an embodiment of the invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a wireless LAN system including a plurality of wireless communication apparatuses according to an embodiment.

  Each wireless communication device 4A, 4B, 4C performs wireless communication with another wireless communication device, and receives packets from a plurality of counterpart stations. The wireless communication device (own station) 4C has a falsification detection device, which will be described later, and sequentially receives packets from the partner stations (transmitting stations) 4A and 4B and detects whether or not each packet is falsified.

FIG. 2 is a diagram showing an overall configuration of the falsification detection device 10 used in the wireless communication device according to the embodiment of the present invention.
In FIG. 2, the falsification detection device 10 decodes the MAC header of the received packet and extracts the address of the transmitting station, etc., from the MIC calculation unit (calculation unit) 1 that performs MIC calculation for falsification detection on the packet. A header decoding unit 2, and a calculated value storage unit 3 having registers 32 a to 32 b for storing the calculation results calculated by performing the MIC calculation on the packet by the MIC calculation unit 1. Configured.

  The header decoding unit 2 includes an address field decoder 21 that decodes the address field of the MAC header, a sequence control field decoder 22 that decodes a sequence control field following the address field, and A more fragment decoder 23 for decoding more fragment fields (More Fragments field) and other decoders are provided, and the decoding results in these decoders are output to the MIC calculation unit 1 and the calculated value storage unit 3.

  The information that is decoded and extracted by the address field decoder 21 includes the source station address. In addition, the fragment number is included in the information decoded and extracted by the sequence control field decoder 22. Furthermore, the information decoded and extracted by the more fragment field decoder 23 includes continuation presence / absence information indicating whether or not there is a subsequent fragment packet transmitted from the same transmission station.

The MIC calculation unit 1 performs MIC calculation processing on the received packet.
The calculated value storage unit 3 includes a plurality of registers 32 a to 32 b (corresponding to the first storage unit and the second storage unit) that store calculation results during the calculation of the MIC calculation, and the address field decoder 21. Based on the result of decoding, the calculation results during the MIC calculation are stored in the registers 32a to 32b corresponding to the source station address. The MIC calculation result stored in the calculation value storage unit 3 is output to the MIC calculation unit 1 when performing the MIC calculation of the next fragment packet received from the same source station. The registers 32a to 32b can be configured by, for example, a semiconductor memory.

  FIG. 3 is a schematic diagram showing a configuration of a fragment packet received by the falsification detection device 10, and FIG. 3A shows a configuration of the last fragment packet having an MIC field, and includes a MAC header, a frame body, and an MIC. It consists of an MIC field in which the calculation result is stored and a frame check sequence FCS. FIG. 3B shows the configuration of a fragment packet other than the last fragment packet that does not have an MIC field, and includes a MAC header, a frame body, and an FCS.

  The MAC header is provided with a sequence control field (including a fragment number) and a more fragment field indicating whether or not there is a subsequent fragment packet transmitted from the same source station. For example, “1” is stored in the mower fragment field when there is a subsequent packet transmitted from the same source station, and the last fragment packet transmitted from the same source station when it is not a divided packet or from the same source station. In this case, “0” is stored. In the MIC field, when the packet is not divided, the MIC calculation result calculated as a result of performing the MIC calculation for the single packet is stored, and when the packet is divided into a plurality of fragment packets, The MIC calculation result calculated as a result of performing the MIC calculation on the packet before being divided is stored. When the packet is divided into a plurality of fragment packets, the value of the MIC field of the last fragment packet is compared with the final MIC calculation result of the received plurality of fragment packets to alter the packet. The presence or absence of can be detected.

Next, FIG. 4 is a flowchart of the MIC calculation process in the case of receiving a mixture of fragment packets from a plurality of stations.
When a fragment packet is received in the reception standby state, the header decoding unit 2 decodes the address field, sequence control field, and more fragment field included in the header of the fragment packet, identifies the source station address in the address field, and further detects the sequence control field. It is determined whether or not the fragment number is 0 (FIG. 4, S11). Since the fragment number 0 is set for the first fragment packet in the sequence control field, it can be determined whether or not it is the first fragment packet by determining whether or not the fragment number is 0.

  If the fragment number is 0 (S11, YES), the process proceeds to step S12, where the MIC key sent in advance from the transmission station corresponding to the transmission station address is set as the initial value of the MIC calculation value, and the MIC calculation is performed. Initialize the value.

  Next, it is determined whether or not the value of the more fragment field is 0 (S13). The mower fragment field stores information (corresponding to continuation presence / absence information) indicating whether or not there is a subsequent fragment packet transmitted from the same source station. In the embodiment, when there is no subsequent fragment packet transmitted from the same source station, 0 is set in the more fragment field.

  If it is determined in step S13 that the value of the more fragment field is not 0 (S13, NO), that is, if there is a subsequent fragment packet transmitted from the same source station, the process proceeds to step S14. , MIC calculation is performed assuming that the MIC field does not exist.

  In the next step S15, the MIC calculation unit 1 stores the calculation result of the MIC calculation in a register corresponding to the source address of the fragment packet (any one of the registers 32a to 32b of the calculation value storage unit 3 in FIG. 2). Return to step S11.

  If the next fragment packet is received in the reception standby state, the process of step S11 described above is executed again to determine whether the fragment number in the sequence control field is 0 or not.

  If the fragment number is not 0 (S11, NO), that is, if the second and subsequent fragment packets are received, the process proceeds to step S16, where the MIC calculation value is read from the register corresponding to the source address of the fragment packet, The value is set as the initial value for the MIC calculation. Thereafter, the process proceeds to step S13 described above, and it is determined whether or not the value of the more fragment field is zero.

  If it is determined in step S13 that the value of the more fragment field is 0, that is, if it is the last fragment packet, the process proceeds to step S17, where the MIC calculation unit 1 corresponds to the source station address of the calculation value storage unit 3. The MIC calculation is performed using the MIC calculation value read from the register as an initial value. In this case, since the MIC field is provided, in the next step S18, it is determined whether or not the calculation result of the MIC and the value of the MIC field match.

  If the MIC calculation result matches the value of the MIC field in step S18 (S18, YES), the process proceeds to step S19, where it is determined that the received plurality of fragment packets have not been tampered with and the packet is resent. To construct.

  If the calculation result does not match the value of the MIC field in step S18 (S18, NO), it is determined that falsification has been performed, and the process proceeds to step S20, where a plurality of fragment packets received from the same source station are discarded. To do.

  FIG. 5 is an explanatory diagram showing the flow of MIC calculation when the wireless communication terminal device provided with the falsification detection device 10 receives a mixture of fragment packets from a plurality of stations, and FIG. FIG. 5B shows a configuration example of a fragment packet, and shows a flow of MIC calculation processing for a received fragment packet sequence.

  As shown in FIG. 5A, first the fragment packet (A-1-0) from station A is received, then the fragment packet (A-1-1) from station A is received, and then The fragment packet (B-1-0) from the station B is received, the fragment packet (A-1-2) from the station A is received again, and then the fragment packet (B-1-1) from the station B is received. Will be described. The letters A and B at the beginning of the code assigned to each fragment packet in FIGS. 5A and 5B indicate the address of the transmitting station A or B, and the first number ( For example, the first number “1” of A-1-2) indicates the number of the packet (packet before division), and the second number (for example, the second number “2” of A-1-2). Indicates the fragment number of the fragment packet.

  As shown in FIG. 5B, the fragment packet (A-1-0) from the station A is first received, and the header fragment unit 2 receives the first fragment packet with the station A and the fragment number 0. And the mower fragment field is not 0 and it is determined that there is a subsequent fragment packet, the MIC calculation is performed using the MIC key as an initial value, and the calculation result is stored in the calculated value storage unit 3 corresponding to the transmitting station A. It is stored in the register 32a (see FIG. 2) (step S1 in FIG. 5).

  Next, when the fragment packet (A-1-1) of the same station A is received and the header decoding unit 2 determines that the source station is the station A and the fragment number is not 0, the station of the calculated value storage unit 3 The MIC calculation value calculated from the fragment packet (A-1-0) received from the station A last time is read from the register 32a corresponding to A, and the MIC calculation is performed using the value as an initial value (step S2). .

  If it is determined in step S2 that the more fragment field of the received fragment packet is not 0 and there is a subsequent fragment packet, the calculation result (intermediate result) of the MIC calculation is stored in the calculation value storage unit 3. It is stored in the register 32a corresponding to the station A (step S3).

  Next, when the fragment packet (B-1-0) of the station B is received and the header decoding unit 2 determines that the source station is the station B, the fragment number is 0, and the value of the more fragment field is not 0, the reception is performed. The calculation result (intermediate result) of the MIC calculation for the fragment packet (B-1-0) is stored in the register 32b corresponding to the station B of the calculated value storage unit 3 (step S4).

  Next, when the fragment packet (A-1-2) from the station A is received and the header decoding unit 2 determines that the source station is the station A and the fragment number is not 0, as described above, the calculation is performed. The MIC calculation value calculated from the fragment packet (A-1-1) received from the previous station A of the MIC calculation is read from the register 32a corresponding to the station A of the value storage unit 3, and the value is used as an initial value. MIC calculation is performed (step S5). Further, when the MIC calculation unit 1 determines that the value of the more fragment field of the received fragment packet is 0 and there is no subsequent fragment packet, it is determined whether or not the value of the MIC field matches the MIC calculation result. Is done. If the calculation results match, the packet is reconstructed from a plurality of fragment packets received from the station A. If the calculation results do not match, the plurality of fragment packets received from station A are discarded.

  Next, when the fragment packet (B-1-1) from the station B is received and the MIC calculation unit 1 determines that the source station is the station B and the fragment number is not 0, the calculated value storage unit 3 The MIC calculation value calculated from the fragment packet (B-1-0) received from the previous station B is read from the register 32b corresponding to the station B, and the MIC calculation is performed using the value as an initial value (step S6). ).

By repeating the processing operations as described above, the MIC calculation of fragment packets transmitted from a plurality of stations can be accurately performed for each station.
In the example shown in FIG. 5, the number of transmitting stations that transmit fragment packets to the station (wireless communication apparatus) provided with the falsification detection device is two. It is easy to set the number of transmitting stations to be transmitted to a plurality of 3 or more.

  Since the tampering detection apparatus 10 according to the present embodiment is configured as described above, even when fragment packets are transmitted from two or more transmitting stations simultaneously to a station (wireless communication apparatus) including the apparatus. The presence or absence of tampering can be detected for each transmitting station in a station equipped with this apparatus.

It is a figure which shows the structure of the radio | wireless communications system of embodiment of this invention. It is a figure which shows the structure of the tampering detection apparatus of embodiment of this invention. FIG. 3A shows the configuration of a fragment packet having an MIC field, and FIG. 3B shows the configuration of a fragment packet having no MIC field. It is a flowchart of MIC calculation processing of an embodiment. FIG. 5A shows a configuration example of a received fragment packet sequence, and FIG. 5B shows a flow of MIC calculation processing for the received fragment packet sequence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 MIC calculation part 2 Header decoding part 3 Calculated value memory | storage part 21 Address field decoder 22 Sequence control field decoder 23 More fragment field decoder 32a-32m Register

Claims (3)

A wireless communication device that receives a mixture of fragment packets sequentially transmitted from a first source station and fragment packets sequentially transmitted from a second source station,
A calculation unit that performs a calculation process for detecting falsification of the fragment packet;
A first storage unit for storing a calculation result calculated as a result of performing the calculation process on the fragment packet transmitted from the first transmission station;
A wireless communication apparatus comprising: a second storage unit that stores a calculation result calculated as a result of performing the calculation process on a fragment packet transmitted from the second transmission station. A header decoding unit for determining continuation presence / absence information and a source station address from the header part of the fragment packet;
It is determined whether or not to store in the storage unit based on the continuation presence / absence information, and when it is determined to store in the storage unit, the calculation result is stored in a storage unit corresponding to the source station address. The wireless communication apparatus according to claim 1. Based on the fragment number determined from the header part of the fragment packet by the header decoding unit, it is determined whether or not it is the first fragment packet. If it is not the first fragment packet, it is stored in the storage unit corresponding to the source station address. The wireless communication apparatus according to claim 2, wherein the calculation process is performed using the stored calculation result as an initial value.

Images