JP4746296B2 - Encryption key setting system, data communication apparatus, and encryption key setting method - Google Patents

Description

  The present invention relates to a technique for setting an encryption key used for encrypting and decrypting communication data transmitted and received via a network in each communication device.

  In recent years, with the development of networks such as a local area network (LAN) and the Internet, various security technologies have been proposed to prevent leakage of communication contents due to wiretapping of communication data and unauthorized intrusion into the network due to impersonation. Yes.

  For example, in a wireless LAN defined by IEEE (Institute of Electrical and Electronics Engineers) 802.11, it is common to a terminal that transmits and receives data (hereinafter referred to as “client”) and an access point that is a wireless LAN repeater. A WEP (Wired Equivalent Privacy) key is set in advance as an encryption key for the client, and data exchanged between the client and the access point is encrypted and decrypted using this WEP key, thereby enabling a third party. A technique for preventing leakage of communication contents to the Internet (hereinafter referred to as “WEP encryption”) has been proposed.

  An example of an access point that performs the above-described WEP encryption is described in Patent Document 1 below.

JP 2001-345819 A

  When performing the above-mentioned WEP encryption, it is necessary to manually set the same WEP key as that set for the access point every time a new client is added, which is cumbersome and inconvenient. It was. Therefore, a method has been proposed in which a WEP key is transmitted from an access point to a client via a wireless LAN, and the WEP key is automatically set in the client.

However, in this setting method, if data including the WEP key is wiretapped, the WEP key is easily obtained by a third party.
Therefore, a method has also been proposed in which data including the WEP key is transmitted by being encrypted with an encryption key that is different from the WEP key and shared by the access point and the client. In this method, like the WEP key, this encryption key needs to be set in advance in the access point and the client. In order to easily perform this setting, when an encryption key is transmitted via a wireless LAN, this encryption key is also obtained by a third party, and as a result, the encrypted WEP key is decrypted, and the third The WEP key is obtained by a person, and there is a risk that the contents of communication will be leaked.

In addition to the WEP encryption described above, in a wireless LAN, a MAC (Media Access Control) address that is individual information of a client is set in an access point in advance, and a connection request from a client other than the client with the set MAC address As a security technology, a technology (hereinafter referred to as “MAC address filtering”) that prevents an unauthorized entry into a wireless LAN when the access point rejects is used.
Also in this MAC address filtering, in order to easily set the MAC address of the client to the access point, the encrypted MAC address and the encryption key used for encryption are transmitted between the client and the access point via the wireless LAN. , The encryption key is obtained by a third party, and as a result, the MAC address is obtained by a third party. As a result, the wireless LAN is illegally infiltrated by impersonation. There was a fear.

  The present invention has been made to solve the above-described problems, and an encryption key used for encrypting and decrypting communication data transmitted / received via a network can be obtained by a third party. It is an object of the present invention to provide a technology for setting the communication devices in a simple manner with a low performance.

  In order to solve at least a part of the above-described problems, an encryption key setting system of the present invention includes two data communication devices connected to each other via a communication path, and transmits and receives between the two data communication devices. An encryption key setting system for setting encryption keys used for encrypting and decrypting communication data to the two data communication devices, respectively, the two data communication devices, A transmission / reception unit that performs transmission / reception of specific data a plurality of times with the data communication device of the other party, and the time required for transmission / reception of the specific data is counted a plurality of times with a predetermined time as a unit, and each time is counted Each of the counters obtained as counter values of a plurality of digits and the corresponding counter values of the counter values obtained by the counter each time A digit determining unit that determines a digit to be generated, and an encryption key generating unit that generates the encryption key based on a basic value indicated by the digit determined by the digit determining unit among the counter values. And

  With this configuration, two data communication devices connected via a communication path perform specific data transmission / reception a plurality of times, and the time required for one or more specific data transmission / receptions is determined by a counter. When the time is counted a plurality of times and the time counted is obtained as a counter value of a plurality of digits each time, the counter values obtained each time are almost equal to each other. Also, the counter values obtained in each data communication device are substantially equal to each other. This is because the distance over which the specific data is transmitted is constant, and the two data communication apparatuses repeat the same process.

  However, since the time required for processing varies in the data communication device, the counter values obtained at each time do not completely match each other, and an error occurs in several digits. Here, since the two data communication apparatuses perform the same processing, the error of the counter value generated in each of the two data communication apparatuses is almost equal, and the error is generated in almost the same digit. .

Here, in each data communication device, when the digits corresponding to the indicated values are determined by comparing the corresponding digits of the counter value obtained each time, the digits excluding the digits with the above-mentioned error are determined. Will be. Therefore, in the two data communication apparatuses, the determined digits are substantially the same, and the basic values indicated by the determined digits are also substantially the same.
And since an encryption key is produced | generated based on this basic value which corresponds substantially, possibility that the same encryption key will be produced | generated and set in two data communication apparatuses becomes high.

The communication path described above may be a communication path configured by a network such as a LAN or the Internet, or may be a communication path configured by a one-to-one connection without using a network. Further, the two data communication apparatuses described above may be a terminal, a server, or the like connected via these communication paths.
In addition, in the case of “obtaining the time counted as a counter value of a plurality of digits” as described above, the counter is reset every time and the time measured is obtained as the counter value. This includes the case where the counter is reset and the difference between the times measured each time is obtained as the counter value.

  Further, with the configuration as described above, the user does not need to manually set an encryption key for each data communication device, and thus can easily set the encryption key.

  Also, data that is sent and received without encryption between the two data communication devices is specific data, and the encryption key and the basic value that is the basis for generating the encryption key are not sent or received. The possibility of being obtained can be reduced.

  Moreover, even if a third party prepares the same counter as that of the two data communication devices and sniffs specific data, the third party transmits the specific data to each data communication device. I cannot know when I received or received it. Therefore, this third party cannot know the counter value obtained by the counter of each data communication device, and cannot know the basic value that is the basis for generating the encryption key. Therefore, it is possible to reduce the possibility of obtaining the encryption key by a third party.

  In the encryption key setting system of the present invention, each of the two data communication devices uses the encryption key generated by the encryption key generation unit to encrypt and transmit the communication data to be transmitted. An encryption / decryption processing unit for decrypting communication data, and in at least one of the two data communication devices, the encryption / decryption processing unit receives the encryption key When the communication data received using the encryption key cannot be decrypted, the encryption key generation unit generates a new encryption key based on a value obtained by correcting the basic value instead of the generated encryption key It is preferable.

As described above, since the time required for processing varies in a data communication device, a carry may occur in a determined digit only in one of the counters of each data communication device. .
In this case, since the basic values do not match in the two data communication devices, the encryption keys generated based on the basic values also do not match in the two data communication devices.
Therefore, as described above, by correcting this basic value in at least one of the data communication devices, the basic values can be made to coincide with each other, and the same encryption key is generated and set by the two data communication devices. It becomes possible to do.

  In the encryption key setting system of the present invention, each of the two data communication devices uses the encryption key generated by the encryption key generation unit to encrypt and transmit the communication data to be transmitted. An encryption / decryption processing unit for decrypting communication data, and in at least one of the two data communication devices, the encryption / decryption processing unit receives the encryption key When the communication data received using cannot be decrypted, the digit determining unit newly determines a digit obtained by reducing the determined digit instead of the determined digit, and the encryption key generating unit Instead of the generated encryption key, it is preferable to generate a new encryption key based on a basic value indicated by a digit newly determined by the digit determining unit in the counter value.

As described above, since the time required for processing varies in the data communication device, the error of the counter value does not match between the two data communication devices, and the error-occurring digits may be different. .
In this case, since the digits to be determined are different, the basic values indicated by these digits do not match each other. Accordingly, the encryption keys generated based on these basic values do not match each other.
Therefore, as described above, by reducing the determined digits in at least one of the data communication devices, the determined digits match and the basic values match in the two data communication devices. The possibility increases. Therefore, it is highly possible that the same encryption key is generated and set in the two data communication apparatuses.

  In the encryption key setting system of the present invention, the communication path is a communication path configured by a wireless LAN, and the two data communication devices include an access point that is a repeater for the wireless LAN, and The client may be connectable to a wireless LAN.

In order to set the same encryption key for the access point and client of the wireless LAN, when the encryption key set for the access point is transmitted to the client via the wireless LAN and set, the radio wave of the wireless LAN is easily intercepted. There is a high possibility that the data including the encryption key is intercepted by a third party and the encryption key is obtained.
Therefore, by using the encryption key setting system of the present invention, it is possible to set the same encryption key in the access point and the client with a low possibility of being obtained by a third party.

  The present invention can be realized as a data communication apparatus in addition to the above-described encryption key setting system. In addition, the present invention is not limited to the above-described aspects of the device invention, and may be realized as a method invention such as an encryption key setting method. Further, aspects as a computer program for configuring those methods and apparatuses, aspects as a recording medium recording such a computer program, data signals embodied in a carrier wave including the computer program, etc. It can also be realized in various ways.

  When the present invention is configured as a computer program or a recording medium on which the program is recorded, the entire program for controlling the encryption key setting system may be configured, or only a part that performs the function of the present invention is configured. It may be a thing. In addition, as a recording medium, various media that can be read by a computer such as a ROM cartridge, a punched card, a printed matter printed with a code such as a bar code, an internal storage device of a computer (memory such as RAM or ROM), and an external storage device Can be used.

Hereinafter, the best mode for carrying out the present invention will be described in the following order based on examples.
A. Example:
A1. System overview:
A2. Initial encryption key setting process:
A3. Effects of the embodiment:
B. Variations:
B1. Modification 1: B8. Modification 8:

A. Example:
A1. System overview:
FIG. 1 is an explanatory diagram showing a schematic configuration of an encryption key setting system according to an embodiment of the present invention.
The encryption key setting system 1000 includes an access point AP and a client CL. These access point AP and client CL are wireless LAN devices compliant with the IEEE802.11b standard. The client CL is installed in a range (communication area AR) where radio waves for wireless LAN communication from the access point AP can reach, and the access point AP and the client CL constitute a wireless LAN.
Here, the access point AP is connected to the wired LAN 900 in addition to the wireless LAN described above, and the client CL connects another client (not shown), a server (not shown) on the wired LAN 900, and the wired LAN 900. Data exchanged with a server (not shown) on the Internet INT connected via the relay is relayed.

  In the encryption key setting system 1000, an access point AP and a client CL exchange data including a WEP key and a MAC address with each other via a wireless LAN, and perform settings necessary for security (hereinafter referred to as “security settings”). System for setting the encryption key used for encrypting and decrypting the exchanged data (hereinafter referred to as “initial encryption key”) in the access point AP and the client CL. It is.

  Here, the initial encryption key is an encryption key in a so-called secret key encryption method that uses the same encryption key for encryption and decryption, and the encryption key setting system 1000 includes an access point AP and a client CL, respectively. Set the same initial encryption key.

FIG. 2 is an explanatory diagram showing a schematic configuration of the access point AP in the present embodiment.
The access point AP mainly includes a CPU 10, a memory 11, a wireless LAN interface unit 12, and a wired LAN interface unit 13, and each is connected to an internal bus 15. Here, the wireless LAN interface unit 12 includes an interface for connecting the access point AP to the wireless LAN, and mainly includes a transmitter and a receiver for transmitting and receiving radio waves, an antenna, and the like. The wired LAN interface unit includes an interface for connecting the access point AP to the wired LAN 900.

  In the initial state, the memory 11 stores a program related to setting of an initial encryption key, a counter program, a temporary encryption key KK, and key usage value determination data KD.

  The CPU 10 functions as the encryption key setting unit 10a, the counter control unit 10b, the encryption / decryption processing unit 10c, and the data transmission / reception unit 10d by executing the program related to the setting of the initial encryption key. Moreover, it functions as a counter CA by executing the above-described counter program. The encryption key setting unit 10a described above corresponds to the digit determination unit and the encryption key generation unit described in the claims.

The temporary encryption key KK described above is stored in the memory 11 before the access point AP is shipped. The temporary encryption key KK is an encryption key stored in the memory in common in shipped wireless LAN devices such as the client CL and other access points. Therefore, since it is commonly used in many wireless LAN devices, it is highly likely to be obtained by a third party.
Therefore, the temporary encryption key KK encrypts data exchanged between the access point AP and the client CL as a temporary encryption key until the initial encryption key is set in the access point AP and the client CL. And used for decoding.
The initial encryption key described above is generated by replacing a part of the temporary encryption key KK with a certain value (hereinafter referred to as “key use value”). Therefore, if the key usage value is the same, the same initial encryption key is generated.

  The key usage value determination data KD described above is data exchanged between the access point AP and the client CL in order to determine the same key usage value between the access point AP and the client CL.

FIG. 3 is an explanatory diagram showing a schematic configuration of the client CL in the present embodiment.
The client CL mainly includes a computer 100 and a wireless LAN adapter 101 attached to the computer 100.
The computer 100 mainly includes a CPU 102, a memory 103, a hard disk 104, and an input / output interface unit 105, and each is connected to an internal bus 106. The computer 100 includes a keyboard 107 and a display 108 in addition to the CPU 102 described above, and the input / output interface unit 105 includes an interface for the keyboard 107 and the display 108 to exchange data with the CPU 102 and the like, respectively. Become.

  The memory 103 stores a temporary encryption key KK and key usage value determination data KD in an initial state. The temporary encryption key KK and the key usage value determination data KD are the same as the temporary encryption key KK and the key usage value determination data KD stored in the memory 11 of the client CL described above.

  On the other hand, the wireless LAN adapter 101 mainly includes a transmitter and receiver for transmitting and receiving radio waves, an antenna, and the like, and is connected to the internal bus 106 of the computer 100.

In the computer 100, a program related to setting of an initial encryption key and a counter program are executed under a predetermined operating system. Various drivers are incorporated in this operating system, and the wireless LAN adapter 101 and the keyboard 107 display 108 are controlled.
When the program related to the initial encryption key setting described above is activated and loaded into the memory 103, the CPU 102 executes the program to thereby execute the encryption key setting unit 102a, counter control unit 102b, encryption / decryption. It functions as the processing unit 102c and the data transmitting / receiving unit 102d. When the above-described counter program is activated and loaded into the memory 103, the CPU 102 functions as the counter CC by executing this program. The encryption key setting unit 102a described above corresponds to the digit determining unit and the encryption key setting unit described in the claims.

  Here, the details of the counter CA and the counter CC will be described. The counter CA and the counter CC are the same counter, but are given different symbols for convenience of explanation.

FIG. 4 is an explanatory diagram illustrating the counter CA and the counter CC in the present embodiment.
The counter CA and the counter CC are counters that count an elapsed time since the start in units of 10 ns. As shown in FIG. 4, the counter CA and the counter CC are from the first digit (the least significant digit) to the sixteenth digit (the most significant digit). This is a binary counter having 16 digits. In the counter CA and counter CC, the first digit is incremented by 10 ns (nanoseconds) (change in value from 0 to 1, or 1 to 0), and the second digit is incremented by 20 ns. The time interval for incrementing the third digit, the fourth digit,... Doubles, and the 16th digit is incremented by approximately 0.33 s (seconds). FIG. 4 shows the counter CA and the counter CC 30 ns after starting.

A2. Initial encryption key setting process:
FIG. 5 is a flowchart illustrating the procedure of the initial encryption key setting process executed by the access point AP and the client CL in the present embodiment.
Now, the client CL is installed in the communication area AR shown in FIG. 1, and the operation (association) for recognizing that the access point AP and the client CL are devices performing wireless LAN communication with each other is completed. Communication between the AP and the client CL via the wireless LAN is possible. A temporary encryption key KK is set as an encryption key used for encryption and decryption in the access point AP and the client CL.

First, the access point AP repeatedly transmits / receives key usage value determination data KD to / from the client CL a predetermined number of times, and each time the key usage value determination data KD is received, the value of the counter CA at that time is stored in the memory. 11 (step S202).
On the other hand, similar processing is performed in the client CL. That is, the client CL repeatedly transmits and receives the key usage value determination data KD to and from the access point AP a predetermined number of times, and each time the key usage value determination data KD is received, the value of the counter CC at that time is stored in the memory. 103 (step S302).

  The processing in step S202 at the access point AP and the processing at step S302 in the client CL will be specifically described with reference to FIGS.

FIG. 6 is an explanatory diagram schematically showing how the key usage value determination data KD is transmitted and received between the access point AP and the client CL.
In FIG. 6, the time axis T is shown in the direction from top to bottom. Note that the number of times the access point AP and the client CL repeatedly transmit / receive the key usage value determination data KD is set to 3 in advance. FIG. 6 shows the value of the counter CA and the value of the counter CC when the key usage value determination data KD is received for the first to third times.

  First, the encryption key setting unit 10a of the access point AP shown in FIG. 2 instructs the encryption / decryption processing unit 10c to encrypt the key usage value determination data KD, and the encryption / decryption processing unit 10c The key usage value determination data KD and the temporary encryption key KK set as the encryption key are read from the memory 11, and the key usage value determination data KD is encrypted with the temporary encryption key KK. Then, the data transmitting / receiving unit 10d of the access point AP transmits the encrypted key usage value determination data KD to the client CL, and the access point AP counter control unit 10b transmits the key usage value determination data KD. The counter CA is reset and started.

  On the other hand, the data transmission / reception unit 102 d of the client CL shown in FIG. 3 receives the encrypted key use digit determination data KD and stores it in the memory 103. Then, the encryption / decryption processing unit 102c of the client CL reads the encrypted key usage value determination data KD and the temporary encryption key KK set as the encryption key from the memory 103, and the temporary encryption key KK. Is used to decrypt the encrypted key use value determination data KD.

  Since the decrypted data is the key usage value determination data KD, the encryption key setting unit 102a of the client CL instructs the encryption / decryption processing unit 102c to encrypt the key usage value determination data KD. The encryption / decryption processing unit 102c reads the key usage value determination data KD and the temporary encryption key KK from the memory 103, and encrypts the key usage value determination data KD with the temporary encryption key KK. Then, the data transmission / reception unit 102d of the client CL transmits the encrypted key usage value determination data KD to the access point AP, and the counter control unit 102b of the client CL performs a counter when transmitting the key usage value determination data KD. Reset and start CC.

  The data transmitting / receiving unit 10d of the access point AP that has received the encrypted key usage value determination data KD transmitted from the client CL causes the memory 11 to store the encrypted key usage value determination data KD. Then, the encryption / decryption processing unit 10c of the access point AP reads the encrypted key usage value determination data KD and the temporary encryption key KK from the memory 11, and is encrypted using the temporary encryption key KK. Decrypt the key usage value determination data KD.

Since the decrypted data is the key usage value determination data KD, the counter control unit 10b of the access point AP stops the started counter CA, and the encryption key setting unit 10a is shown in FIG. The value of the counter CA (first counter value) is stored in the memory 11.
In this way, transmission / reception of the key usage value determination data KD is performed once. Since the predetermined number of times 3 has not been reached, the access point AP again encrypts the key usage value determination data KD and transmits it to the client CL as described above, and resets and starts the counter CA. .

  On the other hand, the client CL that has received the encrypted key usage value determination data KD decrypts the key usage value determination data KD encrypted using the temporary encryption key KK as described above. . Since the decrypted data is the key usage value determination data KD, the counter control unit 102b of the client CL stops the started counter CC, and the encryption key setting unit 102a displays the counter at this time shown in FIG. The value of CC (first counter value) is stored in the memory 103.

  The above process is repeated three times between the access point AP and the client CL. As a result, the counter value (hereinafter referred to as “the first to third counter value”) when the key usage value determination data KD is received for the first to third times as shown in FIG. They are stored in the memory 11 and the memory 103 of the client CL, respectively.

Returning to FIG. 5, next, in the access point AP, the encryption key setting unit 10a reads the three counter values stored in the memory 11, determines the key usage value based on these three counter values, It is stored in the memory 11 (step S204).
On the other hand, also in the client CL, similarly, the encryption key setting unit 102 a reads the three counter values stored in the memory 103, determines the key usage value based on these three counter values, and stores them in the memory 103. (Step S304).

  The process of step S204 in the above-described access point AP and the process of step S304 in the client CL will be specifically described with reference to FIG.

FIG. 7 is an explanatory diagram schematically showing a key usage value determination method based on the counter value.
In FIG. 7, the left side shows the first to third counter values stored in the memory 11 and the key usage value determined from these three counter values at the access point AP, and the right side shows the client CL. The first to third counter values stored in the memory 103 and the key usage value determined from these three counter values are shown.

The aforementioned first to third counter values correspond to the time required for a round trip from when the key usage value determination data KD is transmitted to when it is converted into time.
Here, this round-trip required time is composed of a round-trip propagation time of radio waves between the access point AP and the client CL, a processing time at the access point AP, and a processing time at the client CL. The round-trip propagation time of this radio wave is almost the same for the first to third times because the same data propagates the same distance, and the same processing is repeated for the processing time at the access point AP and the client CL. It becomes almost the same in 1-3 times.
Therefore, the round trip time is substantially the same for the first to third times, and is also substantially the same for the access point AP and the client CL.

  However, the processing time at the access point AP and the client CL varies depending on the processing load of the CPU 10 of the access point AP, the processing load of the CPU 102 of the client CL, and the like. Does not match exactly. Accordingly, the first to third counter values do not completely match, and an error occurs in the lower digit.

  Here, since the access point AP and the client CL perform the same processing in the same system, the digits in which the above-described error occurs are almost the same between the access point AP and the client CL.

  Therefore, the access point AP and the client CL have a high possibility of matching the values indicated by the higher-order digits excluding the lower-order digit in which this error has occurred among the first to third counter values. . Therefore, this value is determined as a key usage value.

For example, it is shown in FIG. 7, for 1-3 times the counter value of the access point AP, to determine the "000010110101" represented by the upper 12 digits up to the 16 digits to fifth digits as a key decision value. On the client CL side, as shown in FIG. 7, since “000010110101” indicated by the upper 12 digits is determined as the key usage value, the same key usage value is determined by the access point AP and the client CL. .

  As described above, there is a high possibility that the same key usage value is determined by the access point AP and the client CL. However, different key usage values may be determined for the access point AP and the client CL.

FIG. 8 is an explanatory diagram showing an example of counter values in the access point AP and the client CL when the key usage values are different.
In FIG. 8, the left side shows the first to third counter values and the determined key usage value at the access point AP, and the right side shows the first to third counter values and the determined key usage value at the client CL. .

  As shown in FIG. 8, there is an error of 10 ns in terms of time between the first counter value of the access point AP and the first counter value of the client CL. This is because the access point AP and the client CL are caused by the degree of the processing load of the CPU 10 of the access point AP, the degree of the processing load of the CPU 102 of the client CL, etc. This is due to variations in processing time.

  In the access point AP, the errors in the counter values from the first time to the second time and from the second time to the third time are +50 ns, respectively, and in the client CL, the counter values from the first time to the second time and from the second time to the third time are counted. Are each −50 ns.

  In the case of such a counter value, as shown in FIG. 8, on the access point AP side and the client CL side, the upper 12 digits match with the first to third counter values. However, the determined key usage value is different between the access point AP and the client CL. This is because a carry occurs in the sixth digit in the first to third counter values of the access point AP, whereas this carry does not occur in the first to third counter values of the client CL. Because.

  In this way, when a carry occurs in the upper digit followed by 0 as a result of obtaining the exclusive OR only in one of the first to third counter values of the access point AP or the client CL, the key is used. The value will be different.

  In such a case, the generated initial encryption key is also different. Therefore, by executing the processing after step S206 in the access point AP and the processing after step S306 in the client CL shown in FIG. Generate an encryption key.

Returning to FIG. 5, the encryption key setting unit 10a of the access point AP reads the determined key usage value and the temporary encryption key KK from the memory 11, replaces a part of the temporary encryption key KK with the key usage value, and performs initial encryption. A key is generated and stored in the memory 11, and an initial encryption key is set as an encryption key instead of the temporary encryption key KK (step S206).
Similarly, the encryption key setting unit 102a of the client CL reads the determined key usage value and the temporary encryption key KK from the memory 103, replaces a part of the temporary encryption key KK with the key usage value, and generates an initial encryption key. The initial encryption key is set instead of the temporary encryption key KK as the encryption key (step S306).

  Next, the encryption / decryption processing unit 10c of the access point AP is set as an encryption key for arbitrary data to which a check code by a CRC (Cyclic Redundancy Check) method or the like is added using the initial encryption key. Encryption is performed using the initial encryption key (step S208).

Next, the data transmission / reception unit 10d of the access point AP transmits the data encrypted by the encryption / decryption processing unit 10c to the client CL via the wireless LAN (step S210).

  On the other hand, in the client CL, the data transmitting / receiving unit 102d receives the encrypted data transmitted from the access point AP and stores it in the memory 103 (step S308).

  Next, the encryption key setting unit 102a and the encryption / decryption processing unit 102c of the client CL modify the initial encryption key set in the client CL so as to match the initial encryption key set in the access point AP. (Hereinafter referred to as “client-side initial encryption key correction processing”) is executed (step S310).

FIG. 9 is a flowchart showing a procedure of client side initial encryption key correction processing.
In the following, for convenience of explanation, the key usage value determined at the access point AP is referred to as “key usage value KA”, and the key usage value determined at the client CL is referred to as “key usage value KC”.

  First, the encryption / decryption processing unit 102c of the client CL reads the received encrypted data and the set initial encryption key from the memory 103, and decrypts the encrypted data using the initial encryption key. (Step S402).

Next, the encryption key setting unit 102a of the client CL calculates a check code by the CRC method or the like based on the decrypted data, and determines whether or not it matches the check code added to the data in advance (step) S404). When the calculated check code matches the check code added to the data in advance, the data has been successfully decrypted, the initial encryption key set by the access point AP, the initial encryption key set by the client CL, Will match.
In this case, since it is not necessary to correct the initial encryption key set by the client CL, the client-side initial encryption key correction processing ends.

  On the other hand, if the calculated check code does not match the check code added to the data in advance, the data is not decrypted, and the encryption key set by the access point AP and the encryption key set by the client CL are It will not match. In this case, the key usage value KA determined at the access point AP is different from the key usage value KC determined at the client CL.

Therefore, in this case, the encryption key setting unit 102a of the client CL stores the assumed difference value Δk of the key usage value KA with respect to the key usage value KC in the memory 103 (step S408), and stores this value in the key usage value KC. The difference value Δk is added and corrected (step S410), the corrected key usage value (KC + Δk) is replaced with a part of the temporary encryption key KK, and the initial encryption key is generated again and set as the encryption key. (Step S412).
Then, the encryption / decryption processing unit 102c of the client CL decrypts the received encrypted data using the reset initial encryption key (step S402), and whether or not the check codes match. Is determined again (step S404).

  Here, the inventor has experimentally found that the difference value between the key usage value KA and the key usage value KC is often a difference of about two digits lower than the key usage value KA and the key usage value KC. . Therefore, if the difference value Δk is expressed in decimal notation for convenience and sequentially determined as -2, -1, +1, +2, the key usage value KC is corrected, and the initial encryption key is generated, the difference value Δk is obtained. In any case, there is a high possibility that the decoding is successful and the check code matches.

  Therefore, has the encryption key setting unit 102a of the client CL corrected the key usage value KC using all of these values −2, −1, +1, +2 as the difference value Δk before the process of step S408? If the key usage value KC is not corrected using all values, the key usage value KC is corrected by setting the next order value to Δk.

Specifically, for example, when the difference value Δk is “−1”, adding “−1” to the key usage value KC “000010110101” shown in FIG. 8 results in “000010110100”, and the key shown in FIG. It does not match the usage value KA. Therefore, the difference value Δk is set to “+1” in the next order, and correction is performed by adding “+1” to the key usage value KC “000010110101”.
As a result of this correction, the key usage value KC is “000010110110”, which matches the key usage value KA, and the encryption key set by the access point AP and the encryption key set by the client CL match.

On the other hand, if the check code does not match in the process of step S404 in spite of correcting the key usage value KC using all the values -2, -1, +1, +2 as the difference value Δk, the difference value Δk is −3 or less or +3 or more in decimal notation.
In this case, the encryption key setting unit 102a of the client CL sets the temporary encryption key KK again as the encryption key instead of the initial encryption key (step S414).

  Returning to FIG. 5, the encryption key setting unit 102a of the client CL encrypts any data to which a check code by the CRC method or the like is added using the encryption key (step S312), and the data transmission / reception unit 102d Transmits this encrypted data to the access point AP via the wireless LAN (step S314).

  On the other hand, the data transmitting / receiving unit 10d of the access point AP that has received the encrypted data stores the encrypted data in the memory 11 (step S212).

  Here, the encryption key used for encryption by the client CL in the processing of step S312 described above is the initial encryption key set by the access point AP and the initial encryption key set by the client CL as a result of the client side initial encryption key modification processing. If the encryption key matches, this is the initial encryption key. Even if the key usage value KC is corrected, the initial encryption key set by the access point AP does not match the initial encryption key set by the client CL. In this case, the temporary encryption key KK is used.

  Since the access point AP does not know the result of the above-described client-side initial encryption key modification process, the data received using the initial encryption key set in the access point AP is decrypted as the subsequent process. And whether or not the decryption has succeeded is determined to determine whether or not the initial encryption key set by the access point AP matches the encryption key set by the client CL. If it is determined that the initial encryption key set by the access point AP and the encryption key set by the client CL do not match without successful decryption, preparation for performing the initial encryption key setting process again Then, in place of the initial encryption key, a process of setting the temporary encryption key KK as the encryption key again (hereinafter referred to as “access point side encryption key modification process”) is executed again (step S214).

FIG. 10 is a flowchart showing the procedure of the access point side encryption key correction process.
First, the encryption / decryption processing unit 10c of the access point AP reads out the received encrypted data and the set initial encryption key from the memory 11, and uses this initial encryption key to decrypt the encrypted data. Decoding is performed (step S502).

Next, the encryption key setting unit 10a of the access point AP calculates a check code based on the CRC method or the like based on the decrypted data, and determines whether or not it matches the check code added to the data in advance ( Step S504). When the calculated check code matches the check code added to the data in advance, the data has been successfully decrypted. Therefore, the encryption key setting unit 10a of the access point AP performs the initial setting set in the access point AP. It is determined that the encryption key matches the initial encryption key set in the client CL.
In this case, the access point side encryption key correction process ends.

  On the other hand, if the calculated check code does not match the check code added to the data in advance, the data has not been successfully decrypted. Therefore, the encryption key setting unit 10a of the access point AP is set in the access point AP. It is determined that the initial encryption key set does not match the initial encryption key set in the client CL.

  In this case, as will be described later, the initial encryption key setting process is executed again. However, the temporary encryption key KK must be set as the encryption key when performing the initial encryption key setting process. The encryption key setting unit 10a of the access point AP sets the temporary encryption key KK again as the encryption key instead of the set initial encryption key (step S506).

Returning to FIG. 5, next, the encryption key setting unit 10a of the access point AP determines whether or not the same initial encryption key is set in the access point AP and the client CL (step S216). As described above, in the access point side encryption key correction process (step S214), when the calculated check code matches the check code added to the data in advance, the access point AP and the client CL have the same initial encryption key. It is determined that it has been set, and the initial encryption key setting process ends.
On the other hand, when the calculated check code does not match the check code added to the data in advance, it is determined that different initial encryption keys are set in the access point AP and the client CL. In this case, the access point AP returns to the process of step S202 and performs the above-described initial encryption key setting process again.

  On the other hand, also in the client CL, the encryption key setting unit 102a determines whether or not the same encryption key is set in the access point AP and the client CL (step S316).

As described above, in the client-side initial encryption key correction process (step S310), when the calculated check code matches the check code previously given to the data without correcting the key usage value KC, or the difference value Δk As a result of correcting the key usage value KC using any of the values -2, -1, +1, and +2, if the check codes match, the same initial encryption key is set in the access point AP and the client CL. The initial encryption key setting process ends.
On the other hand, if the calculated check code does not match even though the key usage value KC is corrected using all the values of −2, −1, +1, +2 as the difference value Δk, the access point AP and the client CL It is determined that a different encryption key is set. In this case, the client CL returns to the process of step S302 and performs the above-described initial encryption key setting process again.

  As a result of the initial encryption key setting process described above, the same initial encryption key is set in the access point AP and the client CL.

In this way, after setting the same initial encryption key between the access point AP and the client CL, the access point AP encrypts the data including the WEP key using the set initial encryption key and transmits it to the client CL. On the other hand, the client CL uses the set initial encryption key to decrypt the received data to obtain the WEP key.
Further, the client CL encrypts the data including the MAC address using the set initial encryption key and transmits the encrypted data to the access point AP, while the access point AP uses the set initial encryption key to transmit the received data. Decrypt and get the MAC address.
Based on the WEP key, MAC address, and the like obtained in this way, security settings are performed at the access point AP and the client CL.

A3. Effects of the embodiment:
As described above, by using the encryption key setting system 1000, the user can set the same initial encryption key for the access point AP and the client CL without manually setting.

  In the encryption key setting system 1000, data transmitted / received between the access point AP and the client CL for setting an initial encryption key includes key use value determination data KD for determining a key use value, and arbitrary data Since the data including the key usage value and the initial encryption key is not transmitted / received, the possibility of obtaining the initial encryption key by a third party can be reduced.

  Further, even if a third party prepares the same counter as the counter CA and the counter CC and wiretaps the key usage value determination data KD, the third party is not able to access the access point AP and the client CL. Since the timing when the counter CA and the counter CC are reset and started cannot be known, the key usage value cannot be known. Therefore, the possibility that the initial encryption key is obtained by a third party can be reduced.

B. Variations:
Note that the present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the scope of the invention. For example, the following modifications are possible. .

B1. Modification 1:
In the above-described embodiment, the number of digits of the counter CA and the number of digits of the counter CC are both 16 digits, but are not limited to 16 digits. For example, the number of digits may be as small as 15 digits or 8 digits, or may be as large as 17 digits or 32 digits. Further, the counter CA and the counter CC may have different numbers of digits.
Further, the counter CA and the counter CC both count the elapsed time since starting up in units of 10 ns, but the unit time for counting (hereinafter referred to as “time accuracy”) is limited to 10 ns. It is not a thing. Further, the time accuracy may be different between the counter CA and the counter CC.
Hereinafter, processing when the number of digits and time accuracy are different between the counter provided in the access point and the counter provided in the client will be described with reference to FIG.

FIG. 11 is an explanatory diagram showing an access point counter CA ′ and a client counter CC ′, which are different in the number of digits and the time accuracy in the first modification.
In FIG. 11, the left side shows a counter CA ′, and the upper right side shows a counter CC ′.
The counter CA ′ is a counter having 16 digits from the first digit to the 16th digit, and the time accuracy is 10 ns. On the other hand, the counter CC ′ is a counter having eight digits from the first digit to the eighth digit, and the time accuracy is 30 ns.

As described above, when the number of digits and the time accuracy are different between the counter CA ′ and the counter CC ′, first, before the access point or the client executes the initial encryption key setting process, Notify the other party of the number of digits and time accuracy.
Then, when the number of digits and the time accuracy of the counter provided therein are different from the notified number of digits and the time accuracy, the receiving side receives the counter value stored in the memory in the initial encryption key setting process as follows: To. That is, the counter value when the key usage value determination data KD is received is converted into time, and the counter value when the converted time is indicated by the counter of the number of digits notified from the other party and the time accuracy is obtained. The counter value is stored in the memory.

Specifically, for example, when the access point notifies the number of digits of the counter CA ′ and the time accuracy, the client is notified of the number of digits “16” of the counter CA ′ and the time accuracy “10 ns” from the access point. It becomes. When the value of the counter CC ′ when the key usage value determination data KD is received at the client is the value shown on the upper right side of FIG. 11, the client first converts the counter value into time “ 510 ns ". Next, the client obtains a counter value in the case where this 510 ns is indicated by a counter with a time precision of 10 ns having 16 digits. As a result, the counter value as shown on the lower right side is stored in the memory of the client.
In this way, the same counter value as that in the case where the client has the same counter as that of the access point can be stored in the memory, and the same initial value is obtained in the access point and the client in the same manner as in the above-described embodiment. An encryption key can be set.

B2. Modification 2:
In the embodiment described above, as shown in FIG. 7 or FIG. 8, the access point AP and the client CL have the same number of digits in the key usage value KA and the key usage value KC.
However, in the access point AP and the client CL, the number of digits of the key use value may differ between the access point AP and the client CL depending on the first to third counter values stored in the memory and the magnitude of the error. is there.
Therefore, in addition to the correction for adding the difference value Δk to the key usage value KC, which is performed in the above-described client-side initial encryption key correction process, the correction for excluding the value indicated by the lower digit of the key usage value KC is performed. You may make it perform.
Hereinafter, correction of the key usage value KC excluding the value indicated by the lower digit will be described with reference to FIG.

FIG. 12 is an explanatory diagram illustrating an example of counter values in the access point AP and the client CL when the number of digits of the key usage value is different between the access point AP and the client CL.
In FIG. 12, the left side shows the first to third counter values and the determined key usage value at the access point AP, and the right side shows the first to third counter values and the determined key usage value at the client CL. .

In the first to third counter values in the client CL, the upper 12 digits match. On the other hand, for each of the first to third counter values at the access point AP, a carry occurs in the sixth digit only in the first counter value, so the upper 10 digits of the 16th to 7th digits match. Will be. Therefore, the number of digits of the key usage value differs between the access point AP and the client CL. And since the number of digits of the key usage value differs between the access point AP and the client CL, the determined key usage values are also different from each other.
When the number of digits of the key usage value is different as described above, the key usage values do not match even when the above-described correction for adding the difference value Δk to the key usage value KC is performed.

  However, in this case, the access point AP and the client CL are both “0000101101” for the upper 10 digits. Therefore, the key usage value can be matched between the access point AP and the client CL by performing correction on the client CL side, excluding the value “01” indicated by the lower two digits of the key usage value “000010110101”. It becomes.

Specifically, in the client CL, when the received encrypted data cannot be decrypted even when correction is made to add all the difference values Δk (−2, −1, +1, +2) to the key usage value KC, A correction that removes the value from the key digit in order from the lowest digit, such as excluding the value indicated by the lower one digit from the key usage value and then excluding the value indicated by the lower two digits. Do.
Each time correction is performed, the initial encryption key is regenerated with the corrected key usage value, and it is determined whether or not the encrypted data received with the regenerated initial encryption key can be decrypted.

  For example, if the encrypted data cannot be decrypted even if the lower two digits are removed, the temporary encryption key KK is set as the encryption key instead of the initial encryption key, and the client side initial value is set. You may make it complete | finish an encryption key correction process. In this case, as described above, the access point AP and the client CL perform the initial encryption key setting process again.

B3. Modification 3:
In the above-described embodiment, in the initial encryption key setting process, the access point AP and the client CL transmit / receive the key usage value determination data KD once (transmit the key usage value determination data KD to the other party, and then send the key usage value determination data KD to the other party. The counter CA and the counter CC are stopped and reset every time the usage value determination data KD is received), but instead of this, a plurality of transmissions / receptions of the key usage value determination data KD are set as one set. Each time, the counter CA and the counter CC may be stopped and reset.
In this way, a sufficiently large key usage value can be secured and the counting accuracy can be increased. By repeating a plurality of sets, a plurality of counter values can be stored in the memory at each of the access point AP and the client CL. Therefore, in the same manner as in the above-described embodiment, the access point AP and the client CL each have a key. A utilization value can be determined.

In addition, while the key usage value determination data KD is transmitted and received between the access point AP and the client CL, the counter CA and the counter CC are not stopped, and each time the key usage value determination data KD is received, The values of the counter CA and counter CC at that time may be stored in the memory.
Even in this case, by obtaining the difference between the stored counter values, it is possible to obtain the counter value corresponding to the required round-trip time from when the key usage value determination data KD described above is transmitted to when it is received. Therefore, the key usage value can be determined by the access point AP and the client CL in the same manner as in the above-described embodiment.

B4. Modification 4:
In the embodiment described above, in the initial encryption key setting process, the key use value determination data KD is first transmitted by the access point AP, but may be the client CL.
The access point AP first transmits the encrypted data after transmitting / receiving the key usage value determination data KD a predetermined number of times, but it may be the client CL. In this case, the above-described client-side initial encryption key correction processing may be performed at the access point AP, and the above-described access point-side encryption key correction processing may be performed at the client CL.

B5. Modification 5:
In the above-described embodiment, the access point AP and the client CL in the encryption key setting system 1000 are wireless LAN devices compliant with the IEEE802.11b standard, but other standards such as IEEE802.11a and IEEE802.11g are used. A compliant wireless LAN device may be used.

In the above-described embodiment, the encryption key setting system 1000 includes the access point AP and the client CL, which are wireless LAN devices, but is not limited thereto. For example, you may comprise with a terminal, a server, etc. which communicate via networks, such as wired LAN and the internet. Moreover, you may comprise with a terminal, a server, etc. which communicate by one-to-one connection not via networks, such as LAN and the internet.
Even in this case, it is possible to set an encryption key for encrypting / decrypting data exchanged on the communication path in these terminals, servers, etc., with a low possibility of being obtained by a third party. It becomes possible.

B6. Modification 6:
In the above-described embodiment, the number of times the access point AP and the client CL repeatedly transmit / receive the key usage value determination data KD is set to 3 times in advance. However, this number is not limited to 3 times. Absent.

B7. Modification 7:
In the embodiment described above, the initial encryption key is generated by replacing a part of the temporary encryption key KK with the key usage value, but the present invention is not limited to this. Based on the key usage value, it may be generated by a known encryption algorithm such as RC4 (Rivest's Cipher4).

B8. Modification 8:
In the embodiment described above, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good. For example, the counter CA and the counter CC may be configured by hardware circuits.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematic structure of the encryption key setting system which is one Example of this invention. Explanatory drawing which shows schematic structure of the access point AP in a present Example. Explanatory drawing which shows the outline | summary structure of the client CL in a present Example. Explanatory drawing which shows counter CA and counter CC in a present Example. The flowchart which shows the procedure of the initial encryption key setting process performed with the access point AP and the client CL in a present Example. Explanatory drawing which shows typically a mode that the key utilization value determination data KD are transmitted / received between the access point AP and the client CL. Explanatory drawing which shows typically the determination method of the key utilization value based on a counter value. Explanatory drawing which shows an example of a counter value in access point AP and the client CL when a key utilization value differs. The flowchart which shows the procedure of a client side initial encryption key correction process. The flowchart which shows the procedure of an access point side encryption key correction process. Explanatory drawing which shows counter CA 'of an access point and counter CC' of a client from which the number of digits and time precision differ in the modification 1 mutually. Explanatory drawing which shows an example of the counter value in access point AP and client CL when the number of digits of a key utilization value differs by access point AP and client CL.

Explanation of symbols

10,102 ... CPU
10a, 102a ... Encryption key setting unit 10b, 102b ... Counter control unit 10c, 102c ... Encryption / decryption processing unit 10d, 102d ... Data transmission / reception unit 11, 103 ... Memory 12. ..Wireless LAN interface 13 ... Wired LAN interface 15, 106 ... Internal bus 100 ... Computer 101 ... Wireless LAN adapter 104 ... Hard disk 105 ... Input / output interface unit 107 ... Keyboard 108 ... Display 900 ... Wired LAN
1000 ... Encryption key setting system AP ... Access point AR ... Communication area CA, CC, CA ', CC' ... Counter CL ... Client INT ... Internet KD ... Key usage value Decision data KK ... Temporary encryption key

Claims (8)

Two data communication devices connected to each other via a communication path, and the two encryption keys used for encrypting and decrypting communication data transmitted and received between the two data communication devices. An encryption key setting system to be set in each data communication device,
The two data communication devices are respectively
An encryption / decryption processing unit for encrypting the specific data for setting the encryption key, and decrypting the encrypted specific data;
A transmission / reception unit for transmitting the specific data encrypted by the encryption / decryption processing unit to a counterpart data communication device, and receiving the specific data encrypted from the counterpart data communication device ;
After transmitting the encrypted identification data, from the data communication apparatus of the other party until decoded by receiving the encrypted identification data were the encryption / decryption processing unit, at least one A counter that obtains the time required for transmission and reception of the specific data a plurality of times in units of a predetermined time, and obtains the time counted as a counter value of a plurality of digits each time, and
A digit determining unit that compares the corresponding digits of the counter value obtained each time by the counter, and determines a digit that matches the indicated value;
An encryption key generation unit that generates the encryption key based on a basic value indicated by a digit determined by the digit determination unit among the counter values;
An encryption key setting system. The encryption key setting system according to claim 1,
The encryption / decryption processing unit having the two communication devices pixel respectively, using the encryption key generated by the encryption key generation unit, and the encryption and reception of the communication data to be transmitted the have the row decoding of the communication data,
In at least one of the two data communication devices, when the encryption / decryption processing unit cannot decrypt the communication data received using the encryption key, the encryption key generation unit A new encryption key is generated based on a value obtained by correcting the basic value instead of the generated encryption key. The encryption key setting system according to claim 1,
The encryption / decryption processing unit having the two communication devices pixel respectively, using the encryption key generated by the encryption key generation unit, and the encryption and reception of the communication data to be transmitted the have the row decoding of the communication data,
In at least one of the two data communication devices, when the encryption / decryption processing unit cannot decrypt the communication data received using the encryption key, the digit determining unit Instead of the determined digit, a digit obtained by reducing the determined digit is newly determined, and the encryption key generation unit replaces the generated encryption key with the digit of the counter value. An encryption key setting system that generates a new encryption key based on a base value indicated by a digit newly determined by a determination unit. The encryption key setting system according to any one of claims 1 to 3,
The communication path is a communication path configured by a wireless LAN,
The encryption data setting system, wherein the two data communication apparatuses are an access point that is a relay for the wireless LAN and a client that can be connected to the wireless LAN. A data communication apparatus that can transmit and receive communication data to and from other data communication apparatuses connected via a communication path, and encrypts and decrypts the communication data using an encryption key. And
An encryption / decryption processing unit for encrypting the specific data for setting the encryption key, and decrypting the encrypted specific data;
A transmission / reception unit for transmitting the specific data encrypted by the encryption / decryption processing unit to the other data communication device, and receiving the specific data encrypted from the other data communication device ;
After transmitting the encrypted identification data, from the data communication apparatus of the other party until decoded by receiving the encrypted identification data were the encryption / decryption processing unit, at least one A counter that obtains the time required for transmission and reception of the specific data a plurality of times in units of a predetermined time, and obtains the time counted as a counter value of a plurality of digits each time, and
A digit determining unit that compares the corresponding digits of the counter value obtained each time by the counter, and determines a digit that matches the indicated value;
An encryption key generation unit that generates the encryption key based on a basic value indicated by a digit determined by the digit determination unit among the counter values;
A data communication device comprising: Encryption keys used for encrypting and decrypting communication data transmitted and received between the two data communication devices are set for two data communication devices connected to each other via a communication path. An encryption key setting method for performing
(A) In each of the data communication apparatus transmits the particular data encrypted a certain data for setting the pre-Symbol encryption key to the data communication apparatus of the other party, The encryption from the data communication apparatus of the other party Receiving the specified data ,
(B) In each data communication device, the encrypted specific data is transmitted by the counter included in each data communication device, and then the encrypted specific data is received from the counterpart data communication device , Time required for at least one transmission / reception of the specific data until the encrypted specific data is decrypted is counted a plurality of times with a predetermined time as a unit, and each time is counted as a plurality of times. Obtaining each digit as a counter value;
(C) in each data communication device, a step of comparing corresponding digits of the counter value obtained each time by the counter to determine corresponding digits of the indicated values;
(D) In each data communication device, the step of generating the encryption key based on the basic value indicated by the determined digit among the counter values;
An encryption key setting method comprising: The communication data is encrypted and decrypted with respect to a computer that can function as a data communication device capable of transmitting and receiving communication data to and from another data communication device connected via a communication path. A computer program for setting an encryption key used for
Before SL encrypt certain data for setting an encryption key, also, a function of decoding the specific data that has been encrypted,
A function of transmitting the encrypted specific data to the other data communication device and receiving the encrypted specific data from the other data communication device;
After the encrypted specific data is transmitted by the counter provided in the computer, until the encrypted specific data is received from the data communication device of the other party, and the encrypted specific data is decrypted The time required for transmitting and receiving the specific data at least once a plurality of times with a predetermined time as a unit, and each time, the function of obtaining the time measured as a counter value of a plurality of digits, respectively,
A function of comparing the corresponding digits of the counter value obtained each time by the counter, respectively, and determining a digit having a matching value;
A function of generating the encryption key based on a basic value indicated by the determined digit of the counter value;
A program for causing the computer to realize the above.   A computer-readable recording medium on which the computer program according to claim 7 is recorded.

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