JP2010250748A - Authentication system and authentication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an authentication system and an authentication method for making it difficult to generate the illegal analysis of a cryptographic arithmetic expression. <P>SOLUTION: A plurality of vehicle keys 2 to be authenticated based on an immobilizer system can be registered in one vehicle 1. Then, a table 18 in which a registration key and a cryptographic arithmetic expression F(x) are associated with each other is prepared for the vehicle 1. The table 18 is configured to define which cryptographic arithmetic expression (x) should be used by the registration key registered in the vehicle 1. In the case of performing challenge response authentication, the cryptographic arithmetic expression F(x) to be used for authentication is changed for each registration key registered in the vehicle 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an authentication system and an authentication method used when a communication master performs personal authentication with a communication partner that is the communication partner.

  In recent years, for example, challenge response authentication (see Patent Documents 1 to 3 and the like) has been widely used as an authentication method of an authentication system for confirming whether or not a communication partner is the person. Challenge response authentication is a type of cryptographic authentication. First, the authenticator sends a random number code whose value changes every time a call is made to the receiver as a challenge. Receiving the random number code, the receiving side calculates the random number code by its own cryptographic operation formula and sends it back to the authentication side as a response. The authentication side obtains a response by using the same cryptographic operation formula for the random number code sent to the receiving side, and collates the response sent from the receiving side with the response calculated by itself. If response verification is established, communication between the two is permitted.

JP 2009-3070 A JP 2008-48166 A JP 2006-512515 A

  By the way, when this type of authentication system is used, for example, in an electronic key system of a vehicle, a plurality of electronic keys on the receiving side may be used for one authentication side, that is, the vehicle. However, in this case, since the same cryptographic operation formula is used on all receivers, for example, if the cryptographic operation formula is stolen on one receiver side, the encryption of the authentication system is interrupted at that point. That is, it will be invalidated. For this reason, there has been a demand for the development of a new authentication method in which the cryptographic operation formula is difficult to analyze.

  An object of the present invention is to provide an authentication system and an authentication method capable of making it difficult to cause an illegal analysis of a cryptographic operation expression.

  In order to solve the above problems, in the present invention, a challenge is sent from the communication master to the communication terminal that is the communication partner, and the communication terminal is made to calculate the response of the challenge by the cryptographic calculation formula, and after the calculation, A challenge response is sent back to the communication master, and the communication master is made to calculate the response of the challenge by a cryptographic operation formula possessed by the communication master, and the authentication of the two parties is performed by comparing the responses of the two parties. In the authentication system of the type, when the communication master enters an authentication state with the communication terminal, registration means capable of registering the communication terminal in the state associated with the cryptographic operation formula in the communication master, and communication at that time A terminal type confirmation unit for confirming a terminal type of the communication terminal as a partner, and a terminal type confirmation unit. The communication terminal thus determined is selected from among the registered terminals registered by the registration means, and the cryptographic operation formula corresponding to the selected registered terminal is used at the time of the authentication. The gist of the invention is that it comprises a cryptographic operation formula switching means for switching a cryptographic operation formula for each registered terminal.

  According to this configuration, the communication terminal can be appropriately registered in the communication master as its own operation terminal by the registration means. When the communication terminal accesses the communication master, challenge response type authentication is performed between the two parties. First, the type of the communication terminal is confirmed by the terminal type confirmation unit. Then, the cryptographic operation formula corresponding to the communication terminal that is the communication partner is selected by the cryptographic operation formula switching means from among the prepared cryptographic operations for challenge response authentication, and authentication is executed by this cryptographic operation formula. Is done. For this reason, since it is possible to change the cryptographic operation formula for authentication for each registered terminal, it is possible to execute authentication with a different cryptographic computation formula for each communication terminal. Therefore, it is possible to increase the resistance against illegal reading of the cryptographic operation formula, and it is possible to make the authentication difficult to analyze.

  In the present invention, the registration means selects a specific one from a plurality of cryptographic operation formula groups prepared in advance for each of the two parties in both the communication master and the communication terminal, Is set for each of the two parties as an arithmetic expression used for the authentication.

  According to this configuration, a plurality of cryptographic operation formulas are prepared in advance for each of the communication master and the communication terminal, and by selecting which of these is used, registration setting of the cryptographic operation formula to be used can be performed. Done. For this reason, when registering the cryptographic operation formula, for example, it is not necessary to take a form of actually exchanging the cryptographic operation formula by communication, so that the cryptographic calculation formula itself does not need to be wiretapped. Therefore, it is possible to further prevent unauthorized reading of the cryptographic operation formula.

  In the present invention, the registration unit has a registration area in which the cryptographic operation formula and an area number are associated as a registration destination of the communication terminal on the communication master side, and when registering the communication terminal in the communication master, By notifying the communication terminal of the area number of the registration area, the encryption arithmetic expression according to the area number is registered as an encryption arithmetic expression used in the communication terminal, while the communication master uses the area number and The gist is that the communication terminal registered on the communication master side is associated with the cryptographic operation formula by associating and registering the communication terminal.

  According to this configuration, when the communication master registers the communication terminal with itself, the communication terminal notifies the communication terminal of the area number of the registration area, causes the communication terminal to select a cryptographic operation formula corresponding to the area number, and performs the cryptographic operation. The expression is registered in the communication terminal as a cryptographic operation expression. Therefore, when registering a cryptographic operation expression used in a communication terminal, it is possible to set the operation expression in a simple format of notifying an area number.

  In the present invention, the terminal type confirmation unit causes the communication terminal to perform verification of the terminal number by including the terminal number of the communication terminal in the challenge, and the response is not established and the response is the communication If it is not returned to the master, this time, the terminal number of the next number is added to the challenge, the terminal number is collated, and this operation is repeated until the response reply is received. The gist is to confirm the communication partner.

  According to this configuration, a key number is sequentially given to the communication partner, and the communication partner is confirmed by checking whether it can respond to the key number. For this reason, it is possible to confirm the communication partner by a simple format in which the key number is output and the presence or absence of the response is seen.

  In the present invention, a challenge is sent from the communication master to the communication terminal that is the communication partner, the communication terminal is made to calculate the response of the challenge by the cryptographic calculation formula, and after the calculation, the response is sent back to the communication master, In the challenge response type authentication method in which the communication master also calculates the response of the challenge by a cryptographic operation formula possessed by the communication master and compares the responses of the two parties to authenticate the two parties. The communication terminal can be registered in a state associated with the cryptographic operation formula, and when the communication master enters an authentication state with the communication terminal, the terminal type of the communication terminal that is a communication partner at that time is set. Confirming and selecting which of the registered terminals the communication terminal is, and selecting the registered The use of encryption arithmetic expression that corresponds to the end during the authentication, is summarized in that switching the encryption arithmetic expression for each of the registered terminal.

  According to the present invention, it is possible to make it difficult for fraud analysis of a cryptographic operation formula used for challenge response authentication to occur.

The block diagram which shows the structure of the immobilizer system in one Embodiment. The block diagram which shows the structure of a key registration system and a cryptography type | formula switching system. A table that defines the relationship between key numbers and cryptographic operations. The sequence chart which shows key registration operation. The sequence chart which shows the switching operation | movement of a cryptographic operation type | formula. The sequence chart which shows the switching operation | movement of a cryptographic operation type | formula.

Hereinafter, an embodiment of an authentication system and an authentication method embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, the vehicle 1 is provided with a key cylinder 3 as an insertion destination of a vehicle key 2 composed of a mechanical key, for example, in the vicinity of a steering wheel. In this case, when the vehicle key 2 is inserted into the key cylinder 3 and the key 2 is turned, if the key groove of the vehicle key 2 matches the key cylinder 3 and the key verification is established, The rotation of the key cylinder 3 rotor is allowed. Then, when the rotor rotational position of the key cylinder 3 is operated to the engine start position (ST position), the starter relay of the ignition switch 4 is switched from OFF to ON, and the engine ECU (overall control of the engine 5) The Electronic Control Unit) 6 is activated and the engine 5 is in the starting state.

  The vehicle 1 is equipped with an immobilizer system 7 as one system for preventing the vehicle 1 from being stolen. In this case, the vehicle 1 is provided with an immobilizer ECU 8 as a control unit that manages the immobilizer system 7. A coil antenna 9 is connected to the immobilizer ECU 8 as an antenna on the vehicle side of the immobilizer system 7. The coil antenna 9 is wound a plurality of times so as to surround the key hole of the key cylinder 3. The immobilizer ECU 8 is connected to the engine ECU 6 via an in-vehicle bus 10 that is one network in the vehicle. The immobilizer ECU 8 corresponds to a communication master.

  On the other hand, the vehicle key 2 includes a transponder 11 as an ID tag capable of wirelessly transmitting a unique ID. The transponder 11 is provided with a transponder ECU 12 that supervises and manages the transponder 11 and a transmission / reception antenna 13 as an antenna of the transponder 11. In the memory 14 of the transponder ECU 12, a transponder code is registered as the above-mentioned unique ID. The transponder 11 can perform communication by so-called short-range wireless communication that communicates with the immobilizer ECU 8 while being close to each other. For example, RFID (Radio Frequency IDentification) is used as the communication format. Further, the transponder 11 is a passive type that does not have its own power source and moves using the radio wave transmitted from the immobilizer ECU 8 as a power source. The transponder 11 corresponds to a communication terminal (communication partner).

  Further, the wireless communication of the immobilizer system 7, so-called immobilizer communication, is encrypted communication encrypted by challenge response authentication. In this case, the cryptographic operation formula F (x) is registered in the memory 15 of the immobilizer ECU 8 as an arithmetic expression on the immobilizer ECU 8 side for challenge response authentication. Also, the cryptographic operation formula F (x) is registered in the memory 14 of the transponder 11 as an arithmetic expression on the transponder 11 side of challenge response authentication. The cryptographic operation formula F (x) corresponds to an encryption key or an encryption algorithm. If the vehicle 1 and the vehicle key 2 form a pair, those having the same algorithm are set.

  When the immobilizer ECU 8 confirms that the vehicle key 2 is inserted into the key cylinder 3, the immobilizer ECU 8 starts immobilizer communication. At this time, the immobilizer ECU 8 first causes the coil antenna 9 to transmit a driving radio wave Svc as a power source for the transponder 11 and a challenge code as a challenge Sch for challenge response authentication. The drive radio wave Svc and the challenge Sch are transmitted by radio waves in the LF (Low Frequency) band. The challenge code is a data string (random number code) whose value changes every time it is transmitted. When the transponder ECU 12 receives this driving radio wave Svc, it starts up using it as a power source, calculates a challenge Sch received thereafter by its own cryptographic operation formula F (x), and generates a response code. Then, the transponder ECU 12 returns this response code and its own transponder code as a response Srs to the immobilizer ECU 8 with LF band radio waves.

  On the other hand, when the immobilizer ECU 8 transmits the challenge Sch, the immobilizer ECU 8 also calculates the response Srs by calculating the challenge code by its own cryptographic operation formula F (x). When the immobilizer ECU 8 receives the response Srs transmitted from the transponder 11 by the coil antenna 9, first, the immobilizer ECU 8 compares the response code calculated by itself with the response code calculated by the transponder 11, and performs response verification. When the immobilizer ECU 8 confirms that the response codes match and the challenge response authentication is established, this time, the immobilizer ECU 8 compares the transponder code included in the same response Srs with the transponder code registered in its own memory 15. Code verification. The immobilizer ECU 8 releases the immobilizer lock when confirming that the two verifications match and the response authentication is established.

  When the immobilizer lock is released, the immobilizer ECU 8 allows the engine ECU 6 to start the engine. At this time, pairing confirmation is performed between the immobilizer ECU 8 and the engine ECU 6, and challenge response authentication is also used for this confirmation. The For this reason, the cryptographic calculation formula F (x) is also registered in the memory 16 of the engine ECU 6 as a calculation formula on the engine ECU 6 side for challenge response authentication. Then, when the immobilizer lock is released, the engine ECU 6 sends a challenge Sch to the immobilizer ECU 8 to perform challenge response authentication. If this authentication is established, the engine 5 is switched to the activated state.

  As shown in FIG. 2, the vehicle 1 is provided with a key registration system 17 that registers a predetermined vehicle key 2 in the vehicle 1 as a key for the host vehicle. The vehicle key 2 is registered with a plurality of vehicle keys 2 for one vehicle 1 when, for example, one family has one vehicle 1 or the vehicle key 2 is lost. Is possible. In the case of this example, a total of eight keys, for example, a first master key 2a to a fifth master key 2e and a first sub key 2f to a third sub key 2h can be registered. The master keys 2a to 2e are keys that can be used for all functions without being limited to use of the vehicle 1. Further, the sub keys 2f to 2h are keys that are positioned so that the use of the vehicle 1 is restricted and only predetermined functions can be operated. Key 2 (2a to 2h) corresponds to a registration terminal.

  The memory 15 of the immobilizer ECU 8 is provided with a table 18 as a registration destination of the vehicle key 2 as shown in FIG. In this table 18, a registration area E, which is a data writing area, is divided in units of keys, and related data (transponder code, key number N) of the vehicle key 2 to be registered is from the head of the registration area E (head of address). The first registration key, the second registration key,... Are written in the order of registration. That is, the key registered in the first registration area E1 is set as the first registration key, the key registered in the second registration area E2 is set as the second registration key, and the same applies to the subsequent registration areas E3 to E8. . Therefore, the keys 2a to 2h are registered in the vehicle 1 in the order in which the registration work is performed. In this example, the table 18 includes a fifth master key 2e, a first master key 2a, a fourth master key 2d, a second subkey 2g, a first subkey 2f, a second master key 2b, a third subkey 2h, Key registration is performed in the order of 3 master keys 2c. The key number N constitutes the terminal type and terminal number.

  As shown in FIG. 2, the immobilizer ECU 8 is provided with a vehicle-side registration execution unit 19 that manages the key registration system 17 on the vehicle 1 side. When the vehicle 1 enters the registration mode of the vehicle key 2, the vehicle-side registration execution unit 19 executes registration communication with the transponder 11 of the vehicle key 2, and the vehicle key 2 that is in the communication state at this time is stored in the table 18. sign up. Further, the transponder ECU 12 is provided with a key side registration execution unit 20 that manages the key registration system 17 on the key 2 side. The key side registration execution unit 20 cooperates with the vehicle side registration execution unit 19 to execute the registration operation of the vehicle key 2 to the vehicle 1. In addition, the vehicle side registration execution part 19 and the key side registration execution part 20 comprise a registration means.

  Further, the vehicle 1 is provided with a cryptographic operation formula switching system 21 that switches the cryptographic operation formula F (x) used for immobilizer verification (that is, challenge response authentication) for each registration key of the vehicle 1. The cryptographic operation formula switching system 21 of this example is a system that uses a different cryptographic operation formula F (x) for each registration key. For example, in the case of the first registration key, the first cryptographic operation formula F1 ( x) is used, and in the case of the second registration key, the second cryptographic calculation formula F2 (x) is used, and the cryptographic calculation formula F (x) used for immobilizer verification (challenge response authentication) for each registration key. Is a system for switching between.

  In this case, the transponder ECU 12 is provided with a key number verification unit 22 for confirming whether the key number N (see FIGS. 5 and 6) sent from the immobilizer ECU 8 at the time of challenge response authentication is correct. The key number N is information indicating what kind of vehicle key 2 is the master keys 2a to 2e and the sub keys 2f to 2h, and consists of a data string of several bits. In addition, the transponder ECU 12 is provided with a response calculation unit 23 that calculates the challenge Sch sent from the immobilizer ECU 8 using its own cryptographic calculation formula F (x) and generates a response Srs.

  Also, in the table 18 shown in FIG. 3, a different cryptographic operation formula F (x) is assigned to each registration key. That is, the first cryptographic operation formula F1 (x), the second cryptographic computation formula F2 (x),... Are assigned to these registration keys in the order of the first registration key, the second registration key,. Therefore, in this example, the first cryptographic operation formula F1 (x) is added to the fifth master key 2e that is the first registration key, and the second cryptographic operation formula F2 (x is added to the first master key 2a that is the second registration key. ) Is the third registration key F3 (x) in the fourth master key 2d, which is the third registration key, and the fourth encryption formula F4 (x) is in the second subkey 2g, which is the fourth registration key, The fifth cryptographic operation formula F5 (x) is the first sub key 2f that is the registration key, the fourth cryptographic operation formula F6 (x) is the seventh registration key and the second master key 2b is the sixth registration key. A seventh cryptographic operation formula F7 (x) is allocated to the 3 subkey 2h, and an eighth cryptographic operation formula F8 (x) is allocated to the third master key 2c that is the eighth registration key.

  On the other hand, the cryptographic operation formula Fa (x) that is different for each key is also registered in the vehicle key 2. In the case of this example, as shown in FIG. 2, each transponder 11 is prepared in advance with the first cryptographic calculation formula F1 (x) to the eighth cryptographic calculation formula F8 (x), as in the case of the vehicle 1. A specific one is selected and set by the key side registration execution unit 20. By the way, since the area number Ner of the registration area E and the cryptographic operation formula F (x) are set in a unique relationship, when the vehicle key 2 is registered in the table 18 of the immobilizer ECU 8, this key registration destination If the area number Ner is known, the number of the cryptographic operation formula F (x) registered in the vehicle key 2 in the table 18 should also be known.

  Therefore, in the case of this example, the vehicle side registration execution part 19 notifies the key side registration execution part 20 of the area number Ner of the registration area E of the key registration destination in the registration mode of the vehicle key 2. When receiving the notification of the use area number Ner, the key-side registration execution unit 20 reads the cryptographic operation formula F (x) corresponding to this area number Ner and sets it as the use operation formula. For example, in the case of the fifth master key 2e, since this is registered in the first registration area E1 of the table 18, the vehicle side registration execution unit 19 uses the first registration area E1 as the area number Ner as the key side registration execution unit 20. Notify Then, the key-side registration execution unit 20 calculates the arithmetic expression F (x) corresponding to the first registration area E1 from among the plurality of cryptographic arithmetic expressions F1 (x) to F8 (x), that is, the first cryptographic arithmetic expression F1. Select (x) and set it as a cryptographic expression used. As a result, the fifth cryptographic key F1 (x) is registered in the fifth master key 2e as in the table 18 of the vehicle 1.

  The immobilizer ECU 8 is provided with an authentication execution unit 24 that manages challenge response authentication on the vehicle 1 side. The authentication execution unit 24 sends, for example, a challenge Sch (driving radio wave Svc, challenge code, key number N, etc.) to the transponder 11, calculates a response code in the cryptographic operation formula F (x) on the immobilizer ECU 8, and transponders Various operations such as authentication for checking whether the response Srs received from 11 is correct or not are executed.

  The immobilizer ECU 8 is provided with a key type confirmation unit 25 for confirming what the communication partner of challenge response authentication is, that is, the type of the vehicle key 2 of the authentication partner. In the case of this example, at the time of the immobilizer verification, the challenge Sch is transmitted with the key number N included therein, the verification of the key number N included in the challenge Sch is established on the transponder 11 side, and the transponder 11 returns the response Srs. This is repeated in the order of registration keys until a response Srs is returned. Therefore, the key type confirmation unit 25 monitors whether or not the response Srs is accepted for the challenge Sch, and confirms that the response is accepted. When the key type confirmation unit 25 confirms the acceptance of the response, the registration key of the key number N included in the challenge Sch sent at this time Recognized as key 2. The key type confirmation unit 25 corresponds to a terminal type confirmation unit.

  Further, the immobilizer ECU 8 is provided with a cryptographic operation formula setting unit 26 for setting a cryptographic operation formula F (x) used at the time of challenge response authentication. The cryptographic operation formula setting unit 26 confirms the authentication partner from the confirmation result of the key type confirmation unit 25, and reads the cryptographic operation formula F (x) corresponding to the communication partner from the table 18 with reference to the table 18. Subsequently, the cryptographic operation formula setting unit 26 sets the cryptographic operation formula F (x) read from the table 18 as the cryptographic operation formula F (x) used for challenge response authentication. Then, the cryptographic operation formula setting unit 26 causes the authentication execution unit 24 to execute response verification using this cryptographic operation formula F (x). The cryptographic operation formula setting unit 26 corresponds to the cryptographic operation formula switching means.

First, the registration procedure of the vehicle key 2 to the immobilizer ECU 8 will be described with reference to FIG.
For example, when a predetermined operation for putting the cryptographic operation switching system 21 into the registration mode of the vehicle key 2 is executed in the vehicle 1, the key registration system 17 enters the registration mode and the vehicle-side registration execution unit 19 is activated. Here, as an example of switching the vehicle 1 to the registration mode of the vehicle key 2, for example, an example in which the door knob of the vehicle 1 is operated a predetermined number of times and in an order can be given. When the operation mode is switched to the registration mode, the vehicle-side registration execution unit 19 transmits the driving radio wave Svc from the coil antenna 9 as an LF radio wave as shown in FIG. 4 in order to activate the transponder 11. This drive radio wave Svc is a radio wave serving as a power source for the transponder 11 that is also transmitted when the immobilizer is collated.

  When the transponder ECU 12 receives this drive radio wave Svc, the key side registration execution unit 20 switches to the activated state. When the key-side registration executing unit 20 confirms that the cryptographic operation formula F (x) is not registered in the power-on radio wave Svc and enters the start-up state, the key-side registration executing unit 20 sets its own operation mode to the registration mode. Then, when entering the registration mode, the key-side registration execution unit 20 returns an ACK with an LF radio wave to notify the vehicle-side registration execution unit 19 to that effect. The vehicle-side registration execution unit 19 recognizes that the transponder 11 has entered the registration mode when it receives an ACK within a predetermined time after entering the registration mode of the vehicle key 2 and transmitting the drive radio wave Svc.

  When the vehicle-side registration execution unit 19 confirms that the transponder 11 has entered the registration mode, the vehicle side registration number E in the registration area E of the table 18 is assigned the area number Ner in which no data (vehicle key 2) is written. It transmits by LF radio wave as a registration destination. For example, when first registering a key in the vehicle 1, the first registration area E1 is transmitted as the area number Ner. If the first registration area E1 and the second registration area E2 are used, the area number Ner is used. The third registration area E3 is transmitted.

  When the key-side registration execution unit 20 receives the area number Ner transmitted from the immobilizer ECU 8, the key-side registration execution unit 20 selects a cryptographic calculation formula F corresponding to the area number Ner from among the cryptographic calculation formulas F (x) registered in its own memory 15. (x) is read and registered. For example, when the area number of the first registration area E1 is received, the first cryptographic calculation formula F1 (x) is registered, and when the area number of the third registration area E3 is received, the third cryptographic calculation formula F3 (x) is registered as a cryptographic operation formula for use. When the key-side registration is completed, the key-side registration execution unit 20 returns an ACK with an LF radio wave. When the vehicle side registration execution unit 19 receives the ACK within a predetermined time after transmitting the area number Ner, the vehicle side registration executing unit 19 recognizes that the selection of the cryptographic operation formula on the vehicle key 2 side is completed, and at this time the area number in the selected state Confirm Ner as the registration destination.

  When the vehicle side registration execution unit 19 confirms that the selection of the cryptographic operation formula on the vehicle key 2 side has been completed, this time, the vehicle side registration execution unit 19 sends a key information notification request to the transponder 11 as a request to notify the transponder code and the key number N. . Upon receiving the key information notification request, the transponder 11 returns its own transponder code and key number N to the immobilizer ECU 8. When receiving the transponder code and the key number N from the transponder 11, the vehicle side registration executing unit 19 writes these information in the determined area number Ner. As a result, the vehicle key 2 registered in the vehicle 1 is registered in the vehicle 1 in a state in which the use encryption arithmetic expression is associated.

Next, operations performed by the cryptographic operation type switching system 21 of this example will be described with reference to FIGS.
When the vehicle key 2 is inserted into the key cylinder 3, the authentication execution unit 24 first transmits a drive radio wave Svc from the coil antenna 9, as shown in FIG. The vehicle key 2 receives this drive radio wave Svc at the transponder 11. When the transponder ECU 12 receives the drive radio wave Svc, the transponder ECU 12 switches to the activated state using the drive radio wave Svc as a power source, and transmits an ACK by LF radio wave to notify the immobilizer ECU 8 that it has entered the activated state. When the ACK is received by the coil antenna 9 after the transmission of the drive radio wave Svc, the authentication execution unit 24 recognizes that the transponder 11 has been switched to the activated state by the drive radio wave Svc transmitted earlier.

  When the authentication execution unit 24 confirms that the transponder 11 has been switched to the activated state, the authentication execution unit 24 enters an operation of identifying the transponder 11 (vehicle key 2) that is the communication partner at this time. In the case of this example, the authentication execution unit 24 firstly has the key number N of the first registration key in the table 18, that is, the key number N written in the first registration area E1 (first address) of the table 18, A challenge code for challenge response authentication is transmitted from the coil antenna 9 by LF radio waves as the challenge Sch of this example. Here, the key number N of the fifth master key 2e is put on the challenge Sch.

  When receiving the challenge Sch from the immobilizer ECU 8, the key number matching unit 22 first checks the key number N by comparing the key number N included in the challenge Sch with its own. At this time, the key number verification unit 22 performs key number verification by comparing the key number N received from the immobilizer ECU 8 with the key number N registered in the memory 14 of the transponder ECU 12. When the key number verification unit 22 confirms that the key number verification is established, the key number verification unit 22 proceeds to the next operation. When the key number verification is not established, the key number verification unit 22 ends the verification operation and waits.

  At this time, if the vehicle key 2 of the communication partner is, for example, the fifth master key 2e, the key number verification unit 22 confirms that the key number verification is established. Then, the response calculation unit 23 calculates the response code by calculating the challenge code included in the challenge Sch using the first cryptographic calculation formula F1 (x) that the response calculation unit 23 has. When the response calculation unit 23 finishes calculating the response code, the response code that is the calculation result and the transponder code registered in its own memory 14 are transmitted as a response Srs from the transmission / reception antenna 13 using LF radio waves.

  Further, when the key type confirmation unit 25 receives the response Srs by the coil antenna 9 within a predetermined time after the transmission of the challenge Sch with the key number N of the fifth master key 2e, the key key 2 of the communication partner becomes the first key. Recognize that it is the 5 master key 2e. That is, if the key type confirmation unit 25 can receive the response Srs as an ack within a predetermined time after transmitting the challenge Sch, the vehicle key 2 with the key number N put on the challenge Sch at this time is the communication partner. recognize. Then, the key type confirmation unit 25 notifies the cryptographic operation equation setting unit 26 of what registration key the communication partner is as a key type confirmation result. In the case of this example, the key type confirmation unit 25 notifies the cryptographic operation formula setting unit 26 that the communication partner is the first registration key.

  Upon receiving the key type confirmation result from the key type confirmation unit 25, the cryptographic operation formula setting unit 26 refers to the table 18 and selects the cryptographic operation formula F (x) corresponding to the communication partner at this time, and selects the selected cryptographic operation. Formula F (x) is set as a cryptographic operation formula. At this time, since the cryptographic operation formula setting unit 26 accepts that the communication partner is the first registration key, that is, the fifth master key 2e, the first cryptographic computation that is the cryptographic operation formula for the first registration key. Formula F1 (x) is set as a cryptographic operation formula.

  After this cryptographic operation formula is set, the authentication execution unit 24 also calculates a challenge code by itself using the first cryptographic calculation formula F1 (x), creates a response code, and uses this response code as the response code received from the transponder 11. Check the response against this. And if the authentication execution part 24 confirms establishment of response collation, it will perform code collation by the transponder code contained in the same response Srs succeedingly. When the authentication execution unit 24 confirms that this code verification is also established, the authentication execution unit 24 recognizes that the challenge response authentication is established, and releases the immobilizer lock.

  On the other hand, for example, as shown in FIG. 6, when the challenge Sch with the key number N of the first registration key (fifth master key 2e) is transmitted from the immobilizer ECU 8, the communication partner is not the fifth master key 2e. Since the key number N does not match between the immobilizer ECU 8 and the transponder ECU 12, the key number matching unit 22 does not recognize the establishment of the key number matching. For this reason, the transponder ECU 12 cannot take the subsequent operation, that is, the response calculation operation, and does not take the operation of returning the response Srs to the immobilizer ECU 8.

  Therefore, even if the authentication execution unit 24 sends the challenge Sch with the key number N of the first registration key, the authentication execution unit 24 cannot receive this response Srs within a predetermined time. 2 Challenge Sch with the key number N of the registration key is transmitted to confirm the communication partner. If the authentication execution unit 24 cannot receive a response within a predetermined time after the challenge transmission, the authentication execution unit 24 transmits a challenge Sch carrying the key number N of the next registration key, and performs this operation until the response Srs is received. Repeat. Then, the authentication execution unit 24 sets the cryptographic calculation formula F (x) according to the registration key of the number that can accept the response Srs as the usage cryptographic calculation formula, and executes response verification.

  If the authentication execution unit 24 does not receive the response Srs from the transponder 11 even if it sends all the key numbers N of the eight vehicle keys 2 registered in itself when the challenge Sch is transmitted, The vehicle key 2 is recognized as a key of another vehicle, and the authentication operation is forcibly terminated. On the other hand, the transponder 11 returns to the power-off state when the power source by the driving radio wave Svc is turned off.

  As described above, in this example, a plurality of vehicle keys 2 can be registered in the vehicle 1, and a plurality of cryptographic operation formulas F (x) for challenge response authentication are prepared in the vehicle 1 according to the number of registration keys. This cryptographic operation formula F (x) can be changed for each registration key. For this reason, for example, it is possible to make it difficult to analyze the cryptographic operation formula F (x) as compared with the case where one cryptographic operation formula F (x) is shared by a plurality of vehicle keys 2, so that the authentication is illegal. There is less worry about being established. Therefore, high security against vehicle theft is ensured. Further, since the vehicle key 2 is a registration type, authentication is performed in the order of registration, so that it is possible to set an authentication order according to the user's request, thereby satisfying user satisfaction.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) Since the cryptographic calculation formula F (x) is divided for each vehicle key 2 registered in the immobilizer ECU 8 (table 18), the cryptographic calculation formula F (x) used for challenge response authentication is set for each registration key. Can be changed. For this reason, since each vehicle key 2 performs authentication with a different cryptographic calculation formula F (x), for example, compared to a case where a plurality of vehicle keys 2 share one and the same cryptographic calculation formula F (x). The resistance against illegal reading of the cryptographic operation formula F (x) can be increased. As a result, it is possible to make it difficult to analyze the cryptographic operation formula F (x), and as a result, security against vehicle theft can be improved.

  (2) A plurality of cryptographic calculation formulas F (x), F (x)... Are prepared in advance in each of the immobilizer ECU 8 and the transponder ECU 12, and these cryptographic calculations are performed when the vehicle key 2 is registered in the vehicle 1. It takes the form of selecting which of the formulas F (x), F (x). Therefore, when registering the cryptographic operation formula F (x), for example, it is not necessary to use a format in which the cryptographic operation formula F (x) is actually skipped to the other side by communication, so that the cryptographic operation formula F (x) itself is wiretapped. The situation does not become. Therefore, it is possible to further prevent unauthorized reading of the cryptographic operation formula F (x).

  (3) Which of the plurality of cryptographic calculation formulas F (x), F (x)... Prepared for the vehicle key 2 is selected and set is determined by the immobilizer ECU 8 from the registration area when the cryptographic calculation formula F (x) is registered. This is executed by notifying the vehicle key 2 of the area number Ner of E. Therefore, the selection setting of the cryptographic operation formula F (x) in the vehicle key 2 can be executed in a simple format in which the vehicle key 2 notifies the vehicle key 2 of the area number Ner of the registration area E.

  (4) At the time of challenge response authentication, the key number N is issued in order with respect to the vehicle key 2, and it is checked whether or not the vehicle key 2 can respond to it, so that the vehicle key 2 becomes the master keys 2a to 2e and the sub keys 2f to 2h. The key type in the is confirmed. For this reason, the type of the vehicle key 2 can be confirmed in a simple format in which the key number N is issued and the presence or absence of the response is seen.

  (5) At the time of challenge response authentication, the key numbers N are sent to the vehicle key 2 in order, and the communication partners are confirmed one by one in order. For this reason, even when a plurality of vehicle keys 2 exist as communication partners for one vehicle 1 as in this example, the situation is such that a plurality of vehicle keys 2 access the vehicle 1 at the same time. Authentication can be executed without any problem.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
The adoption target of the cryptographic operation switching system 21 is not necessarily limited to the immobilizer system 7. For example, the present invention may be applied to a so-called key operation free system in which a request is transmitted as a key reply request from the vehicle 1 and collation is performed using an ID code returned from the key 2 in response to the request.

  The vehicle 1 may include both the key operation free system and the immobilizer system 7 described above. In this case, the function of the transponder 11 of this example may be integrated into a control IC (Integrated Circuit) that manages the key operation free system.

  The start condition for immobilizer verification is not necessarily limited to the vehicle key 2 being inserted into the key cylinder 3. For example, the start condition may be that the brake pedal is depressed while the shift lever is in the parking position.

-The frequency of immobilizer communication is not necessarily performed by radio waves in the LF band, and, for example, a UHF (Ultra High Frequency) band may be used.
The table 18 is not necessarily in the form of a table in which the registration key and the cryptographic operation formula F (x) are associated with each other. In short, which cryptographic operation formula F (x) is given at which key number N If it is known whether to use, the format is not particularly limited.

  -For registration of the vehicle key 2, for example, a cryptographic operation formula F (x) is transmitted from the vehicle key 2 to the vehicle 1 during the registration operation, and this is registered in the vehicle 1 in association with the key information. Also good.

The vehicle key 2 is not limited to having a plurality of cryptographic formulas F (x), F (x)... Prepared in advance, and for example, a configuration in which only one is prepared may be adopted.
The operation mode for setting the key registration system 17 to the registration mode is not necessarily limited to the form using the door knob, and other operation devices installed in the vehicle 1 may be used, or a dedicated registration tool May be used.

  The authentication between the immobilizer ECU 8 and the transponder 11 and the authentication between the immobilizer ECU 8 and the engine ECU 6 are not necessarily limited to using the same cryptographic operation formula F (x), but the cryptographic operation formula F (x ) May be different.

As a method for confirming the type of the vehicle key 2 when entering the registration mode, for example, a method may be employed in which the type is inquired of the vehicle key 2 and the key type is determined.
As the cryptographic operation formula F (x), various types such as AES (Advanced Encryption Standard) cipher and DES (Data Encryption Standard) cipher can be adopted.

The communication format between the communication master and the communication terminal is not necessarily limited to wireless, and may be wired, for example.
-The adoption object of the technical idea of this example is not necessarily limited to the vehicle 1, and may be applied to various apparatuses and devices. Therefore, the communication master is not limited to the immobilizer ECU 8 (vehicle 1), and the communication terminal is not limited to the transponder 11 (vehicle key 2), and various types can be adopted.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(1) In any one of claims 1 to 4, the response includes a response code that is a response to the challenge response authentication and an authentication code that is a unique ID of the communication terminal. The authentication is used to determine whether the response and the authentication code are verified. In this case, the authentication level can be higher.

  2 (2a to 2h): Key as a registration terminal, 8: Immobilizer ECU as a communication master, 11: Transponder as a communication terminal (communication partner), 18 ... Table, 19 ... Vehicle side registration execution unit constituting registration means , 20... Key side registration execution unit constituting the registration unit, 25... Key type confirmation unit as the terminal type confirmation unit, 26... Cryptographic operation formula setting unit as the cryptographic operation type switching unit, Sch. Challenge, Srs. F (x) (F1 (x) to F8 (x))... Cryptographic operation formula, N... Terminal type, key number constituting the terminal number, E (E1 to E8)... Registration area, Ner.

Claims (5)

Sending a challenge from the communication master to the communication terminal that is the communication partner, causing the communication terminal to calculate the response of the challenge by the cryptographic operation formula, and sending the response back to the communication master after the calculation, also to the communication master In the challenge response type authentication system that performs the response of the challenge by the cryptographic operation formula possessed by the communication master and authenticates the two parties by comparing the responses of the two parties,
Registration means capable of registering the communication terminal in a state associated with the cryptographic operation formula in the communication master;
When the communication master enters an authentication state with the communication terminal, a terminal type confirmation unit for confirming a terminal type of the communication terminal that is a communication partner at that time,
The communication terminal determined by the terminal type confirmation unit is selected from among the registered terminals registered by the registration unit, and a cryptographic operation expression corresponding to the selected registered terminal is selected during the authentication. An authentication system comprising: a cryptographic operation formula switching means for switching the cryptographic operation formula for each of the registered terminals when used.   The registration means selects a specific same one from a plurality of groups of cryptographic expressions prepared in advance for each of the two parties in both the communication master and the communication terminal, and uses this for the authentication. The authentication system according to claim 1, wherein each of the two parties is set as an arithmetic expression to be used.   The registration means has a registration area in which the cryptographic operation formula and an area number are associated as a registration destination of the communication terminal on the communication master side, and when registering the communication terminal in the communication master, By notifying the communication terminal of the area number, the cryptographic operation formula according to the area number is registered as the cryptographic operation formula used in the communication terminal, while the communication master includes the area number and the communication terminal. The authentication system according to claim 2, wherein the communication terminal registered on the communication master side and the cryptographic operation expression are associated with each other by registering them in association with each other.   The terminal type confirmation means causes the communication terminal to execute the terminal number verification by including the terminal number of the communication terminal in the challenge, and the response is returned to the communication master without the verification being established. If not, this time, the terminal number of the next number is added to the challenge, the terminal number is collated, and this operation is repeated until a response is received, thereby confirming the communication partner of the communication master. The authentication system according to any one of claims 1 to 3, wherein: Sending a challenge from the communication master to the communication terminal that is the communication partner, causing the communication terminal to calculate the response of the challenge by the cryptographic operation formula, and sending the response back to the communication master after the calculation, also to the communication master In the challenge response type authentication method for performing authentication of the two parties by comparing the responses of the two parties by calculating the response of the challenge by the cryptographic calculation formula possessed by the communication master,
The communication terminal can be registered in the state associated with the cryptographic operation formula in the communication master, and when the communication master enters the authentication state with the communication terminal, the communication terminal that is the communication partner at that time Confirming the terminal type, selecting which of the registered terminals the communication terminal is, and using the cryptographic operation formula corresponding to the selected registered terminal at the time of the authentication, An authentication method characterized by switching for each registered terminal.

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