Electronic key system, onboard apparatus, and portable apparatus

1. An electronic key system comprising:

an onboard apparatus that is mounted to a vehicle; and

a portable apparatus that is carried by a user,

wherein:

the electronic key system establishes wireless communication with a secret key common to the onboard apparatus and the portable apparatus, and authenticates the portable apparatus registered as the portable apparatus of an authorized user through wireless communication;

the portable apparatus includes a portable apparatus code transmitter that transmits to the onboard apparatus a portable apparatus code unique to the portable apparatus when the portable apparatus of the authorized user is to be registered;

the onboard apparatus includes an onboard code transmitter that transmits to the portable apparatus, an onboard apparatus unique code as an onboard code different from the portable apparatus code when the portable apparatus of the authorized user is to be registered, wherein the onboard apparatus unique code is a code unique to the onboard apparatus;

the onboard apparatus further includes

a portable apparatus code receiver that receives the portable apparatus code transmitted from the portable apparatus code transmitter of the portable apparatus when the portable apparatus of the authorized user is to be registered, and

an onboard-side key generation portion that generates the secret key by a cryptographic algorithm common to the portable apparatus while using the onboard apparatus unique code and the portable apparatus code received by the portable apparatus code receiver; and

the portable apparatus further includes

an onboard code receiver that receives the onboard apparatus unique code from the onboard code transmitter when the portable apparatus of the authorized user is to be registered,

a portable-apparatus-side key generation portion that generates the secret key by the cryptographic algorithm common to the onboard apparatus while using the portable apparatus code and the onboard apparatus unique code received by the onboard code receiver, and

a temporary storage that temporarily stores the onboard apparatus unique code received by the onboard code receiver;

the temporary storage erases the onboard apparatus unique code which is temporarily stored, when, at a latest, the portable apparatus of the authorized user is completely registered; and

the portable apparatus only transmits the portable apparatus code.

2. The electronic key system according to claim 1 , further comprising:

at least one different apparatus other than the onboard apparatus, the different apparatus being mounted to the vehicle and communicatively connected to the onboard apparatus,

wherein:

the different apparatus includes a different-apparatus-side storage that stores a different apparatus unique code, which is a code unique to the different apparatus;

the onboard apparatus further includes a different apparatus unique code acquisition portion that acquires the different apparatus unique code of the different apparatus;

the onboard code transmitter not only transmits the onboard apparatus unique code as the onboard code, but also transmits the different apparatus unique code acquired by the different apparatus unique code acquisition portion as the onboard code;

the onboard-side key generation portion generates the secret key by the cryptographic algorithm common to the portable apparatus through the onboard apparatus unique code serving as the onboard code, the different apparatus unique code acquired by the different apparatus unique code acquisition portion as the onboard code, and the portable apparatus code received by the portable apparatus code receiver;

when the portable apparatus of the authorized user is to be registered,

the onboard code receiver of the portable apparatus receives the different apparatus unique code and the onboard apparatus unique code transmitted from the onboard code transmitter of the onboard apparatus as the onboard code; and

the portable-apparatus-side key generation portion generates the secret key by the cryptographic algorithm common to the onboard apparatus from the portable apparatus code, the different apparatus unique code, and the onboard apparatus unique code, which are received as the onboard code by the onboard code receiver.

3. The electronic key system according to claim 1 , wherein:

the onboard apparatus further includes an onboard-side encrypted data transmitter that transmits a predetermined first data and a first encrypted data to the portable apparatus, the first encrypted data being obtained by encrypting the first data with the secret key generated by the onboard-side key generation portion;

the portable apparatus further includes

an onboard-side encrypted data receiver that receives the first data and the first encrypted data from the onboard-side encrypted data transmitter,

a portable-apparatus-side agreement determinator that determines whether data obtained by encrypting the first data received by the onboard-side encrypted data receiver with the secret key generated by the portable-apparatus-side key generation portion agrees with the first encrypted data received by the onboard-side encrypted data receiver, and

a portable-apparatus-side encrypted data transmitter that transmits a predetermined second data and a second encrypted data to the onboard apparatus, the second encrypted data being obtained by encrypting the second data with the secret key generated by the portable-apparatus-side key generation portion; and

the onboard apparatus further includes

a portable-apparatus-side encrypted data receiver that receives the second data and the second encrypted data from the portable-apparatus-side encrypted data transmitter,

an onboard-side agreement determinator that determines whether data obtained by encrypting the second data received by the portable-apparatus-side encrypted data receiver with the secret key generated by the onboard-side key generation portion agrees with the second encrypted data received by the portable- apparatus-side encrypted data receiver, and

a registration permission portion that, when the portable apparatus of the authorized user is to be registered and when both the portable-apparatus-side agreement determinator and the onboard-side agreement determinator have determined that agreement is successful, permits the portable apparatus of the authorized user to be registered.

4. The electronic key system according to claim 1 , wherein:

the portable apparatus further includes an encryptor that encrypts the portable apparatus code by a different algorithm by using the onboard code received by the onboard code receiver as an other secret key different from the secret key, the different algorithm being different from the cryptographic algorithm and being an other cryptographic algorithm common to the onboard apparatus;

the portable apparatus code transmitter transmits the portable apparatus code encrypted by the encryptor to the onboard apparatus; and

the onboard apparatus further includes a decryptor that decrypts the portable apparatus code encrypted by the encryptor and received by the portable apparatus code receiver by the different algorithm by using the onboard code as the secret key.

5. An onboard apparatus that is mounted to a vehicle comprising:

an onboard code transmitter that transmits to a portable apparatus, an onboard apparatus unique code as an onboard code different from a portable apparatus code when the portable apparatus of an authorized user is to be registered, in which the onboard apparatus unique code is a code unique to the onboard apparatus;

a portable apparatus code receiver that receives the portable apparatus code transmitted from a portable apparatus code transmitter of the portable apparatus when the portable apparatus of the authorized user is to be registered; and

an onboard-side key generation portion that generates a secret key by a cryptographic algorithm common to the portable apparatus while using the onboard apparatus unique code and the portable apparatus code received by the portable apparatus code receiver,

wherein:

an electronic key system including the onboard apparatus and the portable apparatus establishes wireless communication with the secret key common to the onboard apparatus and the portable apparatus, and authenticates the portable apparatus registered as the portable apparatus of the authorized user through the wireless communication;

the onboard code transmitter is mounted in the vehicle; and

the onboard code transmitter performs wireless communication with the portable apparatus.

6. A portable apparatus that is carried by a user comprising:

a portable apparatus code transmitter that transmits to an onboard apparatus a portable apparatus code unique to the portable apparatus when the portable apparatus of an authorized user is to be registered;

an onboard code receiver that receives an onboard apparatus unique code from an onboard code transmitter when the portable apparatus of the authorized user is to be registered;

a portable-apparatus-side key generation portion that generates a secret key by a cryptographic algorithm common to the onboard apparatus while using the portable apparatus code and the onboard apparatus unique code received by the onboard code receiver; and

a temporary storage that temporarily stores the onboard apparatus unique code received by the onboard code receiver,

wherein:

the temporary storage erases the onboard apparatus unique code which is temporarily stored, when, at a latest, the portable apparatus of the authorized user is completely registered;

the portable apparatus only transmits the portable apparatus code; and

an electronic key system including the onboard apparatus and the portable apparatus establishes wireless communication with the secret key common to the onboard apparatus and the portable apparatus, and authenticates the portable apparatus registered as the portable apparatus of the authorized user through the wireless communication.