Communication apparatus, communication system, certificate transmission method and program

A communication apparatus comprising:

• a certificate memory part configured to store a first digital certificate and a second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• a certificate update part configured to update an old second digital certificate stored in the certificate memory part when receiving a new second digital certificate from another communication apparatus when communicating with the another communication apparatus and when the validity term of the old second digital certificate is expired;
• and
• a request management unit that stores a criterion to determine execution of an operation according to a request from the another communication apparatus, and allows operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the another communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the another communication apparatus is authenticated by the first digital certificate.

A communication system comprising:

• a first communication apparatus, the first communication apparatus including a certificate memory part configured to store a first digital certificate and a second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• a second communication apparatus, the second communication apparatus including an authentication part configured to authenticate the first communication apparatus with the first digital certificate when communicating with the first communication apparatus and when the validity term of the second digital certificate is expired;
• the second communication apparatus also includes a certificate transmission part configured to transmit a new second digital certificate to the first communication apparatus when the authentication part succeeds in authenticating the first communication apparatus with the first digital certificate;
• and
• the second communication apparatus also includes a request management unit that stores a criterion to determine execution of an operation according to a request from the another communication apparatus, and allows operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the first communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the first communication apparatus is authenticated by the first digital certificate.

A certificate transmission method of a communication apparatus comprising:

• a) authenticating another communication apparatus with a first digital certificate when authentication using a second digital certificate fails due to expiration of the validity term of the second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• b) transmitting a new second digital certificate when the authentication of the other communication apparatus with the first digital certificate in a) succeeds;
• wherein the other communication apparatus is authenticated with the first digital certificate in a) when communicating with the another communication apparatus and when the validity term of the old second digital certificate is expired;
• and
• c) storing a criterion to determine execution of an operation according to a request from the another communication apparatus, and allowing operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the another communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the another communication apparatus is authenticated by the first digital certificate.

A certificate transmission method comprising:

• a) authenticating a communication apparatus with a first digital certificate when authentication using a second digital certificate fails due to expiration of the validity term of the second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• b) transmitting a new second digital certificate when the authentication of the communication apparatus with the first digital certificate in a) succeeds;
• wherein the communication apparatus is authenticated with the first digital certificate in a) when communicating with another communication apparatus and when the validity term of the old second digital certificate is expired;
• and
• c) storing a criterion to determine execution of an operation according to a request from the another communication apparatus, and allowing operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the another communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the another communication apparatus is authenticated by the first digital certificate.

A computer readable medium storing computer executable instructions to be executed by a computer of a communication apparatus, the computer executable instructions comprising:

• a) an authenticating function for authenticating another communication apparatus with a first digital certificate when authentication using a second digital certificate fails due to expiration of the validity term of the second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• b) a transmitting function for transmitting a new second digital certificate when the authentication of the other communication apparatus with the first digital certificate in function a) succeeds;
• wherein the communication apparatus is authenticated with the first digital certificate in function a) when communicating with the another communication apparatus and when the validity term of the old second digital certificate is expired;
• and
• c) a request management function that stores a criterion to determine execution of an operation according to a request from the another communication apparatus, and allows operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the another communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the another communication apparatus is authenticated by the first digital certificate.

A computer readable medium storing computer executable instructions to be installed or executed by a computer of a communication apparatus, the computer executable instructions comprising:

• a) a storing function for storing a first digital certificate and a second digital certificate, the second digital certificate corresponding to a regular public key, the first digital certificate corresponding to a rescue public key, the first digital certificate having a validity term that is longer than the validity term of the second digital certificate;
• b) an updating function for updating an old second digital certificate stored in function a) with a new second digital certificate received from another communication apparatus when communicating with the another communication apparatus and when the validity term of the old second digital certificate is expired;
• and
• c) a request management function that stores a criterion to determine execution of an operation according to a request from the another communication apparatus, and allows operations of the communication apparatus to be executed such that all of the operations are allowed to be executed when the another communication apparatus is authenticated by the second digital certificate according to the stored criterion, and only an operation of transmitting the new second digital certificate is allowed when the another communication apparatus is authenticated by the first digital certificate.