Common key setting method, relay apparatus, and program

A common key setting method for setting a common key in a first apparatus and a second apparatus through a relay apparatus, wherein the first and second apparatuses perform processing according to a protocol including authentication between two apparatuses, sharing of a common key between the two apparatuses by using a cryptography technology, and processing for checking the validity of a common key setting process by using secret information for identifying the common key and communication log information between the two apparatuses, the common key setting method comprising:

• a secret information setting step of setting secret information for identifying the common key, in a secret information setting unit of the first apparatus;
• a first secret information encryption step of generating first encrypted secret information by encrypting the secret information by using a public key of the relay apparatus corresponding to a secret key of the relay apparatus, in a public key encryption processor of the first apparatus;
• an encrypted secret information transmission step of transmitting the first encrypted secret information to the relay apparatus, in a transmitter of the first apparatus;
• a first secret information decryption step of decrypting the first encrypted secret information by using the secret key of the relay apparatus read from the memory of the relay apparatus to extract the secret information, in a decryption processor of the relay apparatus;
• a second secret information encryption step of generating second encrypted secret information by encrypting the secret information by using a public key of the second apparatus, in a public key encryption processor of the relay apparatus;
• an encrypted secret information forwarding step of transmitting the second encrypted secret information to the second apparatus, in a transmitter of the relay apparatus;
• a second secret information decryption step of decrypting the second encrypted secret information by using a secret key of the second apparatus corresponding to the public key of the second apparatus to extract the secret information, in a decryption processor of the second apparatus;
• a first finished message generation step of generating a first finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus, in a finished message generator of the first apparatus;
• a first finished message transmission step of transmitting the first finished message to the relay apparatus, in the transmitter of the first apparatus;
• a second finished message generation step of generating a second finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus, in a finished message generator of the relay apparatus;
• a second finished message transmission step of transmitting the second finished message to the second apparatus, in the transmitter of the relay apparatus;
• a third finished message generation step of generating a third finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus, in a finished message generator of the second apparatus;
• a third finished message transmission step of transmitting the third finished message to the relay apparatus, in a transmitter of the second apparatus;
• a fourth finished message generation step of generating a fourth finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus, in the finished message generator of the relay apparatus;
• and
• a fourth finished message transmission step of transmitting the fourth finished message to the first apparatus, in the transmitter of the relay apparatus.

A relay apparatus, comprising:

• a memory;
• a transmitter;
• a receiver;
• a decryption processor;
• a first finished message generator;
• and
• a second finished message generator;
• wherein the relay apparatus performs a relay operation between a first apparatus and a second apparatus that perform processing according to a protocol including authentication between two apparatuses, sharing of a common key between the two apparatuses by using a cryptography technology, and processing for checking the validity of a common key setting process by using secret information for identifying the common key and communication log information between the two apparatuses;
• the memory stores a secret key of the second apparatus;
• the receiver receives encrypted secret information generated by encrypting secret information used to identify a common key, by using a public key of the second apparatus corresponding to the secret key of the second apparatus;
• the decryption processor decrypts the encrypted secret information by using the secret key of the second apparatus read from the memory to extract the secret information;
• the transmitter transmits the encrypted secret information to the second apparatus;
• the receiver receives a first finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus, from the first apparatus;
• the first finished message generator generates a second finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus;
• the transmitter transmits the second finished message to the second apparatus;
• the receiver receives a third finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus, from the second apparatus;
• the second finished message generator generates a fourth finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus;
• and
• the transmitter transmits the fourth finished message to the first apparatus.

A relay apparatus, comprising:

• a memory;
• a transmitter;
• a receiver;
• a decryption processor;
• a public key encryption processor;
• a first finished message generator;
• and
• a second finished message generator;
• wherein the relay apparatus performs a relay operation between a first apparatus and a second apparatus that perform processing according to a protocol including authentication between two apparatuses, sharing of a common key between the two apparatuses by using a cryptography technology, and processing for checking the validity of a common key setting process by using secret information for identifying the common key and communication log information between the two apparatuses;
• the memory stores a secret key of the relay apparatus;
• the receiver receives first encrypted secret information generated by encrypting secret information used to identify a common key, by using a public key of the relay apparatus corresponding to the secret key of the relay apparatus;
• the decryption processor decrypts the first encrypted secret information by using the secret key of the relay apparatus read from the memory to extract the secret information;
• the public key encryption processor generates second encrypted secret information by encrypting the secret information by using a public key of the second apparatus;
• the transmitter transmits the second encrypted secret information to the second apparatus;
• the receiver receives a first finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus, from the first apparatus;
• the first finished message generator generates a second finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus;
• the transmitter transmits the second finished message to the second apparatus;
• the receiver receives a third finished message corresponding to the secret information and communication log information between the second apparatus and the relay apparatus, from the second apparatus;
• the second finished message generator generates a fourth finished message corresponding to the secret information and communication log information between the first apparatus and the relay apparatus;
• and
• the transmitter transmits the fourth finished message to the first apparatus.