COMMUNICATION SYSTEM, COMMUNICATION APPARATUS, METHOD, AND PROGRAM

1 . A communication system comprising a plurality of communication apparatuses, wherein

the communication apparatuses each include

a first memory; and

a first processor coupled to the first memory and configured to:

generate a shared key for performing encrypted communication with another communication apparatus of the plurality of communication apparatuses by using one or more keys shared with the another communication apparatus by one or more key sharing methods, and

perform encrypted communication with the another communication apparatus using the shared key.

2 . The communication system according to claim 1 , wherein

the first processor is configured to

generate the shared key with a predetermined key derivation function using the one or more keys and one or more pieces of key identification information identifying each of the one or more keys.

3 . The communication system according to claim 2 , wherein

the first processor is configured to

generate, in a case where a plurality of key sharing methods of a same type is included in the one or more key sharing methods, the shared key by further using a label representing each of the plurality of key sharing methods of the same type.

4 . The communication system according to claim 1 , wherein:

the first processor is further configured to perform, when receiving a request for the shared key from the application program, authentication processing of the application program with reference to preset application authentication information,

the communication system further comprises a key sharing system configured to share a key with another key sharing system by the key sharing method, and

the key sharing system is configured to

perform mutual authentication processing with the another shared system and perform authorization processing of a key to be shared with the another key sharing system using preset authorization information.

5 . The communication system according to claim 4 , comprising:

a second memory; and

a second processor coupled to the second memory and configured to:

switch a key sharing method that becomes unable to share a key between the key sharing system and the another key sharing system among the one or more key sharing methods to another key sharing method.

6 . A communication apparatus comprising:

a first memory; and

a first processor coupled to the first memory and configured to:

generate a shared key for performing encrypted communication with another communication apparatus by using one or more keys shared with the another communication apparatus by one or more key sharing methods; and

perform encrypted communication with the another communication apparatus using the shared key.

7 . A method used in a communication system including a plurality of communication apparatuses, the method comprising:

generating, by a communication apparatus of the plurality of communication apparatuses, a shared key for performing encrypted communication with another communication apparatus of the plurality of communication apparatuses by using one or more keys shared with the another communication apparatus by one or more key sharing methods, and

performing, by the communication apparatus, encrypted communication with the another communication apparatus using the shared key.

8 . A non-transitory computer-readable recording medium storing a program for causing a computer to perform the method of claim 7 .