Patent ID: 8380982

Claim:
A communication device configured to perform communication by employing first and second communication units, comprising: an interface configured to receive communication data including a random number generated for every connection with another communication device, a certificate calculated by the random number, and authentication method information indicating an authentication method at said second communication unit, through said first communication unit, wherein said authentication method information is information indicating whether or not the authentication method at said second communication unit is compatible with a public key system; and a hardware processing unit configured to determine, based on the authentication method information included in said communication data, an authentication method which an originator of the communication data accepts; wherein said processing unit determines, based on the authentication method information included in said communication data, whether or not the originator of the communication data accepts the public key system, when said processing unit has determined that the originator of said communication data does not accept the public key system, information included in said communication data is replied to the originator as identification information of the device itself, and the random number included in said communication data is employed as identifier information employed for authentication processing at said second communication unit according to the determination result by said method determining processing unit.