Patent ID: 8306919

Claim:
An IC card comprising: a storage means for storing a plurality of encryption algorithms and first information about an order of priority among the plurality of encryption algorithms; a communication means for communicating with a communication target, the communication target including an other IC card or an other equivalent function to an IC card; a processing means for exchanging information about the stored encryption algorithms with the communication target at the beginning of a mutual authentication with the communication target in order to select an encryption algorithm to use for an authentication procedure and for concealment of a communication message, and receiving information about types of encryption algorithms stored in the communication target and second information about an order of priority among the encryption algorithms stored in the communication target; and an authentication process switching means for switching among the plurality of encryption algorithms, and selecting one of the plurality of encryption algorithms stored in the storage means based on the order of priority among the plurality of encryption algorithms stored in the storage means and the order of priority among the encryption algorithms stored in the communication target received by the processing means.