Mutual authentication system and mutual authentication method

A mutual authentication system comprising a master device and a slave device which are authenticated with each other;

• wherein the master device comprises:
• a storage part which stores a temporary key that is key data temporarily used and a master key that is key data used for authentication;
• a key confirmation unit configured to inquire whether the slave device stores the master key;
• a key introduction unit configured so that, in response to an inquiry of the key confirmation unit, when the slave device does not store the master key, the key introduction unit encrypts the master key by using the temporary key and transmits to the slave device;
• and
• a main authentication unit configured to mutually authenticate with the slave device by using the master key transmitted from the key introduction unit;
• and
• wherein the slave device comprises:
• a storage part which stores the temporary key;
• a key confirmation response unit configured to confirm whether the master key has already been stored in the storage part for an inquiry from the master device and respond;
• a key storage unit configured to decrypt the master key transmitted from the master device by using the temporary key for a response of the key confirmation response unit and store in the storage part;
• and
• a sub-authentication unit configured to mutually authenticate with the master device by using the master key which is stored in the storage part by the key storage unit.