Authentication system and an authentication method

PROBLEM TO BE SOLVED: To provide an authentication system and an authentication method for authenticating a user.SOLUTION: An authentication system includes: an accessory device; and an authentication acceptance device. The authentication system includes: registration means 222 for registering the authentication information of each of one or more users; transmission means 218 for transmitting a predetermined code to the accessory device by direct communication; authentication code generation means 220 for generating an authentication code for each of one or more users by using a predetermined function from the predetermined code and the authentication information of each of one or more users; reception means 228 for receiving an authenticated code from the accessory device by direct communication; and authentication means 232 for determining the success/failure of authentication by collating the authenticated code with the generated authentication code. The accessory device includes authenticated code generation means 256 for generating the authenticated code by using the predetermined function from the received predetermined code and the stored authentication information of the user.