An authentication system comprising: means for storing, for each of one or more objects to be registered, unique pattern information of a surface of the object to be registered, and a personal identification number into storage means in association with each other; acquiring means for acquiring unique pattern information of a surface of an object to be authenticated which is related to an authentication request, and a personal identification number; extracting means for extracting, from the storage means, unique pattern information stored in association with the personal identification number acquired by the acquiring means; characterized by that the system also comprises determining means for determining whether the unique pattern information extracted by the extracting means includes unique pattern information corresponding to the unique pattern information acquired by the acquiring means; wherein: the authentication system further comprises means for accepting, for each of one or more objects to be registered, a registration request for unique pattern information of a surface of the object to be registered and a personal identification number; if a number of records of unique pattern information already stored in the storage means in association with the personal identification number related to the registration request is less than a threshold, the means for storing stores the unique pattern information of the surface of the object to be registered and the personal identification number which are related to the registration request, into the storage means in association with each other; and the authentication system further comprises instructing means for, if the number of records of unique pattern information already stored in the storage means in association with the personal identification number related to the registration request is greater than or equal to the threshold, instructing that a personal identification number related to the registration request be reselected. means for storing, for each of one or more objects to be registered, unique pattern information of a surface of the object to be registered, and a personal identification number into storage means in association with each other; acquiring means for acquiring unique pattern information of a surface of an object to be authenticated which is related to an authentication request, and a personal identification number; extracting means for extracting, from the storage means, unique pattern information stored in association with the personal identification number acquired by the acquiring means; characterized by that the system also comprises determining means for determining whether the unique pattern information extracted by the extracting means includes unique pattern information corresponding to the unique pattern information acquired by the acquiring means; the authentication system further comprises means for accepting, for each of one or more objects to be registered, a registration request for unique pattern information of a surface of the object to be registered and a personal identification number; if a number of records of unique pattern information already stored in the storage means in association with the personal identification number related to the registration request is less than a threshold, the means for storing stores the unique pattern information of the surface of the object to be registered and the personal identification number which are related to the registration request, into the storage means in association with each other; and the authentication system further comprises instructing means for, if the number of records of unique pattern information already stored in the storage means in association with the personal identification number related to the registration request is greater than or equal to the threshold, instructing that a personal identification number related to the registration request be reselected.