1. An information processing method comprising: receiving an input of matching information encrypted with an encryption algorithm allowing a Hamming distance to be calculated with the matching information encrypted, and calculating a first Hamming distance between the received matching information and registered information that is different from encrypted registered information of a user, the registered information being encrypted with the encryption algorithm, using a processor; and determining legitimacy of the matching information based on whether the calculated first Hamming distance falls into a distance distribution representing matches with another person that is different from the user, using a processor.