Encrypted information matching device, encrypted information matching method, and recording medium having encrypted information matching program stored thereon

An encrypted information matching method comprising:

• when one or more pieces of information to be matched are classified into classified groups, based on similarity in a characteristic, and one or more pieces of representative information and the information to be matched are stored on a storage in association with each other, the representative information representing each of the classified groups, and the information to be matched being encrypted and belonging to the classified group,
• by using an information processing device, in matching first input information in the information to be matched,
• encrypting the information to be matched and the first input information;
• calculating a first similarity between the first input information being encrypted and the one or more pieces of representative information stored on the storage;
• matching the first input information in the representative information of the classified groups to be matched;
• identifying, based on the first similarity being calculated, an identified group of the classified groups to be matched with the first input information;
• calculating a second similarity between the first input being encrypted information and the one or more pieces of information to be matched being encrypted in a state that the first input information and the information to be matched are encrypted, the information to be matched belonging to the identified group;
• determining whether or not the information to be matched exists, and the information to be matched has a calculated second similarity that satisfies a criteria exists if the information to be matched exists;
• and
• when the information to be matched whose calculated second similarity satisfies the criteria does not exist in the identified group in which the first similarity between the first input information and the representative information is the largest of the classified groups, changing the identified group to be matched, sequentially in order of a larger similarity of the classified groups, from the classified group in which the first similarity is the second largest of the classified groups.

A non-transitory computer readable recording medium storing an encrypted information matching program that causes

• a computer accessible to a storage that stores, when one or more pieces of information to be matched are classified into classified groups, based on similarity in a characteristic, one or more pieces of representative information and the information to be matched in association with each other, the representative information representing each of the classified groups, and the information to be matched being encrypted and belonging to the classified group, to execute, in matching first input information in the information to be matched:
• processing of encrypting the information to be matched and the first input information;
• processing of calculating a first similarity between the first input information being encrypted and the one or more pieces of representative information stored on the storage;
• processing of matching the first input information in the representative information of the classified groups to be matched;
• processing of identifying, based on the first similarity being calculated, an identified group of the classified groups to be matched with the first input information;
• processing of calculating a second similarity between the first input information being encrypted and the one or more pieces of information to be matched being encrypted in a state that the first input information and the information to be matched are encrypted, the information to be matched belonging to the identified group;
• processing of determining whether or not the information to be matched exists, and the information to be matched has a calculated second similarity that satisfies a criteria exists if the information to be matched exists;
• and
• when the information to be matched whose calculated second similarity satisfies the criteria does not exist in the identified group in which the first similarity between the first input information and the representative information is the largest of the classified groups, processing of changing the identified group to be matched, sequentially in order of a larger similarity of the classified groups, from the classified group in which the first similarity is the second largest of the classified groups.