Program, classification method and system

Abstract

A system and method classifies multiple pieces of private data owned by multiple entities according to data type. Each of the entities has an encryption key. A representative entity is selected that is representative of the entities owning data of the type. Data of each of the representative entity and a target entity is encrypted and the encrypted data is exchanged between the entities. Each piece of the encrypted data that the target entity has obtained is re-encrypted by using its own encryption key to obtain data, and the encrypted data that the representative entity has obtained is re-encrypted by using its own encryption key to obtain data. If dataof the representative entity matches data, it is determined that the representative entity and the target entity have data of an identical type.