Encryption system, encryption processing method of encryption system, encryption device, decryption device, setup device, key generation device, and key delegation device using a user identifier for a user who belongs to a k-th hierarchy in an organization

Abstract

In a wildcard-applicable anonymous hierarchical identity-based encryption system, it is aimed to make the number of pairing operations a fixed number. A user identifier ID and a pattern P are used. The user identifier ID includes k number of hierarchy identifiers. The pattern P includes either of a hierarchy identifier, a wildcard value and a blank value for each hierarchy. An encryption deviceextracts a key value H corresponding to a hierarchy of the wildcard value and a key value H corresponding to a hierarchy of a pattern value from a public key PK, calculates a cipher value Cand a cipher value C, and outputs ciphertext data CT including plaintext cipher value C, the cipher value C, and the cipher value C. A decryption deviceextracts the hierarchy identifier of the hierarchy corresponding to the wildcard value from the user identifier ID, decrypts the plaintext cipher value Cincluded in the ciphertext data CT using the extracted hierarchy identifier, the cipher value Cand the cipher value Cwhich are included in the ciphertext data CT, and outputs plaintext data M.