Encrypted data management device, encrypted data management method, and encrypted data management program

摘要

An invalidation scheme of a secret key is implemented, which is usable for a functional encryption scheme. In a cryptographic processing system 10 employing an encryption scheme with which if attribute information and key information set in encrypted data do not correspond to attribute information and key information set in a secret key, the encrypted data cannot be decrypted using the secret key, an encrypted data management device 200 is provided, which carries out a relay between a user terminal 100 carrying out encryption and decryption of data and an encrypted data storage device 300 storing encrypted data. The encrypted data management device 200 determines whether or not a user whose secret key is invalid is included in users having attribute information set in the encrypted data acquired from the encrypted data storage device 300, and sets a different value as key information in the encrypted data based on the determination result. Then, the encrypted data management device 200 sends the encrypted data in which the key information is set to the user terminal 100.

主权项

1. An encrypted data management device managing encrypted data in an encryption scheme with which if attribute information and key information set in encrypted data do not correspond to attribute information and key information set in a secret key, the encrypted data cannot be decrypted using the secret key, the encrypted data management device comprising:
data acquisition circuitry which acquires encrypted data in which attribute information is set from a storage device; invalidation determination circuitry which determines whether or not a user whose secret key is invalid is included in users having the attribute information set in the encrypted data acquired by the data acquisition circuitry; key information setting circuitry which sets a different value as key information in the encrypted data based on whether or not it is determined that the user whose secret key is invalid is included by the invalidation determination circuitry; and a data transmission circuitry which sends the encrypted data in which the key information is set by the key information setting circuitry to a user terminal, wherein the data acquisition circuitry acquires an encrypted vector including an attribute vector in which the attribute information is set to a coefficient of a basis vector of an attribute basis which is a part of basis of a basis B[t] for each t of t=1, . . . , n (n being an integer of 2 or greater) and a key information vector of a key information basis which is a basis being different from the attribute basis of the basis B[t] as the encrypted data, and wherein the key information setting circuitry adds a vector in which the different value is set to a coefficient of a basis vector of the key information basis to the key information vector.