Fine-grained data access control method based on fragmenting of secret keys

The invention discloses a fine-grained data access control method based on fragmenting of secret keys. The method mainly solves the problems that the safety is low and the calculation amount is large in the prior art. The method comprises the implementation steps that (1) a data owner encrypts shared data to obtain a cryptograph; (2) an attribute authority generates two attribute private keys for an access group user and sends the two attribute private keys to a semi-trusted agency and the access group user respectively; (3) when the access group user meets the requirement of an access control structure, the semi-trusted agency converts the cryptograph into an intermediate result through the first attribute private key, and the access group user decrypts the intermediate result through the second attribute private key to obtain the shared data; (4) the attribute private key fragmenting technology is adopted to control the access group user to obtain an incomplete attribute private key, so that the owner does not need to encrypt the shared data again after executing the undoing operation. By means of the method, fine-grained access control can be provided for the shared data, and the safety of the shared data can be improved. The method can be applied to access of the shared data under cloud shared data access control.