The invention relates to the field of
data security, and relates to a block chain technology-based fine-grained
cloud storage access control method,
system and device. The method comprises the following steps: constructing a
cloud storage sharing model based on a block chain technology, registering a DO and a DU to an intelligent contract and generating a private key; the DO encrypting the
data file with a symmetric key to obtain a data
ciphertext, uploading the data
ciphertext to the CSP, and the CSP returning a
file storage address; the DO performing attribute-based
encryption on the symmetric key and the
file storage address according to the private key, the model public key and the
access control policy tree, sending an attribute-based
ciphertext to the block chain to form a block, and returning a block identifier; the DU sending a
data request to the block chain, returning a corresponding attribute base ciphertext, and decrypting a
file storage address and a symmetric key of the
data file; and the DU sending a request to the CSP according to the decryption address, and decrypting the
data file from the data ciphertext returned by the CSP by using the decrypted symmetric key. According to the invention, the security of key transmission and
data transmission is ensured.