Multi-cloud CP-ABE access control method based on block chain

The invention discloses a multi-cloud CP-ABE access control scheme based on a block chain. The scheme comprises an encryption process and a decryption process, wherein the encryption process comprisesthe steps of generating a data ciphertext CTf and a key ciphertext CTk, sending the data ciphertext CTf to a cloud, segmenting and hiding an access strategy tree T, storing an access strategy tree logic structure T' and decryption security parameters {C,C} into the block chain, storing a ciphertext {Y', Cy, C'y} into each sub-cloud, and the like; and the decryption process comprises the stepsof acquiring the data ciphertext CTf from the cloud, segmenting a user attribute set S to obtain an attribute subset {SCi}, segmenting a user attribute private key SK to obtain an attribute private key subset {SKCi}, decrypting the ciphertext information related to the attribute x hosted on each sub-cloud by each sub-cloud to obtain intermediate node information DNx, aggregating the decryption information DNx of each sub-c