An efficient ciphertext-policy weighted attribute-based encryption with collaborative access for cloud storage

The encryption of user data is crucial when employing cloud storage services to guarantee the security of these data stored on cloud servers. Attribute-based encryption (ABE) scheme is considered a powerful encryption technique that offers flexible and fine-grained access control capabilities. Further, the multi-user collaborative access ABE scheme additionally supports users to acquire access authorization through collaborative works. However, the existing multi-user collaborative access ABE schemes do not consider the different weights of collaboration users. Therefore, using these schemes for weighted multi-user collaborative access results in either redundant attributes or unsuccessful construction of the access control structure. For this, we proposes the special attribute policy (SAP) problem about weighted multi-user collaborative access, and presents an efficient ciphertext-policy weighted attribute-based encryption with collaborative access scheme (CP-WABE-CA), which can provide efficient collaborative access control for multiple users with different weights. In detail, this scheme utilizes a novel weighted access tree to prevent attribute repetition, thereby eliminating redundant attributes and addressing the issue of constructing access control structures. We prove our scheme is resistant against chosen plaintext attack. The experimental results demonstrate that our scheme has significant computational efficiency advantages compared to related works, without increasing storage or communication overhead. Therefore, the CP-WABE-CA scheme can provide an efficient flexible weighted collaborative access control mechanisms for cloud storage.