Achieving Secure, Scalable, and Fine-grained Data Access Control in Cloud Computing

TLDR

Cloud computing delivers infrastructure services over the Internet, but it introduces data security and access‑control challenges, and existing cryptographic key‑distribution solutions impose heavy overhead that hampers fine‑grained, scalable confidentiality. This work seeks to resolve these issues by defining attribute‑based access policies and enabling the data owner to delegate most fine‑grained control tasks to untrusted cloud servers without revealing data contents. The authors combine attribute‑based encryption, proxy re‑encryption, and lazy re‑encryption to implement the policies, providing user‑privilege confidentiality and key accountability. Analysis demonstrates that the scheme is highly efficient and provably secure under current security models.

Abstract

Cloud computing is an emerging computing paradigm in which resources of the computing infrastructure are provided as services over the Internet. As promising as it is, this paradigm also brings forth many new challenges for data security and access control when users outsource sensitive data for sharing on cloud servers, which are not within the same trusted domain as data owners. To keep sensitive user data confidential against untrusted servers, existing solutions usually apply cryptographic methods by disclosing data decryption keys only to authorized users. However, in doing so, these solutions inevitably introduce a heavy computation overhead on the data owner for key distribution and data management when fine-grained data access control is desired, and thus do not scale well. The problem of simultaneously achieving fine-grainedness, scalability, and data confidentiality of access control actually still remains unresolved. This paper addresses this challenging open issue by, on one hand, defining and enforcing access policies based on data attributes, and, on the other hand, allowing the data owner to delegate most of the computation tasks involved in fine-grained data access control to untrusted cloud servers without disclosing the underlying data contents. We achieve this goal by exploiting and uniquely combining techniques of attribute-based encryption (ABE), proxy re-encryption, and lazy re-encryption. Our proposed scheme also has salient properties of user access privilege confidentiality and user secret key accountability. Extensive analysis shows that our proposed scheme is highly efficient and provably secure under existing security models.