OAuth and ABE based authorization in semi-trusted cloud computing: aauth

In cloud computing, inter-operations between data-storage and web-application providers can protect users from locking their data and applications into a single cloud provider. Currently, web-based access control standards are applicable only when data owners and cloud service providers are in the same trusted domain. Unfortunately, this condition cannot be satisfied in untrusted clouds, where cloud providers may access sensitive information without authorization. Most previous studies require end-user certificates or specific APIs and depart from existing standards. In this paper, we propose a new authorization scheme (AAuth) that builds on the OAuth standard by leveraging ciphertext-policy attribute based encryption and an ElGamal-like mask over the HTTP protocol. Our scheme provides end-to-end encryption and ABE-based tokens to enable authorization by both authorities and owners and to move policy enforcement from clouds to destinations. With our user-centric approach, owners can take control of their data when it rests in semi-untrusted cloud storage. Moreover, with most cryptographic functions delegated from owners to authorities, owners can gain computation power from clouds. Security analysis shows that our scheme maintains the same security level as the original encryption scheme and protects users from exposing their credential to application providers. In our extensive simulation, AAuth's greater overhead was balanced by greater security than OAuth's. Furthermore, our scheme works seamlessly with storage providers by retaining the providers' APIs in the usual way.