Recent years have witnessed the trend of leveraging cloud-based services for large scale content storage, processing, and distribution. Data security and privacy are among top concerns for the public cloud environments. Towards these security challenges, we propose and implement CloudaSec framework for securely sharing outsourced data via the public cloud. CloudaSec ensures the confidentiality of content in the public cloud environments with flexible access control policies for subscribers and efficient revocation mechanisms. CloudaSec proposes several cryptographic tools for data owners, based on a novel content hash keying system, by leveraging the Elliptic Curve Cryptography (ECC). The separation of subscription-based key management and confidentiality-oriented asymmetric encryption policies uniquely enables flexible and scalable deployment of the solution as well as strong security for outsourced data in cloud servers. Through experimental evaluation, we demonstrate the efficiency and scalability of CloudaSec, build upon OpenStack Swift testbed