Abstract: Cloud computing has been gradually considered the most significant turning point in the development of information technology during past few years. People reap the benefits from cloud, such as ubiquitous and flexible access, considerable capital expenditure savings, pay-as-you-go computing resources configuration, etc. Many companies, organizations, and individual users have adopted the public cloud storage service to facilitate their business operations, research, or everyday needs. However, in the outsourcing cloud computing model, users’ physical control of the underlying infrastructure including the system hardware and lower levels of software stack, is shifted to third-party public cloud service providers, such as Dropbox, Google Drive, Microsoft SkyDrive and so on. In addition, the sensitive data of users are also outsourced to and stored in the cloud, e.g., they may upload emails, photos, financial reports, and health records to the cloud. Thus, the potential private information leakage and integrity of the outsourced data is one of the primary concerns for the cloud users. To build users’ confidence in such cloud storage service paradigm, tons of attentions have been drawn and a number of related problems have been studied extensively in the literature, such as fine-grained cloud data access control mechanism, secure search over encrypted cloud data, outsourced data integrity auditing, secure deletion for cloud data, etc., which ensure that cloud users enjoy the convenience the cloud offers in a privacy-preserving way. Otherwise, the cloud will become merely a remote storage which provides limited values to all parties. This paper focuses on the enabling and critical cloud computing security protection techniques and surveys on the recent researches in these areas. In addition, we further point out some unsolved but important challenging issues and hopefully provides insight into their possible solutions.