Cloud storage is more and more prevalent in practice, and thus how to check its integrity becomes increasingly essential. A classical solution is identity-based (ID-based) provable data possession (PDP), which supports certificateless cloud storage auditing without entire user data. However, existing ID-PDP protocols always require that cloud users outsource data blocks, authenticators and a small-sized file tag to the cloud, and make use of the heavy elliptic curve cryptography over bilinear pairing. These disadvantages would result in vast storage, communication, and computation costs, which is unexpected, especially for resource-limited cloud users. To improve the performance, this paper proposes a novel cryptographic primitive: ID-based PDP with compressed cloud storage. In this model, cloud storage auditing can be achieved by using only encrypted data blocks in a self-verified way, and original data blocks can be reconstructed from the outsourced data. Thus, data owners no longer need to store original data blocks on the cloud. We also use some basic algebraic operations to realize a concrete ID-based PDP protocol with compressed cloud storage, which is quite efficient due to no heavy cryptographic operations involved. The proposed protocol can easily be extended to support the other practical functions by using the primitive replacement technique. The proposed protocol is strictly proven to have the properties of correctness, privacy, unforgeability and detectability. Finally, we give plenty of theoretical analysis and experimental results to validate the efficiency of the proposed protocol.

Remote data integrity auditing ensures the integrity of cloud storage. In practice, cloud users may not want their sensitive data to be exposed to others. Thus, it is meaningful to investigate how to realize data sharing with sensitive information hiding in cloud storage auditing. Up to now, cloud storage has been proven to achieve the sensitive information hiding property through a third-party sanitizer dedicated to sanitize user data, which leads to high outlays on purchasing and maintaining a special server. To meet this challenge, we design a novel cloud storage auditing protocol to support sensitive information hiding without the need of a third-party sanitizer. In addition, our scheme allows data owners to enable or disable other users to access their sensitive information with the help of the cloud that dose not deviate from the agreement during access control. To be specific, only after receiving the delegations from the data owner, the users can compute the valid warrants that can pass the access verification of the cloud. The proposed protocol is built on identity-based cryptography, thus avoiding the complex certificate management. We validate the advantages of the proposed protocol through massive theoretical analysis and experimental results.

With the widespread application of cloud storage, ensuring the integrity of user outsourced data catches more and more attention. To remotely check the integrity of cloud storage, plenty of protocols have been proposed, implemented by checking the equation constructed by the aggregated blocks, tags, and indices. However, the verifier only has the knowledge of the indices of the audited blocks and tags, which thus requires the cloud to store both data blocks and tags for integrity verification. In this article, we present a compressive secure cloud storage protocol inspired by Goldreich-Goldwasser-Halevi (GGH) cryptosystem. Since the aggregated blocks can be reconstructed from the aggregated tags without the help of data indices, the cloud can only store data tags for providing the verifiable integrity proof. In this way, communication and storage costs can be hugely reduced and user private information can be hidden from the cloud. Furthermore, the proposed protocol only contains a few basic algebraic operations, making it highly efficient. We also provide formal security proof of the proposed protocol regarding forge, replay and replace attacks. In addition, we explore a new technique to support data dynamics. Furthermore, we establish a generic framework of compressive secure cloud storage protocols. Finally, we provide the theoretical analysis and experimental results, which further validate the effectiveness of the proposed protocol.

Code search is to retrieve the method according to the user needs. Many people think of the query as the only one to reflect the user needs. So they start with the query and find the synonyms, semantically similar to the query terms, for query expansion. However, they overlook a fact: the retrieved methods still need to be altered because it does not meet the user needs directly. This implies that the alteration made in the retrieved methods also reflects the user needs. In this paper, we start with the alteration intent (the possible alterations after retrieving methods) and propose to predict the alteration intent and use it for query expansion. The experiment results show that our approach outperforms CodeHow, the approach to use APIs for query expansion, by 59.8% with a precision score of 0.815.

As cloud storage becomes popular, more and more users tend to outsource their data to powerful cloud severs. To prevent a single point of failure, users prefer to store data on multiple cloud servers from different cloud service providers. However, after outsourcing data to cloud servers, users lose the control of their data, which may incur many serious security issues, such as abnormal data tampering and deleting. It is necessary for users to audit multiple cloud storage aperiodically. In this article, we aim to design a decentralized self-auditing solution for multiple cloud storage, in which cloud servers can audit the integrity of each other, and thus no third-party entity is required. First, based on basic algebra, our protocol realizes decentralized self-auditing multiple cloud storage that only involves encrypted user data. Second, we design a proof exchanging mechanism, making any number of cloud servers form the same final integrity proof with a linear number of interactions. Third, our solution can achieve cloud dynamics, which can freely enable and disable a cloud server to provide storage service. At last, security proof and performance evaluation show that the proposed protocol has provable security and high efficiency.