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Among typical range-free localization schemes for sensor networks, DV-Hop has its distinguishing advantage of the capability to localize unknown nodes, which have less than three or even no neighbor anchors. However, existing DV-Hop based localization methods have not considered the problem of packet collisions, which can frequently happen during the throughoutwhole-network broadcast of numerous data packets at the first two steps of DV-Hop. In order to effectively improve the success rate of packet transmission between nodes, this paper proposes a medium access control (MAC) method based on Chinese Remainder Theorem (CRT) protocol sequence for DV-Hop localization. First, a broadcasting strategy is designed for the proposed MAC method. Then, dedicated procedures for both anchor nodes and unknown nodes are presented to implement the designed MAC method in DV-Hop localization. Through simulation and evaluation, the performance of DV-Hop localization with the proposed MAC method is thoroughly investigated. Simulation results show that when the number of protocol sequences is larger than a certain number, the proposed MAC method can provide DV-Hop with better localization accuracy than E-CSMA/CA, while keeping similar localization time.

Before the project PRISM was revealed to the public by Edward Snowden only a few people realized emails were being watched by the government. For the benefits that Big Data technologies such as massive distributed storage and user behavior analysis and so on bring, emails became one of the most popular Big Data that has been aimed at as a huge source of intelligence by some organizations spying on public accounts every hour every day. Our research work was just opposite to what the NSA has done: To design and implement a system that can store emails securely, and destroy them clearly when they expired. In another word, a self-destructing emails system.

As a new software paradigm, cloud computing provides services dynamically according to user requirements. However, it is difficult to control personal privacy information because of the opening, virtualization, multi-tenancy and service outsourcing characters. Therefore, how to protect user privacy information has become a research focus. In this paper, we propose requirement-oriented privacy protection theory analysis architecture and implementation platform. Firstly, the theory analysis architecture is depicted as layers, and we analyze the function and key technologies of every layer. Secondly, we address the privacy property description method with ontology and description logic, and then analyze the theory modules of privacy items conflict checking layer, privacy policy negotiation layer and privacy agreement forensics layer. Thirdly, according to theory architecture, we design the implementation platform of requirement-oriented privacy protection, and discuss the function and workflow. In the end, we conclude and point out the future work. Index Terms-Privacy protection, privacy items, privacy policy, privacy property, cloud computing I. INTRODUCTION Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction [1]. There are some characters, such as service outsourcing, virtualization, distribution and multi-tenancy. These characters enhance the service quality and save the computing resources, for example, service outsourcing enhances the service capability and specialization through service composition [2]. However, the transparency of privacy information to the outsourcing service provider, make users worry that privacy data be illegally propagated and used.

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