The rapid development of mobile Internet has offered the opportunity for WiFi indoor positioning to come under the spotlight due to its low cost. However, nowadays the accuracy of WiFi indoor positioning cannot meet the demands of practical applications. To solve this problem, this paper proposes an improved WiFi indoor positioning algorithm by weighted fusion. The proposed algorithm is based on traditional location fingerprinting algorithms and consists of two stages: the offline acquisition and the online positioning. The offline acquisition process selects optimal parameters to complete the signal acquisition, and it forms a database of fingerprints by error classification and handling. To further improve the accuracy of positioning, the online positioning process first uses a pre-match method to select the candidate fingerprints to shorten the positioning time. After that, it uses the improved Euclidean distance and the improved joint probability to calculate two intermediate results, and further calculates the final result from these two intermediate results by weighted fusion. The improved Euclidean distance introduces the standard deviation of WiFi signal strength to smooth the WiFi signal fluctuation and the improved joint probability introduces the logarithmic calculation to reduce the difference between probability values. Comparing the proposed algorithm, the Euclidean distance based WKNN algorithm and the joint probability algorithm, the experimental results indicate that the proposed algorithm has higher positioning accuracy.

The rapid development of wearable technology has facilitated the collection and sharing of health data, allowing patients to benefit from caretakers and medical research. However, these personal health data often contain sensitive information and it is typically not known in advance with whom the information will be shared. Therefore, messages must be encrypted and shared while adhering to the decoupled communication model. This paper presents NACDA, a secure many-to-many data-sharing service on the Named Data Network (NDN). NACDA uses Identity-Based Encryption with Wildcard Key Derivation (WKD-IBE) to allow naming-based access control, enabling data subjects to share data securely and flexibly regardless of the data processor. In addition, NACDA supplements a decentralized authorization mechanism with blockchain to ensure data subjects’ data ownership and enforce access policies. We developed an NDN-based prototype and performed a security analysis to demonstrate NACDA’s feasibility.

Dynamic taint analysis is a powerful technique for tracking the flow of sensitive information. Different approaches have been proposed to accelerate this process in an online or offline manner. Unfortunately, most of these approaches still have performance bottlenecks and thus reduce analytical efficiency. To address this limitation, we present OFFDTAN, a new approach of offline dynamic taint analysis for binaries. OFFDTAN can be described in terms of four stages: dynamic information acquisition, vulnerability modeling, offline analysis, and backtrace analysis. It first records program runtime information and models the stack buffer overflow vulnerabilities and controlled jump vulnerabilities. Then it performs offline analysis and backtrace analysis to locate vulnerabilities. We implement OFFDTAN on the basis of QEMU virtual machine and apply it to off-the-shelf applications. In order to illustrate how our approach works, we first employ a case study. Furthermore, six applications have been verified so as to evaluate our approach. Experimental results demonstrate that our approach is correct and effective. Compared with other offline analysis tools, OFFDTAN has much lower application runtime overhead.