Abstract-Touchscreen-based devices such as smartphones and tablets are gaining popularity, but their rich input capabilities pose new development and testing complications. To alleviate this problem, we present an approach and tool named RERAN that permits record-and-replay for the Android smartphone platform. Existing GUI-level record-and-replay approaches are inadequate due to the expressiveness of the smartphone domain, in which applications support sophisticated GUI gestures, depend on inputs from a variety of sensors on the device, and have precise timing requirements among the various input events. We address these challenges by directly capturing the low-level event stream on the phone, which includes both GUI events and sensor events, and replaying it with microsecond accuracy. Moreover, RERAN does not require access to app source code, perform any app rewriting, or perform any modifications to the virtual machine or Android platform. We demonstrate RERAN's applicability in a variety of scenarios, including (a) replaying 86 out of the Top-100 Android apps on Google Play; (b) reproducing bugs in popular apps, e.g., Firefox, Facebook, Quickoffice; and (c) fast-forwarding executions. We believe that our versatile approach can help both Android developers and researchers.

Android uses a system of permissions to control how apps access sensitive devices and data stores. Unfortunately, we have little understanding of the evolution of Android permissions since their inception (2008). Is the permission model allowing the Android platform and apps to become more secure? In this paper, we present arguably the first longterm study that is centered around both permission evolution and usage, of the entire Android ecosystem (platform, third-party apps, and pre-installed apps). First, we study the Android platform to see how the set of permissions has evolved; we find that this set tends to grow, and the growth is not aimed towards providing finer-grained permissions but rather towards offering access to new hardware features; a particular concern is that the set of Dangerous permissions is increasing. Second, we study Android third-party and pre-installed apps to examine whether they follow the principle of least privilege. We find that this is not the case, as an increasing percentage of the popular apps we study are overprivileged. In addition, the apps tend to use more permissions over time. Third, we highlight some concerns with pre-installed apps, e.g., apps that vendors distribute with the phone; these apps have access to, and use, a larger set of higher-privileged permissions which pose security and privacy risks. At the risk of oversimplification, we state that the Android ecosystem is not becoming more secure from the user's point of view. Our study derives four recommendations for improving the Android security and suggests the need to revisit the practices and policies of the ecosystem.

Well crystalline gold nanoparticles (AuNPs) of different sizes were fabricated using sundried Coffea arabica seed (CAS) extract at room temperature by controlling the pH of the green extract. The size, shape and crystallinity of the nanoparticles have been studied using electron microscopy and X-ray diffraction. The presence of phenolic groups (revealed through FT-IR studies) from the CAS extract are responsible both for the reduction of Au ions and stabilization of the formed AuNPs. The efficiency of the CAS extract mediated green synthesis technique for the production of AuNPs has been compared to the conventional chemical Turkevich technique, which not only uses a toxic reductant such as NaBH 4 , but also operates around the boiling point of water. It has been observed that the CAS extract mediated synthesis process produces relatively bigger AuNPs at similar pH values of the reaction mixture in comparison to the AuNPs produced in the Turkevich process. Although the AuNPs synthesized using CAS extract are relatively larger and polydisperse in nature, their catalytic efficiencies for the degradation of an aromatic nitro compound (4-nitrophenol) are found to be comparable to the chemically fabricated AuNPs. Probable mechanisms associated with the formation of AuNPs and their size control in the CAS extract mediated green synthesis process have been discussed. Fig. 2 Typical SEM images of GAuNPs (left column) and CAuNPs (right column) synthesized at different pH values of the reaction mixture. Insets show histogram reflecting the size dispersion corresponding to each pH; average size of the NPs vs. number of particles. 24822 | RSC Adv., 2018, 8, 24819-24826 This journal is

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