Today’s smartphone operating systems frequently fail to provide users with visibility into how third-party applications collect and share their private data. We address these shortcomings with TaintDroid, an efficient, system-wide dynamic taint tracking and analysis system capable of simultaneously tracking multiple sources of sensitive data. TaintDroid enables realtime analysis by leveraging Android’s virtualized execution environment. TaintDroid incurs only 32% performance overhead on a CPU-bound microbenchmark and imposes negligible overhead on interactive third-party applications. Using TaintDroid to monitor the behavior of 30 popular third-party Android applications, in our 2010 study we found 20 applications potentially misused users’ private information; so did a similar fraction of the tested applications in our 2012 study. Monitoring the flow of privacy-sensitive data with TaintDroid provides valuable input for smartphone users and security service firms seeking to identify misbehaving applications.

Abstract Summary: Non-linear calibration is a widely used method for quantifying biomarkers wherein concentration-response curves estimated using samples of known concentrations are used to predict the biomarker concentrations in the samples of interest. The R package nCal fills an important gap in the open source, stand-alone software for performing non-linear calibration. For curve fitting, nCal provides a new implementation of a robust, Bayesian hierarchical five-parameter logistic model. nCal supports a simple graphical user interface that can be used by laboratory scientists, and contains functionality for importing data from the multiplex bead array assay instrumentation. Availability: The R package ‘nCal’ is available from http://cran.r-project.org/web/packages/nCal/ under GPL-2 or later. Contact: [email protected] Supplementary information: Supplementary information is available in the form of an R package vignette at the above repository and an FAQ at http://research.fhcrc.org/youyifong/en/resources/ncal.html.

We present the first in-depth analysis of the performance of attempting concurrent AP connections from highly mobile clients. Previous solutions for concurrent Wi-Fi are limited to stationary wireless clients and do not take into account a myriad of mobile factors. Through an analytical model, optimization framework, and numerous outdoor experiments, we show that connection duration, AP response times, channel scheduling, available and offered bandwidth, node speed, and dhcp joins all affect performance. Building on these results, we design, implement, and evaluate a system, Spider, that establishes and maintains concurrent connections to 802.11 APs in a mobile environment. The system uses multi-AP selection, channel-based scheduling, and opportunistic scanning to maximize throughput while mitigating the overhead of association and dhcp. While Spider can manage multiple channels, we empirically demonstrate that it achieves maximum throughput when using multiple APs on a single channel. Our evaluation shows that Spider provides a 400% improvement in throughput and 54% improvement in connectivity over stock Wi-Fi implementations.

Work on delay tolerant networks (DTN) and peer-to-peer replication systems has made rapid advances with the similar goal of permitting reliable message delivery in challenged communication environments. Techniques developed for both types of systems also bear some similarity. Both exploit opportunistic connectivity to route messages and updates to their desired destinations while making minimal assumptions about end-to-end connectivity. However, they also have some unique characteristics. DTNs have recently incorporated forwarding algorithms that make use of historical information on past encounters between participants and predictions of future connectivity. Modern replication systems utilize protocols with low overheads that guarantee eventual consistency and at-most-once delivery while supporting content-based filters. In this paper, we show how a DTN-like messaging system can be readily built as a simple application on top of a peer-to-peer replication platform. To reduce delivery delays while retaining the desirable replication guarantees, we then extend the replication substrate to permit pluggable DTN routing protocols. We describe the implementation of four representative DTN schemes as replication policies and evaluate these extensions with emulations driven by traces of e-mail messaging and vehicular mobility. We conclude that DTNs and replication systems can benefit substantially from a cross-fertilization of ideas.

As more services have come to rely on sensor data such as audio and photos collected by mobile phone users, verifying the authenticity of this data has become critical for service correctness. At the same time, clients require the flexibility to tradeoff the fidelity of the data they contribute for resource efficiency or privacy. This paper describes YouProve, a partnership between a mobile device's trusted hardware and software that allows untrusted client applications to directly control the fidelity of data they upload and services to verify that the meaning of source data is preserved. The key to our approach is trusted analysis of derived data, which generates statements comparing the content of a derived data item to its source. Experiments with a prototype implementation for Android demonstrate that YouProve is feasible. Our photo analyzer is over 99% accurate at identifying regions changed only through meaning-preserving modifications such as cropping, compression, and scaling. Our audio analyzer is similarly accurate at detecting which sub-clips of a source audio clip are present in a derived version, even in the face of compression, normalization, splicing, and other modifications. Finally, performance and power costs are reasonable, with analyzers having little noticeable effect on interactive applications and CPU-intensive analysis completing asynchronously in under 70 seconds for 5-minute audio clips and under 30 seconds for 5-megapixel photos.

We investigate attempting concurrent connections to multiple Wi-Fi access points (APs) from highly mobile clients. Previous multi-AP solutions are limited to stationary wireless clients and do not take into account a myriad of mobile factors. We show that connection duration, AP response times, channel scheduling, available and offered bandwidth, node speed, and dhcp joins all affect performance. Building on these results, we present a system, Spider, that establishes and maintains concurrent connections to 802.11 APs in a mobile environment. While Spider can manage multiple channels, we demonstrate that it achieves maximum throughput when using multiple APs on a single channel.