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Smartphone and Tablet Application (App) Life Cycle Characterization via Apple App Store Rank

Abstract

With the rapid growth of the smartphone and tablet market, mobile application (App) industry that provides a variety of functional devices is also growing at a striking speed. Product life cycle (PLC) theory, which has a long history, has been applied to a great number of industries and products and is widely used in the management domain. In this study, we apply classical PLC theory to mobile Apps on Apple smartphone and tablet devices (Apple App Store). Instead of trying to utilize often-unavailable sales or download volume data, we use open-access App daily download rankings as an indicator to characterize the normalized dynamic market popularity of an App. We also use this ranking information to generate an App life cycle model. By using this model, we compare paid and free Apps from 20 different categories. Our results show that Apps across various categories have different kinds of life cycles and exhibit various unique and unpredictable characteristics. Furthermore, as large-scale heterogeneous data (e.g., user App ratings, App hardware/software requirements, or App version updates) become available and are attached to each target App, an important contribution of this paper is that we perform in-depth studies to explore how such data correlate and affect the App life cycle. Using different regression techniques (i.e., logistic, ordinary least squares, and partial least squares), we built different models to investigate these relationships. The results indicate that some explicit and latent independent variables are more important than others for the characterization of App life cycle. In addition, we find that life cycle analysis for different App categories requires different tailored regression models, confirming that inner-category App life cycles are more predictable and comparable than App life cycles across different categories.

Open access
The conversion of heights of the benchmarks of the detailed vertical reference network into the PL-EVRF2007-NH frame

Abstract

The paper describes the problem of conversion of heights to the European Vertical Reference Frame 2007 for Poland (PL-EVRF2007-NH). The subject of the study is height data, and especially the detailed vertical reference network. The aim of the article is to present an alternative method of conversion to the one recommended by the Polish Head Office of Geodesy and Cartography. The proposed approach is characterised by a low implementation cost while maintaining the required accuracy.

The publication is illustrated by the case of Kętrzyn district (in the north-east part of Poland). The local reference network was converted from Kronstad’60 to PL-EVRF2007-NH in 2017.

Open access
The Best of Both Worlds: Mitigating Trade-offs Between Accuracy and User Burden in Capturing Mobile App Privacy Preferences

Abstract

In today’s data-centric economy, data flows are increasingly diverse and complex. This is best exemplified by mobile apps, which are given access to an increasing number of sensitive APIs. Mobile operating systems have attempted to balance the introduction of sensitive APIs with a growing collection of permission settings, which users can grant or deny. The challenge is that the number of settings has become unmanageable. Yet research also shows that existing settings continue to fall short when it comes to accurately capturing people’s privacy preferences. An example is the inability to control mobile app permissions based on the purpose for which an app is requesting access to sensitive data. In short, while users are already overwhelmed, accurately capturing their privacy preferences would require the introduction of an even greater number of settings. A promising approach to mitigating this trade-off lies in using machine learning to generate setting recommendations or bundle some settings. This article is the first of its kind to offer a quantitative assessment of how machine learning can help mitigate this trade-off, focusing on mobile app permissions. Results suggest that it is indeed possible to more accurately capture people’s privacy preferences while also reducing user burden.

Open access
Black-Box Wallets: Fast Anonymous Two-Way Payments for Constrained Devices

Abstract

Black-box accumulation (BBA) is a building block which enables a privacy-preserving implementation of point collection and redemption, a functionality required in a variety of user-centric applications including loyalty programs, incentive systems, and mobile payments. By definition, BBA+ schemes (Hartung et al. CCS ‘17) offer strong privacy and security guarantees, such as unlinkability of transactions and correctness of the balance flows of all (even malicious) users. Unfortunately, the instantiation of BBA+ presented at CCS ‘17 is, on modern smartphones, just fast enough for comfortable use. It is too slow for wearables, let alone smart-cards. Moreover, it lacks a crucial property: For the sake of efficiency, the user’s balance is presented in the clear when points are deducted. This may allow to track owners by just observing revealed balances, even though privacy is otherwise guaranteed. The authors intentionally forgo the use of costly range proofs, which would remedy this problem.

We present an instantiation of BBA+ with some extensions following a different technical approach which significantly improves efficiency. To this end, we get rid of pairing groups, rely on different zero-knowledge and fast range proofs, along with a slightly modified version of Baldimtsi-Lysyanskaya blind signatures (CCS ‘13). Our prototype implementation with range proofs (for 16 bit balances) outperforms BBA+ without range proofs by a factor of 2.5. Moreover, we give estimates showing that smart-card implementations are within reach.

Open access
Computation on Encrypted Data using Dataflow Authentication

Abstract

Encrypting data before sending it to the cloud protects it against attackers, but requires the cloud to compute on encrypted data. Trusted modules, such as SGX enclaves, promise to provide a secure environment in which data can be decrypted and then processed. However, vulnerabilities in the executed program, which becomes part of the trusted code base (TCB), give attackers ample opportunity to execute arbitrary code inside the enclave. This code can modify the dataflow of the program and leak secrets via SGX side-channels. Since any larger code base is rife with vulnerabilities, it is not a good idea to outsource entire programs to SGX enclaves. A secure alternative relying solely on cryptography would be fully homomorphic encryption. However, due to its high computational complexity it is unlikely to be adopted in the near future. Researchers have made several proposals for transforming programs to perform encrypted computations on less powerful encryption schemes. Yet current approaches do not support programs making control-flow decisions based on encrypted data.

We introduce the concept of dataflow authentication (DFAuth) to enable such programs. DFAuth prevents an adversary from arbitrarily deviating from the dataflow of a program. Our technique hence offers protections against the side-channel attacks described above. We implemented DFAuth using a novel authenticated homomorphic encryption scheme, a Java bytecode-tobytecode compiler producing fully executable programs, and an SGX enclave running a small and program-independent TCB. We applied DFAuth to an existing neural network that performs machine learning on sensitive medical data. The transformation yields a neural network with encrypted weights, which can be evaluated on encrypted inputs in 0.86 s.

Open access
Discontinued Privacy: Personal Data Leaks in Apple Bluetooth-Low-Energy Continuity Protocols

Abstract

Apple Continuity protocols are the underlying network component of Apple Continuity services which allow seamless nearby applications such as activity and file transfer, device pairing and sharing a network connection. Those protocols rely on Bluetooth Low Energy (BLE) to exchange information between devices: Apple Continuity messages are embedded in the pay-load of BLE advertisement packets that are periodically broadcasted by devices. Recently, Martin et al. identified [1] a number of privacy issues associated with Apple Continuity protocols; we show that this was just the tip of the iceberg and that Apple Continuity protocols leak a wide range of personal information.

In this work, we present a thorough reverse engineering of Apple Continuity protocols that we use to uncover a collection of privacy leaks. We introduce new artifacts, including identifiers, counters and battery levels, that can be used for passive tracking, and describe a novel active tracking attack based on Handoff messages. Beyond tracking issues, we shed light on severe privacy flaws. First, in addition to the trivial exposure of device characteristics and status, we found that HomeKit accessories betray human activities in a smarthome. Then, we demonstrate that AirDrop and Nearby Action protocols can be leveraged by passive observers to recover e-mail addresses and phone numbers of users. Finally, we exploit passive observations on the advertising traffic to infer Siri voice commands of a user.

Open access
Editors’ Introduction
Open access
Emotional and Practical Considerations Towards the Adoption and Abandonment of VPNs as a Privacy-Enhancing Technology

Abstract

Virtual Private Networks (VPNs) can help people protect their privacy. Despite this, VPNs are not widely used among the public. In this survey study about the adoption and usage of VPNs, we investigate people’s motivation to use VPNs and the barriers they encounter in adopting them. Using data from 90 technologically savvy participants, we find that while nearly all (98%; 88) of the participants have knowledge about what VPNs are, less than half (42%; 37) have ever used VPNs primarily as a privacy-enhancing technology. Of these, 18% (7) abandoned using VPNs while 81% (30) continue to use them to protect their privacy online. In a qualitative analysis of survey responses, we find that people who adopt and continue to use VPNs for privacy purposes are primarily motivated by emotional considerations, including the strong desire to protect their privacy online, wide fear of surveillance and data tracking not only from Internet service providers (ISPs) but also governments and Internet corporations such as Facebook and Google. In contrast, people who are mainly motivated by practical considerations are more likely to abandon VPNs, especially once their practical need no longer exists. These people cite their access to alternative technologies and the effort required to use a VPN as reasons for abandonment. We discuss implications of these findings and provide suggestions on how to maximize adoption of privacy-enhancing technologies such as VPNs, focusing on how to align them with people’s interests and privacy risk evaluation.

Open access
Inferring Tracker-Advertiser Relationships in the Online Advertising Ecosystem using Header Bidding

Abstract

Online advertising relies on trackers and data brokers to show targeted ads to users. To improve targeting, different entities in the intricately interwoven online advertising and tracking ecosystems are incentivized to share information with each other through client-side or server-side mechanisms. Inferring data sharing between entities, especially when it happens at the server-side, is an important and challenging research problem. In this paper, we introduce Kashf: a novel method to infer data sharing relationships between advertisers and trackers by studying how an advertiser’s bidding behavior changes as we manipulate the presence of trackers. We operationalize this insight by training an interpretable machine learning model that uses the presence of trackers as features to predict the bidding behavior of an advertiser. By analyzing the machine learning model, we can infer relationships between advertisers and trackers irrespective of whether data sharing occurs at the client-side or the server-side. We are able to identify several server-side data sharing relationships that are validated externally but are not detected by client-side cookie syncing.

Open access
Not All Attributes are Created Equal: d X -Private Mechanisms for Linear Queries

Abstract

Differential privacy provides strong privacy guarantees simultaneously enabling useful insights from sensitive datasets. However, it provides the same level of protection for all elements (individuals and attributes) in the data. There are practical scenarios where some data attributes need more/less protection than others. In this paper, we consider dX -privacy, an instantiation of the privacy notion introduced in [6], which allows this flexibility by specifying a separate privacy budget for each pair of elements in the data domain. We describe a systematic procedure to tailor any existing differentially private mechanism that assumes a query set and a sensitivity vector as input into its d X -private variant, specifically focusing on linear queries. Our proposed meta procedure has broad applications as linear queries form the basis of a range of data analysis and machine learning algorithms, and the ability to define a more flexible privacy budget across the data domain results in improved privacy/utility tradeoff in these applications. We propose several d X -private mechanisms, and provide theoretical guarantees on the trade-off between utility and privacy. We also experimentally demonstrate the effectiveness of our procedure, by evaluating our proposed d X -private Laplace mechanism on both synthetic and real datasets using a set of randomly generated linear queries.

Open access