Social relationships are a natural basis on which humans make trust decisions. Online Social Networks (OSNs) are increasingly often used to let users base trust decisions on the existence and the strength of social relationships. While most OSNs allow users to discover the length of the social path to other users, they do so in a centralized way, thus requiring them to rely on the service provider and reveal their interest in each other. This paper presents Social PaL, a system supporting the privacy-preserving discovery of arbitrary-length social paths between any two social network users. We overcome the bootstrapping problem encountered in all related prior work, demonstrating that Social PaL allows its users to find all paths of length two and to discover a significant fraction of longer paths, even when only a small fraction of OSN users is in the Social PaL system - e.g., discovering 70 of all paths with only 40 of the users. We implement Social PaL using a scalable server-side architecture and a modular Android client library, allowing developers to seamlessly integrate it into their apps.
Smokescreen @cite_29 , SMILE @cite_18 , and PIKE @cite_53 support secure private device-to-device handshake and proximity-based communication. introduce SDDR @cite_33 , which allows a device to establish a secure encounter -- i.e., a secret key -- with every device in short radio range, and can be used to recognize previously encountered users, while providing strong unlinkability guarantees. The EnCore platform @cite_42 builds on SDDR to provide privacy-preserving interaction between nearby devices, as well as event-based communication for mobile social applications.
@cite_18 @cite_33 @cite_29 @cite_42 @cite_53
1972656783 2139483853 2534482106 2536064707
Mobile social apps provide sharing and networking opportunities based on a user's location, activity, and set of nearby users. A platform for these apps must meet a wide range of communication needs while ensuring users' control over their privacy. In this paper, we introduce EnCore, a mobile platform that builds on secure encounters between pairs of devices as a foundation for privacy-preserving communication. An encounter occurs whenever two devices are within Bluetooth radio range of each other, and generates a unique encounter ID and associated shared key. EnCore detects nearby users and resources, bootstraps named communication abstractions called events for groups of proximal users, and enables communication and sharing among event participants, while relying on existing network, storage and online social network services. At the same time, EnCore puts users in control of their privacy and the confidentiality of the information they share. Using an Android implementation of EnCore and an app for event-based communication and sharing, we evaluate EnCore's utility using a live testbed deployment with 35 users. Online collaboration tools such as Google+, Face-book or Dropbox have become an important and ubiquitous mediator of many human interactions. In the virtual world, they enable secure interaction by controlling access to shared resources. Yet relying on them to support synchronous direct interactions, such as face-to-face meetings, might be suboptimal as they require reliable online connectivity and even then often introduce delays. A much more efficient way of co-located resource sharing is the use of local communications, such as ad-hoc WiFi. Yet setting up the necessary encryption and authentication mechanisms is often cumbersome. In this paper, we present PIKE, a key exchange protocol that minimizes this configuration effort. PIKE piggybacks the exchange of keys on top of an existing service infrastructure. To support encryption or authentication without Internet connection, PIKE relies on triggers for upcoming personal interactions and exchanges keys before they take place. To evaluate PIKE, we present two example applications and we perform an experimental as well as an analytical analysis of its characteristics. The evaluation indicates that PIKE is broadly applicable, scales well enough to support larger events and provides a level of security that is (at least) comparable to the one provided by the underlying service. In this study, we present WindTalker, a novel and practical keystroke inference framework that allows an attacker to infer the sensitive keystrokes on a mobile device through WiFi-based side-channel information. WindTalker is motivated from the observation that keystrokes on mobile devices will lead to different hand coverage and the finger motions, which will introduce a unique interference to the multi-path signals and can be reflected by the channel state information (CSI). The adversary can exploit the strong correlation between the CSI fluctuation and the keystrokes to infer the user's number input. WindTalker presents a novel approach to collect the target's CSI data by deploying a public WiFi hotspot. Compared with the previous keystroke inference approach, WindTalker neither deploys external devices close to the target device nor compromises the target device. Instead, it utilizes the public WiFi to collect user's CSI data, which is easy-to-deploy and difficult-to-detect. In addition, it jointly analyzes the traffic and the CSI to launch the keystroke inference only for the sensitive period where password entering occurs. WindTalker can be launched without the requirement of visually seeing the smart phone user's input process, backside motion, or installing any malware on the tablet. We implemented Windtalker on several mobile phones and performed a detailed case study to evaluate the practicality of the password inference towards Alipay, the largest mobile payment platform in the world. The evaluation results show that the attacker can recover the key with a high successful rate. The use of radio for communication with medical devices provides important convenience and safety features. However, devices that respond to unauthorized queries may inadvertently disclose their presence. It is reasonable for users to expect that their devices' detectability by third parties to be limited, and thus even eavesdroppers to an authorized conversation (e.g. a command sent to an insulin pump) should observe an access code of minimal utility for triggering future transmissions. Access rights should be revocable in a manner that limits that harm that can be caused by authorized devices in the possession of unauthorized users. In order to detect inappropriate use, it may be desirable for access history to be available for audit. We describe a family of replay-attack resistant protocols suitable for embedding into query messages that can authorize users with a range of differentiated access rights. Implanted devices utilizing these techniques can evade detection by suppressing responses to queries that do not contain appropriate authorization. Techniques are described that can support revocation of authorization and audits of access history. Finally, we observe that the processing of unauthorized queries consumes power and thus can be used to mount a potentially devastating denial-of-service attack against the batteries of both conventional devices and devices that utilize the cryptographic protocols we describe. Since field-powered communication systems (e.g. HF-RFID) contain embedded general-purpose processors that operate using only power extracted from externally applied fields, they are substantially more robust against such forms of attack.