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Becher, M., Freiling, F.C., Hoffmann, J., Holz, T., Uellenbeck, S., Wolf, C..  2011.  Mobile Security Catching Up? Revealing the Nuts and Bolts of the Security of Mobile Devices Security and Privacy (SP), 2011 IEEE Symposium on. :96-111.

We are currently moving from the Internet society to a mobile society where more and more access to information is done by previously dumb phones. For example, the number of mobile phones using a full blown OS has risen to nearly 200% from Q3/2009 to Q3/2010. As a result, mobile security is no longer immanent, but imperative. This survey paper provides a concise overview of mobile network security, attack vectors using the back end system and the web browser, but also the hardware layer and the user as attack enabler. We show differences and similarities between "normal" security and mobile security, and draw conclusions for further research opportunities in this area.

Salman, A., Elhajj, I.H., Chehab, A., Kayssi, A..  2014.  DAIDS: An Architecture for Modular Mobile IDS. Advanced Information Networking and Applications Workshops (WAINA), 2014 28th International Conference on. :328-333.

The popularity of mobile devices and the enormous number of third party mobile applications in the market have naturally lead to several vulnerabilities being identified and abused. This is coupled with the immaturity of intrusion detection system (IDS) technology targeting mobile devices. In this paper we propose a modular host-based IDS framework for mobile devices that uses behavior analysis to profile applications on the Android platform. Anomaly detection can then be used to categorize malicious behavior and alert users. The proposed system accommodates different detection algorithms, and is being tested at a major telecom operator in North America. This paper highlights the architecture, findings, and lessons learned.

Fei Hao, Geyong Min, Man Lin, Changqing Luo, Yang, L.T..  2014.  MobiFuzzyTrust: An Efficient Fuzzy Trust Inference Mechanism in Mobile Social Networks. Parallel and Distributed Systems, IEEE Transactions on. 25:2944-2955.

Mobile social networks (MSNs) facilitate connections between mobile users and allow them to find other potential users who have similar interests through mobile devices, communicate with them, and benefit from their information. As MSNs are distributed public virtual social spaces, the available information may not be trustworthy to all. Therefore, mobile users are often at risk since they may not have any prior knowledge about others who are socially connected. To address this problem, trust inference plays a critical role for establishing social links between mobile users in MSNs. Taking into account the nonsemantical representation of trust between users of the existing trust models in social networks, this paper proposes a new fuzzy inference mechanism, namely MobiFuzzyTrust, for inferring trust semantically from one mobile user to another that may not be directly connected in the trust graph of MSNs. First, a mobile context including an intersection of prestige of users, location, time, and social context is constructed. Second, a mobile context aware trust model is devised to evaluate the trust value between two mobile users efficiently. Finally, the fuzzy linguistic technique is used to express the trust between two mobile users and enhance the human's understanding of trust. Real-world mobile dataset is adopted to evaluate the performance of the MobiFuzzyTrust inference mechanism. The experimental results demonstrate that MobiFuzzyTrust can efficiently infer trust with a high precision.

Cailleux, L., Bouabdallah, A., Bonnin, J.-M..  2014.  A confident email system based on a new correspondence model. Advanced Communication Technology (ICACT), 2014 16th International Conference on. :489-492.

Despite all the current controversies, the success of the email service is still valid. The ease of use of its various features contributed to its widespread adoption. In general, the email system provides for all its users the same set of features controlled by a single monolithic policy. Such solutions are efficient but limited because they grant no place for the concept of usage which denotes a user's intention of communication: private, professional, administrative, official, military. The ability to efficiently send emails from mobile devices creates new interesting opportunities. We argue that the context (location, time, device, operating system, access network...) of the email sender appears as a new dimension we have to take into account to complete the picture. Context is clearly orthogonal to usage because a same usage may require different features depending of the context. It is clear that there is no global policy meeting requirements of all possible usages and contexts. To address this problem, we propose to define a correspondence model which for a given usage and context allows to derive a correspondence type encapsulating the exact set of required features. With this model, it becomes possible to define an advanced email system which may cope with multiple policies instead of a single monolithic one. By allowing a user to select the exact policy coping with her needs, we argue that our approach reduces the risk-taking allowing the email system to slide from a trusted one to a confident one.

Jindal, M., Dave, M..  2014.  Data security protocol for cloudlet based architecture. Recent Advances and Innovations in Engineering (ICRAIE), 2014. :1-5.

Mobile cloud computing is a combination of mobile computing and cloud computing that provides a platform for mobile users to offload heavy tasks and data on the cloud, thus, helping them to overcome the limitations of their mobile devices. However, while utilizing the mobile cloud computing technology users lose physical control of their data; this ultimately calls for the need of a data security protocol. Although, numerous such protocols have been proposed,none of them consider a cloudlet based architecture. A cloudlet is a reliable, resource-rich computer/cluster which is well-connected to the internet and is available to nearby mobile devices. In this paper, we propose a data security protocol for a distributed cloud architecture having cloudlet integrated with the base station, using the property of perfect forward secrecy. Our protocol not only protects data from any unauthorized user, but also prevents exposure of data to the cloud owner.

Hassan, M.M., Hossain, M.A., Al-Qurishi, M..  2014.  Cloud-based mobile IPTV terminal for video surveillance. Advanced Communication Technology (ICACT), 2014 16th International Conference on. :876-880.

Surveillance video streams monitoring is an important task that the surveillance operators usually carry out. The distribution of video surveillance facilities over multiple premises and the mobility of surveillance users requires that they are able to view surveillance video seamlessly from their mobile devices. In order to satisfy this requirement, we propose a cloud-based IPTV (Internet Protocol Television) solution that leverages the power of cloud infrastructure and the benefits of IPTV technology to seamlessly deliver surveillance video content on different client devices anytime and anywhere. The proposed mechanism also supports user-controlled frame rate adjustment of video streams and sharing of these streams with other users. In this paper, we describe the overall approach of this idea, address and identify key technical challenges for its practical implementation. In addition, initial experimental results were presented to justify the viability of the proposed cloud-based IPTV surveillance framework over the traditional IPTV surveillance approach.

Yuxi Liu, Hatzinakos, D..  2014.  Human acoustic fingerprints: A novel biometric modality for mobile security. Acoustics, Speech and Signal Processing (ICASSP), 2014 IEEE International Conference on. :3784-3788.

Recently, the demand for more robust protection against unauthorized use of mobile devices has been rapidly growing. This paper presents a novel biometric modality Transient Evoked Otoacoustic Emission (TEOAE) for mobile security. Prior works have investigated TEOAE for biometrics in a setting where an individual is to be identified among a pre-enrolled identity gallery. However, this limits the applicability to mobile environment, where attacks in most cases are from imposters unknown to the system before. Therefore, we employ an unsupervised learning approach based on Autoencoder Neural Network to tackle such blind recognition problem. The learning model is trained upon a generic dataset and used to verify an individual in a random population. We also introduce the framework of mobile biometric system considering practical application. Experiments show the merits of the proposed method and system performance is further evaluated by cross-validation with an average EER 2.41% achieved.

Teufl, P., Fitzek, A., Hein, D., Marsalek, A., Oprisnik, A., Zefferer, T..  2014.  Android encryption systems. Privacy and Security in Mobile Systems (PRISMS), 2014 International Conference on. :1-8.

The high usability of smartphones and tablets is embraced by consumers as well as the corporate and public sector. However, especially in the non-consumer area the factor security plays a decisive role for the platform-selection process. All of the current companies within the mobile device sector added a wide range of security features to the initially consumer-oriented devices (Apple, Google, Microsoft), or have dealt with security as a core feature from the beginning (RIM, now Blackerry). One of the key security features for protecting data on the device or in device backups are encryption systems, which are available in the majority of current devices. However, even under the assumption that the systems are implemented correctly, there is a wide range of parameters, specific use cases, and weaknesses that need to be considered when deploying mobile devices in security-critical environments. As the second part in a series of papers (the first part was on iOS), this work analyzes the deployment of the Android platform and the usage of its encryption systems within a security-critical context. For this purpose, Android's different encryption systems are assessed and their susceptibility to different attacks is analyzed in detail. Based on these results a workflow is presented, which supports deployment of the Android platform and usage of its encryption systems within security-critical application scenarios.

Patil, M., Sahu, V., Jain, A..  2014.  SMS text Compression and Encryption on Android O.S. Computer Communication and Informatics (ICCCI), 2014 International Conference on. :1-6.

Today in the world of globalization mobile communication is one of the fastest growing medium though which one sender can interact with other in short time. During the transmission of data from sender to receiver, size of data is important, since more data takes more time. But one of the limitations of sending data through mobile devices is limited use of bandwidth and number of packets transmitted. Also the security of these data is important. Hence various protocols are implemented which not only provides security to the data but also utilizes bandwidth. Here we proposed an efficient technique of sending SMS text using combination of compression and encryption. The data to be send is first encrypted using Elliptic curve Cryptographic technique, but encryption increases the size of the text data, hence compression is applied to this encrypted data so the data gets compressed and is send in short time. The Compression technique implemented here is an efficient one since it includes an algorithm which compresses the text by 99.9%, hence a great amount of bandwidth gets saved.The hybrid technique of Compression-Encryption of SMS text message is implemented for Android Operating Systems.

Skillen, A., Mannan, M..  2014.  Mobiflage: Deniable Storage Encryptionfor Mobile Devices. Dependable and Secure Computing, IEEE Transactions on. 11:224-237.

Data confidentiality can be effectively preserved through encryption. In certain situations, this is inadequate, as users may be coerced into disclosing their decryption keys. Steganographic techniques and deniable encryption algorithms have been devised to hide the very existence of encrypted data. We examine the feasibility and efficacy of deniable encryption for mobile devices. To address obstacles that can compromise plausibly deniable encryption (PDE) in a mobile environment, we design a system called Mobiflage. Mobiflage enables PDE on mobile devices by hiding encrypted volumes within random data in a devices free storage space. We leverage lessons learned from deniable encryption in the desktop environment, and design new countermeasures for threats specific to mobile systems. We provide two implementations for the Android OS, to assess the feasibility and performance of Mobiflage on different hardware profiles. MF-SD is designed for use on devices with FAT32 removable SD cards. Our MF-MTP variant supports devices that instead share a single internal partition for both apps and user accessible data. MF-MTP leverages certain Ext4 file system mechanisms and uses an adjusted data-block allocator. These new techniques for soring hidden volumes in Ext4 file systems can also be applied to other file systems to enable deniable encryption for desktop OSes and other mobile platforms.

Rastogi, V., Yan Chen, Xuxian Jiang.  2014.  Catch Me If You Can: Evaluating Android Anti-Malware Against Transformation Attacks. Information Forensics and Security, IEEE Transactions on. 9:99-108.

Mobile malware threats (e.g., on Android) have recently become a real concern. In this paper, we evaluate the state-of-the-art commercial mobile anti-malware products for Android and test how resistant they are against various common obfuscation techniques (even with known malware). Such an evaluation is important for not only measuring the available defense against mobile malware threats, but also proposing effective, next-generation solutions. We developed DroidChameleon, a systematic framework with various transformation techniques, and used it for our study. Our results on 10 popular commercial anti-malware applications for Android are worrisome: none of these tools is resistant against common malware transformation techniques. In addition, a majority of them can be trivially defeated by applying slight transformation over known malware with little effort for malware authors. Finally, in light of our results, we propose possible remedies for improving the current state of malware detection on mobile devices.

Jagdale, B.N., Bakal, J.W..  2014.  Synergetic cloaking technique in wireless network for location privacy. Industrial and Information Systems (ICIIS), 2014 9th International Conference on. :1-6.

Mobile users access location services from a location based server. While doing so, the user's privacy is at risk. The server has access to all details about the user. Example the recently visited places, the type of information he accesses. We have presented synergetic technique to safeguard location privacy of users accessing location-based services via mobile devices. Mobile devices have a capability to form ad-hoc networks to hide a user's identity and position. The user who requires the service is the query originator and who requests the service on behalf of query originator is the query sender. The query originator selects the query sender with equal probability which leads to anonymity in the network. The location revealed to the location service provider is a rectangle instead of exact co-ordinate. In this paper we have simulated the mobile network and shown the results for cloaking area sizes and performance against the variation in the density of users.

Wiesner, K., Feld, S., Dorfmeister, F., Linnhoff-Popien, C..  2014.  Right to silence: Establishing map-based Silent Zones for participatory sensing. Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP), 2014 IEEE Ninth International Conference on. :1-6.

Participatory sensing tries to create cost-effective, large-scale sensing systems by leveraging sensors embedded in mobile devices. One major challenge in these systems is to protect the users' privacy, since users will not contribute data if their privacy is jeopardized. Especially location data needs to be protected if it is likely to reveal information about the users' identities. A common solution is the blinding out approach that creates so-called ban zones in which location data is not published. Thereby, a user's important places, e.g., her home or workplace, can be concealed. However, ban zones of a fixed size are not able to guarantee any particular level of privacy. For instance, a ban zone that is large enough to conceal a user's home in a large city might be too small in a less populated area. For this reason, we propose an approach for dynamic map-based blinding out: The boundaries of our privacy zones, called Silent Zones, are determined in such way that at least k buildings are located within this zone. Thus, our approach adapts to the habitat density and we can guarantee k-anonymity in terms of surrounding buildings. In this paper, we present two new algorithms for creating Silent Zones and evaluate their performance. Our results show that especially in worst case scenarios, i.e., in sparsely populated areas, our approach outperforms standard ban zones and guarantees the specified privacy level.

Jen Ho Yang, Pei Yu Lin.  2014.  An ID-Based User Authentication Scheme for Cloud Computing. Intelligent Information Hiding and Multimedia Signal Processing (IIH-MSP), 2014 Tenth International Conference on. :98-101.

In cloud computing environments, the user authentication scheme is an important security tool because it provides the authentication, authorization, and accounting for cloud users. Therefore, many user authentication schemes for cloud computing have been proposed in recent years. However, we find that most of the previous authentication schemes have some security problems. Besides, it cannot be implemented in cloud computing. To solve the above problems, we propose a new ID-based user authentication scheme for cloud computing in this paper. Compared with the related works, the proposed scheme has higher security levels and lower computation costs. In addition, it can be easily applied to cloud computing environments. Therefore, the proposed scheme is more efficient and practical than the related works.

Silva, F., Castillo-Lema, J., Neto, A., Silva, F., Rosa, P., Corujo, D., Guimaraes, C., Aguiar, R..  2014.  Entity title architecture extensions towards advanced quality-oriented mobility control capabilities. Computers and Communication (ISCC), 2014 IEEE Symposium on. :1-6.

The emergence of new technologies, in addition with the popularization of mobile devices and wireless communication systems, demands a variety of requirements that current Internet is not able to comply adequately. In this scenario, the innovative information-centric Entity Title Architecture (ETArch), a Future Internet (FI) clean slate approach, was design to efficiently cope with the increasing demand of beyond-IP networking services. Nevertheless, despite all ETArch capabilities, it was not projected with reliable networking functions, which limits its operability in mobile multimedia networking, and will seriously restrict its scope in Future Internet scenarios. Therefore, our work extends ETArch mobility control with advanced quality-oriented mobility functions, to deploy mobility prediction, Point of Attachment (PoA) decision and handover setup meeting both session quality requirements of active session flows and current wireless quality conditions of neighbouring PoA candidates. The effectiveness of the proposed additions were confirmed through a preliminary evaluation carried out by MATLAB, in which we have considered distinct applications scenario, and showed that they were able to outperform the most relevant alternative solutions in terms of performance and quality of service.

Bronzino, F., Chao Han, Yang Chen, Nagaraja, K., Xiaowei Yang, Seskar, I., Raychaudhuri, D..  2014.  In-Network Compute Extensions for Rate-Adaptive Content Delivery in Mobile Networks. Network Protocols (ICNP), 2014 IEEE 22nd International Conference on. :511-517.

Traffic from mobile wireless networks has been growing at a fast pace in recent years and is expected to surpass wired traffic very soon. Service providers face significant challenges at such scales including providing seamless mobility, efficient data delivery, security, and provisioning capacity at the wireless edge. In the Mobility First project, we have been exploring clean slate enhancements to the network protocols that can inherently provide support for at-scale mobility and trustworthiness in the Internet. An extensible data plane using pluggable compute-layer services is a key component of this architecture. We believe these extensions can be used to implement in-network services to enhance mobile end-user experience by either off-loading work and/or traffic from mobile devices, or by enabling en-route service-adaptation through context-awareness (e.g., Knowing contemporary access bandwidth). In this work we present details of the architectural support for in-network services within Mobility First, and propose protocol and service-API extensions to flexibly address these pluggable services from end-points. As a demonstrative example, we implement an in network service that does rate adaptation when delivering video streams to mobile devices that experience variable connection quality. We present details of our deployment and evaluation of the non-IP protocols along with compute-layer extensions on the GENI test bed, where we used a set of programmable nodes across 7 distributed sites to configure a Mobility First network with hosts, routers, and in-network compute services.

Biagioni, E..  2014.  Ubiquitous Interpersonal Communication over Ad-hoc Networks and the Internet. System Sciences (HICSS), 2014 47th Hawaii International Conference on. :5144-5153.

The hardware and low-level software in many mobile devices are capable of mobile-to-mobile communication, including ad-hoc 802.11, Bluetooth, and cognitive radios. We have started to leverage this capability to provide interpersonal communication both over infrastructure networks (the Internet), and over ad-hoc and delay-tolerant networks composed of the mobile devices themselves. This network is decentralized in the sense that it can function without any infrastructure, but does take advantage of infrastructure connections when available. All interpersonal communication is encrypted and authenticated so packets may be carried by devices belonging to untrusted others. The decentralized model of security builds a flexible trust network on top of the social network of communicating individuals. This social network can be used to prioritize packets to or from individuals closely related by the social network. Other packets are prioritized to favor packets likely to consume fewer network resources. Each device also has a policy that determines how many packets may be forwarded, with the goal of providing useful interpersonal communications using at most 1% of any given resource on mobile devices. One challenge in a fully decentralized network is routing. Our design uses Rendezvous Points (RPs) and Distributed Hash Tables (DHTs) for delivery over infrastructure networks, and hop-limited broadcast and Delay Tolerant Networking (DTN) within the wireless ad-hoc network.

J. J. Li, P. Abbate, B. Vega.  2015.  "Detecting Security Threats Using Mobile Devices". 2015 IEEE International Conference on Software Quality, Reliability and Security - Companion. :40-45.

In our previous work [1], we presented a study of using performance escalation to automatic detect Distributed Denial of Service (DDoS) types of attacks. We propose to enhance the work of security threat detection by using mobile phones as the detector to identify outliers of normal traffic patterns as threats. The mobile solution makes detection portable to any services. This paper also shows that the same detection method works for advanced persistent threats.

M. Vahidalizadehdizaj, L. Tao.  2015.  "A new mobile payment protocol (GMPCP) by using a new key agreement protocol (GC)". 2015 IEEE International Conference on Intelligence and Security Informatics (ISI). :169-172.

According to the advancement of mobile devices and wireless network technology, these portable devices became the potential devices that can be used for different types of payments. Recently, most of the people would rather to do their activities by their cellphones. On the other hand, there are some issues that hamper the widespread acceptance of mobile payment among people. The traditional ways of mobile payment are not secure enough, since they follow the traditional flow of data. This paper is going to suggest a new protocol named Golden Mobile Pay Center Protocol that is based on client centric model. The suggested protocol downgrade the computational operations and communications that are necessary between the engaging parties and achieves a completely privacy protection for the engaging parties. It avoids transaction repudiation among the engaging parties and will decrease replay attack s risk. The goal of the protocol is to help n users to have payments to each others'. Besides, it will utilize a new key agreement protocol named Golden Circle that is working by employing symmetric key operations. GMPCP uses GC for generating a shared session key between n users.

Sun, H., Luo, H., Wu, T. Y., Obaidat, M. S..  2015.  A PSNR-Controllable Data Hiding Algorithm Based on LSBs Substitution. 2015 IEEE Global Communications Conference (GLOBECOM). :1–7.

There are more and more systems using mobile devices to perform sensing tasks, but these increase the risk of leakage of personal privacy and data. Data hiding is one of the important ways for information security. Even though many data hiding algorithms have worked on providing more hiding capacity or higher PSNR, there are few algorithms that can control PSNR effectively while ensuring hiding capacity. In this paper, with controllable PSNR based on LSBs substitution- PSNR-Controllable Data Hiding (PCDH), we first propose a novel encoding plan for data hiding. In PCDH, we use the remainder algorithm to calculate the hidden information, and hide the secret information in the last x LSBs of every pixel. Theoretical proof shows that this method can control the variation of stego image from cover image, and control PSNR by adjusting parameters in the remainder calculation. Then, we design the encoding and decoding algorithms with low computation complexity. Experimental results show that PCDH can control the PSNR in a given range while ensuring high hiding capacity. In addition, it can resist well some steganalysis. Compared to other algorithms, PCDH achieves better tradeoff among PSNR, hiding capacity, and computation complexity.

Johnson, R., Kiourtis, N., Stavrou, A., Sritapan, V..  2015.  Analysis of content copyright infringement in mobile application markets. 2015 APWG Symposium on Electronic Crime Research (eCrime). :1–10.

As mobile devices increasingly become bigger in terms of display and reliable in delivering paid entertainment and video content, we also see a rise in the presence of mobile applications that attempt to profit by streaming pirated content to unsuspected end-users. These applications are both paid and free and in the case of free applications, the source of funding appears to be advertisements that are displayed while the content is streamed to the device. In this paper, we assess the extent of content copyright infringement for mobile markets that span multiple platforms (iOS, Android, and Windows Mobile) and cover both official and unofficial mobile markets located across the world. Using a set of search keywords that point to titles of paid streaming content, we discovered 8,592 Android, 5,550 iOS, and 3,910 Windows mobile applications that matched our search criteria. Out of those applications, hundreds had links to either locally or remotely stored pirated content and were not developed, endorsed, or, in many cases, known to the owners of the copyrighted contents. We also revealed the network locations of 856,717 Uniform Resource Locators (URLs) pointing to back-end servers and cyber-lockers used to communicate the pirated content to the mobile application.

Alotaibi, S., Furnell, S., Clarke, N..  2015.  Transparent authentication systems for mobile device security: A review. 2015 10th International Conference for Internet Technology and Secured Transactions (ICITST). :406–413.

Sensitive data such as text messages, contact lists, and personal information are stored on mobile devices. This makes authentication of paramount importance. More security is needed on mobile devices since, after point-of-entry authentication, the user can perform almost all tasks without having to re-authenticate. For this reason, many authentication methods have been suggested to improve the security of mobile devices in a transparent and continuous manner, providing a basis for convenient and secure user re-authentication. This paper presents a comprehensive analysis and literature review on transparent authentication systems for mobile device security. This review indicates a need to investigate when to authenticate the mobile user by focusing on the sensitivity level of the application, and understanding whether a certain application may require a protection or not.

Antal, M., Szabó, L. Z..  2015.  An Evaluation of One-Class and Two-Class Classification Algorithms for Keystroke Dynamics Authentication on Mobile Devices. 2015 20th International Conference on Control Systems and Computer Science. :343–350.

In this paper we study keystroke dynamics as an authentication mechanism for touch screen based devices. The authentication process decides whether the identity of a given person is accepted or rejected. This can be easily implemented by using a two-class classifier which operates with the help of positive samples (belonging to the authentic person) and negative ones. However, collecting negative samples is not always a viable option. In such cases a one-class classification algorithm can be used to characterize the target class and distinguish it from the outliers. We implemented an authentication test-framework that is capable of working with both one-class and two-class classification algorithms. The framework was evaluated on our dataset containing keystroke samples from 42 users, collected from touch screen-based Android devices. Experimental results yield an Equal Error Rate (EER) of 3% (two-class) and 7% (one-class) respectively.

Fedosov, Anton, Ojala, Jarno, Niforatos, Evangelos, Olsson, Thomas, Langheinrich, Marc.  2016.  Mobile First?: Understanding Device Usage Practices in Novel Content Sharing Services Proceedings of the 20th International Academic Mindtrek Conference. :198–207.

Today's mobile app economy has greatly expanded the types of "things" people can share –- spanning from new types of digital content like physiological data (e.g., workouts) to physical things like apartments and work tools ("sharing economy"). To understand whether mobile platforms provide adequate support for such novel sharing services, we surveyed 200 participants about their experiences with six types of emergent sharing services. For each domain we elicited device usage practices and identified corresponding device selection criteria. Our analysis suggests that, despite contemporary mobile first design efforts, desktop interfaces of emergent content sharing services are often considered more efficient and easier to use –- both for sharing and access control tasks (i.e., privacy). Based on our findings, we outline device-related design and research opportunities in this space.

Wiese, Oliver, Roth, Volker.  2016.  See You Next Time: A Model for Modern Shoulder Surfers. Proceedings of the 18th International Conference on Human-Computer Interaction with Mobile Devices and Services. :453–464.

Friends, family and colleagues at work may repeatedly observe how their peers unlock their smartphones. These "insiders" may combine multiple partial observations to form a hypothesis of a target's secret. This changing landscape requires that we update the methods used to assess the security of unlocking mechanisms against human shoulder surfing attacks. In our paper, we introduce a methodology to study shoulder surfing risks in the insider threat model. Our methodology dissects the authentication process into minimal observations by humans. Further processing is based on simulations. The outcome is an estimate of the number of observations needed to break a mechanism. The flexibility of this approach benefits the design of new mechanisms. We demonstrate the application of our methodology by performing an analysis of the SwiPIN scheme published at CHI 2015. Our results indicate that SwiPIN can be defeated reliably by a majority of the population with as few as 6 to 11 observations.