PARC Recent Publications

Cyber security technology usability and management

Diana Smetters — Thu, 31 Dec 2009 00:00:00 -0800

Usability and security are no longer at odds, but instead increasingly seen as two critical components of effective cyber systems. This chapter reviews recent results on designing systems that are usable, useful, and secure, and describes general principles important in the management of secure systems.

The capacity of wireless ad hoc networks with multi-packet reception

J.J. Garcia-Luna-Aceves — Thu, 31 Dec 2009 00:00:00 -0800

We compute the throughput capacity of random dense wireless ad hoc networks for multi-pair unicast traffic in which nodes are endowed with multi-packet reception (MPR) capabilities. We show that T([(R(n))^(1- 2/a )]/n^(1/a)) and T (R(n)) bits per second constitute tight bounds for the throughput capacity under the physical and protocol model assumptions, respectively, where n is the total number of nodes in the network, a > 2 is the path-loss parameter in the physcial model, and R(n) is the MPR receiver range. In so doing, we close the gap between the lower and upper bounds of throughput capacity in the physical model. Compared to the capacity of point-to-point communication reported by Gupta and Kumar, MPR increases the order capacity of random wireless ad hoc networks under both protocol and physical models by at least T(log n) and T((log n)^([a-2]/2a)), respectively. We address the cost incurred in increasing the transport capacity of wireless ad hoc networks over what can be attained when sources and destinations communicate over multi-hop paths under the physical model assumption. We define the energy efficiency ?(n) as the bit-meters of information transferred in the network for each unit energy, and compute such energy efficiency for different techniques. We show that a lower energy efficiency is attained in order to achieve higher transport capacity.

An investigation of signal performance enhancements achieved through innovative pixel design across several generations of indirect detection, active matrix, flat-panel arrays

Thu, 31 Dec 2009 00:00:00 -0800

Amorphous silicon thin film transistor image sensors

Bob Street, William Wong, Tse Nga (Tina) Ng and Rene Lujan — Thu, 31 Dec 2009 00:00:00 -0800

Jet-printing: from drops to electronic devices

Jurgen Daniel, Tse Nga (Tina) Ng, Ana Arias, Beverly Russo and Brent Krusor — Wed, 02 Dec 2009 00:00:00 -0800

Printing technology in the fabrication of electronics devices is poised to significantly lower the cost of manufacturing. This is particularly true if combined with roll-to–roll processing. Currently, printing is explored for various applications, including lighting, solar cells, RFID tags, electronic displays, or sensors.

Amongst several printing methods, inkjet printing has the advantages of digital data printing and non-contact material deposition. It is also well suited for prototyping and materials research because of the small amounts of material consumed.

This talk will discuss materials and methods in printed electronics, highlighting the benefits and challenges in using jet-printing. The focus will be on flexible printed active-matrix backplanes for driving electrophoretic displays and on sensor-tapes for recording blast events in the battlefield.

Controlling data in the cloud: outsourcing computation without outsourcing control

Fri, 13 Nov 2009 00:00:00 -0800

Cloud computing is clearly one of today's most enticing technology areas due, at least in part, to its cost-efficiency and flexibility. However, despite the surge in activity and interest, there are significant, persistent concerns about cloud computing that are impeding momentum and will eventually compromise the vision of cloud computing as a new IT procurement model. In this white paper, we clearly characterize the problems and their impact on adoption. In addition, and equally importantly, we describe how the combination of existing research thrusts has strong potential to alleviate many of the concerns impeding adoption. In particular, we argue that with continued research advances in trusted computing and computation-supporting encryption, life in the cloud can be advantageous from a business intelligence standpoint over the isolated alternative that is more common today.

Faking contextual data for fun, profit, and privacy

Richard Chow and Philippe Golle — Mon, 09 Nov 2009 00:00:00 -0800

The amount of contextual data collected, stored, mined, and shared is increasing exponentially. Street cameras, credit card transactions, chat and Twitter logs, e-mail, web site visits, phone logs and recordings, social networking sites, are all examples of data that persists in a manner not under individual control, leading some to declare the death of privacy. We argue here that the ability to generate convincing fake contextual data can be a basic tool in the fight to preserve privacy. One use for the technology is for an individual to make his actual data indistinguishable amongst a pile of false data.

In this paper we consider two examples of contextual data, search engine query data and location data. We describe the current state of faking these types of data and our own efforts in this direction.

Microspring characterization and flip chip assembly reliability

Sun, 01 Nov 2009 00:00:00 -0700

Electronics packaging based on stress-engineered spring interconnects have the potential to enable integrated IC testing, fine-pitch, and compliance not readily available with other technologies. We describe new spring contacts which simultaneously achieve low resistance (<100 mohm) and high compliance (>30 micron) in dense two-dimensional arrays (180 x 180 micron pitch). Mechanical characterization show individual springs operate at ~0.01 gm force. Electrical measurements and simulations imply the interface contact resistance contribution to a single contact resistance is < 40 mohms. Daisy chain test die consisting of 2844 contacts are assembled into flip chip packages with 100% yield. Thermocycle and humidity testing suggest packages with or without underfill can have stable resistance values and no glitches through over 1000 thermocycles or 7000 hrs of humidity. This work suggests that integrated testing and packaging can be performed the springs, enabling new capabilities for markets such as multi-chip modules.

The singularity is not near: slowing growth of Wikipedia

Bongwon Suh, Gregorio Convertino, Ed H. Chi and Peter Pirolli — Sun, 25 Oct 2009 00:00:00 -0700

Prior research on Wikipedia has characterized the growth in content and editors as being fundamentally exponential in nature, extrapolating contemporary trends into the future. We show that recent editing activity suggests that Wikipedia growth has slowed, and perhaps plateaued, indicating that it has come against limits to growth. We measure growth, population shifts, and patterns of editor and administrator activities, contrasting these against past results where possible. Both the rate of page growth and editor growth has declined. We also show that as growth has declined there are indicators of increased coordination and overhead costs, exclusion of newcomers, and resistance to new edits. We discuss some possible explanations for these changes including decreased opportunities for writing up existing knowledge and increased stress on the socio-technical system itself.

Securing network content

Diana Smetters and Van Jacobson — Thu, 15 Oct 2009 00:00:00 -0700

Current networks derive their security from a communication model. The security of content is determined by who (what host) you retrieved that content from, and the properties of the communication channel over which you retrieved it -- was it encrypted, authenticated, and so on. Such security is transient, evaporating after the connection ends, and not transitive -- everyone wanting a piece of content must get it from "the horse's mouth'' in order to trust it. We propose a more scalable model wherein content itself is secured, rather than the connections over which it travels. By authenticating content itself with digital signatures, and adding the ability to retrieve that content by name rather than by the identity of the host on which it happens to be stored, we can build networks with a number of desirable security and performance properties. To make content-based security practial and effective, we argue that we must authenticate the linkage between (arbitrary) names and content, rather than merely authenticating the content or its publisher. We introduce a specific proposal for securing named content effective for both current and future, potentially content-based networks.

Soccer science and the Bayes community: exploring the cognitive implications of modern scientific communication

Jeff Shrager, Dorrit Billman, Gregorio Convertino, JP Massar and Peter Pirolli — Wed, 30 Sep 2009 00:00:00 -0700

Science is a form of distributed analysis involving both individual work that produces new knowledge, and collaborative work to exchange information with the larger community. There are many particular ways in which individual and community can interact in science, and it is difficult to assess how efficient these are, and what the best way might be to support them. This paper reports on a series of experiments in this area, and a prototype implementation using a research platform called CACHE. CACHE both supports experimentation with different structures of interaction between individual and community cognition, and serves as a prototype for computational support for those structures. We particularly focus on CACHE-BC, the Bayes Community version of CACHE, within which the community can break up analytical tasks into "mind-sized" units, and use provenance tracking to keep track of the relationship between these units.

Learning communities in a large enterprise

Tue, 29 Sep 2009 00:00:00 -0700

This paper reports on our study of the deployment of online learning communities in a large enterprise of IT services. We first provide an overview of the learning communities and the research project. Then we report on two case studies of communities of professionals.

Networking named content

Wed, 23 Sep 2009 00:00:00 -0700

Network use has evolved to be dominated by content distribution and retrieval, while networking technology still can only speak of connections between hosts. Accessing content and services requires mapping from the what that users care about to the network’s where. We present Content-Centric Networking (CCN) which takes content as a primitive – decoupling location from identity, security and access, and retrieving content by name. Using new approaches to routing named content, derived heavily from IP, we can simultaneously achieve scalability, security and performance. We have implemented the basic features of our architecture and demonstrate resilience and performance with secure file downloads and VoIP calls.

VoCCN: voice over content-centric networks

Wed, 23 Sep 2009 00:00:00 -0700

A variety of proposals call for a new Internet architecture focused on retrieving content by name, but it has not been clear that any of these approaches can offer the generality to support Internet applications like real-time streaming or email. We present a detailed description of a prototype implementation of one such application – Voice over IP (VoIP) – in a content-based paradigm. This serves as a good example to show how content-based networking can offer advantages for the full range of Internet applications, if the architecture has certain key properties.

The prospects of inkjet printing for displays and sensor tapes

Jurgen Daniel, Ana Arias, Tse Nga (Tina) Ng, Beverly Russo and Brent Krusor — Sun, 20 Sep 2009 00:00:00 -0700

When fabricating electronic devices, an all-additive solution-based process would have the lowest cost and complexity, because it employs the lowest number of processing steps and it consumes the least amount of process material. However, there are still many challenges on the way to achieving electronic circuits by such processes. Here, we present inkjet printing approaches to fabricate displays and sensor circuits.

The 'out-of-avatar experience': object-focused collaboration in Second Life

Greg Wadley and Nic Ducheneaut — Mon, 07 Sep 2009 00:00:00 -0700

Much of our current understanding of collaboration around objects in collaborative virtual environments comes from studies conducted in laboratories five to ten years ago. Since that time, desktop ''virtual worlds'' (VWs) have become a popular form of 3d environment and have been proposed for a variety of workplace scenarios. One popular VW, Second Life, allows its users to create and manipulate content. This provides an opportunity to compare current practices of collaboration with older research. In this paper we present the results of an investigation into collaborative building in SL. We discuss the problems our participants encountered and the techniques they used to overcome them. We present measures of camera movement and verbal reference to objects, and discuss the impact of the user interface upon these behaviors. We argue that while well-documented old problems remain very much alive, their manifestation in SL suggests new possibilities for supporting collaboration in 3d spaces.

Which way am I facing: Inferring user compass orientation from a randomly-oriented wearable device

Kai Kunze, Kurt Partridge, Bo Begole and Paul Lukowicz — Sat, 05 Sep 2009 00:00:00 -0700

We present a method to infer the orientation of mobile device carried in a pocket from the acceleration signal acquired when the user is walking. Whereas previous work has shown how to determine the the orientation in the vertical plane (angle towards earth gravity), we demonstrate how to compute the orientation within the horizontal plane. To validate our method we compare the output of our method with GPS heading information when walking in a straight line. On a total of 16 different orientations and traces we have a mean difference of 5 degrees with 2.5 degrees standard deviation.

Implicit authentication for mobile devices

Markus Jakobsson, Elaine Shi, Philippe Golle and Richard Chow — Tue, 11 Aug 2009 00:00:00 -0700

With the rapid proliferation of mobile commerce and web-based services, there is increased demand for authenticating computers or users. In particular, higher-assurance authentication such as augmenting passwords is beginning to penetrate high-value consumer markets such as banking. However, usability and cost are concerns about these second-factor authentication devices. Furthermore, password entry is complicated by the limitations of input interfaces on mobile internet devices. We introduce the notion of implicit authentication –- the ability to authenticate users based on actions they would carry out anyway. Our preliminary findings support this as a meaningful approach to increasing usable security.

The tyranny of embodiment

Nick Yee and Nic Ducheneaut — Wed, 05 Aug 2009 00:00:00 -0700

Contemporary virtual worlds insist on replicating physical embodiment. The metaphor of embodiment and the expectations it brings directs our attention to replicating physical reality in virtual worlds, including the need to create a legion of artifacts that revolve around our bodies. Thus, a virtual meeting is conceptualized as a collection of virtual chairs, virtual tables, and virtual people. On the other hand, does this insistence on replicating physical reality in virtual worlds limit the kind of work that can be done in virtual worlds? Or put another way, could new forms of work and collaboration be imagined in a world without traditional human embodiment?

Natural and implicit interaction systems

Maurice Chu — Sat, 01 Aug 2009 00:00:00 -0700

Humans constantly seek information about their environment. In doing so, they position their bodies and orient their sensory organs to obtain the best possible data. We see this behavior everyday - for example, shoppers browsing items on shelves in a retail store will bend down and lean forward to more closely examine items that caught their eye. The notion that humans move purposefully to obtain information provides a guiding framework to interpret natural body movements and gestures as implicit cues. With the ability to infer what data a person is seeking, we can design novel interaction systems that provide that data without the need for an explicit input interface.

The nature of technology

Brian Arthur — Sat, 01 Aug 2009 00:00:00 -0700

The Nature of Technology presents a powerful theory of technology's origins and evolution. The author, Brian Arthur, a Visiting Researcher at PARC and an External Professor at the Santa Fe Institute, explains how tranformative new technoloiges arise and how innovation really works. New technologies do not spring from "thinking outside the box" or even from genius or raw creativity. Rather, technologies are put together from pieces - themselves technologies - that already exist. Technologies share common ancestries and combine, morph and combine again to create further technologies.

PixLabeler: User interface for pixel-level labeling of elements in document images

Eric Saund, Jing Lin and Prateek Sarkar — Sun, 26 Jul 2009 00:00:00 -0700

We present a user interface design for labeling elements in document images at a pixel level. Labels are represented by overlay color, which might map to such terms as "handwriting'', "machine print'', "graphics'', etc. The primary purpose is to streamline processes for manual production of groundtruth data, which is necessary for training algorithms and evaluating performance. Unlike general paint-type programs, the UI design is targeted specifically toward selection of collections of foreground pixels that are likely to be meaningful elements in a document image analysis context. Our implementation, called PixLabeler, is available for download and allows customized plug-ins for bootstrapping according to the labeling task.

Classifying foreground pixels in document images

Prateek Sarkar, Eric Saund and Jing Lin — Sun, 26 Jul 2009 00:00:00 -0700

We present a system that classifies pixels in a document image according to marking type such as machine print, handwriting, and noise. A segmenter module first splits an input image into fragments, sometimes breaking connected components. Each fragment is then classified by an automatically trained multi-stage classifier that is fast and considers features of the fragment, as well as its neighborhood. Features relevant for discrimination are picked out automatically from among hundreds of measurements. Our system is trainable from example images in which each foreground pixel has a “ground-truth” label. The main distinction of our system is the level of accuracy achieved in classifying fragments at sub-connected component level, rather than larger aggregate groups such as words or text-lines. We have trained this system to detect handwriting, machine print text, machine print graphics, and noise.

Impact on process by a social annotation system: a social reading experiment

Les Nelson, Gregorio Convertino, Peter Pirolli, Lichan Hong and Ed H. Chi — Sun, 19 Jul 2009 00:00:00 -0700

Social annotation systems such as SparTag.us and del.icio.us have been designed to encourage individual reading and marking behaviors that, when shared, accumulate to build collective knowledge spaces. Prior work reported on the experimental design and performance effects observed in a controlled study of SparTag.us. Study participants working independently on a sensemaking task who had access to a set of expert annotations were compared against participants using SparTag.us without those annotations and participants using only office software for annotation support. A learning effect was shown favoring the participants using existing annotations. In this paper, we consider analysis of the behavioral data captured in the experiment to further explore the causes that would explain these effects.

Activity awareness & social sensemaking 2.0: design of a task force workspace

Gregorio Convertino, Lichan Hong, Les Nelson, Peter Pirolli and Ed H. Chi — Sun, 19 Jul 2009 00:00:00 -0700

Task forces of expert knowledge workers would benefit from more advanced web tools supporting activity awareness and social sensemaking. This paper proposes the design of a task force workspace, which is under development. It introduces the problem through a scenario, specifies requirements, and illustrates an modeling approach and the mockups of the functions in the proposed workspace. Key design issues are finally discussed.

Designed to fit: challenges of interaction design for clothes fitting room technologies

Bo Begole, Takashi Matsumoto, Wei Zhang, Nick Yee, Julia Liu and Maurice Chu — Sun, 19 Jul 2009 00:00:00 -0700

This paper uncovers issues in the design of camera-based technologies to support retail shopping in a physical store, specifically clothes shopping. An emerging class of technology is targeting the enhancement of retail shopping, including the trying on of clothing. Designing such systems requires careful considerations of physical and electronic design, as well as concerns about user privacy. We explore the entire design cycle using a technology concept called the Responsive Mirror through its conception, prototyping and evaluation. The Responsive Mirror is an implicitly controlled video technology for clothes fitting rooms that allows a shopper to directly compare a currently worn garment with images from the previously worn garment. The orientation of images from past trials is matched to the shopper’s pose as he moves. To explore the tension between privacy and publicity, the system also allows comparison to clothes that other people in the shoppers’ social network are wearing. A user study elicited a number of design tradeoffs regarding privacy, adoption, benefits to shoppers and merchants and user behaviors in fitting rooms.

A human-centered model for detecting technology engagement

James Glasnapp and Oliver Brdiczka — Sun, 19 Jul 2009 00:00:00 -0700

This paper proposes a human-centered engagement model for developing interactive media technology. The human-centered engagement model builds on previous interaction models for publicly located ambient displays. It is designed from ethnographic observation with the aim of informing technological innovation from the perspective of the user. The model will be presented along with technological mechanisms to detect human behavior with the aim of responsive media technology development.

User-centered design and evaluation - the big picture

Victoria Bellotti, Shin'ichi Fukuzumi, Toshiyuki Asahi and Shunsuke Suzuki — Sun, 19 Jul 2009 00:00:00 -0700

This paper provides a high-level overview of the field of usability evaluation as context for a panel - Systematization, Modeling and Quantitative Evaluation of Human Interface - in which several authors report on a collaborative effort to apply CogTool, an automated usability evaluation method, to mobile phone interfaces and to assess whether usability predictions made by CogTool correlate with user subjective impressions of usability. If the endeavor, which is still underway at the time of writing, is successful, then CogTool may be applied economically within the product development lifecycle to reduce the risk of usability problems.

A position paper on 'Living Laboratories': rethinking ecological designs and experimentation in human-computer interaction

Ed H. Chi — Sun, 19 Jul 2009 00:00:00 -0700

HCI has long moved beyond the evaluation of a single user sitting in front of a single desktop computer, yet many of our fundamentally held viewpoints about evaluation continues to be ruled by outdated biases derived from this legacy.We need to engage with real users in 'Living Laboratories', in which researchers either adopt or create real systems that are used in real settings. These new experimental platforms will greatly enable researchers to conduct evaluations that span many users, places, time, location, and social factors in ways that are unimaginable before.

Reanalysis of tyrannosaurus rex mass spectra

Marshall Bern, B. S. Phinney and David Goldberg — Wed, 15 Jul 2009 00:00:00 -0700

Asara et al. reported the detection of collagen peptides in a 68-million-year-old T. rex bone by shotgun proteomics. This finding has been called into question as a possible statistical artifact. We reanalyze Asara et al.’s tandem mass spectra using a different search engine and different statistical tools. Our reanalysis shows a sample containing common laboratory contaminants, soil bacteria, and bird-like hemoglobin and collagen.