Ravikanth Pappu

RFID privacy: an overview of problems and proposed solutions

As organizations aggressively deploy radio frequency identification systems, activists are increasingly concerned about RFIDs potential to invade user privacy. This overview highlights potential threats and how they might be addressed using both technology and public policy.

Squealing Euros: Privacy protection in RFID-enabled banknotes

Thanks to their broad international acceptance and availability in high denominations, there is widespread concern that Euro banknotes may provide an attractive new currency for criminal transactions. With this in mind, the European Central Bank has proposed to embed small, radio-frequency-emitting identification (RFID) tags in Euro banknotes by 2005 as a tracking mechanism for law enforcement agencies. The ECB has not disclosed technical details regarding its plan. In this paper, we explore some of the risks to individual privacy that RFID tags embedded in currency may pose if improperly deployed. Acknowledging the severe resource constraints of these tags, we propose a simple and practical system that provides a high degree of privacy assurance. Our scheme involves only elementary cryptography. Its effectiveness depends on a careful separation of the privileges offered by optical vs. radio-frequency contact with banknotes, and full exploitation of the limited access-control capabilities of RFID tags.

An Optimal Q-Algorithm for the ISO 18000-6C RFID Protocol

Passive radio-frequency identification (RFID) systems based on the ISO/IEC 18000-6C (aka EPC Gen2) protocol have typical read rates of up to 1200 unique 96-bit tags per second. This performance is achieved in part through the use of a medium access control algorithm, christened the Q-algorithm, that is a variant of the Slotted Aloha multiuser channel access algorithm. We analyze the medium access control algorithm employed by the ISO/IEC 18000-6C RFID air interface protocol and provide a procedure to achieve optimal read rates. We also show that theoretical performance can be exceeded in many practical use cases and provide a model to incorporate real-world data in read-rate estimation.

Reconfigurable image projection holograms

We introduce reconfigurable image projection RIP holo- grams and a method for computing RIP holograms of three-dimensional 3-D scenes. RIP holograms project one or more series of parallax views of a 3-D scene through one or more holographically reconstructed projection surfaces. Projection surfaces are defined at locations at which the hologram reconstructs a variable number of real or virtual images, called holographic primitives, which collectively compose the surface and constitute exit pupils for the view pixel information. RIP holograms are efficiently assembled by combining a sweep of 2-D parallax views of a scene with instances of one or more precomputed diffractive elements, which are permitted to overlap on the hologram, and which reconstruct the holographic primitives. The technique improves on the image quality of conventional stereograms while affording similar efficient computation: it incorporates realistic computer graphic rendering or high-quality optical capture of a scene, it eliminates some artifacts often present in conven- tional computed stereograms, and its basic multiply-and-accumulate op- erations are suitable for hardware implementation. The RIP approach offers flexible tuning of capture and projection together, according to the sampling requirements of the scene and the constraints of a given dis- play architecture.

An installation of interactive furniture

We report on a project that explored emerging technologies for intuitive and unobtrusive information interfaces in a compelling setting. An installation at the Museum of Modern Art, New York, was part of a public exhibit and included an interactive table that presented information associated with the exhibit to the gallery visitors without visible conventional computing elements. The enabling devices included noncontact sensing of low-cost tags in physical icons, electrostatic detection of hand location in three dimensions, and sensor fusion through lightweight Internet Protocol access.

Wavelets for waveform coding of digital symbols

A wavelet-based coder-decoder (codec) structure is defined for baseband waveform coding. Numerical results for bandwidth efficiency are given, and a comparison between several different wavelets is presented. Moreover, it is shown that wavelets obey the Nyquist pulse shaping condition and provide a unified framework for analog pulse shaping concepts of communications.

On waveform coding using wavelets

We consider a novel baseband waveform coding technique based on wavelets. Wavelets are recognized for their temporal and spectral localization and for their orthogonality across scale and location. We exploit these fundamental properties of wavelets and propose a wavelet-based modulator-demodulator structure to improve communication efficiency. Numerical results for bandwidth occupancy and bandwidth efficiency are given, and a detailed comparison between different families of wavelets is presented.<<ETX>>

Coincident display using haptics and holographic video

In this paper, we describe the implementation of a novel system which enables a user to “carve” a simple free-standing electronic holographic image using a force-feedback device. The force-feedback (or haptic) device has a stylus which is held by the hand like an ordinary cutting tool. The 3D position of the stylus tip is reported by the device, and appropriate forces can be displayed to the hand as it interacts with 3D objects in the haptic workspace. The haptic workspace is spatially overlapped and registered with the holographic video display volume. Within the resulting coincident visuo-haptic workspace, a 3D synthetic cylinder is presented, spinning about its long axis, which a person can see, feel, and lathe with the stylus. This paper introduces the concept of coincident visuo-haptic display and describes the implementation of the lathe simulation. After situating the work in a research context, we present the details of system design and implementation, including the haptic and holographic modeling. Finally, we discuss the performance of this prototype system and future work.

Wavelets for baseband coding of waveforms

We consider a novel baseband waveform coding technique based on wavelets. Wavelets are recognized for their temporal and spectral localization and for their orthogonality across scale and location. We exploit these fundamental properties of wavelets and propose a wavelet-based modulator-demodulator structure to improve communication efficiency. Numerical results for bandwidth occupancy and bandwidth efficiency are given, and a detailed comparison between different families of wavelets is presented. A codec based on the Battle-Lemarie wavelet is shown to outperform traditional BPSK-, QPSK- and MSK-based codecs as well as codecs based on Daubechies wavelets.

Haptic holography: a primitive computational plastic

We describe our work on haptic holography, a combination of computational modeling and multimodal spatial display, which allows a person to see, feel, and interact with three-dimensional freestanding holographic images of material surfaces. In this paper, we combine various holographic displays with a force-feedback device to render multimodal images with programmatically prescribed material properties and behavior. After a brief overview of related work which situates visual display within the manual workspace, we describe our holo-haptic approach and survey three implementations, Touch, Lathe, and Poke, each named for the primitive functional affordance it offers. In Touch, static holographic images of simple geometric scenes are reconstructed in front of the hologram plane, and coregistered with a force model of the same geometry. These images can be visually inspected and haptically explored using a handheld interface. In Lathe, a holo-haptic image can be reshaped by haptic interaction in a dynamic but constrained manner. Finally in Poke, using a new technique for updating interference-modeled holographic fringe patterns, we render a holo-haptic image that permits more flexible interactive reshaping of its reconstructed surface. We situate this work within the context of related research and describe the strengths, shortcomings, and implications of our approach.