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Revocation and tracing schemes for stateless receivers?

21st Annual International Cryptology Conference, CRYPTO 2001

作者： Naor, Dalit Naor, Moni Lotspiech, Jeff IBM Almaden Research Center 650 Harry Road San-JoseCA95120 United States Department of Computer Science and Applied Math Weizmann Institute Rehovot Israel

ISBN: (纸本)3540424563

We deal with the problem of a center sending a messageto a group of users such that some subset of the users is consideredrevoked and should not be able to obtain the content of the *** concentrate on the stateless receiver case, where the users do not(necessarily) update their state from session to session. We present aframework called the Subset-Cover framework, which abstracts a varietyof revocation schemes including some previously known ones. We pro-vide suficient conditions that guarantees the security of a revocationalgorithm in this *** describe two explicit Subset-Cover revocation algorithms;these algo-rithms are very flexible and work for any number of revoked users. Theschemes require storage at the receiver of logN and 12log2 N keys respec-tively (N is the total number of users), and in order to revoke r users therequired message lengths are of r logN and 2r keys respectively. We alsoprovide a general traitor tracing mechanism that can be integrated withany Subset-Cover revocation scheme that satisés a "bifurcation prop-erty". This mechanism does not need an a priori bound on the numberof traitors and does not expand the message length by much comparedto the revocation of the same set of *** main improvements of these methods over previously suggestedmethods, when adopted to the stateless scenario, are: (1) reducingthe message length to O(r) regardless of the coalition size whilemaintaining a single decryption at the user's end (2) provide aseamless integration between the revocation and tracing so that the trac-ing mechanisms does not require any change to the revocation algorithm. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Signal receivers

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Observations on hot potato routing

Observations on hot potato routing

引用

Israel Symposium on the Theory of Computing and Systems

作者： U. Feige Department of Applied Math and Computer Science Weizmann Institute of Science Rehovot Israel

In "hot potato" packet routing problems, packets need to be routed to their respective destinations on a network. At each time step, each communication link can be traversed by at most one packet. Packets must keep on moving until they reach their destinations, even if this means temporarily moving further away from their destinations. We investigate some simple design principles for hot potato routing algorithms. Perhaps our most important negative result is that for a wide class of natural algorithms, the number of deflections that a packet suffers can grow experimentally in the number of other packets in the network. On the positive side, we present some (admitedly weak) upper bounds on the worst case performance for algorithms for general networks, and for special cases such as the mesh, the torus, and the infinite line.< >

关键词： Routing Upper bound Algorithm design and analysis Energy storage Resource management Packet switching

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Extracting semantic information through illumination classification

Extracting semantic information through illumination classif...

引用

Conference on computer Vision and Pattern Recognition (CVPR)

作者： A. Aner-Wolf Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

A system is presented for automatic classification of the atmosphere in motion pictures scenes. This classification is based solely on the extraction of approximate illumination information from single frames. By using well defined film grammar rules regarding scene lighting, it generates high level semantic descriptors for frames and scenes. These illumination descriptors could be further combined with other descriptors like motion and sound, to generate a complete automatic semantic analysis system of video media.

关键词： Data mining Lighting Layout Reflectivity Atmosphere computer Society computer vision Pattern recognition Brightness Distributed computing

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Dense shape reconstruction of a moving object under arbitrary, unknown lighting

Dense shape reconstruction of a moving object under arbitrar...

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International Conference on computer Vision (ICCV)

作者： Simakov Frolova Basri Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

We present a method for shape reconstruction from several images of a moving object. The reconstruction is dense (up to image resolution). The method assumes that the motion is known, e.g., by tracking a small number of feature points on the object. The object is assumed Lambertian (completely matte), light sources should not be very close to the object but otherwise arbitrary, and no knowledge of lighting conditions is required. An object changes its appearance significantly when it changes its orientation relative to light sources, causing violation of the common brightness constancy assumption. While a lot of effort is devoted to deal with this violation, we demonstrate how to exploit it to recover 3D structure from 2D images. We propose a new correspondence measure that enables point matching across views of a moving object. The method has been tested both on computer simulated examples and on a real object.

关键词： Shape Image reconstruction Brightness Light sources Stereo vision Information resources Cameras Calibration computer science Image resolution

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A step towards sequence-to-sequence alignment

A step towards sequence-to-sequence alignment

引用

Conference on computer Vision and Pattern Recognition (CVPR)

作者： Y. Caspi M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

The paper presents an approach for establishing correspondences in time and in space between two different video sequences of the same dynamic scene, recorded by stationary uncalibrated video cameras. The method simultaneously estimates both spatial alignment as well as temporal synchronization (temporal alignment) between the two sequences, using all available spatio-temporal information. Temporal variations between image frames (such as moving objects or changes in scene illumination) are powerful cues for alignment, which cannot be exploited by standard image-to-image alignment techniques. We show that by folding spatial and temporal cues into a single alignment framework, situations which are inherently ambiguous for traditional image-to-image alignment methods, are often uniquely resolved by sequence-to-sequence alignment. We also present a "direct" method for sequence-to-sequence alignment. The algorithm simultaneously estimates spatial and temporal alignment parameters directly from measurable sequence quantities, without requiring prior estimation of point correspondences, frame correspondences, or moving object detection. Results are shown on real image sequences taken by multiple video cameras.

关键词： Layout Cameras Video sequences Electrical capacitance tomography Lighting Spatial resolution Pixel computer science Space stations Image resolution

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Degeneracies, dependencies and their implications in multi-body and multi-sequence factorizations

Degeneracies, dependencies and their implications in multi-b...

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Conference on computer Vision and Pattern Recognition (CVPR)

作者： L. Zelnik-Manor M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

The body of work on multi-body factorization separates between objects whose motions are independent. In this work we show that in many cases objects moving with different 3D motions will be captured as a single object using these approaches. We analyze what causes these degeneracies between objects and suggest an approach for overcoming some of them. We further show that in the case of multiple sequences linear dependencies can supply information for temporal synchronization of sequences and for spatial matching of points across sequences.

关键词： Layout Character generation Cameras Shape Bismuth computer science Subspace constraints Video sequences Stacking

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Space-time video completion

Space-time video completion

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Conference on computer Vision and Pattern Recognition (CVPR)

作者： Y. Wexler E. Shechtman M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

We present a method for space-time completion of large space-time "holes" in video sequences of complex dynamic scenes. The missing portions are filled-in by sampling spatio-temporal patches from the available parts of the video, while enforcing global spatio-temporal consistency between all patches in and around the hole. This is obtained by posing the task of video completion and synthesis as a global optimization problem with a well-defined objective function. The consistent completion of static scene parts simultaneously with dynamic behaviors leads to realistic looking video sequences. Space-time video completion is useful for a variety of tasks, including, but not limited to: (i) Sophisticated video removal (of undesired static or dynamic objects) by completing the appropriate static or dynamic background information, (ii) Correction of missing/corrupted video frames in old movies, and (iii) Synthesis of new video frames to add a visual story, modify it, or generate a new one. Some examples of these are shown in the paper.

关键词： Video sequences Layout Sampling methods computer science Motion pictures Laboratories Constraint optimization Image texture Filling Heuristic algorithms

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Foundations of e-Democracy

arXiv

引用

arXiv 2017年

作者： Shapiro, Ehud Department of Computer Science & Applied Math Weizmann Institute of Science Rehovot Israel

The Internet revolution of democracy, which will transform earthly representative democracies by employing the communication and collaboration capabilities of the Internet, has yet to come. Here, we enlist the wisdom of our forefathers to lead the way. By consulting the 1789 Declaration of the Rights of Man and of the Citizen, we distill core values of democracy and derive from them requirements for the foundations of e-democracy. Building these foundations can usher the urgently-needed revolution of democracy. Copyright © 2017, The Authors. All rights reserved.

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Event-based analysis of video

Event-based analysis of video

引用

Conference on computer Vision and Pattern Recognition (CVPR)

作者： L. Zelnik-Manor M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

ISBN: (纸本)0769512720

Dynamic events can be regarded as long-term temporal objects, which are characterized by spatio-temporal features at multiple temporal scales. Based on this, we design a simple statistical distance measure between video sequences (possibly of different lengths) based on their behavioral content. This measure is non-parametric and can thus handle a wide range of dynamic events. We use this measure for isolating and clustering events within long continuous video sequences. This is done without prior knowledge of the types of events, their models, or their temporal extent. An outcome of such a clustering process is a temporal segmentation of long video sequences into event-consistent sub-sequences, and their grouping into event-consistent clusters. Our event representation and associated distance measure can also be used for event-based indexing into long video sequences, even when only one short example-clip is available. However, when multiple example-clips of the same event are available (either as a result of the clustering process, or given manually), these can be used to refine the event representation, the associated distance measure, and accordingly the quality of the detection and clustering process.

关键词： Video sequences Motion pictures Length measurement Dynamic range Indexing Information analysis Parametric statistics Stochastic processes computer science Event detection

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Alignment of non-overlapping sequences

Alignment of non-overlapping sequences

引用

International Conference on computer Vision (ICCV)

作者： Y. Caspi M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

ISBN: (纸本)0769511430

This paper shows how two image sequences that have no spatial overlap between their fields of view can be aligned both in time and in space. Such alignment is possible when the two cameras are attached closely together and are moved jointly in space. The common motion induces "similar" changes over time within the two sequences. This correlated temporal behavior is used to recover the spatial and temporal transformations between the two sequences. The requirement of "coherent appearance" in standard image alignment techniques is therefore replaced by "coherent temporal behavior", which is often easier to satisfy. This approach to alignment can be used not only for aligning nan-overlapping sequences, but also for handling other cases that are inherently difficult for standard image alignment techniques. We demonstrate applications of this approach to three real-world problems: (i) alignment of non-overlapping sequences for generating wide-screen movies, (ii) alignment of images (sequences) obtained at significantly different zooms, for surveillance applications, and (iii) multi-sensor image alignment for multi-sensor fusion.

关键词： Cameras Image sequences Layout Robot vision systems computer science Motion pictures Surveillance Hardware

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