Showing papers by "Technion – Israel Institute of Technology published in 1987"

How to play ANY mental game

Abstract: We present a polynomial-time algorithm that, given as a input the description of a game with incomplete information and any number of players, produces a protocol for playing the game that leaks no partial information, provided the majority of the players is honest. Our algorithm automatically solves all the multi-party protocol problems addressed in complexity-based cryptography during the last 10 years. It actually is a completeness theorem for the class of distributed protocols with honest majority. Such completeness theorem is optimal in the sense that, if the majority of the players is not honest, some protocol problems have no efficient solution [C].

Towards a theory of software protection and simulation by oblivious RAMs

Abstract: Software protection is one of the most important issues concerning computer practice. There exist many heuristics and ad-hoc methods for protection, but the problem as a whole has not received the theoretical treatment it deserves. In this paper, we make the first steps towards a theoretic treatment of software protection: First, we distill and formulate the key problem of learning about a program from its execution. Second, assuming the existence of one-way permutations, we present an efficient way of executing programs such that it is infeasible to learn anything about the program by monitoring its executions. How can one efficiently execute programs without allowing an adversary, monitoring the execution, to learn anything about the program? Traditional cryptographic techniques can be applied to keep the contents of the memory unknown throughout the execution, but are not applicable to the problem of hiding the access pattern. The problem of hiding the access pattern efficiently corresponds to efficient simulation of Random Access Machines (RAM) on an oblivious RAM. We define an oblivious RAM to be a (probabilistic) RAM for which (the distribution of) the memory access pattern is independent of the input. We present an (on-line) simulation of t steps of an arbitrary RAM with m memory cells, by less than t·me steps of an oblivious RAM with 2m memory cells, where e>0 is an arbitrary constant.

Simultaneous determination of production cycle and inspection schedules in a production system

Abstract: Classical Economic Manufacturing Quantity EMQ models have usually ignored the possibility of process deterioration and the existence of defective items in the production lot. Moreover, the use of machine inspection for maintenance and restoration purposes has not been considered. On the other hand, past studies on maintenance models do not consider the length of a production run to be a decision variable. This paper addresses the problem of joint control of production cycles or manufacturing quantities and maintenance by inspection. A simple relationship has been developed to determine the effectiveness of maintenance by inspection. Furthermore, when maintenance by inspection is adopted, it is shown that the optimal inspection intervals are equally-spaced. The problem of simultaneous determination of EMQ and the inspection schedules is solved by using an approximation to the cost function. The resulting EMQ is found to be an adjustment to the classical EMQ. Finally, the relationships between different parameter values and the magnitudes of the cost penalty for using the classical EMQ are examined.

Group-invariant solutions of differential equations

Abstract: We introduce the concept of a weak symmetry group of a system of partial differential equations, that generalizes the “nonclassical” method introduced by Bluman and Cole for finding group-invariant...

Double phase-conjugate mirror: analysis, demonstration, and applications.

Abstract: We report on the operation of the double phase-conjugate mirror (DPCM). Two inputs to opposite sides of a photorefractive barium titanate crystal, which may carry different spatial images, are shown to pump the same four-wave mixing process mutually and are self-refracted without any external or internal crystal surface. This results in the phase-conjugate reproduction of the two images simultaneously. This device is analyzed theoretically, and applications in image processing, interferometry, and rotation sensing are discussed. We also demonstrate the operation of a ring laser, using the DPCM, as well as a photorefractive resonator with two facing DPCM’s that can support spatial information in its oscillations.

Amplitude and phase modes in trans -polyacetylene: Resonant Raman scattering and induced infrared activity

Abstract: The resonant Raman scattering (RRS) from the three ${A}_{g}$ modes of trans-polyacetylene and the charged-induced ir modes are analyzed with use of the amplitude- and phase-mode theories. It is shown that the observed phonon frequencies and the relative intensities of all modes obtained at various laser excitation energies \ensuremath{\Elzxh}${\ensuremath{\omega}}_{L}$ is accounted for by a single phonon propagator which also describes the charge-induced infrared-active modes. The dispersion of the RRS frequencies with \ensuremath{\Elzxh}${\ensuremath{\omega}}_{L}$ exhibits inhomogeneity of the sample which in turn provides the functional dependence of the \ensuremath{\pi}-electron gap ${E}_{g}$ on an effective coupling parameter \ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{}. We show that inhomogeneity in both the electron-phonon and the electron-electron interaction parameters yields inhomogeneity in \ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{}. The experimental gap-versus-\ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{} relation is consistent with the Peierls model but allows for weak electron-electron interactions which enhance the gap. We propose a method by which the distribution in \ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{}, P(\ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{}), is directly derived from the experimental spectra. It appears that different samples show different breadth for the distribution function; samples with sharper RRS features have narrower P(\ensuremath{\lambda}\ifmmode \tilde{}\else \~{}\fi{}). We give an experimental estimate of the \ensuremath{\sigma}-bond contribution to the force constant of the carbon-carbon stretching mode and the electron-phonon interaction parameter. The pinning parameter of the charged carriers and its distribution are derived directly from the infrared absorption spectra induced either by doping or by photogeneration. The pinning of the doping-induced carriers is stronger and its distribution is wider; giving thus rise to the broader lines in the doping-induced infrared spectra. The mass of the photogenerated solitons is estimated from the relative strength of the infrared spectra and is approximately equal to the band effective mass of the electrons.

Is construction project planning really doing its job? A critical examination of focus, role and process

Abstract: There is growing concern over the failure of construction planning to achieve its goals in spite of the considerable resources allocated to it. Deficient planning techniques are commonly blamed for this state. This view is challenged here following analyses of observations and studies by researchers and practitioners. The paper discusses normative planning vis a vis a deficient reality, and its probable causes. Planning effectiveness can be expected only after management modifies planning policy and prevailing practices are fundamentally changed. Future research should address planning from a wider, holistic perspective to include organizational, human and information-handling aspects, in addition to planning techniques as such.

Extrapolation methods for vector sequences

Abstract: This paper derives, describes, and compares five extrapolation methods for accelerating convergence of vector sequences or transforming divergent vector sequences to convergent ones. These methods are the scalar epsilon algorithm (SEA), vector epsilon algorithm (VEA), topological epsilon algorithm (TEA), minimal polynomial extrapolation (MPE), and reduced rank extrapolation (RRE). MPE and RRE are first derived and proven to give the exact solution for the right 'essential degree' k. Then, Brezinski's (1975) generalization of the Shanks-Schmidt transform is presented; the generalized form leads from systems of equations to TEA. The necessary connections are then made with SEA and VEA. The algorithms are extended to the nonlinear case by cycling, the error analysis for MPE and VEA is sketched, and the theoretical support for quadratic convergence is discussed. Strategies for practical implementation of the methods are considered.

Decidability and expressiveness aspects of logic queries

Abstract: This paper addresses some basic problems regarding logic programming based queries over relational databases. We re-examine the query classes H and YE+ defined by Chandra and Harel [2] We define H+ and YE++ which differ from H and YE+ in that the use of equality (=) and inequality (≠) is prohibited. We show that H+ is more expressive than YE++ and that any H+ program can be transformed into an equivalent H+ program containing a single recursive predicate without using the equality or inequality operators. As a corollary we obtain a fixpoint formula characterization of H+ queries.We consider the problems of determining containment, equivalence, and satisfiability of logic based queries. The containment and equivalence problems addressed here extend the work of Aho, Sagiv and Ullman on relational queries [1] and Papadimitrious on Prolog [10]. As corollaries we show that determining safety and literal redundancy are both undecidable problems.

First Mover Disadvantages with Private Information

Abstract: We consider a leader-follower game with output quantities as strategies, so as to demonstrate the reduced advantages of the Stackleberg leader in a stochastic environment with private information. At the equilibrium, the strategy of the leader reveals to the follower information about the demand. In an attempt to signal low demand, the leader contracts his output. Nevertheless, unless the leader's information is infinitely noisy, the follower can always correctly infer his signal. We find a wide range of parameter values over which the follower is better off compared to the leader.

Adiabatic theorems and applications to the quantum hall effect

Abstract: We study an adiabatic evolution that approximates the physical dynamics and describes a natural parallel transport in spectral subspaces. Using this we prove two folk theorems about the adiabatic limit of quantum mechanics: 1. For slow time variation of the Hamiltonian, the time evolution reduces to spectral subspaces bordered by gaps. 2. The eventual tunneling out of such spectral subspaces is smaller than any inverse power of the time scale if the Hamiltonian varies infinitly smoothly over a finite interval. Except for the existence of gaps, no assumptions are made on the nature of the spectrum. We apply these results to charge transport in quantum Hall Hamiltonians and prove that the flux averaged charge transport is an integer in the adiabatic limit.

On the time-complexity of broadcast in radio networks: an exponential gap between determinism randomization

Abstract: The time-complexity of deterministic and randomized protocols for achieving broadcast (distributing a message from a source to all other nodes) in arbitrary multi-hop radio networks is investigated. In many such networks, communication takes place in synchronous time-slots. A processor receives a message at a certain time-slot if exactly one of its neighbors transmits at that time-slot. We assume no collision-detection mechanism; i.e., it is not always possible to distinguish the case where no neighbor transmits from the case where several neighbors transmit simultaneously. We present a randomized protocol that achieves broadcast in time which is optimal up to a logarithmic factor. In particular, with probability 1 --E, the protocol achieves broadcast within O((D + log n/s) ‘log n) time-slots, where n is the number of processors in the network and D its diameter. On the other hand, we prove a linear lower bound on the deterministic time-complexity of broadcast in this model. Namely, we show that any deterministic broadcast protocol requires 8(n) time-slots, even if the network has diameter 3, and n is known to all processors. These two results demonstrate an exponential gap in complexity between randomization and determinism. l i ‘ 1992 Academic press, IX

An algorithm to find maximal state constraint sets for discrete-time linear dynamical systems with bounded controls and states

Abstract: An algorithm to find a polyhedral approximant to the maximal state constraint set, given state and input bounds, is suggested for linear discrete-time dynamical systems.

Analysis of electromagnetic scattering from dielectric cylinders using a multifilament current model

Abstract: A moment solution is presented for the problem of transverse magnetic (TM) scattering from homogeneous dielectric cylinders. The moment solution uses fictitious filamentary currents to simulate both the field scattered by the cylinder and the field inside the cylinder and in turn point-matches the continuity conditions for the tangential components of the electric and magnetic fields across the cylinder surface. The procedure is simple to execute and is general in that cylinders of arbitrary shape and complex permittivity can be handled effectively. Metallic cylinders are treated as reduced cases of the general procedure. Results are given and compared with available analytic solutions, which demonstrate the very good performance of the procedure.

How to Solve any Protocol Problem - An Efficiency Improvement (Extended Abstract)

Abstract: Consider n parties having local inputs x 1,x 2,...,x n respectively. and wishing to compute the value f(x 1,...,x n). where f is a predetermined function. Loosely speaking. an n-party protocol for this purpose has maximum privacy if whatever a subset of the users can efficiently compute when participating in the protocol, they can also compute from their local inputs and the value f(x 1,..., x n).

A robustness approach to facilities design

Abstract: The single period plant layout problem under uncertainty is discussed. Solution procedures for dealing with this problem, mainly the robustness approach, are recommended. The effectiveness of the robustness approach to this problem is illustrated by a numerical example.

Two remarks concerning the Goldwasser-Micali-Rivest signature scheme

Abstract: The focus of this note is the Goldwasser-Micali-Rivest Signature Scheme (presented in the 25th FOCS, 1984) The GMR scheme has the salient property that, unless factoring is easy, it is infeasible to forge any signature even through an adaptive chosen message attack We present two technical contributions with respect to the GMR scheme: 1) The GMR scheme can be made totally "memoryless": That is, the signature generated by the signer on message M does not depend on the previous signed messages (In the original scheme, the signature to a message depends on the number of messages signed before) 2) The GMR scheme can be implemented almost as efficiently as the RSA: The original implementation of the GMR scheme based on factoring, can be speeded-up by a factor of |N| Thus, both signing and verifying take time O (|N| 3log2 |N|) (Here N is the moduli)

The effect of fire on nutrients in a pine forest soil

Abstract: The effect of a hot summer fire on soil nutrient contents in the upper 2 cm of Aleppo pine forest with a dense woody understory was studied from September 1985 to May 1986.

Dynamics of dense lattices.

Abstract: We derive the equations governing the nonlinear dynamics of one-, two-, and three-dimensional lattices in a close to continuum condition (i.e., a dense lattice). The described method correctly captures all terms to a given order in discreteness and, unlike previous approaches, leads to well-behaved partial-differential equations for these problems. In general, the dispersion born out of discreteness counteracts the steepening of waves caused by the nonlinearity and leads to the formation of permanent nonlinear structures.

Binding of [3H]Ro 5-4864 and [3H]PK 11195 to cerebral cortex and peripheral tissues of various species: species differences and heterogeneity in peripheral benzodiazepine binding sites.

Abstract: The binding of [3H]PK 11195 and [3H]Ro 5–4864 to membrane preparations from cerebral cortex and peripheral tissues of various species was studied. [3H]PK 11195 (0.05–10 nM) bound with high affinity to rat and alf cerebral cortical and kidney membranes. [3H]Ro 5–4864 (0.05–30 nM) also successfully labeled rat cerebral cortical and kidney membranes, but in calf cerebral cortical and kidney membranes, its binding capacity was only 3 and 4%, respectively, of that of [3H]PK 11195. Displacement studies showed that unlabeled Ro 5–4864, diazepam, and flunitrazepam were much more potent in displacing [3H]PK 11195 from rat cerebral cortex and kidney membranes than from calf, tissues. The potency of unlabeled Ro 5–4864 in displacing [3H]PK 11195 from the cerebral cortex of various other species was also tested, and the rank order of potency was rat = guinea pig < cat = dog < rabbit < calf. Analysis of these displacement curves revealed that Ro 5–4864 bound to two populations of binding sites from rat and calf kidney and from rat, guinea pig, rabbit, and calf cerebral cortex but to a single population of binding sites from cat and dog cerebral cortex. Using [3H]PK 11195 as a ligand, the rank order of binding capacity in cerebral cortex of various species was cat < calf < guinea pig < rabbit < dog < rat, whereas when [3H]Ro 5–4864 was used, the rank order of binding capacity was cat < guinea pig < rat < rabbit < calf < dog. These results further demonstrate species differences of “peripheral-type” benzodiazepine binding sites and also provide evidence of their heterogeneity in the kidney of rat and calf and in the cerebral cortex of rat, guinea pig, rabbit, and calf.

Proof of Straley's argument for bootstrap percolation

Abstract: We prove thatPc=1 for bootstrap percolation with large void instabilities (in particular, ifm=3 on the square lattice).

Formation of composition-modulated alloys by electrodeposition

Abstract: A method has been developed to produce composition-modulated alloys by electrodeposition. The method was demonstrated for the copper-nickel couple. Salts of the two component metals are dissolved in a common electrolyte and the potential is alternately pulsed for fixed durations between values above and below the reduction potential of the less noble component. Co-deposition of the nobler metal into the other metal layer is diminished by setting unfavourable diffusion conditions during the more cathodic pulse. Modulation was achieved down to 0.8 nm thick layers. The resulting composition-modulated alloys were analysed by Auger spectroscopy and X-ray diffraction.

Role of arginine-tRNA in protein degradation by the ubiquitin pathway

Abstract: Degradation of intracellular proteins through the ubiquitin and ATP-dependent proteolysis pathway involves several steps. Initially, ubiquitin is covalently linked to the proteolytic substrate in an ATP-requiring reaction. Proteins marked by ubiquitin may then be selectively lysed in a reaction that also requires ATP (for reviews see refs 1-3). A major question concerns the structural features of a protein that make it a specific substrate for ubiquitin-mediated degradation. It was shown that a free alpha-NH2 group is one important feature of the protein structure recognized by the ubiquitin ligation system, and that the half-life in vivo of a protein with an exposed amino terminus depends on its amino terminal residue. We have previously demonstrated that transfer RNA (tRNA) is essential for conjugation of ubiquitin and for the subsequent degradation of proteins with acidic amino termini (aspartate or glutamate). We now show that tRNA is required for post-translational conjugation of arginine to acidic amino termini of proteins, a modification that is essential for their degradation by the ubiquitin pathway.

How to prove all NP-statements in zero-knowledge, and a methodology of cryptographic protocol design

Abstract: Under the assumption that encryption functions exist, we show that all languages in NP possess zero-knowledge proofs.That is, it is possible to demonstrate that a CNF formula is satisfiable without revealing any other property of the formula. In particular, without yielding neither a satisfying assignment nor weaker properties such as whether there is a satisfying assignment in which x1=TRUE, or whether there is a satisfying assignment in which x1=x3 etc.The above result allows us to prove two fundamental theorems in the field of (two-party and multi-party) cryptographic protocols. These theorems yield automatic and efficient transformations that, given a protocol that is correct with respect to an extremely weak adversary, output a protocol correct in the most adversarial scenario. Thus, these theorems imply powerful methodologies for developing two-party and multiparty cryptographic protocols.

Further characterisation of the extracellular matrix in the mandibular condyle in neonatal mice.

Abstract: This study provides newer information concerning the extracellular matrix of neonatal condylar cartilage--a genuine representative of a secondary type of cartilage. In addition, the data presented hereby indicate that the condylar cartilage contains a population of progenitor cells that synthesise Type I collagen rather than Type II. Under normal conditions in vivo local biomechanical factors influence the progenitor cells to differentiate into cartilage cells and thereby to shift their synthetic pathway from Type I collagen to Type II collagen--the typical collagen of cartilage extracellular matrix. In the absence of such biomechanical effects the condylar progenitor cells seem to proceed with their inherent differentiation pathway and express an osteogenic phenotype (Fig. 21).