6124477
A counterexample to a Voronoi region conjecture
Given a 2D-symmetric lattice /spl Lambda/, it was conjectured by Forney (1989) that the projection of the Voronoi region R(/spl Lambda/) onto two coordinates equals the Voronoi region of the constituent 2D-sublattice /spl Lambda//spl nu//sub 2/. We present a three-dimensional counterexample. >
15003245
Probabilistic treatment of MIXes to hamper traffic analysis
The goal of anonymity providing techniques is to preserve the privacy of users, who has communicated with whom, for how long, and from which location, by hiding traffic information. This is accomplished by organizing additional traffic to conceal particular communication relationships and by embedding the sender and receiver of a message in their respective anonymity sets. If the number of overall participants is greater than the size of the anonymity set and if the anonymity set changes with time due to unsynchronized participants, then the anonymity technique becomes prone to traffic analysis attacks. We are interested in the statistical properties of the disclosure attack, a newly suggested traffic analysis attack on the MIXes. Our goal is to provide analytical estimates of the number of observations required by the disclosure attack and to identify fundamental (but avoidable) 'weak operational modes' of the MIXes and thus to protect users against a traffic analysis by the disclosure attack.
45546568
Multi-channel Attacks
We introduce multi-channel attacks, i.e., side-channel attacks which utilize multiple side-channels such as power and EM simultaneously. We propose an adversarial model which combines a CMOS leakage model and the maximum-likelihood principle for performing and analyzing such attacks. This model is essential for deriving the optimal and very often counter-intuitive techniques for channel selection and data analysis. We show that using multiple channels is better for template attacks by experimentally showing a three-fold reduction in the error probability. Developing sound countermeasures against multi-channel attacks requires a rigorous leakage assessment methodology. Under suitable assumptions and approximations, our model also yields a practical assessment methodology for net information leakage from the power and all available EM channels in constrained devices such as chip-cards. Classical DPA/DEMA style attacks assume an adversary weaker than that of our model. For this adversary, we apply the maximum-likelihood principle to such design new and more efficient single and multiple-channel DPA/DEMA attacks.
43442738
The turbo decoding algorithm and its phase trajectories
This paper analyzes phase trajectories and fixed points of the turbo decoding algorithm as a function of the signal-to-noise ratio (SNR). By exploiting the large length of turbo codes, the turbo decoding algorithm is treated as a single-parameter dynamical system, parameterized (approximately) by the SNR. This parameterization, along "with" extensive simulations at practical SNRs and asymptotic analysis as SNR goes to zero and infinity, is used to subdivide the entire SNR range into three regions with the "waterfall region" in the middle. The turbo decoding algorithm has distinctive phase trajectories and convergence properties in these three SNR regions. This paper also investigates existence and properties of fixed points in these SNR regions. The main fixed points of the turbo decoding algorithm are classified into two categories. In a wide range of SNRs (corresponding to bit-error rates less than 10/sup -1/), the decoding algorithm has "unequivocal" fixed points which correspond to mostly correct decisions on the information bits. Within this range, toward the lower values of SNR, there is another fixed point which corresponds to many erroneous decision on the information bits. Fixed points of this type are referred to as "indecisive" fixed points. It turns out that the indecisive fixed points bifurcate and disappear for SNRs in the waterfall region. This paper associates the qualitative transition of phase trajectories in the waterfall region to the bifurcation of indecisive fixed points. These bifurcations also explain empirically observed quasi-periodic and periodic phase trajectories of the turbo decoding algorithm.
14060994
On nearest neighbor indexing of nonlinear trajectories
In recent years, the problem of indexing mobile objects has assumed great importance because of its relevance to a wide variety of applications. Most previous results in this area have proposed indexing schemes for objects with linear trajectories in one or two dimensions. In this paper, we present methods for indexing objects with nonlinear trajectories. Specifically, we identify a useful condition called the convex hull property and show that any trajectory satisfying this condition can be indexed by storing a careful representation of these objects in a traditional index structure. Since a wide variety of relevant nonlinear trajectories satisfy this condition, our result significantly expands the class of trajectories for which nearest neighbor indexing schemes can be devised. We also show that even though many non-linear trajectories do not satisfy the convex hull condition, an approximate representation can often be found which satisfies it. We discuss examples of techniques which can be utilized to find representations that satisfy the convex hull property. We present empirical results to demonstrate the effectiveness of our indexing method.
9570200
Templates as Master Keys
We introduce two new attacks: the single-bit template attack and the template-enhanced DPA attack. The single-bit template attack can be used very effectively to classify even single bits in a single side channel sample with a high probability of correctness. The template-enhanced DPA attack, combines traditional DPA with single-bit template attacks to show that if an adversary has access to a test card with even a slightly biased RNG, then he/she can break protected cryptographic implementations on a target card even if they have perfect RNGs. In support of our claim, we report results from experiments on breaking two implementations of DES and AES protected by the masking countermeasure running on smartcards of different manufacturers. 
 
In light of these results, the threat of template attacks, generally viewed as intrinsically difficult to mount, needs to be reconsidered.
43408451
Network Intrusion Detection System Using Random Projection Technique
12552557
Minimizing the effect of deafness and hidden terminal problem in wireless ad hoc networks using directional antennas
In this work we addresses the issue of deafness and hidden terminal problem in Mobile Ad Hoc Networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) 5 which employs a novel Enhanced Directional Network Allocation Vector (EDNAV) scheme and, and an efficient technique of Diametrically Opposite Directions (DOD) transmission of RTS and CTS. We compare MDA with IEEE 802.11 and two recently proposed directional MAC schemes and results show that MDA outperforms these protocols in the majority of scenarios investigated. We also point out that the performance does depend on the network topology and the traffic pattern.
12069872
A Pipelined Pseudoparallel System Architecture for Real-Time Dynamic Scene Analysis
In this paper we introduce the concept of pseudoparallelism, in which the serial algorithm is partitioned into several noninteractive independent subtasks so that parallelism can be used within each subtask level. This approach is illustrated by applying it to a real-time dynamic scene analysis. Complete details of such a pseudoparallel architecture with an emphasis to avoid interprocessor communications have been worked out. Problems encountered in the course of designing such a system with a distributed operating system (no master control) have been outlined and necessary justifications have been provided. A scheme indicating various memory modules, processing elements, and their data-path requirements is included and ways to provide continuous flow of partitioned information in the form of a synchronized pipeline are described.
11725951
Strategies for enhancing routing security in protocols for mobile ad hoc networks
Mobile ad hoc network (MANET) is a new emerging field with its potential applications in extremely unpredictable and dynamic environments. These characteristics require the networks to have much harder security requirements than the contemporary networks. While current routing protocols do seem to adjust well to dynamically changing conditions, they offer either no security mechanisms at all or have only partial solutions for ensuring the correct routing. It is hard to simultaneously achieve both security and robustness in the routing protocols. In this paper, we analyze various possible threats to the routing protocols and introduce strategies to address the same. On one hand, routing protocol can be disrupted due to attacks from intruder nodes that do not belong to the network. On the other hand, routing is severely affected by the presence of compromised nodes that inflict unpredictable and undetectable Byzantine failure. We have addressed the issue of attacks from intruders by means of authentication techniques that rely on mutual trust between nodes. We also study the behavioral patterns of the nodes and isolate compromised nodes using a distributed approach. The effectiveness of our schemes is illustrated by means of extensive simulations using ns-2 simulator. The routing protocol chosen for the study is AODV. We have observed the performance of the network with and without our secured routing scheme.
206414100
Parameters for System Effectiveness Evaluation of Distributed Systems
In a Distributed Computing System (DCS), the failure of one or more system components causes the degradation in its effectiveness to complete a given task as opposed to a complete network breakdown. This paper addresses the issue of degraded system effectiveness evaluation by introducing two static measures, namely, Distributed Program Performance Index (DPPI) and Distributed System Performance Index (DSPI). These metrics can be used to compare networks with different features for application execution. It can be used to determine if the network with high reliability and low capacity, or low reliability and high capacity is better for a given program execution. An algorithm is also developed for computing these indices, and it is shown to be not only efficient, but general enough to compute many other existing measures such as computer networks, distributed systems, transaction based systems, etc.