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.
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.
7357174
On the design and quantification of privacy preserving data mining algorithms
The increasing ability to track and collect large amounts of data with the use of current hardware technology has lead to an interest in the development of data mining algorithms which preserve user privacy. A recently proposed technique addresses the issue of privacy preservation by perturbing the data and reconstructing distributions at an aggregate level in order to perform the mining. This method is able to retain privacy while accessing the information implicit in the original attributes. The distribution reconstruction process naturally leads to some loss of information which is acceptable in many practical situations. This paper discusses an Expectation Maximization (EM) algorithm for distribution reconstruction which is more effective than the currently available method in terms of the level of information loss. Specifically, we prove that the EM algorithm converges to the maximum likelihood estimate of the original distribution based on the perturbed data. We show that when a large amount of data is available, the EM algorithm provides robust estimates of the original distribution. We propose metrics for quantification and measurement of privacy-preserving data mining algorithms. Thus, this paper provides the foundations for measurement of the effectiveness of privacy preserving data mining algorithms. Our privacy metrics illustrate some interesting results on the relative effectiveness of different perturbing distributions.
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.
11059176
Policy-based validation of SAN configuration
Historically, storage has been directly connected to servers for fast local access and easy configuration. In recent years, storage area networks (SANs) have defined an alternative storage paradigm that allows storage to be shared among servers using fast interconnects. One of the key challenges of SAN management is the large number of configuration problems that are encountered in a typical SAN deployment. These configuration problems can be addressed by SAN management software. However, hard-coding the SAN configuration rules into the management software is not a viable option since it is not possible to easily modify or replace old configuration rules and specify new policies and guidelines. In this paper, we propose a novel policy-based SAN configuration validation system that can be used to specify, store, and evaluate configuration policies for SANs. We also introduce five new operators for collection policies that are useful for evaluating a wide variety of practical SAN configuration policies found in practice. The policy-based SAN configuration checking approach proposed in this paper is discussed within the context of device interoperability constraints. However, this approach is extensible as it can also be used to enforce performance, reliability, and security-related configuration constraints.
59852137
Energy Efficient Session Key Establishment in Wireless Sensor Networks
Key distribution and management is the foundation of any secure services of wireless sensor networks. Due to the resource constraints, establishing cryptographic keys between communicating sensors in large-scale wireless sensor networks is a big challenge. Traditional asymmetric key cryptography is not suitable for wireless sensor environment because of its complexity. Based on the polynomial-key pre-distribution scheme, an improved session key establishment method is proposed in this paper. Compared with existing key distribution schemes, our proposed scheme has lower energy consumption, less key storage and lower communication overheads as well as better network resilience against node capture attacks.
11667524
A Novel Technique for Computing Negabinary Squares
A novel technique for computing squares of negabinary numbers is described in this correspondence. The basic principle is to use an arithmetic algorithm normally utilized for the square-root operation. Asuitable recursive combinations are shown to reduce the problem of obtaining the square of "n" bit number to the addition of [n/3] operands and the change of sign in the last step is shown to be helpful in reducing the hardware. One way for further improvement is also suggested.
22896366
Design and Performance of Generalized Interconnection Networks
This paper introduces a general class of self-routing interconnection networks for tightly coupled multiprocessor systems. The proposed network, named a "generalized shuffle network (GSN)," is based on a new interconnection pattern called a generalized shuffle and is capable of connecting any number of processors M to any number of memory modules N. The technique results in a variety of interconnection networks depending on how M nd N are factored. The network covers a broad spectrum of interconnections, starting from shared bus to crossbar switches and also includes various multistage interconnection networks (MIN's).
37780110
A Duplication Based Compile Time Scheduling Method for Task Parallelism
The cost of inter-processor communication is one of the major bottlenecks of a distributed memory machine (DMM) which can be offset with efficient algorithms for task partitioning and scheduling. Based on the data dependencies, the task partitioning algorithm partitions the application program into tasks and represents them in the form of a directed acyclic graph (DAG) or in compiler intermediate forms. The scheduling algorithm schedules the tasks onto individual processors of the DMM in an effort to lower the overall parallel time. It has been long proven that obtaining an optimal schedule for a generic DAG is an NP-hard problem. This chapter presents a Scalable Task Duplication based Scheduling (STDS) algorithm which can schedule the tasks of a DAG with a worst case complexity of O(|v|2), where v is the set of tasks of the DAG. STDS algorithm generates an optimal schedule for a certain class of DAGs which satisfy a Cost Relationship Condition (CRC), provided the required number of processors are available. In case the required number of processors are not available the algorithm scales the schedule down to the available number of processors. The performance of the scheduling algorithm has been evaluated by its application to practical DAGs and by comparing the parallel time of the schedule generated against the absolute or the theoretical lowerbound.
19483456
Performance evaluation for IEEE 802.11e enhanced distributed coordination function
The IEEE 802.11e working group aims to enhance the current 802.11 medium access control (MAC) to support integrated data and voice (or video) communications. Till now, a draft of the IEEE 802.11e enhanced distributed coordination function (EDCF) has been proposed. In the literature, there is very limited analysis about EDCF since it is a new protocol, and most related work are only confined to simulation or saturation state. In this paper, we evaluate the performance of EDCF by dividing the traffic into two groups, namely real-time packets and non-real-time packets, and use an analytical model to quantify the performance of both IFS priority and contention window (CW) priority in the EDCF. In our analysis, we assume that the traffic arrival is a Poisson process. We provide a queue model for EDCF. Since there are multiple stations contending for one channel in the system, the queue model for EDCF cannot be a regular M/G/1 model. We redefine the service time and the waiting time so that we can still use M/G/1 model in the analysis. To validate the accuracy of our analytical results, we have done extensive simulations and we observed that EDCF does provide service differentiation between different traffic categories. But due to the inherent contention characteristic of carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol, the delay cannot be guaranteed, even for the highest priority traffic. A lot more work needs to be done for the MAC protocol to effectively support service differentiation in the future. Copyright © 2004 John Wiley & Sons, Ltd.