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Information Theory Workshop (ITW), 2012 IEEE

Date 3-7 Sept. 2012

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Displaying Results 1 - 25 of 141
  • Index

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    Freely Available from IEEE
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  • An information-theoretic protocol compiler

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (277 KB) |  | HTML iconHTML  

    One of the most fundamental goals in cryptography is to design protocols that remain secure when adversarial participants can engage in arbitrary malicious behavior. In 1986, Goldreich, Micali, and Wigderson presented a powerful paradigm for designing such protocols: their approach reduced the task of designing secure protocols to designing protocols that only guarantee security against “honest-but-curious” participants. By making use of zero-knowledge proofs, the GMW paradigm enforces honest behavior without compromising secrecy. Over the past two decades, this approach has been the dominant paradigm for cryptographic protocol design, based on zero-knowledge protocols based on computational hardness assumptions. In this work, we describe a new general paradigm/protocol compiler for secure protocol design known as the IPS compiler, that departs considerably from the GMW framework, and provides a method for obtaining efficient protocols with information-theoretic security guarantees in settings where appropriate channels exist. This new approach also reduces the task of designing secure protocols to designing protocols that only guarantee security against honest-but-curious participants. However, the new approach avoids the use of zero-knowledge proofs, and instead makes use of multi-party protocols in a much simpler setting - where the majority of participants are completely honest (such multi-party protocols can exist with information-theoretic security guarantees without assuming any special channels). The IPS paradigm yields protocols that rely on Oblivious Transfer channels (OT) as a building block. This offers a number of advantages in generality and efficiency. In contrast to the GMW paradigm, by avoiding the use of zero-knowledge proofs, the IPS paradigm is able to treat all of its building blocks as “black boxes”. This allows improvement over previous results in the area of secure computation. In particular, the IPS compiler - ields conceptually simpler and more efficient ways for basing unconditionally secure cryptography on OT and other noisy channels; more efficient protocols for generating a large number of OTs using a small number of OTs; and secure and efficient protocols which only make a blackbox use of cryptographic primitives or underlying algebraic structures in settings where no such protocols were known before. View full abstract»

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  • To code or not to code: Revisited

    Page(s): 5 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    We revisit the dilemma of whether one should or should not code when operating under delay constraints. In those curious cases when the source and the channel are probabilistically matched so that symbol-by-symbol coding is optimal in terms of the average distortion achieved, we show that it also achieves the dispersion of joint source-channel coding. Moreover, even in the absence of such probabilistic matching between the source and the channel, symbol-by-symbol transmission, though asymptotically suboptimal, might outperform not only separate source-channel coding but also the best known random-coding joint source-channel coding achievability bound in the finite blocklength regime. View full abstract»

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  • Results on combinatorial joint source-channel coding

    Page(s): 10 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    This paper continues the investigation of the combinatorial formulation of the joint source-channel coding problem. In particular, the connections are drawn to error-reducing codes, isometric embeddings and list-decodable codes. The optimal performance for the repetition construction is derived and is shown to be achievable by low complexity Markov decoders. The compound variation of the problem is proposed and some initial results are put forward. View full abstract»

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  • On uncoded transmission and blocklength

    Page(s): 15 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (461 KB) |  | HTML iconHTML  

    This work considers the definition of the excess-distortion exponent, used to measure the asymptotic finite blocklength behavior of joint source-channel coding. We arrive at the conclusion that it is not a meaningful measure for the operational tradeoffs of a scheme. We propose a new definition, which makes a distinction between the processing block of the coding scheme (which implies delay and may be connected to complexity), the fidelity blocklength (reflecting the quality of the reconstruction as required by the application), and the resource blocklength (depending on hardware or shared medium considerations). As an aside, the exponent of uncoded schemes is analyzed. This results in finding the joint source-channel coding excess-distortion exponent in some cases where it was not known previously. View full abstract»

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  • Reduced complexity window decoding schedules for coupled LDPC codes

    Page(s): 20 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1592 KB) |  | HTML iconHTML  

    Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison. View full abstract»

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  • A simple proof of threshold saturation for coupled vector recursions

    Page(s): 25 - 29
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    Convolutional low-density parity-check (LDPC) codes (or spatially-coupled codes) have now been shown to achieve capacity on binary-input memoryless symmetric channels. The principle behind this surprising result is the threshold-saturation phenomenon, which is defined by the belief-propagation threshold of the spatially-coupled ensemble saturating to a fundamental threshold defined by the uncoupled system. Previously, the authors demonstrated that potential functions can be used to provide a simple proof of threshold saturation for coupled scalar recursions. In this paper, we present a simple proof of threshold saturation that applies to a wide class of coupled vector recursions. The conditions of the theorem are verified for the density-evolution equations of: (i) joint decoding of irregular LDPC codes for a Slepian-Wolf problem with erasures, (ii) joint decoding of irregular LDPC codes on an erasure multiple-access channel, and (iii) admissible protograph codes on the BEC. This proves threshold saturation for these systems. View full abstract»

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  • Efficient termination of spatially-coupled codes

    Page(s): 30 - 34
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    Spatially-coupled low-density parity-check codes attract much attention due to their capacity-achieving performance and a memory-efficient sliding-window decoding algorithm. On the other hand, the encoder needs to solve large linear equations to terminate the encoding process. In this paper, we propose modified spatially-coupled codes. The modified (dl, dr, L) codes have less rate-loss, i.e., higher coding rate, and have the same threshold as (dl, dr, L) codes and are efficiently terminable by using an accumulator. View full abstract»

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  • Common randomness amplification: A constructive view

    Page(s): 35 - 39
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    Common randomness is an important resource in many areas such as game theory and cryptography. We discuss the general problem of common randomness amplification between two distrustful parties connected by a communication channel and sharing some initial randomness. In this setting, both parties wish to agree on a common value distributed according to a target distribution by using their initial amount of common randomness and exchanging messages. Our results show that no protocol which is secure in a composable sense can significantly amplify the entropy initially shared by the parties. View full abstract»

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  • Scheduling with privacy constraints

    Page(s): 40 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB) |  | HTML iconHTML  

    In multi-tasking systems where a finite resource is to be shared, a scheduler dictates how the resource is divided among competing processes. Examples of systems which have schedulers include, a computer where the CPU needs to be shared between the different threads running, a cloud computing infrastructure with shared computing resources, a network router serving packets from different streams etc. In such situations, when a processor is shared by multiple users, the delays experienced by jobs from one user are a function of the arrival pattern of jobs from other users, and the scheduling policy of the server. Consequently, a scheduling system creates a timing side channel in which information about arrival pattern from one user is inadvertently leaked to another. In this work, this information leakage is studied for a two user scheduling system. We first introduce a measure of privacy and then demonstrate that no scheduler can provide maximum privacy without idling/taking vacations, and consequently no policy can simultaneously be delay and privacy optimal. View full abstract»

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  • A new achievable region for Gaussian multiple descriptions based on subset typicality

    Page(s): 45 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    This paper addresses the L-channel multiple descriptions problem for a Gaussian source under mean squared error (MSE) distortion metric. We focus on particular cross-sections of the general rate-distortion region where a subset the 2L - 1 distortion constraints are not imposed. Specifically, we assume that certain descriptions are never received simultaneously at the decoder and thereby the transmitted codewords require joint typicality only within prescribed subsets. We derive a new encoding scheme and an associated rate-distortion region wherein joint typicality of codewords only within the prescribed subsets is maintained. We show that enforcing joint typicality of all the codewords entails strict suboptimality in the achievable rate-distortion region. Specifically, we consider a 3 descriptions scenario wherein descriptions 1 and 3 are never received simultaneously at the decoder and show that a strictly larger achievable region is obtained when the encoder maintains joint typicality of codewords only within the required subsets. To prove these results, we derive a lemma called the `subset typicality lemma' which plays a critical role in establishing the new achievable region. View full abstract»

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  • On transmission of multiple Gaussian sources over a Gaussian MAC using a VQLC mapping

    Page(s): 50 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    In this paper we generalize an existing distributed zero-delay joint source-channel coding scheme for communication of a multivariate Gaussian on a Gaussian Multiple Access Channel named Distributed Quantization Linear Coder (DQLC) to arbitrary code length. Although the DQLC is well performing, it leaves a certain gap to the performance upper bound (or distortion lower bound) based on arbitrary code length. The purpose of this paper is to determine if the generalization of the DQLC to arbitrary code length, named Vector Quantization Linear Coder (VQLC), can close the gap to the bound when the code length is large. Our results show that the VQLC mapping has the potential to reach the upper bound for any number of Gaussian sources at high SNR when the sources are uncorrelated. We also approximately determine the VQLC performance as a function of code length for the special case of two sources. View full abstract»

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  • Source coding with conditionally less noisy side information

    Page(s): 55 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We consider a lossless multi-terminal source coding problem with one transmitter, two receivers and side information. The achievable rate region of the problem is not well understood. In this paper, we characterise the rate region when the side information at one receiver is conditionally less noisy than the side information at the other, given this other receiver's desired source. The conditionally less noisy definition includes degraded side information and a common message as special cases, and it is motivated by the concept of less noisy broadcast channels. The key contribution of the paper is a new converse theorem employing a telescoping identity and the Csiszár sum identity. View full abstract»

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  • On the role of deterministic models in K × K × K wireless networks

    Page(s): 60 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB) |  | HTML iconHTML  

    This paper establishes a connection between the capacity region of the K × K × K wireless network under the AWGN channel model and under a truncated deterministic channel model, which allows any outer bound on the capacity region of the truncated network to be translated into an outer bound on the capacity region of the AWGN network. The result is obtained through the utilization of a recent worst-case noise theorem [1], which shows that perturbing the noise distribution in AWGN networks only increases the capacity region. View full abstract»

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  • Proof of the outage probability conjecture for MISO channels

    Page(s): 65 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    It is conjectured in [6] that the covariance matrices minimizing the outage probability under a power constraint for MIMO channels with Gaussian fading are diagonal with either zeros or constant values on the diagonal. In the MISO setting, this is equivalent to conjecture that the Gaussian quadratic forms having largest tail probability correspond to such diagonal matrices. This paper provides a proof of the conjecture in this MISO setting. View full abstract»

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  • Source coding for dependent sources

    Page(s): 70 - 74
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    In this work, we address the capacity region of multi-source multi-terminal network communication problems, and study the change in capacity when one moves form independent to dependent source information. Specifically, we ask whether the trade off between capacity and source independence is of continuous nature. We tie the question at hand to that of edge removal which has seen recent interest. View full abstract»

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  • The arithmetic codex

    Page(s): 75 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    In this invited talk,1 we introduce the notion of arithmetic codex, or codex for short. It encompasses several well-established notions from cryptography (arithmetic secret sharing schemes, which enjoy additive as well as multiplicative properties) and algebraic complexity theory (bilinear complexity of multiplication) in a natural mathematical framework. Arithmetic secret sharing schemes have important applications to secure multi-party computation and even to two-party cryptography. Interestingly, several recent applications to two-party cryptography rely crucially on the existing results on “asymptotically good families” of suitable such schemes. Moreover, the construction of these schemes requires asymptotically good towers of function fields over finite fields: no elementary (probabilistic) constructions are known in these cases. Besides introducing the notion, we discuss some of the constructions, as well as some limitations. View full abstract»

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  • The complexity of information theoretic secure computation

    Page(s): 80
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (115 KB) |  | HTML iconHTML  

    Summary form only given. A protocol for secure computation allows two or more parties to perform a distributed computation on their local inputs while hiding the inputs from each other. In the so-called “information theoretic” setting for secure computation, the parties are assumed to communicate over secure channels and the inputs should remain hidden even from computationally unbounded parties. It is known that every computation can done securely when there is a majority of honest parties, or alternatively when the parties are given access to certain types of correlated secret randomness. However, the true cost of such secure computations remains wide open. The talk will survey some recent progress and open questions in this area. View full abstract»

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  • Differential privacy as a protocol constraint

    Page(s): 81 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (135 KB) |  | HTML iconHTML  

    Differential privacy, introduced in 2006, has become a standard definition of privacy for statistical computations. Most of the research on differential privacy has explored questions arising in the client-server setting, where privacy guarantees are one-sided and cover data held by just one of the protocol participants. We observe that differential privacy complements the classic definition of secure multi-party computations by allowing one to quantify information leaked through the output of the computation. This view leads to a number of interesting questions, where differential privacy is treated as a constraint on the protocol. We survey the state-of-the-art of differential privacy in a multi-party setting and formulate several open problems. View full abstract»

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  • Throughput maximization for an energy harvesting communication system with processing cost

    Page(s): 84 - 88
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    In wireless networks, energy consumed for communication includes both the transmission and the processing energy. In this paper, point-to-point communication over a fading channel with an energy harvesting transmitter is studied considering jointly the energy costs of transmission and processing. Under the assumption of known energy arrival and fading profiles, optimal transmission policy for throughput maximization is investigated. Assuming that the transmitter has sufficient amount of data in its buffer at the beginning of the transmission period, the average throughput by a given deadline is maximized. Furthermore, a “directional glue pouring algorithm” that computes the optimal transmission policy is described. View full abstract»

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  • Gaussian wiretap channel with a batteryless energy harvesting transmitter

    Page(s): 89 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB) |  | HTML iconHTML  

    We study the Gaussian wiretap channel with an energy harvesting transmitter which does not have a battery to save energy. In the absence of a battery, the necessary transmission energy is maintained by an i.i.d. energy arrival process. We observe that this channel is an instance of the state-dependent wiretap channel with state available only to the transmitter causally, where the state is the available energy at the transmitter. We prove that the entire capacity-equivocation region can be obtained by single-letter Shannon strategies and its boundary is achieved by input distributions with support set of Lebesgue measure zero. View full abstract»

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  • The energy harvesting multiple access channel with energy storage losses

    Page(s): 94 - 98
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    This work considers a Gaussian multiple access channel with two energy harvesting transmitters with lossy energy storage. The power allocation policy maximizing the average weighted sum rate given the energy harvesting profiles is found. In particular, it is shown that the optimal policy has a double-threshold structure on each of the transmit powers, while the two transmit powers interact through the multivariate achievable rate function which determines the thresholds. For the special case of sum rate maximization in a Gaussian MAC channel, it is shown that the thresholds apply to the sum power, and the optimal policy consists of three thresholds, rather than four, which enables the user with a more efficient battery to be given priority in energy storage. View full abstract»

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  • On secure multiparty sampling for more than two parties

    Page(s): 99 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (245 KB) |  | HTML iconHTML  

    We investigate secure multi-party sampling problems involving more than two parties. In the public discussion model, we give a simple characterization of the distributions that can be sampled without any setup. In a model which allows private point-to-point communication, we reduce the problem of characterizing distributions that can be securely sampled using pairwise setups to the problem of characterizing distributions that can be sampled without any setups. View full abstract»

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  • Characterizing pseudoentropy

    Page(s): 104 - 108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (227 KB) |  | HTML iconHTML  

    We provide a characterization of “pseudoentropy” in terms of hardness of sampling: Let (X, B) be jointly distributed random variables such that B takes values in a polynomial-sized set. We show that no polynomial-time algorithm can distinguish B from some random variable of higher Shannon entropy given X if and only if there is no probabilistic polynomial-time S such that (X, S(X)) has small KL divergence from (X, B). As an application of this characterization, we show that if f is a one-way function (f is easy to compute but hard to invert), then (f(Un),Un) has “next-bit pseudoentropy” at least n + log n, establishing a conjecture of Haitner, Reingold, and Vadhan (STOC '10). Plugging this into the construction of Haitner et al., we obtain a simpler construction of pseudorandom generators from one-way functions. View full abstract»

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