Non-trivial Communication Research Articles

Communication with forgetful liars

I consider multiround cheap talk communication environments in which, after a lie, the informed party has no memory of the content of the lie. I characterize the equilibria with forgetful liars in such settings assuming that a liar's expectation about his past lie coincides with the equilibrium distribution of lies aggregated over all possible realizations of the states. The approach is used to shed light on when the full truth is almost surely elicited, and when multiple lies can arise in equilibrium. Elaborations are proposed to shed light on why nontrivial communication protocols are used in criminal investigations.

Interactive Information Complexity

The primary goal of this paper is to define and study the interactive information complexity of functions. Let $f(x,y)$ be a function, and suppose Alice is given $x$ and Bob is given $y$. Informally, the interactive information complexity $\mathsf{IC}(f)$ of $f$ is the least amount of information Alice and Bob need to reveal to each other to compute $f$. Previously, information complexity has been defined with respect to a prior distribution on the input pairs $(x,y)$. Our first goal is to give a definition that is independent of the prior distribution. We show that several possible definitions are essentially equivalent. We establish some basic properties of the interactive information complexity $\mathsf{IC}(f)$. In particular, we show that $\mathsf{IC}(f)$ is equal to the amortized (randomized) communication complexity of $f$. We also show a direct sum theorem for $\mathsf{IC}(f)$ and give the first general connection between information complexity and (nonamortized) communication complexity. This connection implies that a nontrivial exchange of information is required when solving problems that have nontrivial communication complexity. We explore the information complexity of two specific problems: equality and disjointness. We show that only a constant amount of information needs to be exchanged when solving equality with no errors, while solving disjointness with a constant error probability requires the parties to reveal a linear amount of information to each other. This paper originally appeared in [SIAM J. Comput., 44 (2015), pp. 1698--1739]. The present version has been slightly updated with some recent developments.

An efficient trust negotiation strategy towards the resource-limited mobile commerce environment

Automated trust negotiation (ATN) offers an attractivemeans for trust establishments, which establishesmutual trust among strangers wishing to share resources or conduct business, but it comes at the cost of non-trivial computation and communication overheads. The deployment of ATN strategies on a resource-constrained mobile device may lead to user-obstructive latency for operations. In this paper, we propose a trust negotiation strategy called trust target Petri nets negotiation strategy (TPNNS). It highly reduces the negotiation latency in the mobile device compared with other negotiation strategies, since it considers all the alternative responses at each step and chooses the best one. TPNNS supports cycle avoidance and employs skipped TPN which is a new approach presented in this paper. What is more, it is complete and ensures no irrelevant credentials are disclosed during the trust negotiation.

PCPOR: Public and constant-cost proofs of retrievability in cloud1

For data storage outsourcing services, it is important to allow users to efficiently and securely verify that cloud storage servers store their data correctly. To address this issue, a number of Proof of Retrievability (POR) and Proof of Data Possession (PDP) schemes have been proposed wherein servers must prove to a verifier that data are stored correctly. While existing POR and PDP schemes offer decent solutions addressing various practical issues, they either have non-trivial (linear or quadratic) communication and computational complexity, or only consider private verification. In this paper, we propose the first POR scheme with public verifiability, constant communication and computational costs on users. In our scheme, messages exchanged between cloud servers and users are composed of a constant number of group elements and random numbers; computational tasks required on users are also constant; batch auditing of multiple tasks is also efficiently supported. We achieved these by a unique design based on our novel polynomial-based authenticators. Extensive experiments on Amazon EC2 cloud and different client devices (contemporary and mobile devices) show that our design allows a user to audit the integrity of a file of any size with a constant computational cost of 150 ms on PC (2.11 s on mobile device) and a communication cost of 2.34 kB for 99% error detection probability when employing an erasure coding with 1% fault tolerance rate. We prove the security of our scheme based on the Computational Diffie-Hellman problem, the t-Strong Diffie-Hellman problem and the Static Diffie-Hellman problem.

Almost quantum correlations.

Quantum theory is not only successfully tested in laboratories every day but also constitutes a robust theoretical framework: small variations usually lead to implausible consequences, such as faster-than-light communication. It has even been argued that quantum theory may be special among possible theories. Here we report that, at the level of correlations among different systems, quantum theory is not so special. We define a set of correlations, dubbed 'almost quantum', and prove that it strictly contains the set of quantum correlations but satisfies all-but-one of the proposed principles to capture quantum correlations. We present numerical evidence that the remaining principle is satisfied too.

Efficient public verification proof of retrievability scheme in cloud

Cloud storage is an important service of cloud computing. After data file is outsourced, data owner no longer physical controls over the storage. To efficiently verify these data integrity, several Proof of Retrievability (POR) schemes were proposed to achieve data integrity checking. The existing POR schemes offer decent solutions to address various practical issues, however, they either have a non-trivial (linear or quadratic) communication cost, or only support private verification. And most of the existing POR schemes exist active attack and information leakage problem in the data checking procedure. It remains open to design a secure POR scheme with both public verifiability and constant communication cost. To solve the above problems , we propose a novel preserving-private POR scheme with public verifiability and constant communication cost based on end-to-end aggregation authentication in this paper. To resist information leakage, we include zero-knowledge technique to hide the data in the integrity checking process. Our scheme is shown to be secure and efficient by security analysis and performance analysis. The security of our scheme is related to the Computational Diffie---Helleman Problem and Discrete logarithm problem. Finally, we also extend the POR scheme to support multi-file integrity checking and simulation results show that the verifier only needs less computational cost to achieve data integrity checking in our extended scheme.

Communication activity in a social network: relation between long-term correlations and inter-event clustering

Human communication in social networks is dominated by emergent statistical laws such as non-trivial correlations and temporal clustering. Recently, we found long-term correlations in the user's activity in social communities. Here, we extend this work to study the collective behavior of the whole community with the goal of understanding the origin of clustering and long-term persistence. At the individual level, we find that the correlations in activity are a byproduct of the clustering expressed in the power-law distribution of inter-event times of single users, i.e. short periods of many events are separated by long periods of no events. On the contrary, the activity of the whole community presents long-term correlations that are a true emergent property of the system, i.e. they are not related to the distribution of inter-event times. This result suggests the existence of collective behavior, possibly arising from nontrivial communication patterns through the embedding social network.

Quantum Correlations Require Multipartite Information Principles

Identifying which correlations among distant observers are possible within our current description of nature, based on quantum mechanics, is a fundamental problem in physics. Recently, information concepts have been proposed as the key ingredient to characterize the set of quantum correlations. Novel information principles, such as information causality or nontrivial communication complexity, have been introduced in this context and successfully applied to some concrete scenarios. We show in this work a fundamental limitation of this approach: no principle based on bipartite information concepts is able to singleout the set of quantum correlations for an arbitrary number of parties. Our results reflect the intricate structure of quantum correlations and imply that new and intrinsically multipartite information concepts are needed for their full understanding.

The Computational Hardness of Estimating Edit Distance

We prove the first nontrivial communication complexity lower bound for the problem of estimating the edit distance (aka Levenshtein distance) between two strings. To the best of our knowledge, this is the first computational setting in which the complexity of estimating the edit distance is provably larger than that of Hamming distance. Our lower bound exhibits a trade-off between approximation and communication, asserting, for example, that protocols with $O(1)$ bits of communication can obtain only approximation $\alpha\geq\Omega(\log d/\log\log d)$, where d is the length of the input strings. This case of $O(1)$ communication is of particular importance since it captures constant-size sketches as well as embeddings into spaces like $l_1$ and squared-$l_2$, two prevailing algorithmic approaches for dealing with edit distance. Indeed, the known nontrivial communication upper bounds are all derived from embeddings into $l_1$. By excluding low-communication protocols for edit distance, we rule out a strictly richer class of algorithms than previous results. Furthermore, our lower bound holds not only for strings over a binary alphabet but also for strings that are permutations (aka the Ulam metric). For this case, our bound nearly matches an upper bound known via embedding the Ulam metric into $l_1$. Our proof uses a new technique that relies on Fourier analysis in a rather elementary way.

Emergence of communication in embodied agents evolved for the ability to solve a collective navigation problem

In this paper, we present the results of an experiment in which a collection of simulated robots that have been evolved for the ability to solve a collective navigation problem develop a communication system that allows them to co-operate better. The analysis of the results obtained indicates how evolving robots develop a non-trivial communication system and exploit different communication modalities. The results also indicate how the possibility of co-adapting the robots’ individual and social/communicative behaviour plays a key role in the development of progressively more complex and effective individuals.

Predicting the Cost and Benefit of Adapting Data Parallel Applications in Clusters

This paper examines the problem of adapting data parallel applications in a shared dynamic environment of PC or workstation clusters. We developed an analytic framework to compare and contrast a wide range of adaptation strategies: dynamic load balancing, migration, processor addition and removal. These strategies have been evaluated with respect to the cost and benefit they provide for three representative parallel applications: an iterative jacobi solver for Laplace's equation, gaussian elimination with partial pivoting, and a gene sequence comparison application. We found that the cost and benefit of each method can be predicted with high accuracy (within 10%) for all applications and show that the framework is applicable to a wide variety of parallel applications. We then show that accurate prediction allows the most appropriate method to be selected dynamically. Performance improvement for the three applications ranged from 25% to 45% using our adaptation library. In addition, we dispel the conventional wisdom that migration is too expensive, and show that it can be beneficial even for running parallel applications with non-trivial communication.

Towards a practitioners' approach to Abadi and Lamport's method

Abstract Our own basic intuitions are presented when introducing the method developed by Abadi and Lamport in [AbL88a] for proving refinement between specifications of nondeterministic programs correct to people unacquainted with it. The example we use to illustrate this method is a nontrivial communication protocol that provides a mechanism analogous to message passing between migrating processes within a fixed finite network of nodes due to Kleinman, Moscowitz, Pnueli and Shapiro [KMP91]. Especially the cruel last step of a three step refinement proof of that protocol gives rise to a deeper understanding of, and some small enhancements to, Abadi and Lamport's 1988 method.

Parallel Computation of Gröbner Bases on Distributed Memory Machines

This paper reports our work on parallelizing an algorithm computing Gröbner bases on a distributed memory parallel machine. When computing Gröbner bases, the efficiency of computation is dominated by the total number of S-polynomials. To decrease the total number of S-polynomials it is necessary to apply a selection strategy that selects the minimum polynomial as a new element of an intermediate base. On a distributed memory parallel machine, as opposed to a shared memory parallel machine, we have to take into account non-trivial communication costs between processors. To reduce such communication costs, it is better to employ coarse grained parallelism rather than fine grained parallelism. We adopt a manager-worker model. S-polynomials are reduced in worker processes in parallel, and the minimum polynomial is selected in the manager process. To implement the selection strategy in this parallel model, synchronization between worker processes is required for every selection of a new element of the intermediate base. However, in spite of synchronization, introducing the selection strategy produces not only a better absolute computation speed but also better speedup with multi-processors. We achieved about 8 times speedup with 64 processors for large problems, T-6 and Ex-17.

Performance evaluation of a processor farm model for power system state-estimators on distributed-memory computers

In this work we present a preliminary performance and scalability analysis of a distributed state estimator for power systems when run on a massively parallel machine with a 2D mesh interconnection topology. The parallel algorithm is based on the processor farm, or master-slave, programming model which results in additional modelling complexity from process-to-processor mapping, non-trivial communication overhead and extra computation not present in the serial case. The effect of applying sparsity programming techniques further complicates the computational procedure, and hence the performance analysis. Our objective is to investigate the feasibility of the architecture for the algorithm in hand. To achieve it, we derive an accurate performance model, mainly for the communication overhead, and examine the efficiency of the architecture. Furthermore, we use this model to derive the scaling behaviour of the system, i.e. information on how the system performs if we allow the input size to grow as the number of processors increases. The convergence between theoretical estimates and simulation results obtained is also investigated.

Protocol Verification via Projections

The method of projections is a new approach to reduce the complexity of analyzing nontrivial communication protocols. A protocol system consists of a network of protocol entities and communication channels. Protocol entities interact by exchanging messages through channels; messages in transit may be lost, duplicated as well as reordered. Our method is intended for protocols with several distinguishable functions. We show how to construct image protocols for each function. An image protocol is specified just like a real protocol. An image protocol system is said to be faithful if it preserves all safety and liveness properties of the original protocol system concerning the projected function. An image protocol is smaller than the original protocol and can typically be more easily analyzed. Two protocol examples are employed herein to illustrate our method. An application of this method to verify a version of the high-level data link control (HDLC) protocol is described in a companion paper.