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14
Secure communication in minimal connectivity models
 Journal of Cryptology
, 1998
"... Abstract. Problems of secure communication and computation have been studied extensively in network models. In this work, we ask what is possible in the informationtheoretic setting when the adversary is very strong (Byzantine) and the network connectivity is very low (minimum needed for crashtole ..."
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Cited by 55 (1 self)
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Abstract. Problems of secure communication and computation have been studied extensively in network models. In this work, we ask what is possible in the informationtheoretic setting when the adversary is very strong (Byzantine) and the network connectivity is very low (minimum needed for crashtolerance). For some natural models, our results imply a sizable gap between the connectivity required for perfect security and for probabilistic security. Our results also have implications to the commonly studied simple channel model and to general secure multiparty computation. 1
Exploring Message Authentication in Sensor Networks
 In Proc. of European Workshop on Security of Ad Hoc and Sensor Networks (ESAS), LNCS
, 2004
"... This paper explores the design space for message authentication in sensor networks. Several types of authentication are put into relation: endtoend, hoptohop, and physical and virtual multipath authentication. ..."
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Cited by 15 (2 self)
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This paper explores the design space for message authentication in sensor networks. Several types of authentication are put into relation: endtoend, hoptohop, and physical and virtual multipath authentication.
Using Approximation Hardness to Achieve Dependable Computation
 In: Proc. of the Second International Conference on Randomization and Approximation Techniques in Computer Science, LNCS 1518
, 1998
"... Abstract. Redundancy has been utilized to achieve fault tolerant computation and to achieve reliable communication in networks of processors. These techniques can only be extended to computations solely based on functions in one input in which redundant hardware or software (servers) are used to com ..."
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Cited by 10 (9 self)
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Abstract. Redundancy has been utilized to achieve fault tolerant computation and to achieve reliable communication in networks of processors. These techniques can only be extended to computations solely based on functions in one input in which redundant hardware or software (servers) are used to compute intermediate and end results. However, almost all practical computation systems consist of components which are based on computations with multiple inputs. Wang, Desmedt, and Burmester have used AND/OR graphs to model this scenario. Roughly speaking, an AND/OR graph is a directed graph with two types of vertices, labeled ∧vertices and ∨vertices. In this case, processors which need all their inputs in order to operate could be represented by ∧vertices, whereas processors which can choose one of their “redundant” inputs could be represented by ∨vertices. In this paper, using the results for hardness of approximation and optimization problems, we will design dependable computation systems which could defeat as many malicious faults as possible. Specifically, assuming certain approximation hardness result, we will construct kconnected AND/OR graphs which could defeat a ckactive adversary (therefore a ckpassive adversary also) where c> 1 is any given constant. This result improves a great deal on the results for the equivalent communication problems. 1
Integrity Preservation for Communication in Sensor Networks
, 2004
"... We propose a novel data integrity protection scheme, which relies on multiple, intervoven authentication chains instead of data origin authentication. ..."
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Cited by 8 (3 self)
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We propose a novel data integrity protection scheme, which relies on multiple, intervoven authentication chains instead of data origin authentication.
Efficient reliable communication over partially authenticated networks
 In Proceedings of the 22nd Symposium on Principles of Distributed Computing — PODC ’03
, 2003
"... Reliable communication between parties in a network is a basic requirement for executing any protocol. Dolev [4] and Dolev et al. [5] showed that reliable communication is possible if and only if the communication network is sufficiently connected. Beimel and Franklin [1] showed that the connectivit ..."
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Cited by 7 (1 self)
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Reliable communication between parties in a network is a basic requirement for executing any protocol. Dolev [4] and Dolev et al. [5] showed that reliable communication is possible if and only if the communication network is sufficiently connected. Beimel and Franklin [1] showed that the connectivity requirement can be relaxed if some pairs of parties share authentication keys. That is, costly communication links can be replaced by authentication keys. In this work, we continue this line of research. We consider the scenario where there is a specific sender and a specific receiver. In this case, the protocol of [1] has rounds even if there is a single Byzantine processor. We present a more efficient protocol with round complexity of, where is the number of processors in the network and is an upper bound on the number of Byzantine processors in the network. Specifically, our protocol is polynomial when the number of Byzantine processors is, and for every its round complexity is bounded by. The same improvements hold for reliable and private communication. The improved protocol is obtained by analyzing the properties of a “communication and authentication graph ” that characterizes reliable communication. 1.
On private computation in incomplete networks
 Distributed Computing
"... Suppose that some parties are connected by an incomplete network of reliable and private channels. The parties cooperate to execute some protocol. However, the parties are curious – after the protocol terminates each party tries to learn information from the communication it heard. We say that a fun ..."
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Cited by 3 (1 self)
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Suppose that some parties are connected by an incomplete network of reliable and private channels. The parties cooperate to execute some protocol. However, the parties are curious – after the protocol terminates each party tries to learn information from the communication it heard. We say that a function can be computed privately in a network if there is a protocol in which each processor learns only the information implied by its input and the output of the function (in the information theoretic sense). The question we address in this paper is what functions can be privately computed in a given incomplete network. Every function can be privately computed in twoconnected networks with at least three parties. Thus, the question is interesting only for non twoconnected networks. Generalizing results of [Bläser et al. CRYPTO 2002], we characterize the functions that can be computed privately in simple networks – networks with one separating vertex and no leaves. We then deal with private computations in arbitrary non twoconnected networks: we reduce this question to private computations of related functions on trees, and give some sufficient conditions and necessary conditions on the functions that can be privately computed on trees.
Models For Dependable Computation with Multiple Inputs and Some Hardness Results
, 2000
"... We consider the problem of dependable computation with multiple inputs. The goal is to study when redundancy can help to achieve survivability and when it cannot. We use AND/OR graphs to model fault tolerant computations with multiple inputs. While there is a polynomial time algorithm for finding ve ..."
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Cited by 3 (1 self)
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We consider the problem of dependable computation with multiple inputs. The goal is to study when redundancy can help to achieve survivability and when it cannot. We use AND/OR graphs to model fault tolerant computations with multiple inputs. While there is a polynomial time algorithm for finding vertex disjoint paths in networks, we will show that the equivalent problem in computation systems with multiple inputs is NPhard. Our main results are as follows. (1) We present a general model for fault tolerant computation systems with multiple inputs: AND/OR graphs. (2) We show that it is NPhard to find two vertex disjoint solution graphs in an AND/OR graph. It follows that in the general case redundancy cannot help to achieve survivability, assuming P6=NP. Keywords: Dependable computation, complexity theory, NPhardness.
Mechanism Design and Communication Networks ∗
, 2010
"... for helpful discussions and comments. Anonymous referees and the editor are gratefully acknowledged for suggestions improving the paper. We owe this piece of work to a discussion Murali Agastya and one of the author had few years ago. Renou thanks the hospitality of Fuqua Business School at Duke Uni ..."
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Cited by 1 (0 self)
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for helpful discussions and comments. Anonymous referees and the editor are gratefully acknowledged for suggestions improving the paper. We owe this piece of work to a discussion Murali Agastya and one of the author had few years ago. Renou thanks the hospitality of Fuqua Business School at Duke University.
AlmostEverywhere Secure Computation with Edge Corruptions ∗
"... We consider secure multiparty computation (MPC) in a setting where the adversary can separately corrupt not only the parties (nodes) but also the communication channels (edges), and can furthermore choose selectively and adaptively which edges or nodes to corrupt. Note that if an adversary corrupts ..."
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We consider secure multiparty computation (MPC) in a setting where the adversary can separately corrupt not only the parties (nodes) but also the communication channels (edges), and can furthermore choose selectively and adaptively which edges or nodes to corrupt. Note that if an adversary corrupts an edge, even if the two nodes that share that edge are honest, the adversary can control the link and thus deliver wrong messages to both players. We consider this question in the informationtheoretic setting, and require security against a computationally unbounded adversary. In a fully connected network the above question is simple (and we also provide an answer that is optimal up to a constant factor). What makes the problem more challenging is to consider the case of sparse networks. Partially connected networks are far more realistic than fully connected networks, which led Garay and Ostrovsky [Eurocrypt’08] to formulate the notion of (unconditional) almost everywhere (a.e.) secure computation in the nodecorruption model, i.e., a model in which not all pairs of nodes are connected by secure channels and the adversary can corrupt some of the nodes (but not the edges). In such a setting, MPC amongst all honest nodes cannot be guaranteed due to the possible poor connectivity of some honest nodes with other honest nodes, and hence some
On Private Computation in Incomplete Networks*
, 2006
"... Abstract Suppose that some parties are connected by an incomplete network of reliable and private channels.The parties cooperate to execute some protocol. However, the parties are curious after the protocol ..."
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Abstract Suppose that some parties are connected by an incomplete network of reliable and private channels.The parties cooperate to execute some protocol. However, the parties are curious after the protocol