4,177 research outputs found
Unconditionally Reliable Message Transmission in Directed Neighbour Networks
The problem of unconditionally reliable message transmission (URMT) is to design a protocol which when run by players in a network enables a sender S to deliver a message to a receiver R with high probability, even when some players in the network are under the control of an unbounded adversary. Renault and Tomala [JoC2008] gave a characterization of undirected neighbour networks over which URMT tolerating Byzantine adversary is possible. In this paper, we generalize their result to the case of directed networks
Making Code Voting Secure against Insider Threats using Unconditionally Secure MIX Schemes and Human PSMT Protocols
Code voting was introduced by Chaum as a solution for using a possibly
infected-by-malware device to cast a vote in an electronic voting application.
Chaum's work on code voting assumed voting codes are physically delivered to
voters using the mail system, implicitly requiring to trust the mail system.
This is not necessarily a valid assumption to make - especially if the mail
system cannot be trusted. When conspiring with the recipient of the cast
ballots, privacy is broken.
It is clear to the public that when it comes to privacy, computers and
"secure" communication over the Internet cannot fully be trusted. This
emphasizes the importance of using: (1) Unconditional security for secure
network communication. (2) Reduce reliance on untrusted computers.
In this paper we explore how to remove the mail system trust assumption in
code voting. We use PSMT protocols (SCN 2012) where with the help of visual
aids, humans can carry out addition correctly with a 99\% degree of
accuracy. We introduce an unconditionally secure MIX based on the combinatorics
of set systems.
Given that end users of our proposed voting scheme construction are humans we
\emph{cannot use} classical Secure Multi Party Computation protocols.
Our solutions are for both single and multi-seat elections achieving:
\begin{enumerate}[i)]
\item An anonymous and perfectly secure communication network secure against
a -bounded passive adversary used to deliver voting,
\item The end step of the protocol can be handled by a human to evade the
threat of malware. \end{enumerate} We do not focus on active adversaries
Mechanism Design and Communication Networks
This paper characterizes the class of communication networks for which, in any environment (utilities and beliefs), every incentive-compatible social choice function is (partially) implementable. Among others, in environments with either common and independent beliefs and private values or a bad outcome, we show that if the communication network is 2-connected, then any incentive-compatible social choice function is implementable. A network is 2-connected if each player is either directly connected to the designer or indirectly connected to the designer through at least two disjoint paths. We couple encryption techniques together with appropriate incentives to secure the transmission of each player’s private information to the designer.Mechanism design; incentives; Bayesian equilibrium; communication networks; encryption; secure transmission; coding
Interplay between (Im)perfectness, Synchrony and Connectivity: The Case of Reliable Message Transmission
For unconditionally reliable message transmission (URMT) in synchronous directed networks of n nodes, a subset of which may be Byzantine faulty, it is well-known that the minimum connectivity requirements for zero-error (perfect) protocols to exist is strictly higher than those where a negligible yet non-zero error probability is allowed (Monte Carlo protocols).
In this work, we study the minimum connectivity requirements for the existence of (a) synchronous Las Vegas protocols, (b) asynchronous Monte Carlo protocols, and (c) asynchronous Las Vegas protocols for URMT. Interestingly, we prove that in any network, synchronous Las Vegas URMT protocol exists if and only if asynchronous Monte Carlo URMT protocol exists too. We further show that asynchronous Las Vegas URMT protocols exist if and only if synchronous perfect protocols exist. We conclude with another interesting result: there exists networks where the number of critical edges for the ‘easier’ randomized variants are asymptotically higher than that for the perfect variant. Thus, our results establish an interesting interplay between (im)perfectness, synchrony and connectivity for the case of URMT
Unconditionally Reliable and Secure Message Transmission in Undirected Synchronous Networks: Possibility, Feasibility and Optimality
We study the interplay of network connectivity and the issues related to the ‘possibility’, ‘feasibility’ and ‘optimality’ for unconditionally reliable message transmission (URMT) and unconditionally secure message transmission (USMT) in an undirected
synchronous network, under the influence of an adaptive mixed adversary having unbounded computing power, who can corrupt some of the nodes in the network in Byzantine, omission, fail-stop and passive fashion respectively. We consider two types of adversary, namely threshold and non-threshold. One of the important conclusions we arrive at from our study is that allowing a negligible error probability significantly helps in the ‘possibility’, ‘feasibility’ and ‘optimality’ of both reliable and secure message transmission protocols. To design our protocols, we propose several new techniques which are of independent interest
Centralized and Cooperative Transmission of Secure Multiple Unicasts using Network Coding
We introduce a method for securely delivering a set of messages to a group of
clients over a broadcast erasure channel where each client is interested in a
distinct message. Each client is able to obtain its own message but not the
others'. In the proposed method the messages are combined together using a
special variant of random linear network coding. Each client is provided with a
private set of decoding coefficients to decode its own message. Our method
provides security for the transmission sessions against computational
brute-force attacks and also weakly security in information theoretic sense. As
the broadcast channel is assumed to be erroneous, the missing coded packets
should be recovered in some way. We consider two different scenarios. In the
first scenario the missing packets are retransmitted by the base station
(centralized). In the second scenario the clients cooperate with each other by
exchanging packets (decentralized). In both scenarios, network coding
techniques are exploited to increase the total throughput. For the case of
centralized retransmissions we provide an analytical approximation for the
throughput performance of instantly decodable network coded (IDNC)
retransmissions as well as numerical experiments. For the decentralized
scenario, we propose a new IDNC based retransmission method where its
performance is evaluated via simulations and analytical approximation.
Application of this method is not limited to our special problem and can be
generalized to a new class of problems introduced in this paper as the
cooperative index coding problem
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