22,427 research outputs found
Fair Loss-Tolerant Quantum Coin Flipping
Coin flipping is a cryptographic primitive in which two spatially separated
players, who in principle do not trust each other, wish to establish a common
random bit. If we limit ourselves to classical communication, this task
requires either assumptions on the computational power of the players or it
requires them to send messages to each other with sufficient simultaneity to
force their complete independence. Without such assumptions, all classical
protocols are so that one dishonest player has complete control over the
outcome. If we use quantum communication, on the other hand, protocols have
been introduced that limit the maximal bias that dishonest players can produce.
However, those protocols would be very difficult to implement in practice
because they are susceptible to realistic losses on the quantum channel between
the players or in their quantum memory and measurement apparatus. In this
paper, we introduce a novel quantum protocol and we prove that it is completely
impervious to loss. The protocol is fair in the sense that either player has
the same probability of success in cheating attempts at biasing the outcome of
the coin flip. We also give explicit and optimal cheating strategies for both
players.Comment: 12 pages, 1 figure; various minor typos corrected in version
Flipping quantum coins
Coin flipping is a cryptographic primitive in which two distrustful parties
wish to generate a random bit in order to choose between two alternatives. This
task is impossible to realize when it relies solely on the asynchronous
exchange of classical bits: one dishonest player has complete control over the
final outcome. It is only when coin flipping is supplemented with quantum
communication that this problem can be alleviated, although partial bias
remains. Unfortunately, practical systems are subject to loss of quantum data,
which restores complete or nearly complete bias in previous protocols. We
report herein on the first implementation of a quantum coin-flipping protocol
that is impervious to loss. Moreover, in the presence of unavoidable
experimental noise, we propose to use this protocol sequentially to implement
many coin flips, which guarantees that a cheater unwillingly reveals
asymptotically, through an increased error rate, how many outcomes have been
fixed. Hence, we demonstrate for the first time the possibility of flipping
coins in a realistic setting. Flipping quantum coins thereby joins quantum key
distribution as one of the few currently practical applications of quantum
communication. We anticipate our findings to be useful for various
cryptographic protocols and other applications, such as an online casino, in
which a possibly unlimited number of coin flips has to be performed and where
each player is free to decide at any time whether to continue playing or not.Comment: 17 pages, 3 figure
Experimental Quantum Fingerprinting
Quantum communication holds the promise of creating disruptive technologies
that will play an essential role in future communication networks. For example,
the study of quantum communication complexity has shown that quantum
communication allows exponential reductions in the information that must be
transmitted to solve distributed computational tasks. Recently, protocols that
realize this advantage using optical implementations have been proposed. Here
we report a proof of concept experimental demonstration of a quantum
fingerprinting system that is capable of transmitting less information than the
best known classical protocol. Our implementation is based on a modified
version of a commercial quantum key distribution system using off-the-shelf
optical components over telecom wavelengths, and is practical for messages as
large as 100 Mbits, even in the presence of experimental imperfections. Our
results provide a first step in the development of experimental quantum
communication complexity.Comment: 11 pages, 6 Figure
Cryptocurrency: History, Advantages, Disadvantages, and the Future
Cryptocurrency is a digital asset that has seen a large amount of attention within the past five years. Its origin is intriguing to some based upon its newness, yet it has invoked mysticism and skepticism in others. Bitcoin is the most recognizable currency, receiving heavy media attention. There are several other cryptocurrencies as well, less in the spotlight. Most appealing to cryptocurrency could include lack of government oversight, and increased privacy available to the consumer(s) (Bunjaku, Gjorgieva-Trajkovska, and Miteva-Kacarski, 2017, p. 37). Additional advantages include the simplicity in the start-up process, the ease of transferability, and the opportunity to have a seamless process in investing and/or exchanging monies. Cryptocurrency creates the ability to invest for some people groups that could never invest before and diversify investment portfolios (Theron and van Vuure, 2018, p. 2). While the newness of cryptocurrency certainly has been appealing for some, it also has been perceived oppositional by others. There has been concerns identified with regard to the level of trust required, an obvious and significant drawback if valid. Another identified disadvantage to cryptocurrency is its low amount of oversight and liquidity hurt for investing future. The ability for cryptocurrency to be used for illegal and/or evil activity is an ethical drawback (Nian and Chuen, 2015, p. 15). Lastly, the uncertainty of the future is a significant drawback. The future of cryptocurrency requires much economic forecasting. The new changes that cryptocurrency will bring to traditional economic institutes is an area which cryptocurrency needs to explored more. Lastly, is cryptocurrency a fad or an economic bubble
Reasoning about the Reliability of Diverse Two-Channel Systems in which One Channel is "Possibly Perfect"
This paper considers the problem of reasoning about the reliability of fault-tolerant systems with two "channels" (i.e., components) of which one, A, supports only a claim of reliability, while the other, B, by virtue of extreme simplicity and extensive analysis, supports a plausible claim of "perfection." We begin with the case where either channel can bring the system to a safe state. We show that, conditional upon knowing pA (the probability that A fails on a randomly selected demand) and pB (the probability that channel B is imperfect), a conservative bound on the probability that the system fails on a randomly selected demand is simply pA.pB. That is, there is conditional independence between the events "A fails" and "B is imperfect." The second step of the reasoning involves epistemic uncertainty about (pA, pB) and we show that under quite plausible assumptions, a conservative bound on system pfd can be constructed from point estimates for just three parameters. We discuss the feasibility of establishing credible estimates for these parameters. We extend our analysis from faults of omission to those of commission, and then combine these to yield an analysis for monitored architectures of a kind proposed for aircraft
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