12,576 research outputs found
Low Cost and Compact Quantum Cryptography
We present the design of a novel free-space quantum cryptography system,
complete with purpose-built software, that can operate in daylight conditions.
The transmitter and receiver modules are built using inexpensive off-the-shelf
components. Both modules are compact allowing the generation of renewed shared
secrets on demand over a short range of a few metres. An analysis of the
software is shown as well as results of error rates and therefore shared secret
yields at varying background light levels. As the system is designed to
eventually work in short-range consumer applications, we also present a use
scenario where the consumer can regularly 'top up' a store of secrets for use
in a variety of one-time-pad and authentication protocols.Comment: 18 pages, 9 figures, to be published in New Journal of Physic
The Crypto-democracy and the Trustworthy
In the current architecture of the Internet, there is a strong asymmetry in
terms of power between the entities that gather and process personal data
(e.g., major Internet companies, telecom operators, cloud providers, ...) and
the individuals from which this personal data is issued. In particular,
individuals have no choice but to blindly trust that these entities will
respect their privacy and protect their personal data. In this position paper,
we address this issue by proposing an utopian crypto-democracy model based on
existing scientific achievements from the field of cryptography. More
precisely, our main objective is to show that cryptographic primitives,
including in particular secure multiparty computation, offer a practical
solution to protect privacy while minimizing the trust assumptions. In the
crypto-democracy envisioned, individuals do not have to trust a single physical
entity with their personal data but rather their data is distributed among
several institutions. Together these institutions form a virtual entity called
the Trustworthy that is responsible for the storage of this data but which can
also compute on it (provided first that all the institutions agree on this).
Finally, we also propose a realistic proof-of-concept of the Trustworthy, in
which the roles of institutions are played by universities. This
proof-of-concept would have an important impact in demonstrating the
possibilities offered by the crypto-democracy paradigm.Comment: DPM 201
Experimental investigation of practical unforgeable quantum money
Wiesner's unforgeable quantum money scheme is widely celebrated as the first
quantum information application. Based on the no-cloning property of quantum
mechanics, this scheme allows for the creation of credit cards used in
authenticated transactions offering security guarantees impossible to achieve
by classical means. However, despite its central role in quantum cryptography,
its experimental implementation has remained elusive because of the lack of
quantum memories and of practical verification techniques. Here, we
experimentally implement a quantum money protocol relying on classical
verification that rigorously satisfies the security condition for
unforgeability. Our system exploits polarization encoding of weak coherent
states of light and operates under conditions that ensure compatibility with
state-of-the-art quantum memories. We derive working regimes for our system
using a security analysis taking into account all practical imperfections. Our
results constitute a major step towards a real-world realization of this
milestone protocol.Comment: 10 pages, 5 figure
AND Protocols Using Only Uniform Shuffles
Secure multi-party computation using a deck of playing cards has been a
subject of research since the "five-card trick" introduced by den Boer in 1989.
One of the main problems in card-based cryptography is to design
committed-format protocols to compute a Boolean AND operation subject to
different runtime and shuffle restrictions by using as few cards as possible.
In this paper, we introduce two AND protocols that use only uniform shuffles.
The first one requires four cards and is a restart-free Las Vegas protocol with
finite expected runtime. The second one requires five cards and always
terminates in finite time.Comment: This paper has appeared at CSR 201
Experimental open air quantum key distribution with a single photon source
We present a full implementation of a quantum key distribution (QKD) system
with a single photon source, operating at night in open air. The single photon
source at the heart of the functional and reliable setup relies on the pulsed
excitation of a single nitrogen-vacancy color center in diamond nanocrystal. We
tested the effect of attenuation on the polarized encoded photons for inferring
longer distance performance of our system. For strong attenuation, the use of
pure single photon states gives measurable advantage over systems relying on
weak attenuated laser pulses. The results are in good agreement with
theoretical models developed to assess QKD security
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