1,922 research outputs found
High-dimensional decoy-state quantum key distribution over 0.3 km of multicore telecommunication optical fibers
Multiplexing is a strategy to augment the transmission capacity of a
communication system. It consists of combining multiple signals over the same
data channel and it has been very successful in classical communications.
However, the use of enhanced channels has only reached limited practicality in
quantum communications (QC) as it requires the complex manipulation of quantum
systems of higher dimensions. Considerable effort is being made towards QC
using high-dimensional quantum systems encoded into the transverse momentum of
single photons but, so far, no approach has been proven to be fully compatible
with the existing telecommunication infrastructure. Here, we overcome such a
technological challenge and demonstrate a stable and secure high-dimensional
decoy-state quantum key distribution session over a 0.3 km long multicore
optical fiber. The high-dimensional quantum states are defined in terms of the
multiple core modes available for the photon transmission over the fiber, and
the decoy-state analysis demonstrates that our technique enables a positive
secret key generation rate up to 25 km of fiber propagation. Finally, we show
how our results build up towards a high-dimensional quantum network composed of
free-space and fiber based linksComment: Please see the complementary work arXiv:1610.01812 (2016
Security proof of quantum key distribution with detection efficiency mismatch
In theory, quantum key distribution (QKD) offers unconditional security based
on the laws of physics. However, as demonstrated in recent quantum hacking
theory and experimental papers, detection efficiency loophole can be fatal to
the security of practical QKD systems. Here, we describe the physical origin of
detection efficiency mismatch in various domains including spatial, spectral,
and time domains and in various experimental set-ups. More importantly, we
prove the unconditional security of QKD even with detection efficiency
mismatch. We explicitly show how the key generation rate is characterized by
the maximal detection efficiency ratio between the two detectors. Furthermore,
we prove that by randomly switching the bit assignments of the detectors, the
effect of detection efficiency mismatch can be completely eliminated.Comment: 35 pages, 7 figure
Privacy Vulnerabilities in the Practices of Repairing Broken Digital Artifacts in Bangladesh
This paper presents a study on the privacy concerns associated with the practice of repairing broken digital objects in Bangladesh. Historically, repair of old or broken technologies has received less attention in ICTD scholarship than design, development, or use. As a result, the potential privacy risks associated with repair practices have remained mostly unaddressed. This paper describes our three-month long ethnographic study that took place at ten major repair sites in Dhaka, Bangladesh. We show a variety of ways in which the privacy of an individual’s personal data may be compromised during the repair process. We also examine people’s perceptions around privacy in repair, and its connections with their broader social and cultural values. Finally, we discuss the challenges and opportunities for future research to strengthen the repair ecosystem in developing countries. Taken together, our findings contribute to the growing discourse around post-use cycles of technology
QKD from a microsatellite: the SOTA experience
The transmission and reception of polarized quantum-limited signals from
space is of capital interest for a variety of fundamental-physics experiments
and quantum-communication protocols. Specifically, Quantum Key Distribution
(QKD) deals with the problem of distributing unconditionally-secure
cryptographic keys between two parties. Enabling this technology from space is
a critical step for developing a truly-secure global communication network. The
National Institute of Information and Communications Technology (NICT, Japan)
performed the first successful measurement on the ground of a quantum-limited
signal from a satellite in experiments carried out on early August in 2016. The
SOTA (Small Optical TrAnsponder) lasercom terminal onboard the LEO satellite
SOCRATES (Space Optical Communications Research Advanced Technology Satellite)
was utilized for this purpose. Two non-orthogonally polarized signals in the
~800-nm band and modulated at 10 MHz were transmitted by SOTA and received in
the single-photon regime by using a 1-m Cassegrain telescope on a ground
station located in an urban area of Tokyo (Japan). In these experiments, after
compensating the Doppler effect induced by the fast motion of the satellite, a
QKD-enabling QBER (Quantum Bit Error Rate) below 5% was measured with estimated
key rates in the order of several Kbit/s, proving the feasibility of quantum
communications in a real scenario from space for the first time.Comment: 10 pages, 14 figure
Roadmap on optical security
Postprint (author's final draft
Enhanced Stegano-Cryptographic Model for Secure Electronic Voting
The issue of security in Information and Communication Technology has been identified as the most critical barrier in the widespread adoption of electronic voting (e-voting). Earlier cryptographic models for secure e-voting are vulnerable to attacks and existing stegano-cryptographic models can be manipulated by an eavesdropper. These shortcomings of existing models of secure e-voting are threats to confidentiality, integrity and verifiability of electronic ballot which are critical to overall success of e-democratic decision making through e-voting.This paper develops an enhanced stegano-cryptographic model for secure electronic voting system in poll-site, web and mobile voting scenarios for better citizens’ participation and credible e-democratic election. The electronic ballot was encrypted using Elliptic Curve Cryptography and Rivest-Sharma-Adleman cryptographic algorithm. The encrypted voter’s ballot was scattered and hidden in the Least Significant Bit (LSB) of the cover media using information hiding attribute of modified LSB-Wavelet steganographic algorithm. The image quality of the model, stego object was quantitatively assessed using Peak Signal to Noise Ratio (PSNR), Signal to Noise Ratio (SNR), Root Mean Square Error (RMSE) and Structural Similarity Index Metrics (SSIM).The results after quantitative performance evaluation shows that the developed stegano-cryptographic model has generic attribute of secured e-voting relevant for the delivery of credible e-democratic decision making. The large scale implementation of the model would be useful to deliver e-voting of high electoral integrity and political trustworthiness, where genuine e-elections are conducted for the populace by government authority. Keywords: Electronic Voting, Cryptography, Steganography, Video, Image, Wavelet, Securit
The Quantum Frontier
The success of the abstract model of computation, in terms of bits, logical
operations, programming language constructs, and the like, makes it easy to
forget that computation is a physical process. Our cherished notions of
computation and information are grounded in classical mechanics, but the
physics underlying our world is quantum. In the early 80s researchers began to
ask how computation would change if we adopted a quantum mechanical, instead of
a classical mechanical, view of computation. Slowly, a new picture of
computation arose, one that gave rise to a variety of faster algorithms, novel
cryptographic mechanisms, and alternative methods of communication. Small
quantum information processing devices have been built, and efforts are
underway to build larger ones. Even apart from the existence of these devices,
the quantum view on information processing has provided significant insight
into the nature of computation and information, and a deeper understanding of
the physics of our universe and its connections with computation.
We start by describing aspects of quantum mechanics that are at the heart of
a quantum view of information processing. We give our own idiosyncratic view of
a number of these topics in the hopes of correcting common misconceptions and
highlighting aspects that are often overlooked. A number of the phenomena
described were initially viewed as oddities of quantum mechanics. It was
quantum information processing, first quantum cryptography and then, more
dramatically, quantum computing, that turned the tables and showed that these
oddities could be put to practical effect. It is these application we describe
next. We conclude with a section describing some of the many questions left for
future work, especially the mysteries surrounding where the power of quantum
information ultimately comes from.Comment: Invited book chapter for Computation for Humanity - Information
Technology to Advance Society to be published by CRC Press. Concepts
clarified and style made more uniform in version 2. Many thanks to the
referees for their suggestions for improvement
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