6,358 research outputs found
Covert Communication over Classical-Quantum Channels
The square root law (SRL) is the fundamental limit of covert communication
over classical memoryless channels (with a classical adversary) and quantum
lossy-noisy bosonic channels (with a quantum-powerful adversary). The SRL
states that covert bits, but no more, can be reliably
transmitted in channel uses with bits of secret
pre-shared between the communicating parties. Here we investigate covert
communication over general memoryless classical-quantum (cq) channels with
fixed finite-size input alphabets, and show that the SRL governs covert
communications in typical scenarios. %This demonstrates that the SRL is
achievable over any quantum communications channel using a product-state
transmission strategy, where the transmitted symbols in every channel use are
drawn from a fixed finite-size alphabet. We characterize the optimal constants
in front of for the reliably communicated covert bits, as well as
for the number of the pre-shared secret bits consumed. We assume a
quantum-powerful adversary that can perform an arbitrary joint (entangling)
measurement on all channel uses. However, we analyze the legitimate
receiver that is able to employ a joint measurement as well as one that is
restricted to performing a sequence of measurements on each of channel uses
(product measurement). We also evaluate the scenarios where covert
communication is not governed by the SRL
Security for the Industrial IoT: The Case for Information-Centric Networking
Industrial production plants traditionally include sensors for monitoring or
documenting processes, and actuators for enabling corrective actions in cases
of misconfigurations, failures, or dangerous events. With the advent of the
IoT, embedded controllers link these `things' to local networks that often are
of low power wireless kind, and are interconnected via gateways to some cloud
from the global Internet. Inter-networked sensors and actuators in the
industrial IoT form a critical subsystem while frequently operating under harsh
conditions. It is currently under debate how to approach inter-networking of
critical industrial components in a safe and secure manner.
In this paper, we analyze the potentials of ICN for providing a secure and
robust networking solution for constrained controllers in industrial safety
systems. We showcase hazardous gas sensing in widespread industrial
environments, such as refineries, and compare with IP-based approaches such as
CoAP and MQTT. Our findings indicate that the content-centric security model,
as well as enhanced DoS resistance are important arguments for deploying
Information Centric Networking in a safety-critical industrial IoT. Evaluation
of the crypto efforts on the RIOT operating system for content security reveal
its feasibility for common deployment scenarios.Comment: To be published at IEEE WF-IoT 201
Multiphoton communication in lossy channels with photon-number entangled states
We address binary and quaternary communication channels based on correlated
multiphoton two-mode states of radiation in the presence of losses. The
protocol are based on photon number correlations and realized upon choosing a
shared set of thresholds to convert the outcome of a joint photon number
measurement into a symbol from a discrete alphabet. In particular, we focus on
channels build using feasible photon-number entangled states (PNES) as two-mode
coherently-correlated (TMC) or twin-beam (TWB) states and compare their
performances with that of channels built using feasible classically correlated
(separable) states. We found that PNES provide larger channel capacity in the
presence of loss, and that TWB-based channels may transmit a larger amount of
information than TMC-based ones at fixed energy and overall loss. Optimized bit
discrimination thresholds, as well as the corresponding maximized mutual
information, are explicitly evaluated as a function of the beam intensity and
the loss parameter. The propagation of TMC and TWB in lossy channels is
analyzed and the joint photon number distribution is evaluated, showing that
the beam statistics, either sub-Poissonian for TMC or super-Poissonian for TWB,
is not altered by losses. Although entanglement is not strictly needed to
establish the channels, which are based on photon-number correlations owned
also by separable mixed states, purity of the support state is relevant to
increase security. The joint requirement of correlation and purity individuates
PNES as a suitable choice to build effective channels. The effects of losses on
channel security are briefly discussed.Comment: 8 pages, 19 figure
On Coding for Reliable Communication over Packet Networks
We present a capacity-achieving coding scheme for unicast or multicast over
lossy packet networks. In the scheme, intermediate nodes perform additional
coding yet do not decode nor even wait for a block of packets before sending
out coded packets. Rather, whenever they have a transmission opportunity, they
send out coded packets formed from random linear combinations of previously
received packets. All coding and decoding operations have polynomial
complexity.
We show that the scheme is capacity-achieving as long as packets received on
a link arrive according to a process that has an average rate. Thus, packet
losses on a link may exhibit correlation in time or with losses on other links.
In the special case of Poisson traffic with i.i.d. losses, we give error
exponents that quantify the rate of decay of the probability of error with
coding delay. Our analysis of the scheme shows that it is not only
capacity-achieving, but that the propagation of packets carrying "innovative"
information follows the propagation of jobs through a queueing network, and
therefore fluid flow models yield good approximations. We consider networks
with both lossy point-to-point and broadcast links, allowing us to model both
wireline and wireless packet networks.Comment: 33 pages, 6 figures; revised appendi
Quantum key distribution using non-classical photon number correlations in macroscopic light pulses
We propose a new scheme for quantum key distribution using macroscopic
non-classical pulses of light having of the order 10^6 photons per pulse.
Sub-shot-noise quantum correlation between the two polarization modes in a
pulse gives the necessary sensitivity to eavesdropping that ensures the
security of the protocol. We consider pulses of two-mode squeezed light
generated by a type-II seeded parametric amplification process. We analyze the
security of the system in terms of the effect of an eavesdropper on the bit
error rates for the legitimate parties in the key distribution system. We also
consider the effects of imperfect detectors and lossy channels on the security
of the scheme.Comment: Modifications:added new eavesdropping attack, added more references
Submitted to Physical Review A [email protected]
Joint source-channel coding with feedback
This paper quantifies the fundamental limits of variable-length transmission
of a general (possibly analog) source over a memoryless channel with noiseless
feedback, under a distortion constraint. We consider excess distortion, average
distortion and guaranteed distortion (-semifaithful codes). In contrast to
the asymptotic fundamental limit, a general conclusion is that allowing
variable-length codes and feedback leads to a sizable improvement in the
fundamental delay-distortion tradeoff. In addition, we investigate the minimum
energy required to reproduce source samples with a given fidelity after
transmission over a memoryless Gaussian channel, and we show that the required
minimum energy is reduced with feedback and an average (rather than maximal)
power constraint.Comment: To appear in IEEE Transactions on Information Theor
- …