339 research outputs found
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
The Wiretap Channel with Feedback: Encryption over the Channel
In this work, the critical role of noisy feedback in enhancing the secrecy
capacity of the wiretap channel is established. Unlike previous works, where a
noiseless public discussion channel is used for feedback, the feed-forward and
feedback signals share the same noisy channel in the present model. Quite
interestingly, this noisy feedback model is shown to be more advantageous in
the current setting. More specifically, the discrete memoryless modulo-additive
channel with a full-duplex destination node is considered first, and it is
shown that the judicious use of feedback increases the perfect secrecy capacity
to the capacity of the source-destination channel in the absence of the
wiretapper. In the achievability scheme, the feedback signal corresponds to a
private key, known only to the destination. In the half-duplex scheme, a novel
feedback technique that always achieves a positive perfect secrecy rate (even
when the source-wiretapper channel is less noisy than the source-destination
channel) is proposed. These results hinge on the modulo-additive property of
the channel, which is exploited by the destination to perform encryption over
the channel without revealing its key to the source. Finally, this scheme is
extended to the continuous real valued modulo- channel where it is
shown that the perfect secrecy capacity with feedback is also equal to the
capacity in the absence of the wiretapper.Comment: Submitted to IEEE Transactions on Information Theor
Secure Degrees of Freedom Regions of Multiple Access and Interference Channels: The Polytope Structure
The sum secure degrees of freedom (s.d.o.f.) of two fundamental multi-user
network structures, the K-user Gaussian multiple access (MAC) wiretap channel
and the K-user interference channel (IC) with secrecy constraints, have been
determined recently as K(K-1)/(K(K-1)+1) [1,2] and K(K-1)/(2K-1) [3,4],
respectively. In this paper, we determine the entire s.d.o.f. regions of these
two channel models. The converse for the MAC follows from a middle step in the
converse of [1,2]. The converse for the IC includes constraints both due to
secrecy as well as due to interference. Although the portion of the region
close to the optimum sum s.d.o.f. point is governed by the upper bounds due to
secrecy constraints, the other portions of the region are governed by the upper
bounds due to interference constraints. Different from the existing literature,
in order to fully understand the characterization of the s.d.o.f. region of the
IC, one has to study the 4-user case, i.e., the 2 or 3-user cases do not
illustrate the generality of the problem. In order to prove the achievability,
we use the polytope structure of the converse region. In both MAC and IC cases,
we develop explicit schemes that achieve the extreme points of the polytope
region given by the converse. Specifically, the extreme points of the MAC
region are achieved by an m-user MAC wiretap channel with (K-m) helpers, i.e.,
by setting (K-m) users' secure rates to zero and utilizing them as pure
(structured) cooperative jammers. The extreme points of the IC region are
achieved by a (K-m)-user IC with confidential messages, m helpers, and N
external eavesdroppers, for m>=1 and a finite N. A byproduct of our results in
this paper is that the sum s.d.o.f. is achieved only at one extreme point of
the s.d.o.f. region, which is the symmetric-rate extreme point, for both MAC
and IC channel models.Comment: Submitted to IEEE Transactions on Information Theory, April 201
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