77 research outputs found
The MIMO wiretap channel
We study the MIMO wiretap channel, a MIMO broadcast channel where the transmitter sends some confidential information to one user which is a legitimate receiver, while the other user is an eavesdropper. Perfect secrecy is achieved when the transmitter and the legitimate receiver can communicate at some positive rate, while ensuring that the eavesdropper gets zero bits of information. In this paper, we compute the perfect secrecy capacity of the multiple antenna MIMO broadcast channel, where the number of antennas is arbitrary for both the transmitter and the two receivers. Our technique involves a careful study of a Sato-like upper bound via the solution of a certain algebraic Riccati equation
Secrecy Capacity Region of Fading Broadcast Channels
The fading broadcast channel with confidential messages (BCC) is
investigated, where a source node has common information for two receivers
(receivers 1 and 2), and has confidential information intended only for
receiver 1. The confidential information needs to be kept as secret as possible
from receiver 2. The channel state information (CSI) is assumed to be known at
both the transmitter and the receivers. The secrecy capacity region is first
established for the parallel Gaussian BCC, and the optimal source power
allocations that achieve the boundary of the secrecy capacity region are
derived. In particular, the secrecy capacity region is established for the
Gaussian case of the Csiszar-Korner BCC model. The secrecy capacity results are
then applied to give the ergodic secrecy capacity region for the fading BCC.Comment: Proc. of IEEE International Symposium on Information Theory (ISIT),
June 200
Techniques for Enhanced Physical-Layer Security
Information-theoretic security--widely accepted as the strictest notion of
security--relies on channel coding techniques that exploit the inherent
randomness of propagation channels to strengthen the security of communications
systems. Within this paradigm, we explore strategies to improve secure
connectivity in a wireless network. We first consider the intrinsically secure
communications graph (iS-graph), a convenient representation of the links that
can be established with information-theoretic security on a large-scale
network. We then propose and characterize two techniques--sectorized
transmission and eavesdropper neutralization--which are shown to dramatically
enhance the connectivity of the iS-graph.Comment: Pre-print, IEEE Global Telecommunications Conference (GLOBECOM'10),
Miami, FL, Dec. 201
Towards the Secrecy Capacity of the Gaussian MIMO Wire-tap Channel: The 2-2-1 Channel
We find the secrecy capacity of the 2-2-1 Gaussian MIMO wire-tap channel,
which consists of a transmitter and a receiver with two antennas each, and an
eavesdropper with a single antenna. We determine the secrecy capacity of this
channel by proposing an achievable scheme and then developing a tight upper
bound that meets the proposed achievable secrecy rate. We show that, for this
channel, Gaussian signalling in the form of beam-forming is optimal, and no
pre-processing of information is necessary.Comment: Submitted to IEEE Transactions on Information Theor
Secure Transmission in Amplify-and-Forward Diamond Networks with a Single Eavesdropper
Unicast communication over a network of -parallel relays in the presence
of an eavesdropper is considered. The relay nodes, operating under individual
power constraints, amplify and forward the signals received at their inputs.
The problem of the maximum secrecy rate achievable with AF relaying is
addressed. Previous work on this problem provides iterative algorithms based on
semidefinite relaxation. However, those algorithms result in suboptimal
performance without any performance and convergence guarantees. We address this
problem for three specific network models, with real-valued channel gains. We
propose a novel transformation that leads to convex optimization problems. Our
analysis leads to (i)a polynomial-time algorithm to compute the optimal secure
AF rate for two of the models and (ii) a closed-form expression for the optimal
secure rate for the other.Comment: 12pt font, 18 pages, 1 figure, conferenc
On the Secrecy Capacity of Fading Channels
We consider the secure transmission of information over an ergodic fading
channel in the presence of an eavesdropper. Our eavesdropper can be viewed as
the wireless counterpart of Wyner's wiretapper. The secrecy capacity of such a
system is characterized under the assumption of asymptotically long coherence
intervals. We first consider the full Channel State Information (CSI) case,
where the transmitter has access to the channel gains of the legitimate
receiver and the eavesdropper. The secrecy capacity under this full CSI
assumption serves as an upper bound for the secrecy capacity when only the CSI
of the legitimate receiver is known at the transmitter, which is characterized
next. In each scenario, the perfect secrecy capacity is obtained along with the
optimal power and rate allocation strategies. We then propose a low-complexity
on/off power allocation strategy that achieves near-optimal performance with
only the main channel CSI. More specifically, this scheme is shown to be
asymptotically optimal as the average SNR goes to infinity, and interestingly,
is shown to attain the secrecy capacity under the full CSI assumption.
Remarkably, our results reveal the positive impact of fading on the secrecy
capacity and establish the critical role of rate adaptation, based on the main
channel CSI, in facilitating secure communications over slow fading channels.Comment: 18 pages, 3 figures, Submitted to the IEEE Trans. on Information
Theor
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