327 research outputs found
Capacity Results for Relay Channels with Confidential Messages
We consider a communication system where a relay helps transmission of
messages from {a} sender to {a} receiver. The relay is considered not only as a
helper but as a wire-tapper who can obtain some knowledge about transmitted
messages. In this paper we study a relay channel with confidential
messages(RCC), where a sender attempts to transmit common information to both a
receiver and a relay and also has private information intended for the receiver
and confidential to the relay. The level of secrecy of private information
confidential to the relay is measured by the equivocation rate, i.e., the
entropy rate of private information conditioned on channel outputs at the
relay. The performance measure of interest for the RCC is the rate triple that
includes the common rate, the private rate, and the equivocation rate as
components. The rate-equivocation region is defined by the set that consists of
all these achievable rate triples. In this paper we give two definitions of the
rate-equivocation region. We first define the rate-equivocation region in the
case of deterministic encoder and call it the deterministic rate-equivocation
region. Next, we define the rate-equivocation region in the case of stochastic
encoder and call it the stochastic rate-equivocation region. We derive explicit
inner and outer bounds for the above two regions. On the
deterministic/stochastic rate-equivocation region we present two classes of
relay channels where inner and outer bounds match. We also evaluate the
deterministic and stochastic rate-equivocation regions of the Gaussian RCC.Comment: 31 pages, 8 figure
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
A Secure Communication Game with a Relay Helping the Eavesdropper
In this work a four terminal complex Gaussian network composed of a source, a
destination, an eavesdropper and a jammer relay is studied under two different
set of assumptions: (i) The jammer relay does not hear the source transmission,
and (ii) The jammer relay is causally given the source message. In both cases
the jammer relay assists the eavesdropper and aims to decrease the achievable
secrecy rates. The source, on the other hand, aims to increase it. To help the
eavesdropper, the jammer relay can use pure relaying and/or send interference.
Each of the problems is formulated as a two-player, non-cooperative, zero-sum
continuous game. Assuming Gaussian strategies at the source and the jammer
relay in the first problem, the Nash equilibrium is found and shown to be
achieved with mixed strategies in general. The optimal cumulative distribution
functions (cdf) for the source and the jammer relay that achieve the value of
the game, which is the Nash equilibrium secrecy rate, are found. For the second
problem, the Nash equilibrium solution is found and the results are compared to
the case when the jammer relay is not informed about the source message.Comment: 13 pages, 11 figures, to appear in IEEE Transactions on Information
Forensics and Security, Special Issue on Using the Physical Layer for
Securing the Next Generation of Communication Systems. This is the journal
version of cs.IT:0911.008
Secure Communication over Parallel Relay Channel
We investigate the problem of secure communication over parallel relay
channel in the presence of a passive eavesdropper. We consider a four terminal
relay-eavesdropper channel which consists of multiple relay-eavesdropper
channels as subchannels. For the discrete memoryless model, we establish outer
and inner bounds on the rate-equivocation region. The inner bound allows mode
selection at the relay. For each subchannel, secure transmission is obtained
through one of two coding schemes at the relay: decoding-and-forwarding the
source message or confusing the eavesdropper through noise injection. For the
Gaussian memoryless channel, we establish lower and upper bounds on the perfect
secrecy rate. Furthermore, we study a special case in which the relay does not
hear the source and show that under certain conditions the lower and upper
bounds coincide. The results established for the parallel Gaussian
relay-eavesdropper channel are then applied to study the fading
relay-eavesdropper channel. Analytical results are illustrated through some
numerical examples.Comment: To Appear in IEEE Transactions on Information Forensics and Securit
Multiple Access Channels with Generalized Feedback and Confidential Messages
This paper considers the problem of secret communication over a multiple
access channel with generalized feedback. Two trusted users send independent
confidential messages to an intended receiver, in the presence of a passive
eavesdropper. In this setting, an active cooperation between two trusted users
is enabled through using channel feedback in order to improve the communication
efficiency. Based on rate-splitting and decode-and-forward strategies,
achievable secrecy rate regions are derived for both discrete memoryless and
Gaussian channels. Results show that channel feedback improves the achievable
secrecy rates.Comment: To appear in the Proceedings of the 2007 IEEE Information Theory
Workshop on Frontiers in Coding Theory, Lake Tahoe, CA, September 2-6, 200
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