19,285 research outputs found
Lossy Source Coding with Reconstruction Privacy
We consider the problem of lossy source coding with side information under a
privacy constraint that the reconstruction sequence at a decoder should be kept
secret to a certain extent from another terminal such as an eavesdropper, a
sender, or a helper. We are interested in how the reconstruction privacy
constraint at a particular terminal affects the rate-distortion tradeoff. In
this work, we allow the decoder to use a random mapping, and give inner and
outer bounds to the rate-distortion-equivocation region for different cases
where the side information is available non-causally and causally at the
decoder. In the special case where each reconstruction symbol depends only on
the source description and current side information symbol, the complete
rate-distortion-equivocation region is provided. A binary example illustrating
a new tradeoff due to the new privacy constraint, and a gain from the use of a
stochastic decoder is given.Comment: 22 pages, added proofs, to be presented at ISIT 201
Rate-Distortion-Based Physical Layer Secrecy with Applications to Multimode Fiber
Optical networks are vulnerable to physical layer attacks; wiretappers can
improperly receive messages intended for legitimate recipients. Our work
considers an aspect of this security problem within the domain of multimode
fiber (MMF) transmission. MMF transmission can be modeled via a broadcast
channel in which both the legitimate receiver's and wiretapper's channels are
multiple-input-multiple-output complex Gaussian channels. Source-channel coding
analyses based on the use of distortion as the metric for secrecy are
developed. Alice has a source sequence to be encoded and transmitted over this
broadcast channel so that the legitimate user Bob can reliably decode while
forcing the distortion of wiretapper, or eavesdropper, Eve's estimate as high
as possible. Tradeoffs between transmission rate and distortion under two
extreme scenarios are examined: the best case where Eve has only her channel
output and the worst case where she also knows the past realization of the
source. It is shown that under the best case, an operationally separate
source-channel coding scheme guarantees maximum distortion at the same rate as
needed for reliable transmission. Theoretical bounds are given, and
particularized for MMF. Numerical results showing the rate distortion tradeoff
are presented and compared with corresponding results for the perfect secrecy
case.Comment: 30 pages, 5 figures, accepted to IEEE Transactions on Communication
On SDoF of Multi-Receiver Wiretap Channel With Alternating CSIT
We study the problem of secure transmission over a Gaussian multi-input
single-output (MISO) two receiver channel with an external eavesdropper, under
the assumption that the state of the channel which is available to each
receiver is conveyed either perfectly () or with delay () to the
transmitter. Denoting by , , and the channel state information
at the transmitter (CSIT) of user 1, user 2, and eavesdropper, respectively,
the overall CSIT can then alternate between eight possible states, i.e.,
. We denote by the
fraction of time during which the state occurs. Under these
assumptions, we first consider the Gaussian MISO wiretap channel and
characterize the secure degrees of freedom (SDoF). Next, we consider the
general multi-receiver setup and characterize the SDoF region of fixed hybrid
states , , and . We then focus our attention on the symmetric
case in which . For this case, we establish bounds
on SDoF region. The analysis reveals that alternating CSIT allows synergistic
gains in terms of SDoF; and shows that, by opposition to encoding separately
over different states, joint encoding across the states enables strictly better
secure rates. Furthermore, we specialize our results for the two receivers
channel with an external eavesdropper to the two-user broadcast channel. We
show that, the synergistic gains in terms of SDoF by alternating CSIT is not
restricted to multi-receiver wiretap channels; and, can also be harnessed under
broadcast setting.Comment: To Appear in IEEE Transactions on Information Forensics and Securit
Rate-Distortion Theory for Secrecy Systems
Secrecy in communication systems is measured herein by the distortion that an
adversary incurs. The transmitter and receiver share secret key, which they use
to encrypt communication and ensure distortion at an adversary. A model is
considered in which an adversary not only intercepts the communication from the
transmitter to the receiver, but also potentially has side information.
Specifically, the adversary may have causal or noncausal access to a signal
that is correlated with the source sequence or the receiver's reconstruction
sequence. The main contribution is the characterization of the optimal tradeoff
among communication rate, secret key rate, distortion at the adversary, and
distortion at the legitimate receiver. It is demonstrated that causal side
information at the adversary plays a pivotal role in this tradeoff. It is also
shown that measures of secrecy based on normalized equivocation are a special
case of the framework.Comment: Update version, to appear in IEEE Transactions on Information Theor
Delay-Exponent of Bilayer Anytime Code
In this paper, we study the design and the delay-exponent of anytime codes
over a three terminal relay network. We propose a bilayer anytime code based on
anytime spatially coupled low-density parity-check (LDPC) codes and investigate
the anytime characteristics through density evolution analysis. By using
mathematical induction technique, we find analytical expressions of the
delay-exponent for the proposed code. Through comparison, we show that the
analytical delay-exponent has a close match with the delay-exponent obtained
from numerical results.Comment: Accepted for presentation in ITW-2014. 5 Pages, 3 Figure
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