93 research outputs found
Strongly Secure Communications Over the Two-Way Wiretap Channel
We consider the problem of secure communications over the two-way wiretap
channel under a strong secrecy criterion. We improve existing results by
developing an achievable region based on strategies that exploit both the
interference at the eavesdropper's terminal and cooperation between legitimate
users. We leverage the notion of channel resolvability for the multiple-access
channel to analyze cooperative jamming and we show that the artificial noise
created by cooperative jamming induces a source of common randomness that can
be used for secret-key agreement. We illustrate the gain provided by this
coding technique in the case of the Gaussian two-way wiretap channel, and we
show significant improvements for some channel configurations.Comment: 11 pages, 7 figures, submitted to IEEE Transactions on Information
Forensics and Security, Special Issue: "Using the Physical Layer for Securing
the Next Generation of Communication Systems
Security for correlated sources across wiretap network
A thesis submitted in ful llment of the requirements
for the degree of Doctor of Philosophy
in the
School of Electrical and Information Engineering
Faculty of Engineering
University of the Witwatersrand
July 2015This thesis presents research conducted for the security aspects of correlated sources
across a wiretap network. Correlated sources are present in communication systems
where protocols ensure that there is some predetermined information for sources to
transmit. Systems that contain correlated sources are for example broadcast channels,
smart grid systems, wireless sensor networks and social media networks. In these systems
there exist common information between the nodes in a network, which gives rise to
security risks as common information can be determined about more than one source.
In this work the security aspects of correlated sources are investigated. Correlated source
coding in terms of the Slepian-Wolf theorem is investigated to determine the amount of
information leakage for various correlated source models. The perfect secrecy approach
developed by Shannon has also been incorporated as a security approach. In order to
explore these security aspects the techniques employed range from typical sequences used
to prove Slepian-Wolf's theorem to coding methods incorporating matrix partitions for
correlated sources.
A generalized correlated source model is presented and the procedure to determine the
information leakage is initially illustrated using this model. A novel scenario for two
correlated sources across a channel with eavesdroppers is also investigated. It is a basic
model catering for the correlated source applications that have been detailed. The
information leakage quanti cation is provided, where bounds specify the quantity of information
leaked for various cases of eavesdropped channel information. The required
transmission rates for perfect secrecy when some channel information has been wiretapped
is further determined, followed by a method to reduce the key length required
for perfect secrecy. The implementation thereafter provided shows how the information
leakage is determined practically. In the same way using the information leakage
quanti cation, Shannon's cipher system approach and practical implementation a novel
two correlated source model where channel information and some source data symbols
(predetermined information) are wiretapped is investigated. The adversary in this situation
has access to more information than if a link is wiretapped only and can thus
determine more about a particular source. This scenario caters for an application where
the eavesdropper has access to some predetermined information. The security aspects
and coding implementation have further been developed for a novel correlated source
model with a heterogeneous encoding method. The model caters for situations where a
wiretapper is able to easily access a particular source.
iii
The interesting link between information theory and coding theory is explored for the
novel models presented in this research. A matrix partition method is utilized and the
information leakage for various cases of wiretapped syndromes are presented.
The research explores the security for correlated sources in the presence of wiretappers.
Both the information leakage and Shannon's cipher system approach are used to achieve
these security aspects. The implementation shows the practicality of using these security
aspects in communications systems. The research contained herein is signi cant as
evident from the various applications it may be used for and to the author's knowledge
is novel
Lists that are smaller than their parts: A coding approach to tunable secrecy
We present a new information-theoretic definition and associated results,
based on list decoding in a source coding setting. We begin by presenting
list-source codes, which naturally map a key length (entropy) to list size. We
then show that such codes can be analyzed in the context of a novel
information-theoretic metric, \epsilon-symbol secrecy, that encompasses both
the one-time pad and traditional rate-based asymptotic metrics, but, like most
cryptographic constructs, can be applied in non-asymptotic settings. We derive
fundamental bounds for \epsilon-symbol secrecy and demonstrate how these bounds
can be achieved with MDS codes when the source is uniformly distributed. We
discuss applications and implementation issues of our codes.Comment: Allerton 2012, 8 page
Secure Lossless Compression with Side Information
Secure data compression in the presence of side information at both a
legitimate receiver and an eavesdropper is explored. A noise-free, limited rate
link between the source and the receiver, whose output can be perfectly
observed by the eavesdropper, is assumed. As opposed to the wiretap channel
model, in which secure communication can be established by exploiting the noise
in the channel, here the existence of side information at the receiver is used.
Both coded and uncoded side information are considered. In the coded side
information scenario, inner and outer bounds on the compression-equivocation
rate region are given. In the uncoded side information scenario, the
availability of the legitimate receiver's and the eavesdropper's side
information at the encoder is considered, and the compression-equivocation rate
region is characterized for these cases. It is shown that the side information
at the encoder can increase the equivocation rate at the eavesdropper. Hence,
the side information at the encoder is shown to be useful in terms of security;
this is in contrast with the pure lossless data compression case where side
information at the encoder would not help.Comment: To appear in the Proceedings of the 2008 IEEE Information Theory
Workshop, Porto, Portugal, May 5-9, 200
Secure Multiterminal Source Coding with Side Information at the Eavesdropper
The problem of secure multiterminal source coding with side information at
the eavesdropper is investigated. This scenario consists of a main encoder
(referred to as Alice) that wishes to compress a single source but
simultaneously satisfying the desired requirements on the distortion level at a
legitimate receiver (referred to as Bob) and the equivocation rate --average
uncertainty-- at an eavesdropper (referred to as Eve). It is further assumed
the presence of a (public) rate-limited link between Alice and Bob. In this
setting, Eve perfectly observes the information bits sent by Alice to Bob and
has also access to a correlated source which can be used as side information. A
second encoder (referred to as Charlie) helps Bob in estimating Alice's source
by sending a compressed version of its own correlated observation via a
(private) rate-limited link, which is only observed by Bob. For instance, the
problem at hands can be seen as the unification between the Berger-Tung and the
secure source coding setups. Inner and outer bounds on the so called
rates-distortion-equivocation region are derived. The inner region turns to be
tight for two cases: (i) uncoded side information at Bob and (ii) lossless
reconstruction of both sources at Bob --secure distributed lossless
compression. Application examples to secure lossy source coding of Gaussian and
binary sources in the presence of Gaussian and binary/ternary (resp.) side
informations are also considered. Optimal coding schemes are characterized for
some cases of interest where the statistical differences between the side
information at the decoders and the presence of a non-zero distortion at Bob
can be fully exploited to guarantee secrecy.Comment: 26 pages, 16 figures, 2 table
Hiding Symbols and Functions: New Metrics and Constructions for Information-Theoretic Security
We present information-theoretic definitions and results for analyzing
symmetric-key encryption schemes beyond the perfect secrecy regime, i.e. when
perfect secrecy is not attained. We adopt two lines of analysis, one based on
lossless source coding, and another akin to rate-distortion theory. We start by
presenting a new information-theoretic metric for security, called symbol
secrecy, and derive associated fundamental bounds. We then introduce
list-source codes (LSCs), which are a general framework for mapping a key
length (entropy) to a list size that an eavesdropper has to resolve in order to
recover a secret message. We provide explicit constructions of LSCs, and
demonstrate that, when the source is uniformly distributed, the highest level
of symbol secrecy for a fixed key length can be achieved through a construction
based on minimum-distance separable (MDS) codes. Using an analysis related to
rate-distortion theory, we then show how symbol secrecy can be used to
determine the probability that an eavesdropper correctly reconstructs functions
of the original plaintext. We illustrate how these bounds can be applied to
characterize security properties of symmetric-key encryption schemes, and, in
particular, extend security claims based on symbol secrecy to a functional
setting.Comment: Submitted to IEEE Transactions on Information Theor
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