29,624 research outputs found
Byzantine Multiple Access Channels -- Part I: Reliable Communication
We study communication over a Multiple Access Channel (MAC) where users can
possibly be adversarial. The receiver is unaware of the identity of the
adversarial users (if any). When all users are non-adversarial, we want their
messages to be decoded reliably. When a user behaves adversarially, we require
that the honest users' messages be decoded reliably. An adversarial user can
mount an attack by sending any input into the channel rather than following the
protocol. It turns out that the -user MAC capacity region follows from the
point-to-point Arbitrarily Varying Channel (AVC) capacity. For the -user MAC
in which at most one user may be malicious, we characterize the capacity region
for deterministic codes and randomized codes (where each user shares an
independent random secret key with the receiver). These results are then
generalized for the -user MAC where the adversary may control all users in
one out of a collection of given subsets.Comment: This supercedes Part I of arxiv:1904.1192
Byzantine Multiple Access Channels -- Part II: Communication With Adversary Identification
We introduce the problem of determining the identity of a byzantine user
(internal adversary) in a communication system. We consider a two-user discrete
memoryless multiple access channel where either user may deviate from the
prescribed behaviour. Owing to the noisy nature of the channel, it may be
overly restrictive to attempt to detect all deviations. In our formulation, we
only require detecting deviations which impede the decoding of the
non-deviating user's message. When neither user deviates, correct decoding is
required. When one user deviates, the decoder must either output a pair of
messages of which the message of the non-deviating user is correct or identify
the deviating user. The users and the receiver do not share any randomness. The
results include a characterization of the set of channels where communication
is feasible, and an inner and outer bound on the capacity region. We also show
that whenever the rate region has non-empty interior, the capacity region is
same as the capacity region under randomized encoding, where each user shares
independent randomness with the receiver. We also give an outer bound for this
randomized coding capacity region.Comment: arXiv admin note: substantial text overlap with arXiv:2105.0338
Byzantine Attack and Defense in Cognitive Radio Networks: A Survey
The Byzantine attack in cooperative spectrum sensing (CSS), also known as the
spectrum sensing data falsification (SSDF) attack in the literature, is one of
the key adversaries to the success of cognitive radio networks (CRNs). In the
past couple of years, the research on the Byzantine attack and defense
strategies has gained worldwide increasing attention. In this paper, we provide
a comprehensive survey and tutorial on the recent advances in the Byzantine
attack and defense for CSS in CRNs. Specifically, we first briefly present the
preliminaries of CSS for general readers, including signal detection
techniques, hypothesis testing, and data fusion. Second, we analyze the spear
and shield relation between Byzantine attack and defense from three aspects:
the vulnerability of CSS to attack, the obstacles in CSS to defense, and the
games between attack and defense. Then, we propose a taxonomy of the existing
Byzantine attack behaviors and elaborate on the corresponding attack
parameters, which determine where, who, how, and when to launch attacks. Next,
from the perspectives of homogeneous or heterogeneous scenarios, we classify
the existing defense algorithms, and provide an in-depth tutorial on the
state-of-the-art Byzantine defense schemes, commonly known as robust or secure
CSS in the literature. Furthermore, we highlight the unsolved research
challenges and depict the future research directions.Comment: Accepted by IEEE Communications Surveys and Tutoiral
When the Hammer Meets the Nail: Multi-Server PIR for Database-Driven CRN with Location Privacy Assurance
We show that it is possible to achieve information theoretic location privacy
for secondary users (SUs) in database-driven cognitive radio networks (CRNs)
with an end-to-end delay less than a second, which is significantly better than
that of the existing alternatives offering only a computational privacy. This
is achieved based on a keen observation that, by the requirement of Federal
Communications Commission (FCC), all certified spectrum databases synchronize
their records. Hence, the same copy of spectrum database is available through
multiple (distinct) providers. We harness the synergy between multi-server
private information retrieval (PIR) and database- driven CRN architecture to
offer an optimal level of privacy with high efficiency by exploiting this
observation. We demonstrated, analytically and experimentally with deployments
on actual cloud systems that, our adaptations of multi-server PIR outperform
that of the (currently) fastest single-server PIR by a magnitude of times with
information theoretic security, collusion resiliency, and fault-tolerance
features. Our analysis indicates that multi-server PIR is an ideal
cryptographic tool to provide location privacy in database-driven CRNs, in
which the requirement of replicated databases is a natural part of the system
architecture, and therefore SUs can enjoy all advantages of multi-server PIR
without any additional architectural and deployment costs.Comment: 10 pages, double colum
Representation c. 800: Arab Byzantine Carolingian
What could or should be visually represented was a contested issue across the medieval Christian and Islamic world around the year 800. This article examines how Islamic, Byzantine, Carolingian and Palestinian Christian attitudes toward representation were expressed, and differed, across the seventh and eighth centuries. Islamic prohibitions against representing human figures were not universally recognised, but were particularly – if sometimes erratically – focused on mosque decoration. Byzantine ‘iconoclasm’ – more properly called iconomachy – was far less destructive than its later offshoots in France and England, and resulted in a highly nuanced re-definition of what representation meant in the Orthodox church. Carolingian attitudes toward images were on the whole far less passionate than either Islamic or Orthodox views, but certain members of the elite had strong views, which resulted in particular visual expressions. Palestinian Christians, living under Islamic rule, modulated their attitudes toward images to conform with local social beliefs. Particularly in areas under Orthodox or Islamic control, then, representation mattered greatly around the year 800, and this article examines how and why this impacted on local production
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